Quick Die Change (SMED) originated in Japan in the early 1950s and was developed by Shigeo Shingo in Toyota. Single means less than 10 minutes (Minutes). It was originally used in automobile manufacturing plants to achieve rapid molds. Switch (Exchange of Dies), it helps Toyota Enterprise products to shorten the switching time from 4 hours to 3 minutes.

China only began to research and develop punch presses and injection molding machines in the late 1980s. After nearly two decades of hard work, they developed from scratch. As the products of the household appliance industry are updated rapidly, and household appliances are also a product with large investment and quick results, this kind of rapid mold change has been systematically studied in the United States, Italy, Japan and other countries as early as the early 1950s.

1What is the SMED method?

The full name of SMED is "Single Minute Exchange of Die" (Single Minute Exchange of Die), which is a fast and effective switching method. The concept of rapid mold change points out that all transformations (and activations) can and should be Less than 10 minutes-----that's why there is a single minute. Therefore, it is also known as the single-minute rapid mold change method, the mold change method within 10 minutes, and the rapid job changeover. It is a method used to continuously change the equipment quickly and adjust the difficult point-to minimize the possible line change time (instant line change ). It can quickly switch an ongoing production process to the next production process. The fast die change method also often refers to fast switching. The quick die change method can and is often used to start a program and quickly make it run with minimal waste.

SMED (Single Minutes Exchange of Die) is a set of useful technologies that Japan's Toyota Motor Corporation explored in the early 1950s to deal with multiple batches and small quantities, reduce inventory, and improve the rapid response capability of the production system. This method was pioneered by Shigeo Shingo of Japan and has been demonstrated in many companies. Single means less than 10 minutes (Minutes). When Mr. Xinxiang witnessed the changeover time as high as 1 hour, his reaction "must make the flow smoother."

Based on Mr. Xinxiang's rich experience, he developed a method that can analyze the mold change process, so as to find the reason for the long mold change time for the on-site personnel and how to reduce it accordingly. In many cases under his leadership, the changeover time has even been reduced to less than ten minutes, so this quick changeover method was named "quick changeover per minute". Initially used in automobile manufacturing plants to achieve rapid exchange of Dies.

As the name suggests, its purpose is to shorten the time of job conversion, and its key point is to delineate internal job conversion and external job conversion, and convert internal job conversion into external job conversion as much as possible, and then shorten the internal and external job conversion as much as possible. Job conversion time.

2 Explanation of terms for quick die change

1. Die change: Anything that requires the machine or production line to stop production due to product change in order to perform the change action. Also known as settings.

2. Mold change time: The time when the machine or production line stops production due to the mold change action, that is, the interval between the last qualified part of the previous batch and the first qualified part of the next batch.

3. In-line mold change (internal operation): refers to the mold change action that must be performed when the machine stops production. Also called "internal homework" or "internal preparation".　　

4. Off-line operation (off-line operation): refers to the mold change action that can still be performed while the machine is in production. It is also called "off-line operation" or "external preparation". 　

3 basic points of 3SMED method

Distinguish inside and outside

The distinction between inside and outside refers to the division of mold change operations into internal preparation operations, adjustment preparation operations, and external preparation operations.

The so-called internal preparation work refers to the preparation work that must be done only when the machine is stopped, such as the disassembly and installation of molds.

The equipment adjustment operation refers to the operation from the completion of the mold installation to the output of the first qualified product.

External preparation work refers to the preparation work that can be done during the operation of the machine, such as the repair of molds, the preparation of tools and materials used for mold replacement, etc.

From inside to outside, from inside to outside is to transfer internal preparations to external preparations as much as possible.

The preparation work that can only be started when the machine is stopped, after improvement, becomes a work that can be completed in advance while the machine is running.

For example, in the injection molding process of a plastic injection molding machine, the next time the mold is to be produced by the upper mold, the metal mold can be preheated in advance. It is not necessary to wait for the equipment to be preheated before the preheating operation. Warm operation time.

Optimize inside and outside

Optimizing internal and external means shortening the time of internal preparation work and the time of external preparation work.

4The realm of quick mold change

Realm 1: No concept of Quick Changeover

Realm 2: Single Minutes Exchange Die

Realm Three: Zero Exchange Die

Realm 4: One Touch Exchange Die One Touch Exchange Die

Realm 5: One Cycle Exchange Die 　　

Realm Six: No Need Exchange Die

5 SMED steps

Step 1: Observe the current process

Purpose: To collect the current data about line change, to ensure that the number of observers and the number of tool placement personnel are the same.

