In order to improve performance of mold, many manufacturers will properly process their molds. Mold processing refers to processing of forming and billet tools, also includes shearing dies and die-cutting dies. It will also reflect processing defects, resulting in a decline in mold performance, so how to build mold processing defects? Following seven measures can solve defects of mold processing.
1. Reasonably select and dress grinding wheel. Grinding wheel of white corundum is better. Its performance is hard and brittle, and it is easy to produce new cutting edges. Therefore, cutting force is small and grinding heat is small. Use medium particle size in particle size, such as 46-60 mesh is better, medium-soft and soft (ZR1, ZR2 and R1, R2) are used in hardness of grinding wheel, that is, coarse-grained, low-hardness grinding wheels, and good self-excitation can reduce cutting heat.
It is very important to choose appropriate grinding wheel for fine grinding. For high vanadium and high molybdenum conditions of mold steel, it is more suitable to choose GD single crystal corundum grinding wheel. When processing cemented carbide and materials with high quenching hardness, diamond with organic binder is preferred. Grinding wheel, organic bond grinding wheel has good self-grinding property, roughness of workpiece can reach Ra0.2μm.
In recent years, with application of new materials, CBN (cubic boron nitride) grinding wheels have shown very good processing effects, finishing effect on CNC forming grinders, coordinate grinding machines, and CNC internal and external cylindrical grinding machines is better than other types of grinding wheels.
During grinding process, it is necessary to pay attention to dressing grinding wheel in time to keep grinding wheel sharp. When grinding wheel is passivated, it will slide and squeeze on the surface of workpiece, causing burns on the surface of workpiece and reducing its strength.
2. Rationally use cooling lubricating fluid to play three major functions of cooling, washing and lubricating, keep cooling and lubricating clean, so as to control grinding heat within allowable range, so as to prevent thermal deformation of workpiece. Improve cooling conditions during grinding, such as using oil-immersed grinding wheels or internal cooling grinding wheels. Cutting fluid is introduced into center of grinding wheel, cutting fluid can directly enter grinding area to exert an effective cooling effect and prevent surface of workpiece from being burned.
3. Reduce quenching stress after heat treatment to a minimum, because phase transformation of quenching stress and reticular carbonized structure under action of grinding force can easily cause cracks in workpiece. For high-precision molds, in order to eliminate residual stress of grinding, low-temperature aging treatment should be carried out after grinding to improve toughness.
4. To eliminate grinding stress, mold can also be immersed in a 260-315℃ salt bath for 1.5 minutes, then cooled in 30℃ oil, so that hardness can be reduced by 1HRC, residual stress can be reduced by 40%-65%.
5. For precision grinding of precision molds with dimensional tolerances within 0.01 mm, attention should be paid to influence of ambient temperature, and constant temperature grinding is required. It can be seen from calculation that for a steel piece with a length of 300mm, when temperature difference is 3℃, material will change by about 10.8μm, (10.8=1.2×3×3, deformation per 100mm is 1.2μm/℃), and influence of this factor must be fully considered in each finishing process.
6. Electrolytic grinding is used to improve precision and surface quality of mold manufacturing. During electrolytic grinding, grinding wheel scrapes off oxide film instead of grinding metal, so grinding force is small, grinding heat is also small, and there will be no grinding burrs, cracks, burns, etc., and general surface roughness can be better than Ra0 .16μm;
In addition, wear of grinding wheel is small, such as grinding cemented carbide, wear amount of silicon carbide grinding wheel is about 400% to 600% of weight of ground carbide. 50% to 100% of alloy removal amount.

7. Reasonably choose amount of grinding, and use a fine grinding method with a small radial feed rate or even fine grinding. If radial feed and speed of grinding wheel are appropriately reduced, and axial feed is increased, contact area between grinding wheel and workpiece is reduced, and heat dissipation conditions are improved, thereby effectively controlling increase in surface temperature.

Confirm cooling water channel, screw screwed into board is 1.5-1.8 times screw diameter. If screwing is insufficient, it is easy to slip teeth, and there is a risk of mold falling off. Confirm whether operators, materials, tools, documents, equipment and auxiliary machines required for production are complete.

When hanging mold is not level, there will be different step differences between front and rear mold cavities of installed mold. For production of precision products, there will be poor concentricity, poor step difference, poor tooth profile accuracy, and poor distance.
When installing mold, we must pay attention to this problem. When hanging mold goes in and closes to a small position that can be pushed by hand, stop mold closing. Loosen and tighten lifting ring, take front mold as reference (because front mold is fixed by positioning ring), and watch rear mold part. When level of front mold is the best, position of mold cavity is consistent. Continue to close mold until it is completed, but it is best not to start the high pressure. (For the first clamping of upper mold, high pressure must not be applied first, and high pressure can only be activated after confirming that clamping can be normal).

 

For low temperature molds with a mold temperature below 50 degrees, mold can be closed until high pressure is started, front and rear molds are tightened diagonally until all 8 screws are screwed. When mold temperature is above 50 degrees, do not tighten screws too tightly before mold temperature reaches. After mold temperature reaches high pressure start, tighten screws diagonally.
As temperature rises, mold material will expand and its volume will increase. It is more obvious when mold temperature is high. If screw is tightened before temperature rises, it will have a certain impact on the life of mold and its precision.

When thickness of mold is not enough, it is necessary to install a mold plate. When mold temperature is high, it is best to install a heat shield between machine plate and mold. Whether it is a mold base or a heat shield, its flatness must be as small as possible.
If flatness is large, front and rear molds of mold are not parallel, and there will be differences after high-pressure closing, which will affect product quality. When mold temperature reaches set value, check actual temperature of mold and adjust mold thickness once.