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Combining people and equipment according to the principle of specialization gives rise to another problem: the product that the consumer needs is not tied to one department. To turn into what the consumer needs, it roams through different departments. Design, supply and financing are handled by different departments. Many value streams flow through these departments, so every time a product is transferred to the next department, there is a delay. The one-piece flow assumes that you consistently build all technological operations into a single line, which allows you to complete the customer's order in the shortest possible time.

On fig. Figure 8.1 is a schematic representation of a computer firm consisting of three departments. One department manufactures system units, the second produces monitors and connects them to the system unit, and the third tests finished computers (in fact, many companies and departments are involved in the manufacturing of a computer in the technological chain). With this structure, the transport department considers it appropriate to move a batch of 10 units at a time. Each department spends one minute per unit, so a batch of computers goes through each department in 10 minutes. Without taking into account the time of movement between departments, it will take 30 minutes to manufacture and test the first batch of 10 units. It will take 21 minutes to get the first computer ready for shipping and shipping, despite the fact that it only takes three minutes to add value to the manufacturing process.

In Ohno's system, the efficiency of a single process or the performance of a transport department does not determine the ideal lot size. The ideal lot size with a lean approach is unchanged - it's one product. Ohno did not try to optimize the use of people and equipment in isolated departments. The first Toyota factory worked exactly according to the Ford factory method. But that didn't work, because Toyota couldn't compete with Ford in terms of production volume and economies of scale. So Ohno decided to optimize the flow of material so that it could move through the plant faster. This meant the reduction of the party. And to do this, the easiest way was to break down the barriers between departments and instead of islands that specialized in individual operations, create work cells organized by products, not by processes.

On fig. Figure 8.2 shows the same computer manufacturing process organized as a work cell through which a stream of one-off items passes. If Ohno were to undertake this process, he would take the equipment needed to make the system unit from one department, the equipment for making the monitor and the test bench from the testing department from another department, and build a sequential chain from these operations. In other words, he would create a cell for one-piece flow. Then he would make sure that the operators do not create inventory between these three operations. For example, the one who makes the system blocks should not be taken to the production of the next block until the monitor for the previous block is made and until the finished product is created from these two assemblies. In other words, no one should produce more than what is needed immediately. As a result, operators of such a cell produce 10 computers in 12 minutes. In addition, this lean process allows the first working computer to be ready for shipment in just three minutes instead of 21. Those three minutes represent pure value-added time. The flow made it possible to get rid of overproduction and stocks.

Why, with flow, "faster" means "better"

Often it seems to us that speeding up the process leads to lower quality, faster means sloppier. But the flow leads to quite the opposite result - as a rule, the quality increases. On fig. Figures 8.1 and 8.2 show a defective computer whose monitor is crossed out. During the testing phase, it could not be enabled. With the release of a large batch according to the scheme shown in Fig. 8.1, by the time the problem is identified, there will be at least 21 products in operation, and it is possible that all of them will have the same defect. If this is a defect that was made through the fault of the department that produces the system units, then the testing department will know about it only after 21 minutes. On fig. 8.2, when a defect is discovered, there are only two computers with the same defect in operation, and it will take only two minutes to figure out which operation made a mistake. Thus, in the production of large batches, work in progress can lie between individual operations for weeks, and weeks and even months can pass from the moment a defect is made to the moment it is discovered. But the trace will already “cool down”, and it will be almost impossible to identify the cause of the defect.

The same logic chain applies to any technological or business process. If you allow isolated departments to do their work in batches and transfer those batches to other departments, you are guaranteed delays in completing the work. There will be bureaucratic delays, officials will begin to set standards for each department, and many non-value-added positions will be created to track the flow. Projects will spend most of their time waiting for action or decisions. This will lead to confusion and poor quality. Pick up the right people that add value, determine the sequence of operations and run the project through the created chain, taking care of how to connect their actions, and you will get the pace, productivity and quality you need.

Takt time: single piece flow pulse

In rowing competitions important role plays the helmsman, who sits on the stern and shouts "and one, and one, and one." He coordinates the activities of all rowers, making sure that they act in harmony and row at the same speed. What happens if one of the rowers is faster than the others? That's right, the order is broken, and the boat moves more slowly. Excess force and speed slows down movement.

Something similar happens in any work, whether we are talking about production or the provision of services. If an individual department is over-capacitated, it will overwhelm other departments with mountains of inventory and paperwork, resulting in confusion and slowing down the process. The activities of the departments must be coordinated. How do you determine how fast your one-piece flow cell should run? What should be the capacity of the equipment? How many people will be needed? To do this, you need to determine the takt time.

The German word takt means rhythm or tempo. Takt time is determined by consumer demand - the rate of product acquisition. If the working day is 7 hours 20 minutes (440 minutes), 20 days a month, and the consumer purchases 17,600 units of products per month, then 880 units must be produced per day, that is, one product in 30 seconds. With a properly organized one-piece flow, each stage of the process should take 30 seconds. If work go faster, this will lead to overproduction, if slower - a bottleneck will appear in the process. The concept of "tact" is used when it is necessary to determine the pace of production and not allow workers to fall behind it or be in too much of a hurry.

Continuous flow and takt time are most easily applied in batch production of goods or services. However, with a creative approach, these concepts apply to any iterative process, if you list its stages and identify and eliminate waste (see Chapter 21). An example of such a list at a US Navy shipyard is given at the end of this chapter. My colleagues and I have come across many other examples in the course of our work: filling out invoices for the design of ships, screening people by the security service of the Navy shipyard, admitting new members to a professional association, reimbursement of employees, working with applicants for jobs ... You yourself can find many others examples. Of course, the concept of takt time and one-piece flow is most easily applied to repetitive maintenance operations that require a certain amount of per-unit cycle time stability, but the Toyota Way is not about looking for the easy way out.

Benefits of the one-piece flow

Creating a flow of single products involves a broad program of measures to eliminate all kinds of muda (waste). Let's take a closer look at some of the benefits of flow.

1. Embedded quality. The one-piece flow greatly simplifies the build-in of quality. Each operator is also a controller and tries to solve the problem on the spot, without passing it on to the next stage. Even if he missed the defects and they went further, they will be found very quickly and the problem will be immediately identified and corrected.

2. Genuine flexibility. If the equipment becomes part of the production line, our ability to use it for other purposes will be reduced. But the lead time is reduced to the limit, which means that we are more flexible in responding to customer requests, making what he really needs. Instead of waiting weeks for the system to which the order is given to issue products, we can complete the order within a few hours. The transition to a new product range, which is required by changing consumer demand, is carried out almost instantly.

3. Improve performance. When work was divided into departments, you felt like you were maximizing productivity, because work efficiency was measured by the workload of people and equipment. It is actually difficult to determine how many people it takes to produce a given number of units in high volume production because productivity is not measured in terms of value-added work. Who knows what the productivity loss is when people are "loaded" with producing surplus parts that then have to be sent to the warehouse? How much time is wasted searching for defective parts and repairing finished products? If there is a one-piece flow cell, non-value-adding work such as moving materials is minimized. You can immediately see who is overloaded and who is left idle. It is very easy to create a cost estimate for value-adding work and calculate how many people are required to achieve a given performance. When it comes to transferring a supplier working on the system mass production, per line organized in accordance with TPS, the Toyota Supplier Support Center in each case achieves an increase in labor productivity of at least 100%.

4. The release of space in the shop. When the equipment is distributed among the sites, significant areas between them disappear, although most of them are occupied by deposits of reserves. In a one-piece flow cell, all blocks fit together and inventory takes up almost no space. If the production areas are used more efficiently, the construction of new facilities can be avoided.

5. Increased security. As one of America's first adopters of TPS, Wiremold Corporation has achieved exemplary security performance and has been the recipient of numerous national security awards. However, when the company decided to take on the challenge of transforming high-volume production into a single-piece flow, it was decided that a special safety improvement program was not needed. The reorganization was led by Art Byrne, ex-president a company that studied TPS and realized that the flow of one-pieces would automatically increase safety by reducing the amount of material that had to be moved around the plant. Reducing the volume of cargo allows you to get rid of forklifts, which are often the cause of accidents. The volume of containers that need to be lifted and moved will also decrease, which means that the number of accidents when lifting containers will decrease. If you deal with the flow, security increases by itself, even if you do not pay special attention to it.

6. Increased morale. In Wiremold when organizing lean manufacturing found that employee morale improved year after year. Prior to the transformation, only 60% of employees in surveys said they worked for a good company. This figure has grown every year and in the fourth year of transformation it exceeded 70% (Emilani, 2002). The flow of one-off products leads to the fact that most of the time people are busy creating added value and can quickly see the fruits of their labor, and when they see their successes, they feel satisfaction.

7. Reducing inventory. By not investing in stocks that lie idle, you can use them for something else. At the same time, you will also save on bank interest, which must be paid for funds frozen in stocks. You will also avoid stock obsolescence.

