Seven challenges in the processing of injection molds

There are often various problems when doing injection mold processing, what are the general problems that occur when injection mold processing?

First, the size, plastic materials have shrinkage, mold size to multiply the material shrinkage.

Second, the design of the flow channel should be reasonable and balanced, and the exhaust should be done well.

Third, the flying model is not good, and the product will have a shawl.

Fourth, in terms of demolding ejection, whether the cavity demolding slope is enough, the surface polishing is good, the thimble arrangement should be reasonable, and the stroke of the oblique top row should be enough.

Fifth, whether the cooling water channel can quickly and evenly cool the mold.

Sixth, the size of the glue inlet is suitable, too large to make the product separation difficult, too small rubber parts are not enough.

Seventh, the assembly mold should not be less misequipped parts, and the movement between the modules should be smooth.

What aspects should be considered in the design of injection molds?

In injection mold processing, the design of injection mold is an important link, and the main aspects to consider are as follows:

1. Considering the process characteristics of plastic raw materials, molding performance and the type selection of injection molding machine may have an impact on the molding quality, so corresponding measures should be taken in the injection mold design process.

2. To consider the plastic parts on the injection mold guidance requirements, reasonable design of the guide structure is also very important, should also calculate the working size of the molded parts, because the injection mold requires overall strength and rigidity.

3, considering the requirements of mold trial and mold repair, mold design and manufacturing are closely related to mold processing, the success or failure of raw material processing generally depends on the quality of mold manufacturing, and plastic mold products are established in the correct above three steps basically include the essentials of injection mold design, because these points are related to the quality of injection mold processing.

In many cases, the hardware mold processing will also reflect the processing defects, resulting in the decline of mold performance, so how to reduce Changzhou mold processing defects?

1, reasonable selection and trimming of grinding wheel, the use of white corundum grinding wheel is better, its performance is hard and brittle, and easy to produce new cutting edge, so the cutting force is small, grinding heat is small, the use of medium particle size in the particle size, such as 46 ~ 60 mesh is better, in the hardness of the grinding wheel using medium soft and soft (ZR1, ZR2 and R1, R2), that is, coarse grain size, low hardness grinding wheel, good self-excitation can reduce cutting heat. Fine grinding when choosing the appropriate grinding wheel is very important, for the mold steel high vanadium high molybdenum condition, the selection of GD single crystal corundum grinding wheel is more suitable, when processing cemented carbide, quenching hardness of high materials, priority use of organic binder diamond grinding wheel, organic binder grinding wheel self-grinding good, grinding out workpiece roughness up to Ra0.2 μm, in recent years, with the application of new materials, CBN (cubic boron nitride) grinding wheel shows a very good processing effect, in CNC molding grinder, coordinate grinder, CNC internal and external cylindrical grinding machine finishing, the effect is better than other types of grinding wheels. In the grinding process, pay attention to timely trimming the grinding wheel, keep the grinding wheel sharp, when the grinding wheel passivated, it will slip and squeeze on the surface of the workpiece, causing burns on the surface of the workpiece and reducing the strength.

2. Rational use of cooling lubricant, play the three major roles of cooling, washing and lubrication, keep cooling lubrication clean, so as to control the grinding heat within the allowable range to prevent the thermal deformation of the workpiece. Improve cooling conditions during grinding, such as oil-immersed or internally cooled grinding wheels. The cutting fluid is introduced into the center of the grinding wheel, and the cutting fluid can directly enter the grinding area, exerting an effective cooling effect and preventing burns on the surface of the workpiece.

3. Reduce the quenching stress after heat treatment to the lowest limit, because the quenching stress and network carbonization structure under the action of grinding force, the structure produces phase change, which is very easy to cause cracks in the workpiece. For high-precision molds, in order to eliminate the residual stress of grinding, low-temperature aging treatment should be carried out after grinding to improve toughness.

4. To eliminate the grinding stress, the mold can also be immersed in a salt bath at 260~315 °C for 1.5min, and then cooled in 30°C oil, so that the hardness can be reduced by 1HRC and the residual stress can be reduced by 40%~65%.

5. For the precision grinding of precision molds with a dimensional tolerance of 0.01mm, pay attention to the influence of ambient temperature, and require constant temperature grinding. It can be seen from the calculation that 300mm long steel parts, when the temperature difference is 3 °C, the material has a change of about 10.8μm, (10.8=1.2×3×3, and the deformation per 100mm is 1.2μm/°C), and each finishing process needs to fully consider the influence of this factor.

6. Electrolytic grinding is used to improve mold manufacturing accuracy and surface quality. When electrolytic grinding, the grinding wheel scrapes off the oxide film: instead of grinding the metal, so the grinding force is small, the grinding heat is also small, and there will be no grinding burrs, cracks, burns and other phenomena, and the general surface roughness can be better than Ra0.16μm; in addition, the wear of the grinding wheel is small, such as grinding cemented carbide, the wear amount of the silicon carbide grinding wheel is about 400% ~ 600% of the weight of the ground carbide, when grinding with electrolysis, the wear amount of the grinding wheel is only 50% ~ 100% of the grinding amount of cemented carbide.

7. Reasonably select the grinding amount, and adopt the fine grinding method with a small radial feed or even fine grinding. If the radial feed and grinding wheel speed are appropriately reduced, and the axial feed is increased, the contact area between the grinding wheel and the workpiece is reduced, and the heat dissipation conditions are improved, so as to effectively control the increase of surface temperature.