The flat injection molded parts have a large area and a large amount of shrinkage. Due to the extremely serious molecular orientation of the large injection molded parts and the uneven cooling of the mold, the shrinkage of the injection molded parts in all directions is inconsistent, which makes the thin and large flat injection molded parts susceptible to deformation and distortion. Sometimes one side of a large flat injection molded part is designed with a support bone, and the injection molded part must be bent toward the bone side.
To solve the problem of deformation of large-scale injection molded parts completely is a problem. In production, we have summarized some effective methods to improve the deformation problem:
1. Change the mold into multi-point water (usually three-plate mold), and the large-plane injection molded parts above 24 amps should reach 4 points or more. This can reduce the degree of molecular alignment and reduce the inconsistency of the inconsistent contractions.
2. Appropriately increase the mold temperature, ABS material is usually kept above 60 °C, to reduce the cooling rate of the injection molded parts, reduce the temperature difference deformation caused by the chill transition, and at the same time reduce the degree of molecular orientation.
3. The most important one is to increase the injection pressure or holding pressure, and greatly extend the time of injection or pressure retention, so that the size of the injection molded part is increased, and the amount of shrinkage is reduced. Significant improvements have been made. Therefore, extending the time of spraying or holding pressure (such as extending 10 to 15 seconds) has become an important means for us to solve the deformation problem.
4. If the above three measures fail to achieve the desired results, only the method of modeling and setting is adopted. Because most people don't use it very well, it takes a little skill.
to sum up:
First of all, it is necessary to take the injection molded part out of the mold early, and then take it in a state of several tens of degrees of high temperature (it should still be very hot, this is very important), put it on the workbench with a fixture, the key is the shaping fixture. Design needs to be appropriate. At the same time, it is necessary to consider the degree of rebound of the injection molded parts. Usually, the rebound will be basically stopped after 12 hours, and the lower the temperature of the mold is, the larger the rebound amount will be. The so-called sputum must be too positive, so the amount of overpressure should be studied during production.
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