On fig. 8.3 shows a traditional shop, where the equipment is grouped by type. One tool that can be used to schematically represent material paths is the Spaghetti Diagram. If we plot the flow of materials in the shop on a diagram, we get something resembling spaghetti, which are randomly mixed on a plate. The product moves randomly in different directions. The work of individual sections during the movement of the product is not coordinated. No amount of schedules and plans can eliminate the variability inherent in a system in which material moves randomly.

On fig. In Figure 8.4, which shows the lean cell, we see a different picture. Equipment is grouped according to the flow of material as it becomes a finished product. At the same time, the equipment is placed in the shape of the letter U, since such an arrangement contributes to the efficient movement of materials and people and facilitates the exchange of information. You can organize the cell in the form of a straight line or the letter L. In this case, we have shown the trajectory of the movement of two people who serve the cell. What if demand drops by half? Leave one operator per cell. What if demand doubles? Place four people on the cell service. Of course, in order to serve different technological operations, people must be prepared to combine professions, such are the requirements of Toyota factories.

Why is it difficult to create a flow

Do you think that as soon as you create cells for the flow of one-off products, life will immediately improve and all problems and misfortunes will disappear? Do not even hope! If you start thinking in terms of lean, life will become much more difficult for a while, at least until you learn how to constantly improve the process. Taiichi Ohno says:

In 1947, we arranged the machines in parallel lines, and in some places arranged them with the letter L and tried to put one worker on three or four machines in accordance with the technological route. Although it was not about working overtime, the workers fought back fiercely. The machine operators did not like that the new layout required them to combine professions. They did not like the transition from the system "one operator - one machine" to the system "one operator - many machines for various operations." They could be understood. In addition, other problems emerged. When it became clear what kind of problems these were, I was able to decide in which direction to move. Although I was young and energetic, I decided not to push for immediate, radical change, but to be patient (Ohno, 1988).

If, in traditional mass production, one of the process steps fails, for example, it takes a long time to change over a machine, someone is absent from work due to illness, or equipment fails, other “independent” process steps will continue as before, because you have plenty of stock. When you link individual operations, creating a one-piece flow, if a failure occurs in one area, the entire cell stops. Either you swim together, or you all go down together. So why not make your life easier and create a reserve stock? However, any stockpiles - accumulations of material or virtual accumulations of information that are waiting in the wings for a long time - prevent problems and inefficiencies from being identified. Stocks develop the bad habit of sidestepping problems. If you avoid solving problems, you are not improving processes. One-piece flow and continuous improvement (kaizen) go hand in hand! If your competitor decides to take the difficult and thorny path of lean, no amount of inventory will help you, you will face bankruptcy. Minora, former president of Toyota Motor Manufacturing and student of Taiichi Ohno, says:

Someone who has started production on a one-piece flow system fails to keep the desired number of products, so at first everyone is discouraged and does not know what to do. But it makes people think: how can you get the right amount? This is the essence of TPS, we can say that we deliberately confuse people so that they are forced to change their approach to the problem.

Many companies I've visited have made one of two mistakes when implementing flow. The first was that the stream was not real. The second mistake was to immediately abandon the flow as soon as problems arose.

An example of a pseudo-flow was a hardware swap. By sliding blocks of equipment together, the company created an external semblance of a cell for the flow of one-off products, but at each stage continued to be engaged in mass production, without thinking about the takt time, which is determined by the consumer. It looked like a cell for the flow of products, but the work went on in the old fashioned way, according to the principle of mass production.

The Will-Burt Company in Orville, Ohio makes various products from billet steel. One product that is produced in high volume is a family of telescopic steel masts that are used in radar vans or film crews. Each mast has its own characteristics depending on the application, so all products are different. This company called the process of making masts a cell and believed that they had created lean manufacturing. When I, as a lean consultant, helped organize the process review, the production manager warned us that the inventory of parts was so diverse that we were unlikely to improve the existing flow.

During the week-long kaizen workshop, the current situation was analyzed, and it turned out that we are dealing with a classic pseudo-flow. The time required to create one mast (value-added processing time) was 431 minutes. However, the pieces of equipment that were used to manufacture each mast were located so far apart that large pallets of mast had to be moved with forklifts from one workplace to another. Each workplace was stocked with work in progress. The total lead time from raw material to finished product, taking into account the length of stay in the state of incompleteness, was 37.8 days. Most of this time was occupied by the storage of tubular blanks and finished products. In terms of processing time at the factory, the job, which took 431 minutes, from sawing to the final stage - welding - took four days. Moving within the plant, each mast covered a distance of 1792 feet (546 meters. - Approx. scientific ed.). To solve these problems, it was proposed to place equipment blocks closer to each other, handle products one by one, refuse to use a forklift between operations (to move products between operations that could not be carried out side by side, a special trolley was designed, the height of which appropriate for the workplace). In addition, it was proposed to issue a separate work order for each mast instead of a set of work orders for a set of masts. The result of these changes was a significant reduction in lead times (see Figure 8.5), reduced inventory, and saved production space.

Among other things, it was checked how long it takes to place a job order, and this allowed to get an additional positive effect by eliminating the old method. The accumulation of batches of work orders generated a lot of losses; and when such a system was ended, the time was reduced from 207 minutes to 13 minutes. On fig. Figure 8.6 shows the flow before and after the week-long kaizen workshop. It can be seen that the “before” situation is actually a pseudo-flow. The pieces of equipment seem to be located side by side, but there is really nothing like a flow of one-off products. The employees working in the plant did not fully understand what flow was and did not realize that they were dealing with a pseudo-flow. The “after” situation improved qualitatively, which surprised and delighted everyone in the company. They were shocked that this was done in just a week.

The second mistake that those who implement the flow make is the abandonment of the chosen course. As soon as it becomes clear that the creation of a flow can lead to certain costs, the company abandons the decision. This can happen in any of the following situations:

Stopping one of the equipment blocks leads to the fact that the entire cell stops working.

Reconfiguring one piece of equipment takes longer than expected and slows down the cell as a whole as production comes to a halt.

When creating a flow, you have to invest in a technological operation that was previously carried out in another enterprise (for example, heat treatment) in order to produce it on site.

I've seen companies drop flow in cases like this. They thought flow was great as long as the benefits of batch size reduction and the flow system were shown to you in a theoretical model. But it is far from being so good when we try it in action, and we see that it immediately causes all sorts of troubles and costs. Once a one-piece flow cell is created, maintaining it requires discipline, which is impossible for many manufacturing companies because they do not fully realize the complexities and challenges of continuous improvement. However, in the long run, these annoyances and short-term costs will certainly pay off, leading to amazing results.

In any process, Toyota strives to create a true one-off flow by eliminating waste, as stated in Principle 2: A continuous flow process helps identify problems. To create a flow means to link together operations that were previously separated. When such a connection is established, the team works more smoothly, the system responds quickly to quality problems, the process becomes manageable, and immediate problem solving becomes a pressing need, forcing people to think and develop. Ultimately, for the Toyota approach, the main benefit of one-piece flow is that it forces people to think and improve.

Emphasizing the need to think, Toyota stands for the name of its production system, TPS, as "Thinking Production System" ("Thinking Production System"). For the sake of identifying problems, Toyota is ready to stop production, knowing that this will force the team members to find a solution. Stocks hide problems and allow you to postpone their solution indefinitely. With Toyota's approach, the problem is solved as soon as it is discovered. Chapter 11 (on jidoka) talks about this in more detail.

Case Study: Describing Processes at a Navy Ship Repair Plant

An excellent example of how one-piece flow can be applied to a repair shop is the Navy Shipyard in Puget Sound. Here they began to use the flow of single products in the fall of 2001. The plant is not engaged in construction, but in the repair of Navy ships - from submarines to aircraft carriers. The repair of each ship is unique, so the work is carried out in close contact with engineers who diagnose the problem and set the task for the upcoming repair work. Technical documentation, including instructions for performing work, is folded into a folder that is transferred to the factory so that qualified workers can carry out the appropriate repairs. As a result, mechanics had to deal with permits, funding, and other paperwork to get the job done. The instruction folder often became a bottleneck in the planning process and led to additional costs.

To improve the process, a week-long kaizen workshop was held. It was preceded by thorough preparation. Preparations were underway for the reorganization, in the office a room was allocated for a cross-functional cell, which was supposed to deal with production tasks. The workshop focused on mapping the existing process and developing a new process. A step by step review of the process identified wastage including rework, redundant systems, various storage media (e.g. summary sheets), waiting for forms, verification, redundant checks and approvals, ill-conceived filing system, lack of necessary reference materials, extra walking, waiting and incomplete information.