Observe the entire thread change process-from the last product before the thread change to the first product after the thread change; including time, record all actions, find any problems or opportunities, and record activities through video where necessary.　

Step 2: Distinguish between internal preparation time and external preparation time

Purpose: Distinguish the internal changeover time from the external changeover time, and eliminate the external preparation time, which can greatly shorten the mold change time.

Analyze the current data collected in the first step, and divide the mold change operations into two types: internal preparation operations and external preparation operations. The external preparation operations are done before and after the shutdown, thereby eliminating the time for external preparation operations.

In order to avoid abnormalities in the mold change process, a "mold change check table" must be formulated before the mold change starts. The check content includes mold change tools, trolleys or cranes, processed objects, testing instruments, etc.

Step 3: Remove the waste of internal preparation

Purpose: Eliminate the waste in the internal preparation time, thereby shortening the mold change time.

The conventional method is to use the following methods to eliminate the waste in changing the line:

Parallel operation, rotary one-time locking method, touch clamping system, tool placement method/position uniformity, uniform tool size, uniform screw head size, detailed tool replacement table, improved settings, avoiding debugging

Step 4: External preparation of continuous internal preparation

Purpose: To shorten the time of mold change through the subdivision of internal preparation work

Step 5: remove adjustments

Purpose: Reduce the debugging time and shorten the mold change time by removing adjustments. Through highly standardized molds, process parameters are entered into the equipment in advance, etc.

6 SMED project implementation

Pre-preparation: Choose a representative handover job, set up a team and prepare the SMED research, the list of items required for the SMED research. Equipment checklist: cameras, video tapes, stopwatches, whiteboards, projectors, video recorders/TVs. Material checklist: film, tape, scissors, notepad, marker, notice post

Observe the current process: Observe and record the detailed process of the current switching, and record the whole process of the switching without pause, so that you can use the video to analyze the time of each step. Pay attention to the hand, eye, and body movements of the switching personnel.

Observe and improve: review the video content in the conference room and record the time of each activity with a stopwatch, observe the switching-use the post-it note to list each step of the switching on the pink post-it note, and record the time of each step in the Paste the white notice, and record the observed results on the yellow notice

For example, the operator goes to get the wrench and walks to the parts cabinet. The head of the clamp is difficult to position on the machine. Show the current situation in the form of a chart, describe the current situation in short language, and describe the current situation in text, including the length of the switching time, who usually completes the task, and special events that occur during the switching process. Including the number of people, tools, parts, etc.　

Set improvement goals: Write the goals, including the target value of the switching time and the time period for improvement. This is only the prediction of the reduction of the switching time by the SMED team members, but the final result is usually better than the forecast.　　

According to the three stages of SMED, the improvement plan is established and implemented step by step: the first step: distinguishing internal and external work, the second step: transforming internal operations into external operations, and the third step: optimizing all aspects of the switching operation. Check the results obtained, standardize the switching operation and train the operators 　　

The advantages of SMED: flexible production, no need for additional inventory to meet customer requirements. Fast delivery, shorten the delivery time, that is, the funds are not pressured on the additional inventory. Excellent quality, reduce possible errors in the adjustment process. Efficient production, shorten the switch The parking time means higher production efficiency, that is, OEE improvement. 　 It is possible to realize JIT and greatly reduce product scrap

The benefits of SMED are mainly in two aspects: increase process capacity and increase the frequency of line changes.

7 SMED mold changing skills and rules

Rule 1: Parallel operation　

The so-called parallel operation refers to two or more people jointly engaged in the switching action. Parallel work is the easiest to immediately obtain the effect of shortening the internal work time. If a person engages in the switching action slowly, it may take an hour to complete. If two people can work together, it may be completed in 40 or 20 minutes.

Then the entire switching time is reduced from the original 1 hour to between 20 minutes and 40 minutes. The labor time required in parallel operations may increase, remain unchanged, or decrease, which is not the focus of consideration. Because the other effects obtained by shortening the switching time are far greater than the labor cost, this point is easier for ordinary people to ignore. When engaging in parallel operations, the cooperative actions between the two must be practiced skillfully, and safety must be paid special attention to, and accidental injury should not be caused by negligence.

