CPK is complex process capability’s  index is an indicator used by modern enterprises to indicate process capability. Process capability is the ratio of the maximum allowable range of process performance to the normal deviation of the process. The process capability study is to confirm the degree to which these characteristics meet the specifications, so as to ensure that the non-conformity rate of the finished products of the process is above the required level, as the basis for continuous improvement of the process. A larger CPK value indicates better quality.

High-precision motor housing products not only have tolerance requirements, CPK also has certain requirements, especially for automotive parts, there must be CPK control. It is particularly important to improve the management of CPK tensile molds. The maintenance management to keep the mold in the initial state is the maintenance of the mold. To understand the status of the stamping factory, just observe the situation of the mold maintenance department, and you can make a certain degree of judgment. If there are many molds to be repaired in the maintenance department, the general situation is that the productivity is low and there are many defective

Differentiation of mold maintenance

Routine maintenance

refers to normal mold cleaning, spot inspection, and oiling of movable parts. This operation is often to confirm that the mold is in a normal state, and abnormalities can be detected early.

Accident maintenance

The life of each part constituting the mold is different. So the timing of maintenance is also different. This situation must be recognized for proper maintenance. But instead of repeating maintenance, the mold can be used continuously. There must be a criterion for judging mold life (total life).

Cutting edge tools

Punch and die for blanking. It is the part with the shortest maintenance cycle in the mold. Tool shape, clearance, surface roughness, material, etc. all affect tool life. When used in an abnormally worn state, the amount of grinding will increase and the life of the tool will be shortened. Can be managed from both the number of machining operations and the burr height

Slip fitting tool

Punches and dies made by bending and extension. These parts slide the material with the R surface and the side (bearing surface). Therefore, in the initial period, the sliding surface will appear orange peel, in the middle period, there will be indentations, and in the later period, the entire shape will collapse, because the change is very slow, similar to the burr of the cutting tool, because there is no obvious state change, it will usually be too slow. maintain. The management of surface and shape is the focus.

If foreign matter is mixed in, the sliding surface will be damaged, and the damaged part will be copied to the product. The daily management is the main reason. Factors that affect tool life include tool material, tool shoulder shape, surface roughness, and lubricants. The surface treatment of the tool may also extend the life.

spring

Many springs are used on the mold, but they are rarely properly managed. Accidents caused by wear and tear caused by long-term use can cause great damage to the mold. Because it is usually used in an invisible state, it will be found slowly, so the damage of the mold will also be larger. Since it is difficult to judge the condition from the appearance, it should be replaced periodically according to the number of processes. For the use of the spring, it can be used as far as possible with a small total deflection.

(guidepostbush)

The guide post bushing of the dieset and inner guide (SUB-GUIDE) are the important parts to maintain the precision of the mold. The abrasion caused by the influence of the oil state, eccentric load, etc., will expand the gap between the column bushings, it will be difficult to maintain the accuracy of the relationship between the upper and lower molds, and problems will occur in various parts of the mold. Surprisingly, there are many molds that are not very sure in this part of management. It must be replaced regularly.

Burn-in often occurs, mostly due to poor verticality of the post or too much eccentric load. And this reason mostly comes from the mold design or production stage. When burn-in occurs due to eccentric load, the load center should be considered, and measures such as staggering the position of the die device on the punching machine must be taken. When the verticality is poor, the column bushing must be reorganized.

(Plate)

The mold will produce minimal elastic deformation during processing. Therefore, when used for many years, the constituent plates may warp, which is the reason that affects the accuracy of the mold. Reverse warping must be eliminated regularly. Of course, the surface that is in contact with the material of the mold and the stripper will leave a mark. If this state is very serious, the material will be pressed incorrectly, which is the cause of poor product shape.

Similarly, the contact surface of the bottom part or backing plate will also be recessed in the case of long-term use. When this part is eliminated, regular surface regeneration should be performed at the same time. Plates are important parts that support mold accuracy. If the degradation of the plate exceeds a certain limit, the total life of the mold will also end. For example, the gap between a dowel pin hole, a guide post bushing hole, and an insertion hole becomes larger. Local distortion of the die holder or template surface becomes larger. Although mold maintenance is performed, it is often necessary to repair it before regular maintenance.

Other

(1) Shim management

Because the mold maintenance is repeated, the number of separators in the punch and the mold sub-section will increase. Without proper management, even if the mold is maintained, problems will occur immediately. Just limit the number of separators.

(2) Strip bolt

After long-term use of the demolding bolt, the thread part is damaged, the head is worn, the contact surface of the demolding bolt is dented, etc., which is the cause of the poor parallelism of the demoulder. Particular attention should be paid to the parts that are easy to miss.

(3) Bolt

Most molds use bolts with hexagonal holes. Due to the implementation of locking confirmation, repeated assembly and disassembly may sometimes deform the hexagonal hole and fail to obtain sufficient locking force. Small bolts are particularly problematic. If such a bolt is found, it must be replaced. If the bolt used for the main stop switch is loosened slightly, the bolt may be damaged, and a large accident may occur.

(4)pilot

The guide is an important part that determines the position of the progressive mold. It is necessary to implement management related to shape, wear and distortion.

Designing mold construction for easier maintenance

In the maintenance of the mold, the ease of assembly and disassembly of the mold is an important factor in performing maintenance operations. The maintenance of molds still has no clear status in most mold factories, but in stamping processing, the maintenance of molds plays a vital role in the management of CPK value, but important molds must be maintained and managed. If you do not know anything after making the mold, it is incorrect. Attention must be paid to the balance between mold manufacturing, mold maintenance, and stamping.