As a solution, it was proposed to develop a cross-functional cell to collect all work instructions together. As a result, handovers have been reduced and non-value-adding transactions have been eliminated. Taking into account the need for work instructions (these needs are very easy to predict) and the time required to develop them, the takt time was determined. The most important was the selection of employees who do the bulk of the work, and the removal of barriers that separated them. The cell was set up in the office, and a folder of work instructions was transferred from one position to another in record time. Previously, in the office, employees were grouped according to their functions, and the rooms were separated by high partitions so that everyone had their own office. Now, with the presence of a cell, the tables of leading experts were located around a round table. Production tasks were passed along the table from one specialist to another, forming a stream of single objects. The timing of the time spent on creating added value before and after the transformation showed amazing results. Note that some time wasted on non-value-adding processes is unavoidable, such as filling out a number of paperwork in accordance with the Navy regulations, although these paperwork is not always necessary for the work of mechanics. We have presented such time costs in a separate column, separate from the "waiting time", which is a waste in its purest form. The results of the reorganization are shown in fig. 8.7.

Principle 3: Use the pull system to avoid overproduction

The more inventory a company has... the less hope it will have what it needs.

Taiichi Ohno

Imagine that you have learned about a wonderful online ordering service. Now all dairy products will be brought to your home, and even with a good discount. There is only one difficulty - you need to determine the number of products for the week in advance. The company can only guarantee one thing - delivery within a week. The company asks you to decide on the order in advance, because it needs to know how much and what products need to be shipped from the warehouse. This will allow her to sell all the products received. Products will be left on your porch in a special refrigerator container. You count how many eggs, milk and butter you usually consume in a week. But you don't know what day they'll be picked up. It might be Monday, or it might be Friday. Therefore, you have to keep a reserve supply of food in the refrigerator. If groceries arrive on Monday and you already have a week's supply of dairy products in your fridge, you're having a hard time finding room for new ones. You buy another refrigerator and put it in the garage. If you go on vacation and forget to cancel a week's order, when you return, you will find a container on the porch with a week's supply of spoiled food.

This is an example of a stock push system. Wholesalers often push goods and services into retailers, whether or not the retailer can sell them. The retailer, in turn, pushes goods and services to you, without asking if you need them now or not. As a result, you accumulate an excess amount of inventory that you do not need at the moment, and you yourself retailer also has to keep huge stocks.

Now imagine that the mentioned Internet service, having received many complaints, decided to improve the service system. They sent you a special transmitter that has a button for each of the products you need. When you open a new bottle of milk or a carton of eggs, you press the corresponding button. The next day, exactly as many products as you unpacked will be delivered to you. As a result, you will have one printed package plus one more. Stocks will be, but very small. If you know you're going to need a lot of milk, you can just go online or call and you'll get what you need immediately. The company itself revised agreements with suppliers of dairy products. If consumers order a lot of products, the company informs the suppliers, and they bring products in quantities that do not exceed the required. This is an example of a "pull" system. You get what you need when you need it, and the retailer orders products based on consumer demand. I guess you'd be willing to pay a little more for on-demand service to avoid being pushed out.

As noted in the first part of the article, any production planning technique that limits the level of operational backlog will create a so-called logistical pull.

It is customary to distinguish five basic types of "pulling" logistics systems Pull Scheduling:

• replenishment of the "supermarket" (Supermarket Replenishment);
• limited FIFO queues (Capped FIFO Lanes);
• the drum-buffer-rope method (Drum Buffer Rope);
• work in progress limit (WIP Cap);
• method of computed priorities (Priority Sequenced Lanes).

We have already discussed two of them in detail in the first part of the article.

The "pull" logistics system is usually understood as the "supermarket" replenishment system developed in Japan in the middle of the last century. It is associated with a kind of "locomotive", pulling the cars behind it (that is, with such an organization material flows when one consumer successively pulls out the supplies carried out by the previous links of suppliers included in the general chain). But, as we saw in the example of the FIFO limited queue method, in production logistics, a “pull” logistics scheme at the level of production organization is also understood as such a situation when a work plan drawn up for only one production unit automatically generates operational plans works for all other sections included in the technological chain. This is the same "locomotive", but here it is no longer required that it be placed in front of the entire train!

Both the “supermarket” replenishment logistics scheme and FIFO limited queues can be used quite successfully in mass and large-scale production, where the output volume is quite high and the technological process is constant for the entire family of manufactured products.

How well does this logistical "locomotive" cope with the tasks of management in custom production (that is, small-scale and single type) will be discussed in this article.

Drum-Buffer-Rope Method (DBR)

The Drum-Buffer-Rope (DBR) method is one of the original variants of the “push” logistics system developed in TOC (Theory of Constraints) - the theory of constraints. It is very similar to the FIFO limit queue system, except that it does not limit the inventory in individual FIFO queues.

Instead, an overall inventory limit is set between the single scheduling point and the resource that limits the performance of the entire system, the ROP (in the example shown in Figure 1, the ROP is site 3). Each time the ROP completes one unit of work, the scheduling point can release another unit of work into production. This in this logistic scheme is called a rope (Rope). Rope is a limitation control mechanism against ROP overload. Essentially, it is a material issue schedule that prevents work from entering the system at a faster rate than it can be processed in the ROP. The rope concept is used to prevent WIP at most points in the system (except for critical points protected by planned buffers).

Since the ROP dictates the rhythm of the entire production system, the schedule for its work is called the “drum” (Drum). In the DBR method Special attention It is the performance-limiting resource that is given, since it is this resource that determines the maximum possible output of the entire production system as a whole, since the system cannot produce more than its least powerful resource. Inventory limit and time resource of equipment (its time effective use) are distributed so that the ROP can always start on time new job. In this method, it is called a buffer (Buffer). "Buffer" and "rope" create conditions that prevent underloading or overloading the ROP.

Note that in the "pull" DBR logistics system, the buffers created before the ROP are temporary, not material.

The time buffer is a slack provided to protect the scheduled start time of processing, taking into account the spread in arrivals at the EPR of a particular job. For example, if the EPR schedule calls for a specific job in Section 3 to begin on Tuesday, then material for that activity must be released early enough so that all of the pre-PRB steps (Sections 1 and 2) are completed on Monday (i.e., in one full work day). day before the due date). Buffer time serves to protect the most valuable resource from downtime, since the loss of time for this resource is equivalent to the irretrievable loss in the end result of the entire system. The receipt of materials and production tasks can be carried out on the basis of filling the cells of the "supermarket". The transfer of parts to subsequent stages of processing after they have passed through the ROP is no longer limited by FIFO, since the productivity of the corresponding processes is obviously higher.

It should be noted that only critical points in the production chain are protected by buffers (Fig. 2). These critical points are:

• the resource itself with limited performance (section 3);
• any subsequent step in the process where the part machined by the bounding resource is assembled with other parts;
• shipment of finished products containing parts machined by the limiting resource.

Since in the DBR method, protection against possible deviations is concentrated in the most critical places in the production chain and is eliminated in all other places, time production cycle can be reduced sometimes by 50% or more without compromising reliability in meeting deadlines for shipping products to customers. Of course, in the DBR logistics scheme, EPR requires constant dispatch control (Fig. 3).

The DBR algorithm is a generalization of the well-known OPT method, which many experts call electronic implementation. Japanese method"kanban", although in fact there is a significant difference between the logistics schemes for replenishing the "supermarket" cells and the "drum-buffer-rope" method, as we have already seen.

The disadvantage of the "drum-buffer-rope" (DBR) method is the requirement for the existence of a ROP localized at a given planning horizon (at the interval for calculating the schedule for the work performed), which is possible only in conditions of serial and large-scale production. However, for small-scale and single-piece production, it is generally not possible to localize the ROP for a sufficiently long time interval, which significantly limits the applicability of the considered logistics scheme for this case.

If we draw an analogy with the movement of a “train”, then the DBR method can be considered as a kind of “semaphore” that periodically prohibits or allows movement in the direction of the ROP, depending on the current load on the path leading to it.

Limit of work in progress (WIP)

A "pull" logistics system with a work in progress (WIP) limit is similar to the DBR method. Its difference lies in the fact that temporary buffers are not created here, but a certain fixed limit is set. inventories, which is distributed to all processes of the system, and does not end only in the ROP. The scheme is shown in fig. 4.

This approach to building a "pull" control system is much simpler than the above logistic schemes, it is easier to implement and in some cases is more effective. As in the "pull" logistics systems discussed above, there is a single planning point here - section 1 in Fig. 4.

The WIP limit logistics system has some advantages over the DBR method and the FIFO limited queue system:

• malfunctions, production fluctuations and other process headroom issues will not lead to production shutdown due to lack of work for the EPR and will not reduce the overall system throughput;
• only one process should obey the scheduling rules;
• it is not required to fix (localize) the position of the ROP;
• it is easy to locate the current section of the ROP. In addition, such a system gives fewer false signals compared to limited FIFO queues.

An important feature of the "push" logistics systems discussed above is the ability to calculate the release time (processing cycle) of products using the well-known Little formula:

Release time = WIP/rhythm,

where WIP- the volume of work in progress, rhythm- the number of products produced per unit of time.

