Techniques for solving the problem of deformation of large-size flat plastic parts

Large-size flat plastic parts have a large area and a large shrinkage. Due to the serious molecular orientation arrangement of large plastic parts, and the uneven cooling of the mold, the shrinkage rate of the plastic parts in all directions is inconsistent, resulting in the deformation and distortion of thin large flat plastic parts after injection molding. Sometimes a support rib is designed on one side of a large flat injection molded part, then the injection molded part must be bent toward the side with the support rib.
It is indeed a difficult problem to completely solve the problem of deformation of large flat plastic parts. In production, we have summarized some more effective measures to improve the problem of deformation:
1) Change the mold to a multi-point gate (usually a three-plate mold). Correspondingly, choose an injection molding machine with a clamping force of 24t or more, and the number of gates for large flat plastic parts should be more than 4 points. This can reduce the degree of molecular orientation and reduce the gap of inconsistent shrinkage in all directions.
2) Properly increase the mold temperature. ABS plastics are usually kept above 60°C to reduce the cooling rate of the plastic parts, reduce the deformation caused by excessive cooling, and reduce the degree of molecular orientation.
3) The most important item is to increase the injection or holding pressure, and greatly extend the injection or holding time, so that the size of the injection molded part is increased, and its shrinkage is reduced. The degree of deformation will therefore be obvious Improvement. Therefore, extending the time of injection or holding pressure (such as extending 10~155) has become an important means for us to solve the deformation problem.
4) If the above three measures fail to achieve the desired effect, you can only take the method of demoulding and shaping. Because this process is more difficult to use, so you need to pay attention to the following points.
First of all, the plastic parts should be demolded early, and then placed on the workbench while the plastic parts are still at a high temperature of tens of degrees Celsius, and used fixtures to shape them. Pay attention to the design of the shaping fixtures. At the same time, the degree of resilience of the plastic parts must be considered. Usually, the resilience will basically stop after 12h, and the lower the demolding temperature, the greater the elasticity.
The last thing to emphasize is that attention must be paid to the packaging and placement of injection molded parts. This is very important, otherwise all of the above-mentioned efforts will be wiped out. Under normal circumstances, the injection molded parts can be packed side by side, of course, the form of placement must be determined according to the shape of the injection molded parts. Never let the plastic parts squeeze each other, or let a certain part of the injection part hang in the air, otherwise the injection part will begin to deform after a few days.