Rule 2: Do not move your feet

The switching action is mainly dependent on the completion of the action of the hands, and the foot must reduce the chance of moving or walking. Therefore, the props, molds, cleaning, etc. that must be used when switching must be placed on a special trolley, and they must be sorted in order to reduce the search time. The moving lines for the in and out of molds or switching items must also be designed to be easy to enter and exit, and the sequence of switching actions must be rationalized and standardized.

Rule 3: Special props

The so-called tools are general-purpose appliances; props are special-purpose appliances. Just like the playing cards used by the magician's performance, they are specially designed. If you buy ordinary playing cards at a stationery store, it will be more difficult for the magician to perform some wonderful magic. So the tools used by magicians are called props, not tools.　　

The switching action is to use props and not tools as much as possible. Because props can improve the efficiency of switching, and shorten the switching time. In addition, the measuring instruments should also be made into props, and block gauges or grid bars should be used instead of measuring scales or meters to measure the reading values. The most important point is to try to reduce the types of props, in order to reduce the time to find, pick and put into the game.

Rule 4: Eliminate the screw 　　

When switching actions, screws are the most common method used to fix the mold. The use of screws is of course necessary, but the action of loading and unloading screws usually takes up a lot of switching time. If you observe carefully, you will find that there are too many places where screws are abused. For example, originally only four screws are enough, but six are used. There are too many turns of the screws and it takes time.

The screw really exerts its tightening function only in the last lap. Therefore, the best countermeasure for improvement is to eliminate the use of screws. You must have the mentality that you are not in harmony with screws, and you must go and hurry up. For example, bolts, pressure rods, intermediate clamps, card sockets, shaft cam locks, positioning plates, etc. can be used to replace the use of screws.

Rule 5: One turn is set

Limited to certain conditions, when bolts and screws must still be used, try to reduce the time for tightening and removing the screws. The goal of improvement is to be able to achieve the locking function without removing the bolts and screws. The main method can be tightening or loosening with only one rotation. For example, the C-shaped opening washer can be placed under the nut. After the nut is loosened one turn, the C-shaped washer can be removed from the opening to achieve the purpose of complete relaxation. When tightening, the reverse operation is performed, and the purpose of tightening can be achieved by only one rotation. In addition, methods such as gourd holes can also achieve this purpose.　　

The second method is to fix the height of the locking part. The locking part that is too high should be cut down to the standard height; the locking part that is too low can be added with a pad to achieve the standard height. After the height of the locking part of each mold is standardized, the tightening part of the nut will not change. This can reduce the number of rotations for locking and loosening, and of course, it also reduces the switching time.

Rule 6: Standardization

The switching action is due to different products and different molds or working conditions must be changed. Therefore, adjustments must also be made to set new standards. The adjustment action usually takes about 50%-70% of the entire switching time, and the length of the adjustment varies greatly. When you are lucky, you can adjust it all at once. When you are unlucky, it takes tens of minutes, or even count. It is often seen in hours. For adjustment actions, it is a waste to make adjustments first, and it is necessary to eliminate adjustment holes as the goal of improvement.

It is necessary to eliminate the waste of adjustment, and to grasp the law of the standard in the method. In other words, the standard that has been set on the machine should not be changed because of the replacement of the mold. In practice, the adjustment action of the inner operation can be moved to the outer operation, and the set action can be done in advance; it is also possible not to disassemble the entire mold, keep the mold base, and only replace the mother-child structure of the mold cavity to eliminate the mold setting action ; Or you can use a shared fixture to do the switching action in a two-group way, that is, one group is being processed, and the other group of materials has been set. When switching, just rotate it to immediately achieve the switching Purpose. The high degree of standardization of the mold can also save the adjustment stroke. Another example is that the injection molding machine must adjust and set several different strokes or conditions according to the molds that are frequently used. When adjusting, a template can be set, and all of them can be set at the same time with a single dial on the mold.

More importantly, it is necessary to cancel the determination of working conditions by means of scale or meter reading of values, and try to use block gauges, fast limits and other easy-to-access settings to reduce the adjustment time and shorten the switching time.

Rule 7: Prepare beforehand

Preparatory work is a work that belongs to outside work. If the external operation is not done well, it will affect the smooth progress of the internal operation, and the switching time will be longer. For example, if the external work is not fully prepared, when the internal work cannot find the required props or the mold is wrong or defective, it is necessary to temporarily stop to look for the props or repair the mold, which causes the internal work time to become longer.