However, for small-scale and single-piece production, the concept of “production rhythm” becomes very vague, since this type of production cannot be called rhythmic. Moreover, statistics show that, on average, the entire machine system in such industries remains half underloaded, which occurs due to the constant overloading of one equipment and the simultaneous downtime of another in anticipation of work related to products lying in line at previous stages of processing. Moreover, idle times and overloads of machines constantly migrate from site to site, which does not allow them to be localized and apply none of the above logistic pull schemes.

It was previously noted that these logistics systems work well for rhythmic industries with a stable product range, debugged and unchanging technological processes, which usually corresponds to mass, large-scale and mass production. But in the production of single and small-scale production, where new orders with the original technology of their manufacture are constantly launched into production, where the timing of the release of products is dictated by the consumer and can, generally speaking, change directly in the process of manufacturing products, the above-mentioned "pull" production logistics systems lose their effectiveness. .

Another feature of small-scale and single-piece production is the need to fulfill orders in the form of a whole set of parts and assembly units by a fixed date. This greatly complicates the task of production management, since the parts included in this set (order) can be technologically subjected to various processing processes, and each of the sections can represent an ROP for some orders without causing problems when processing other orders. Thus, in the productions under consideration, the effect of the so-called virtual bottleneck (Virtual Bottle-Neck) arises: the entire machine system, on average, remains underloaded, and its throughput low. For such cases, the most effective "pull" logistics system is the method of calculated priorities.

Computed Priority Method

The method of calculated priorities is a kind of generalization of the two "push" logistics systems discussed above: the "supermarket" replenishment system and the system with limited FIFO queues. Its difference lies in the fact that in this system not all empty cells in the "supermarket" are replenished in without fail, and production tasks, being in a limited queue, move from site to site not according to the FIFO rules (that is, the mandatory discipline “in the order of receipt” is not observed), but according to other calculated priorities. The rules for calculating these priorities are assigned at a single point in production planning - in the example shown in fig. 5, this is the second production site, following the first "supermarket". At each subsequent production area operates its own production execution system (Manufacturing Execution System, MES), the task of which is to ensure the timely processing of incoming tasks taking into account their current priority, optimize the internal material flow and timely show emerging problems associated with this process. Significant deviation in processing specific task on one of the sites can affect the calculated value of its priority.

The “pulling” procedure is carried out due to the fact that each subsequent section can begin to perform only those tasks that have the highest possible priority, which is expressed in the priority filling at the “supermarket” level of not all available cells, but only those that correspond to priority tasks. The subsequent section 2, although it is the only planning point that determines the work of all other production links, is itself forced to perform only these top-priority tasks. Numerical values ​​of job priorities are obtained by calculating the values ​​of a common criterion for all of them in each section. The type of this criterion is set by the main planning link (site 2), and each production site independently calculates its values ​​for its tasks - either queued for processing, or located in the filled cells of the "supermarket" at the previous stage.

For the first time, such a method of replenishing the cells of the "supermarket" began to be used at the Japanese enterprises of the company "Toyota" and was called the production leveling procedure, or "Heijunka". Now the process of filling the Heijunka box is one of the key elements"pull" scheduling system used in TPS (Toyota Production System), when the priorities of incoming jobs are assigned or calculated outside the production sites that perform them against the background of the current "pull" replenishment system of the "supermarket" ("kanban"). An example of assigning one of the directive priorities to an executed order (emergency, urgent, scheduled, transitional, etc.) is shown in Fig. 6.

Naturally, in small-scale and especially single-piece production, the scheme of intrashop material flows has a much more complex structure than its simplified image shown in Fig. 5. It is known that different parts included in the same order can be simultaneously processed in different production areas. Nevertheless, considering the intrashop route of only one part or assembly unit (ASU), this scheme can be considered fair: all ASUs move from one area to another as they are processed in accordance with the technological process - fig. 7. For example, for a specific part, this may be a sequence of technological operations: milling -> boring -> grinding, etc.

The queue of production tasks transferred from section 2 to section 3 (Fig. 7) is limited (limited), but, unlike the case shown in Fig. 8, tasks can change places in it, that is, change the sequence of their arrival depending on their current (calculated) priority. In fact, this means that the performer himself cannot choose which task to start work with, but in the event of a change in the priority of tasks, he may have to unfinish the current task (turning it into the current WIP) and switch to the execution of the highest priority. Of course, in such a situation, with a significant number of tasks and a large number of machines on the production site, it is necessary to use MES, that is, to carry out local optimization of material flows passing through the site (to optimize the execution of tasks that are already being processed). As a result, for the equipment of each site, which is not the only planning point, a local operational production schedule is compiled, which is subject to correction every time the priority of the executable tasks changes. To solve internal optimization problems, their own criteria are used, called equipment loading criteria. Jobs waiting to be processed between non-supermarket locations are ordered by queue selection rules (see Figure 8), which, in turn, can also change over time.

If the rules for calculating priorities for tasks are assigned from the outside in relation to each production site (process), then the criteria for loading the equipment of the site determine the nature of the passage of internal material flows. These criteria are associated with the use of MES optimization procedures at the site, which are intended exclusively for internal use. They are selected directly by the site manager in real time - see fig. 8.

In the method of calculated priorities, as a rule, MES systems are already used, which operate with smaller assignment dimensions compared to APS - up to 200 machines and 10 thousand operations on the planning horizon, which is usually no more than 10-15 work shifts. The reduction in dimension is due to the fact that MES takes into account much more technological constraints.

Systems of this type, when optimizing material flows within a production site, usually operate not with one or two scheduling criteria, but often with several dozen, which gives the site manager the opportunity to build a schedule taking into account various production situations. It is MES-systems that operate with the so-called vector, integral criteria for scheduling, when several particular criteria are collected in one criterion, which makes it possible to calculate the priorities of the tasks being performed.

Efficiency in compiling and recalculating the schedule is also the prerogative of MES, since recalculation can be carried out with a one-minute increment. This does not mean, of course, that new tasks will be given to the worker every minute, but it indicates that all processes at the production site are monitored in real time, and this allows you to anticipate possible violations of schedules in advance and take appropriate measures in time (Fig. 9). ).

In some cases, MES systems can schedule not only machines, but also Vehicle, teams of adjusters and other service devices. Not under the power of any other systems are such features of planning as the formation of technological charges, planning the release of products with parallel planning for the manufacture of the required set of equipment (devices, unique tools).

An important property of MES systems is the feasibility of their schedules. If APS system schedules are more suitable for scheduling in high-volume production, where sharp deviations from production program, as a rule, does not happen (sustainable nature of production), then MES systems are indispensable in small-scale and custom-made production. It is noteworthy that parts waiting to be processed on a particular machine can change their order, which is achieved in MES by correcting the current schedule with changed priority values.

The method of calculated priorities assumes that some nimble "switchman" in the form of an MES system should run ahead of this logistical "engine", switching the switches encountered on the way in an optimal way. How this difficult task is solved in practice, we will consider in the next article.

The second group of principles includes most of the TPS tools used to improve production processes, development methods new products and provision of services. This is often referred to as the "philosophy of lean manufacturing". However, as important and effective as these tools and processes are, they are only a tactical aspect of Toyota's approach and can only deliver long-term results when combined with an appropriate company-wide management philosophy.

Principle 2. Organization of the production process in the form of a continuous flow, which helps to identify problems.

This principle presupposes a transformation technological process in such a way as to create a continuous flow that effectively adds value. At the same time, the time that work in progress is without movement must be reduced to a minimum.

The flow means that the consumer's order is a signal to receive the raw materials that are necessary to fulfill this particular order. Raw materials are immediately delivered to supplying enterprises, where workers produce components that are immediately delivered to the plant. There, workers assemble the product, after which the consumer receives it in ready-made. The entire process takes hours or days instead of weeks or months as with mass production. At the same time, work is constantly underway to eliminate losses in this stream.

Unlike mass production, organized according to the principle of specialization (grouping similar works) and releasing goods in batches, one of the main elements of TPS are the so-called "cells" that create flow of single items.

A cell is a collection of people, machines or jobs organized and operating in accordance with the sequence of technological operations. They are created to ensure the flow of single products (services) that one by one undergo various technological operations. The speed of such processing is determined by the needs of the consumer. In practice, the ultimate goal of lean manufacturing is the organization of the flow of one-piece products in relation to all types of work, whether it be design, order taking, or production itself.

Cell formation implies the so-called multi-process system of labor organization, that is, the maintenance by each employee of several machines of various functional purposes (as opposed to a multi-machine system, in which one operator serves the same machines). This allows you to reduce the number of production personnel (that is, increase labor productivity) and at the same time ensure that each employee acquires several qualifications instead of one.

The lean way of organizing production in comparison with the traditional approach is schematically shown in Fig. 22 and 23 on the example of the process of creating computers.

Rice. 22.

Rice. 23.

As you can see, the creation of a flow of single products involves the almost complete abandonment of stocks. According to the Lean philosophy, inventory prevents problems from being identified. Indeed, under the traditional approach, if one of the steps in the process fails, the other steps will proceed as before, as long as there is sufficient inventory. When organizing the flow of single products, in the event of an error in any area, the entire cell stops, and this gives rise to the need immediately eliminate the cause of the failure. In this way. flow is the key to continuous improvement ("kaizen") and development of people.

