Why is there a crack in the injection molding process? Injection molding refers to the use of injection molding machine to plasticize plastic melt and melt, and then injection into the cavity of the molding die, after cooling and cooling, melt solidification and demoulding, injection molding machine injection molding products. The variety of injection molding products is relatively versatile, especially in the electronic processing, light industry and car manufacturing industry, there are many shapes of plastic products injection molding and work accessories.
Cracking during plastic processing is a common phenomenon in injection molding, and it also has a direct impact on product quality and economic benefits. Now we analyze the three aspects of processing skills, data quality and mold precision.
A, processing skills:
1. Excessive processing pressure, too fast speed, more filling, injection, and too long pressure keeping will cause excessive internal stress and cracking;
2. Adjusting the mold opening speed and pressure to avoid rapid drawing of the parts to form demoulding cracking;
3, the injection pressure is too low or the injection speed is too fast;
4. Precautions due to weld marks, the plastic injection molding process degradation of Dongguan constitutes the mechanical strength becomes low and cracking occurs;
5. Appropriate use of the release agent, pay attention to substances such as aerosols that often eliminate the adhesion of the mold surface;
6. Residual stress of the workpiece can be reduced by eliminating the internal stress by annealing heat treatment immediately after forming;
7, no lubrication or lubrication but the function is not safe;
8, properly increase the mold temperature, so that the parts are easy to demould, properly lower the temperature to avoid differentiation;
9. When the product is produced, due to the uneven cooling and unevenness of the plastic in the cavity and the unreasonable product structure planning, it simply causes various shortcomings of the product;
10. Poor plasticization, that is, the melt cannot be completely and uniformly melted;
B. Data quality:
1. The content of recycled materials is too high, and the strength of the components is too low;
2, the humidity is too large, constitutes a chemical reaction between some plastics and water vapor, and the strength is reduced and cracking occurs;
3, the original capital guessed impurities or recycled material overrun;
4. The original data has too much water content;
5. The data itself is not suitable for the environment or quality that is being processed, and the pollution will cause cracking.
6. The volatiles in the original guess are out of specification;
C, mold precision:
1. The balance should be balanced. For example, if the number of ejector pins and the cross-sectional area are to be satisfied, the draft angle should be satisfied, and the cavity surface should satisfy the lubrication, so as to avoid cracking due to the external force causing the residual stress to gather.
2, the structure of the workpiece can not be too thin, the transition part should try to use the arc transition, to avoid the sharp corners, chamfers constitute the stress gathering.
3. Minimize the use of metal inserts to avoid the increase in internal stress caused by the different shortening rates of the inserts and parts.
4. The molding process is imperfect. The main performance is that the connotation quality of the convex and concave die forging is poor, the heat treatment skills and the process are problematic, and the convex and concave molds are impervious, and there are soft spots and uneven hardness;
5. Appropriate stripping air inlet holes should be set for deep-bottom parts to avoid vacuum negative pressure;
6. The main flow channel meets the requirements of the ambassador’s gate material to be demolded in the future, so that it is easy to demould;
7. The joint of the main runner bushing and the nozzle should avoid the dragging of the chilled material and cause the workpiece to stick to the fixed mold;
8. The problem of mold structure planning, the die structure is unreasonable. The slender punch has no planned reinforcement equipment, the discharge port is not smooth, and the unloading force is too large, so that the punch accepts the alternating load and so on;
9. The mold temperature of the injection molding process is too low and the fluidity of the melt is too poor;