How to determine plastic pressure drop in injection molding?

The large area of flat injection molded parts results in a large shrinkage. The molecular orientation of large injection molded parts is extremely serious, and the cooling of the mold is not uniform, which makes the shrinkage rate of the injection molded parts in all directions inconsistent, resulting in the deformation and distortion of large, thin, flat injection molded parts. Sometimes there is a support bone on one side of the large plane injection molded part, and the injection molded part must be bent toward the side with the bone at this time.

To completely solve the problem of deformation of large flat injection molded parts is indeed a difficult problem, we have summarized some more effective measures to improve the deformation in production.

1. change the mold into a multi-point entry (usually three plate mold), and it is best to reach more than 4 points for large flat injection molded parts above 24 amps. This can reduce the degree of molecular orientation arrangement and reduce the gap of inconsistent shrinkage in all directions.

2. Properly increase the mold temperature, ABS material is usually kept above 60 ℃ to reduce the cooling rate of the injection molded parts, reduce the temperature difference deformation caused by the transition of cooling while reducing the degree of molecular orientation.

3. The most important thing 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 will increase, reduce its shrinkage, and the degree of deformation will be significantly improved. Therefore, extending the injection or holding time (such as extending 10 to 15 seconds) has become an important tool to solve the deformation problem.

4. If the above three measures fail to achieve the desired effect, the only way to take out of the mold is to set. Because the general use of people is not very good, so a little skill is needed.

To sum up.
First of all, the injection molded parts should be taken out of the mold early, then, take advantage of the fact that they are still in the state of several tens of degrees high temperature (should still be very hot, this is very critical), put them on the workbench and use the fixture to set the shape, the key is that the design of the fixture needs to be suitable.

At the same time, we should also consider the rebound degree of the injection molded parts, usually 12 hours after the rebound will stop, and the lower the temperature out of the mold, the greater the rebound amount. As the saying goes, the overkill must be corrected, so the amount of overpressure should be studied during production.