To characterize the speed of the cell, the concept is introduced "tact", the time of which is determined by the rate of acquisition of products by the consumer.

So, if the working day is 8 hours (480 minutes), 20 days a month, and the consumer purchases 19,200 units of products per month, then 960 units must be produced per day, that is, one product in 30 seconds. With a properly organized one-piece flow, each stage of the process should take 30 seconds. If the work goes faster, it will lead to overproduction, if it goes slower, a bottleneck will appear in the process.

Continuous flow and takt time are most easily applied in batch production of goods or services. However, in principle, these concepts are applicable to any repetitive process, if you list its stages and identify and eliminate waste.

The advantages of such an organization of production include:

• 1) quality embedding- each operator is simultaneously a controller and tries to solve the problem on the spot, without passing it on to the next stage; if he missed defects, they will be found very quickly and the problem will be immediately corrected;
• 2) true flexibility- reducing the lead time of the order allows you to produce what the consumer really needs at this particular moment in time;
• 3) productivity increase- the organization of the cells allows you to immediately see who is overloaded and who is left idle. In this way, it is easy to calculate value-adding work and calculate how many people are required to achieve a given productivity;
• 4) release of space- in the cells, all blocks are fitted to each other, and stocks take up almost no space;
• 5) security enhancement- reducing the number of material movements automatically reduces the number of accidents at work;
• 6) morale boost- employees can quickly see the fruits of their labor, which increases job satisfaction;
• 7) destocking, which leads to a reduction in the cost of storage, physical and obsolescence of materials, reduces the number of defects from excessive loading and transportation operations, and also frees up working capital.

Speaking about the practice of implementing TPS, J. Liker warns business leaders against the following possible mistakes.

• 1) Creating a Pseudo Thread consisting in a simple rearrangement of equipment. By sliding blocks of equipment together, companies create an external semblance of a cell, but at each stage they continue to be mass-produced, without thinking about the takt time, which is determined by the consumer.
• 2) Immediate abandonment of the stream when problems occur. As soon as it becomes clear that the creation of a flow can lead to certain costs, the company abandons the decision. This can happen in any of the following situations:
  • - stopping one of the equipment blocks leads to the termination of the cell;
  • - changeover of one of the equipment blocks takes more time than expected and slows down the operation of the cell as a whole;
  • - you have to invest in a technological operation that was previously carried out at another enterprise in order to produce it on site.

Cell maintenance requires a discipline that is very difficult for many businesses to maintain. However, in the long term, all the troubles and costs are paid off by achieving high results.

Principle 3: Use a "pull" system to avoid overproduction.

One of the fundamental principles of TPS is "pull"

- the ability to design and produce what the customer really needs at the right time and in the right quantity.

This system is an alternative to the "push" that is carried out on most modern enterprises: the goods are produced according to the plan, in batches, and "pushed" to the market for sale.

A true one-piece flow is zero inventory system, which produces goods only when they are needed by the consumer. But since such a flow is almost impossible to create, since it is impossible to achieve the same duration of all operations, as a compromise between the ideal option and pushing, small stocks are created between the stages of the process, the volume of which is strictly controlled.

The concept of pull is based on the principle of operation of American supermarkets. In any supermarket, stocks of goods on the shelves are replenished as they are taken apart by buyers, that is, as they are consumed. In the shop floor, this means that the production or replenishment of parts in Stage 1 should be carried out as the next Stage 2 uses up almost all the stock of parts manufactured in Stage 1 (i.e., only a small spare number of parts remains). In TPS, the next batch of parts from Stage 1 is requested only when the number of parts used in Stage 2 has been reduced to a predetermined minimum. Thus, until the consumer has used a certain product (did not “pull it off the shelf”), it lies in stock and there is no replenishment of the stock. Overproduction does not go beyond a limited number of products, and a close relationship is established between the needs of the consumer and the volume of production.

A special alarm system lets you know that the stock needs to be replenished. In lean manufacturing, it looks extremely simple: empty containers and special cards are used as alerts. If an empty container is returned to you, this is a signal that you need to refill it with a certain number of parts or send a card back with detailed information about the part and its location. This system of work is called "kanban system"at and its purpose - manage material flow, ensuring the smooth operation of the just-in-time system. The functions and rules for using this system are shown in Table 15.

Table 15

Functions and rules for using the Kanban system

Terms of Use

1. Provides information about the place and time of receipt and transportation of products. 2. Provides information about the products themselves. 3. Prevents overproduction and use of excess transport. 4.Used as a work order. 5. Prevents the production of defective products by identifying at which stage defects appear. 6.Detects existing problems and helps control production volumes

1. Parts enter the subsequent process from the previous one in the quantity specified in the kanban. 2. In the previous process, the parts are produced in the quantity and sequence specified in the kanban. 3. No part is produced or moved without a kanban. 4. The kanban card is always attached to the products. 5. Defective products do not go to the next process. As a result, 100 % defect-free products. 6. The fewer kanbans, the more valuable they are

• 1 Kanban has many meanings: sign, card, tag, door sign, poster, bulletin board. In a broader sense, it denotes a signal.

Thus, the third principle of lean manufacturing implies that:

the internal consumer who accepts the work gets what he needs, at the right time and in the right quantity. At the same time, the stock of products is replenished only as they are consumed;

• - WIP and stockpiling are kept to a minimum. A small quantity of finished goods is held in stock and replenished as the consumer picks them up;
• - production is sensitive to real daily fluctuations in customer demand, and is not based on a pre-arranged schedule that reflects only the expected demands of customers.

Principle 4. Even distribution of the amount of work (“heijunka”).

As already noted, the main principle of TPS is the elimination of waste (Toyota managers and workers use the term “m#tsa” to refer to them). However, this is only one of the conditions for the success of lean manufacturing. In practice, the enterprise must get rid of three causes of inefficiency, representing single system.

• 1) Moo da - activities that do not add value. They include the eight types of losses mentioned above.
• 2) M$ri - overloading people or equipment. Muri forces a machine or a person to work to the limit. The transfer of people threatens their safety and causes quality problems. Overloading equipment leads to accidents and defects.
• 3) M$ra - irregularity production schedule, in some way is the result of the first two causes. Causes of unevenness - improper scheduling or fluctuation in production volumes caused by internal problems (downtime, missing parts, etc.) The uneven level of production makes it necessary to match the available resources (equipment, materials, people) with the maximum volume of orders, even if in fact its average level is much lower, and this leads to overproduction - the main type of muda.

"Heijunka" is the alignment of production both in terms of volume and product range To prevent sudden ups and downs, products are not released in the order in which consumers order. First, orders are collected over a period of time, after which they are planned in such a way as to produce the same assortment of products in the same quantity every day.

Consider the leveling system using the example of the production of two types of products - A and B. If there is a flow of single products, you can manufacture them in the order of receipt of orders (for example, A, B, A, B, A, A, B, B, B, A .. .). However, this means that the production will be random. Therefore, if on Monday there are twice as many orders as on Tuesday, then on the first day the staff will have to work overtime, and on the second day they will have to go home before the end of the working day. To align the schedule, you need to find out the consumer's requests (for example, for a week), decide on the nomenclature and volume, and draw up a balanced schedule for each day. Suppose we know that for every five A's, five B's are made. Then we can even out production and produce them in the sequence A, B, A, B, A, B. This is leveled production with mixed stock, since heterogeneous products are produced, but at the same time, based on the demand forecast, a certain sequence of production of different products is built with a balanced level of volume and nomenclature.

Leveling the schedule gives the company the opportunity to:

• - balance usage labor resources and equipment;
• - balance the orders issued to the previous processes and suppliers (at the previous stage, a stable set of orders is received, which reduces the amount of stocks, and, consequently, costs).

Thus, the use of heijunka eliminates muri and mura and standardizes work, which greatly simplifies the identification of losses of other species.

The production of a variety of products in small batches requires the use of specialized and at the same time easily readjustable machines and production mechanisms, as well as the maximum reduction in their changeover time. That is why Toyota is very careful in choosing equipment. In addition, she trains all her workers in the so-called "quick changeover" technique and constantly works to improve it.

Principle 5. Stop the production process if there are quality problems.

Lean manufacturing assumes that quality should be built into the manufacturing process. It means application of methods of prompt detection of defects and automatic stop of production in case of their detection(system jidoka). Jidoka involves equipping equipment with devices that detect deviations and automatically stop the machine. Such a system

is called "bye-yoke"- error protection. The following examples of its action can be given:

in case of an error in the workflow, the part will not fit the tool;

if a defect is found on the part, the machine will not turn on;

• - in case of an error in the workflow, the machine will not start processing the part;
• - in case of errors in the workflow or omission of one of the operations, corrections are automatically made and processing continues;
• - if one operation is skipped, the next stage will not start.

As for the employees, if any of them noticed a deviation from the standard, he is given the right to press a special button or pull the cord and stop the assembly line. When the equipment stops, flags or indicator lights accompanied by music or an audible alarm signal that assistance is required. This signaling system is called "andon" .

The jidoka system is often referred to as autonomy - endowing the equipment with human intelligence. Autonomization prevents the production of defective products and overproduction, and automatically stops the abnormal course of the production process, allowing you to deal with the situation. This method is much cheaper than checking quality and correcting defects after the fact. In addition, autonomization changes the essence of equipment operation. If the working process proceeds normally, the machine does not need an operator. Human intervention is required only in case of failures in the production process. Therefore, one operator can serve several machines. Thus, thanks to autonomization, the number of employed workers is reduced and the overall efficiency of production is increased. Note that TPS creator Taiichi Ohno believes this system one of the two basic principles of lean manufacturing (the other is just-in-time).

It should be noted that building quality first of all depends on the staff, and then on the technologies used. Employees of the company must take responsibility for quality assurance - this should be decisive in their value system. Technologies are just tools to help implement the philosophy of quality in practical activities.

So, the fifth principle of lean manufacturing is described by the following provisions:

• - quality determines the real value of the products;
• — use equipment that can independently recognize problems and stop when they are detected, as well as a visual system for notifying the team leader and team members that a machine or process requires their attention. Jidoka (machines with elements of human intelligence) - the foundation for "embedding" quality;
• - it is necessary to use all available modern methods of quality assurance;

the organization must have a support system ready to promptly resolve problems and take corrective actions;

The technology for stopping the process when problems occur should provide required quality"from the first time" and become an integral part of the company's production culture.

principle b. Task standardization for continuous improvement.

The basis of flow and pull in TPS is standardization, i.e. use of stable reproducible working methods, which makes it possible to make the result more predictable, increases the coherence of work and the uniformity of output, and facilitates the process of building quality.

Three elements form the basis of the standard of work in lean manufacturing:

• - takt time;
• - sequence of operations;

the amount of inventory a worker must have on hand to complete a given standardized job.

These positions are reflected in sheets of standard operations, which hang above each workplace and are an important means of visual control of the production process.

The Toyota approach involves not only the unification of tasks performed by shop workers, but also the standardization of work processes that are performed by employees and engineering workers. In addition, Toyota applies standards to product development and industrial equipment.

Contrary to the popular belief that standardization makes work mechanical, in lean manufacturing, on the contrary, it empowers workers and is basis for innovation in the workplace. According to the TPS ideology, continuous improvement requires process stabilization, because only after learning how to perform a standard procedure, you can think about improving it. In other words, it is impossible to make improvements in the work that you do every time in a new way.

Thus, the most important task in standardizing processes in lean manufacturing is to find the optimal combination of two components:

• 1) providing employees with a strict procedure that they must adhere to;
• 2) giving them the freedom to innovate, allowing them to be creative in solving complex problems in terms of costs, quality, delivery discipline, etc.

The key to achieving this balance is in a certain approach to the creation of standards.

Firstly, standards should be specific enough,

to serve as guidelines for practical activities, but still quite wide. to allow some flexibility. Implementation standards handmade repetitive nature, have a high level of specification. When designing, where fixed quantitative indicators missing, the standard should be more flexible.

Secondly, the improvement of standards should be done by people who themselves do this work. No one likes to be forced to follow the rules and procedures developed by others. Imposed rules, followed by strict enforcement, lead to friction between management and workers. However, those who are satisfied with their work and understand that they have a chance to improve the procedure for its implementation will fulfill the requirements fixed in the standard without dissatisfaction. At the same time, the Toyota approach involves fixing the accumulated knowledge and best practices in new standards. Thus, the experience accumulated by one employee is transferred to the one who will replace him. And that is why standardization in lean manufacturing is the basis for continuous improvement, innovation and staff development.

Principle 7. Use of funds visual control so that no problem goes unnoticed.

In order for employees to easily determine the current state of any process, lean manufacturing uses a number of visual aids, the totality of which forms visual control system.

Visual inspection includes any means of communication used in production that allows you to understand at a glance how work should be done and whether there are deviations from the standard. It may provide for the designation of a place reserved for any objects; an indication of the number of objects that should be installed in this place; a visual description of the standard procedures for performing any work and other types of information important for organizing the flow. In the broadest sense visual control is a set of information of all kinds, provided by the system "just in time" in order to quickly and properly carry out operations and processes. The visual control system ensures the transparency of the working environment and thus minimizes possible losses.

In fact, many of the tools associated with lean manufacturing are visual inspection tools used to identify deviations from the standard and ensure a smooth flow of one-piece products. Examples of such tools are kanban, andon, and standard operations. If there is no kanban card on the container that requires it to be filled, then the container is not in place. A full container without a kanban card is a sign of overproduction. The andon signalizes deviations from standard operating conditions. A diagram of the job's standard procedure is posted so that the best known method of ensuring flow at each job site can be seen at a glance. Noticeable deviations from the standard procedure are indicative of a problem.

The visual control system is closely related to the so-called program« 5S”, widely used in Japanese enterprises. The elements of this program (called seiri, seiton, seiso, seiketsu, and shitsuke in Japanese; Sort, Stabilize, Shine, Standardize, Sustain in English) are listed below.

• 1) Sort(remove unnecessary) - sort objects or information and leave only what is needed, getting rid of unnecessary.
• 2) keep order(order) - "everything has its place, and everything is in its place."
• 3) Keep clean- The cleaning process is often a form of inspection that identifies deviations and factors that can cause an accident and damage quality or equipment.
• 4) Standardize- Develop systems and procedures to maintain and track the first three S's.
• 5) Improve- constantly support workplace okay, implement a continuous process of improvement.
• 5S together provide a continuous process of improving working conditions, as shown in fig. 24.

Rice. 24.

You need to start by sorting out what is in the office or workshop. In the sorting process, what is needed for daily work to create added value, is separated from what is used rarely or not used at all. Rarely used items are tagged and removed from the work area. Then a permanent place is determined for each part or tool, while all frequently used parts should be at hand. The next item is cleanliness, which must be maintained constantly. The support for the first three S's is standardization. "Improvement" is a team-oriented approach to teaching and sustaining the first four S's. Managers play a crucial role in its implementation and must conduct regular reviews of its implementation.

One example of visualization within the framework of the 5S program is stands for tools. On the place allotted for the tool on the stand, its contour is shown. The outline of the hammer shows where the hammer should be, and if it is not in place, it is immediately visible. Thus, these stands help visualize the standard that determines the location of the tools, and one glance at them is enough to see deviations from this standard.

The controls used in TPS (tags, stands, beeps, etc.) are very simple and often even seem primitive. However, the frequent rejection of the latest information technologies in favor of such tools is not accidental. Toyota believes that when working with a computer, which is usually done alone, the employee loses contact with the team and, more importantly, usually (unless his direct duties require the use of a computer) leaves the area of ​​\u200b\u200bits practical activity. Adequately, however, the problem can only be assessed seeing everything with my own eyes. That is why lean production uses controls that do not replace, but complement a person with sense organs. And the most visible visual tools are right in the workplace, where they can't be overlooked and where, thanks to such tools, hearing, sight or touch tells the employee whether he is meeting the standard or deviating from it.

The need for visualization determines a number of standards for the design of service documentation. Thus, Toyota management imposes a strict requirement on managers at any level, as well as on ordinary employees: to fit their reports and problem-solving projects on one side of a sheet of A3 format (this is the largest sheet that can be sent by fax). As a rule, such a document is a detailed and Full description any process. It must contain brief description problems, description of the current situation, identification of the root cause of the problem, proposal of alternative solutions, reasoning for choosing one of them, cost-benefit analysis. All this needs to fit on one sheet of paper, using as many numbers and graphs as possible. Over the past few years, there has been a move at Toyota to move towards A4-size reporting, as the company believes that more can be expressed in less. the very core of the problem under study.

Thus, the visual control system used in lean manufacturing implies:

• - the use of simple visual aids to help employees quickly identify the location of deviations from the standard;
• - refusal to use computers, monitors, etc., if they

distract the worker from the zone of his practical activity;

• - the use of visual controls in the workplace, which should help maintain flow and stretch;
• - if possible, reduce the volume of reports (to one sheet), even when it comes to the most important financial decisions.

The results of applying a well-thought-out visual control system are increased productivity, quality and safety of activities, facilitated intra-organizational communication, reduced costs and an overall increase in the transparency of the working environment.

Principle 8. Use of reliable proven technologies.

This principle is revealed in the following provisions:

Technology is designed to help people, not replace them. Before introducing additional hardware, it is often necessary to do the process manually first;

new technologies are often unreliable and difficult to standardize, jeopardizing the flow. Instead of untested technology, it is better to use a known, proven process;

• - before introducing new technology and equipment, tests should be carried out in real-life conditions;
• - it is necessary to reject or change technologies that go against corporate culture, as well as violating the stability, reliability or predictability of processes;
• - with all this, it is necessary to quickly introduce proven technologies that have been tested and make the flow more perfect.

Toyota's approach to the introduction of new technologies is fully consistent with the strategy of "great companies" (according to J. Collins), which we have already described in this manual, namely: technology is only implemented if it meets the “hedgehog concept” lean enterprise(improving the organization of the flow of single products) and its corporate culture.

In the process of acquiring new technologies, Toyota prefers to move slowly, often coming to the conclusion that one or another new technology does not meet the strict requirements of supporting people, process and values, and rejecting it in favor of simpler manual methods. However, at the same time, the company can serve as a global benchmark for the use of modern methods in order to optimize the process of adding value.

New technologies at Toyota are introduced only after pilot testing with the participation of a wide range of specialists representing different functional divisions. Thus, each technology is thoroughly evaluated and tested to confirm its suitability for creating added value. The company carefully analyzes the impact that this innovation can have on existing processes. It is in them that, first of all, the nature of work to create added value is explored, additional opportunities are sought for eliminating losses and leveling the flow. Toyota then uses the pilot site to improve the process with existing equipment, technology, and people. Once the process has been improved as much as possible, the company again asks if the introduction of new technology will lead to further process improvement. If the answer is yes, the new tool is carefully reviewed to determine if it is in conflict with Toyota's philosophy and principles, which suggest that: the value of the human being is greater than the value of the technology;

• - decisions should be made by consensus;
• - the main attention in the process of work should be given to the elimination of losses.

If a technology does not conform to these principles, or there is even the slightest chance that it will adversely affect stability, reliability, or flexibility, Toyota rejects it or delays implementation until such issues are resolved.

If the new technology proves to be acceptable, it is then implemented in a way that ensures continuous flow throughout the manufacturing process and helps workers perform tasks more efficiently within Toyota standards. It means that innovation should not distract people from the work of creating value(i.e. be suitable for use directly at the workplace), and obya- it is necessary to provide visualization of the process.

The described approach applies to all types of technologies, including information technologies. The company sees them as just a tool that exists to support people and processes. To improve the performance of any activity, you must first change the way it is done. Information technology, on the other hand, most often only reflects the processes existing in the company, and therefore, by itself, is not able to eliminate losses.

• This technology also often referred to as a "just in time" (Just In Time - JIT) system
• The author of the "quick changeover" methodology, which is applicable to almost any equipment or process, is Shigeo Shingo, who, along with Taintm Oio, is considered one of the creators of the Toyota Production System. The principles of Shingo, first tested in Japanese enterprises, are now actively used in many European and American corporations. For more on this, see: Shingo Shigeo. Quick changeover: Revolutionary production optimization technology - M: Alpina Business Books, 2006. - 344 p.
• 2 Initially, the devices were called "baka-yoke" ("fool protection"), but one of their creators, Si-geo Xinyu, noticed that the workers were unhappy with this name. Therefore, later the term was replaced by “poka-yoke (“error protection”), which reflects the logic of the production process, since defects can be caused not only by “foolish” people.
• The word "andon" means "light signal calling for help."
• Taiichi Ohno. Toyota production system. Moving away from mass production. - M.: Institute for Complex Strategic Studies. - 2006. - S. 34.

Principle 4: Equalize the amount of work (heijunka)

When you implement TPS, you must start by leveling production. This is the primary responsibility of those involved in production management. Perhaps the alignment of the production schedule may require you to speed up or delay the shipment of some products, and you will have to ask some of the customers to wait a little. If the production level stays more or less constant throughout the month, you can apply the pull system and keep the assembly line running balanced. But if the level of production—yield—changes from day to day, there's no point in trying to apply all the other systems, because in these circumstances you simply won't be able to standardize work.
Fujio Te, president of Toyota Motor Corporation

Following Dell Computer and other successful companies, many American enterprises are striving to create an "assembly-to-order" production model. They are guided only by what and when the consumer needs, that is, they strive to create flawless lean production. Unfortunately, consumers are often unpredictable and their orders change monthly or even weekly. If you make products on a first-come, first-served basis, you will periodically have to push employees and equipment to their limits, producing a huge amount of products, and pay for overtime work. After that, there will be periods of calm, people will have nothing to do, and equipment will be idle. With this kind of work, you do not know how many components to order from suppliers, and will be forced to keep a huge stock of what the consumer may need. It is impossible to conduct lean production with this approach. Rigorous adherence to the assemble-to-order model leads to huge inventory, which hides problems and ultimately leads to a decrease in quality. The chaos in the enterprise is growing, and the lead time is increasing. Toyota found that in order to create the best possible lean manufacturing and achieve an increase in the quality of customer service, it is necessary to level the production schedule, not always strictly following the order of receipt of orders.

A number of companies I have worked with that have attempted to work on a "make to order" basis have most often made the consumer wait six to eight weeks for the ordered product. At the same time, “especially valuable” customers could wedge into the queue, and their orders were urgently fulfilled to the detriment of the rest. But is it worth it to break the rhythm of work in order to fulfill some order today, if the consumer still receives the ordered product only after six weeks? Wouldn't it be better to collect orders and even out the production schedule instead? This will allow you to expedite order fulfillment, reduce stocks of parts, and all customers will be pleased to know that standard lead times have been significantly reduced. Isn't that better than the alternating work and downtime required by the "make to order" principle?

When talking about waste, Toyota managers and workers use the term m'uda, and eliminating m'uda is the essence of lean manufacturing. But for the organization of such production, two other Ms are also important, and these three Ms represent a single system. Engaging in only the eight kinds of loss (m'uda) will only hurt effective work people and production system. The Toyota Way document talks about "eliminating m'ud, m'uri, m'ura." What are the three "M's"?

Muda are actions that do not add value. The best known M includes the eight types of losses mentioned above. These are activities that increase lead time, cause unnecessary travel to deliver a part or tool, build up extra inventory, or keep you waiting.

Muri - overload of people or equipment. In a certain sense, it is the opposite of m'ud. M'uri pushes a machine or person to their limits. Overloading people threatens their safety and causes quality problems. Overloading equipment leads to accidents and defects.

Mura - unevenness. This "M" is in some way the result of the action of the first two. At times, in normally functioning production systems, there is more work than people and equipment can handle, and sometimes there is not enough work. The cause of unevenness is an incorrect schedule or fluctuation in production volumes caused by internal problems, such as downtime, missing parts, or defects. M'uda is the result of mura. The uneven level of production makes it necessary to match the available resources (equipment, materials, people) with the maximum volume of production, even if in fact its average level is much lower.

Imagine that your production schedule fluctuates wildly, that it is uneven and unreliable. You have decided to move to a lean manufacturing system and are only thinking about how to eliminate mud from your production system. You start to reduce inventory levels. Then you try to maintain an even pace of work and reduce the number of people in the system*. After that, you work on organizing the workplaces to eliminate unnecessary movements. Finally, you start the system. And sadly you discover that the system is running out of steam due to peaks in customer demand that force people and equipment to work too hard, and therefore inefficient! Production is now organized as a flow of single items, there are no stocks, but the pace of production and the range of products are constantly and dramatically changing. All you have achieved is an extremely erratic flow of one-pieces. Your workers are overwhelmed. Equipment fails more often than before. You are missing details. And you conclude: "Lean does not work here."

* Toyota never fires or demotes workers who have had to be removed due to productivity gains. Such a short-sighted move, which at first sight reduces costs, is sure to generate hostility towards the company, and the rest of the workers will be reluctant to participate in kaizen work in the future. For those who lost their jobs as a result of manufacturing improvements, Toyota is always looking for alternative value-added jobs.

Curiously, paying more attention to m'uda is a very common approach when implementing "lean tools" because it's not that hard to identify and eliminate costs. But most companies forget about more complex process stabilizing the system and achieving uniformity” — creating a balanced, lean flow. This is a concept called heijunka, which requires the alignment of the work schedule. This is perhaps the most consciously applied principle within the Toyota Way. The realization of heijunka is a prerequisite for the elimination of mura, and this, in turn, is necessary for the elimination of muri and muda.

Overloading followed by underloading leads to constant starts and stops and is incompatible with high quality, standardization of work, productivity and continuous improvement. As Taiichi Ohno said:

The slow but stubborn tortoise does not create so many losses and is much better than the hurried hare, which rushes forward at breakneck speed, and from time to time stops to take a nap. The Toyota Production System can only be understood when all workers become turtles (Ohno, 1998).

From other Toyota executives, I have heard more than once: “We prefer to be slow and persistent like a turtle than to jump like a hare.” Manufacturing systems The US makes workers hares. They work to the point of exhaustion, and then take a break. In many American factories, workers unite in pairs - while one works for two, the other is free. If this does not affect the daily rate of production, managers turn a blind eye to this.

Heijunka - alignment of production and work schedule

Heijunka represents the leveling of production both in terms of volume and product range. To prevent sudden ups and downs, products are not released in the order in which the consumer orders them. First, orders are collected over a period of time, after which they are planned in such a way as to produce the same assortment of products in the same quantity every day. From the very beginning, TPS was designed to produce small batches of products, taking into account the needs of the consumer (both external and internal). If you have a one-piece flow, you can manufacture items A and B according to the order in which orders come in (for example, A, B, A, B, A, B, B, B, A, B…). But this means that the production of parts will be disordered. So if there are twice as many orders on Monday as on Tuesday, you will have to pay workers for overtime on Monday and send them home before the end of the working day on Tuesday. In order to even out your work schedule, you should find out the needs of the consumer, decide on the range and volume, and create a balanced schedule for each day. For example, you know that for every five A's you make five B's. You can level production and produce them in the ABABAB sequence. This is called leveled mixed-production production because you produce heterogeneous products, but at the same time, anticipating customer demand, you build a certain sequence of production of different products with a balanced level of volume and nomenclature.

On fig. Figure 10.2 shows an example of an unbalanced schedule in a small lawnmower engine manufacturing plant (one factory example).

In this case, the production line produces three types of motors: small, medium and large. Medium engines are in the highest demand, so they are made at the beginning of the week: on Monday, Tuesday and part of Wednesday. Then the line is reconfigured, which takes several hours, and the production of small engines begins, which are made the rest of Wednesday, Thursday and Friday morning. The least demand for large engines, which are manufactured on Friday. This misaligned schedule creates four problems:

1. It is usually impossible to predict the order in which consumers purchase engines. Consumers are buying medium and large engines all week. So if a customer unexpectedly decides to buy a large batch of large engines at the beginning of the week, the plant will have problems. They can be solved by keeping in stock a large number of finished engines of all kinds, but these stocks, due to the associated costs, will cost the company very much.
2. It is not always possible to sell all engines. If the plant doesn't sell all medium engines made Monday through Wednesday, it will have to keep them in stock.
3. Unbalanced use of resources. It is likely that different sized motors require different labor inputs, with large motors being the most labor intensive. Therefore, at the beginning of the week, the level of labor costs is average, then it decreases, and at the end of the week it increases sharply. Therefore, m'uda and m'ura are pronounced here. 4. Uneven requirements are imposed on the previous stages of the process. This is perhaps the most serious problem. As the plant buys different parts for three types of engines, it is asking suppliers to send in one type of part Monday through Wednesday, and different types of other parts for the rest of the week. Experience shows that consumer demand is constantly changing and the plant somehow fails to stick to this schedule. There are often sudden changes in the product mix, such as a rush order for large engines, and the factory is busy all week with just that type of product. Suppliers have to be prepared for the worst case scenario and keep at least a week's supply of parts for each of the three engine types. The so-called shepherd's whip effect leads to the fact that the manufacturer's behavior is transmitted up the supply chain to its beginning, that is, with a small wave of the hand, a huge force is created at the tip of the whip. So a slight change in the schedule at the engine assembly plant leads to the creation of more and more stocks at all stages of the supply chain, as we move from the end consumer to its beginning.

The goal of mass production is to achieve economies of scale for each piece of equipment. Changeover of tools for the transition from product A to product B leads to equipment downtime during the changeover, and therefore to losses. You have to pay the operator the time during which his machine is readjusted. It would seem that the conclusion suggests itself - before switching to product B, make a large batch of product A, but for a heidzuik, this approach is unacceptable.

In the engine example, the factory carefully analyzed the situation and found that the line changeover was taking so long due to the need to ship, return, install and dismantle parts and tools for different types engines. Pallets (pallets) were used for different engines different sizes. It was decided to supply the line operator with a small amount of all kinds of parts on mobile racks. The tools required for all three engines were installed above the production line. In addition, it was necessary to create a pallet on which engines of any size could be installed. This avoided a complete changeover of the equipment, allowing the plant to produce engines in any sequence. As a result, it became possible to determine the repeating sequence for the manufacture of engines of all three types, taking into account customer orders. Graph flattening provided four benefits:

1. Flexibility - now the plant can give the consumer what he needs at the right time. This leads to a reduction in inventories and the elimination of other related problems.
2. Reducing the risk that finished products will not be sold. If a factory only makes what the customer orders, it doesn't have to worry about holding costs.
3. Balanced use of labor resources and machines. The plant can now standardize work and level production with the fact that some engines require less labor than others, and if one big engine that requires more intensive work is not followed by another, workers can handle the load successfully. If the enterprise aligns the schedule taking into account labor costs, it is possible to ensure a balanced and even workload during the day.
4. Balance of requests issued to previous processes and suppliers. If a plant uses a just-in-time system and suppliers deliver parts several times a day, suppliers will have a stable set of orders. This will allow them to reduce the amount of inventory, and therefore the costs, which will be reflected in the cost price, which means that everyone will benefit from the leveling.

Dao Toyota Liker Jeffrey

Benefits of the one-piece flow

Creating a flow of single products involves a broad program of measures to eliminate all kinds of m?yes(loss). Let's take a closer look at some of the benefits of flow.

1. Embedded Quality. The one-piece flow greatly simplifies the build-in of quality. Each operator is also a controller and tries to solve the problem on the spot, without passing it on to the next stage. Even if he missed the defects and they went further, they will be found very quickly and the problem will be immediately identified and corrected.

2. True Flexibility. If the equipment becomes part of the production line, our ability to use it for other purposes will be reduced. But the lead time is reduced to the limit, which means that we are more flexible in responding to customer requests, making what he really needs. Instead of waiting weeks for the system to which the order is given to issue products, we can complete the order within a few hours. The transition to a new product range, which is required by changing consumer demand, is carried out almost instantly.

3. Productivity increase. When work was divided into departments, you felt like you were maximizing productivity, because work efficiency was measured by the workload of people and equipment. It is actually difficult to determine how many people it takes to produce a given number of units in high volume production because productivity is not measured in terms of value-added work. Who knows what the productivity loss is when people are "loaded" with producing surplus parts that then have to be sent to the warehouse? How much time is wasted searching for defective parts and repairing finished products? If there is a one-piece flow cell, non-value-adding work such as moving materials is minimized. You can immediately see who is overloaded and who is left idle. It is very easy to create a cost estimate for value-adding work and calculate how many people are required to achieve a given performance. When it comes to moving a mass-produced supplier to a TPS line, the Toyota Supplier Support Center achieves at least 100% productivity gains in every case.

4. Free up space in the workshop. When the equipment is distributed among the sites, significant areas between them disappear, although most of them are occupied by deposits of reserves. In a one-piece flow cell, all blocks fit together and inventory takes up almost no space. If the production areas are used more efficiently, the construction of new facilities can be avoided.

5. Enhance Security. As one of America's first adopters of TPS, Wiremold Corporation has achieved exemplary security performance and has been the recipient of numerous national security awards. However, when the company decided to take on the challenge of transforming high-volume production into a single-piece flow, it was decided that a special safety improvement program was not needed. The reorganization was led by Art Byrne, a former president of the company, who studied TPS and understood that the flow of one-pieces would automatically increase safety by reducing the amount of material that had to be moved around the plant. Reducing the volume of cargo allows you to get rid of forklifts, which are often the cause of accidents. The volume of containers that need to be lifted and moved will also decrease, which means that the number of accidents when lifting containers will decrease. If you deal with the flow, security increases by itself, even if you do not pay special attention to it.

6. Morale Boost. Wiremold's lean organization found that employee morale improves every year. Prior to the transformation, only 60% of employees in surveys said they worked for a good company. This figure has grown every year and in the fourth year of transformation it exceeded 70% (Emilani, 2002). The flow of one-off products leads to the fact that most of the time people are busy creating added value and can quickly see the fruits of their labor, and when they see their successes, they feel satisfied.

7. Stock reduction. By not investing in stocks that lie idle, you can use them for something else. At the same time, you will also save on bank interest, which must be paid for funds frozen in stocks. You will also avoid stock obsolescence.

On fig. 8.3 shows a traditional shop, where the equipment is grouped by type. One tool that can be used to schematically represent material paths is the Spaghetti Diagram. If we plot the flow of materials in the shop on a diagram, we get something resembling spaghetti, which are randomly mixed on a plate. The product moves randomly in different directions. The work of individual sections during the movement of the product is not coordinated. No amount of schedules and plans can eliminate the variability inherent in a system in which material moves randomly.

Rice. 8.3. Unordered flow when combining the same type of equipment

On fig. In Figure 8.4, which shows the lean cell, we see a different picture. Equipment is grouped according to the flow of material as it becomes a finished product. At the same time, the equipment is placed in the shape of the letter U, since such an arrangement contributes to the efficient movement of materials and people and facilitates the exchange of information. You can organize the cell in the form of a straight line or the letter L. In this case, we have shown the trajectory of the movement of two people who serve the cell. What if demand drops by half? Leave one operator per cell. What if demand doubles? Place four people on the cell service. Of course, in order to serve different technological operations, people must be prepared to combine professions, such are the requirements of Toyota factories.

Rice. 8.4. U cell for piece flow

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