Stress in plastic parts
Stress is a common problem after injection molding.
Whether it’s warping, cracking and other molded part defect, this is particularly a problem that manufacturers face and follow up with their engineering teams to continually work on. Stress is often thought of as problems occurring during the remova or ejectionl of the part or object from the mold or when the object is in transit. But sometimes the objects undergoes stress during the injection molding process itself. This article offers some information about Stress during or after injection molding.
The “pre-stress’ that happened during the manufacturing process can also affect the performance of the object, sometimes the object can withstand stress during the ejection process from the mold, but will later on show significant defects when already in transit or already in use. The object may get warped or show some defects when the temperature is elevated or it has been exposed to certain conditions. When force is applied to the object it also causes stresses measured through PSI (pounds per square inch). But manufacturers set limits or tolerances for these objects as guidelines to avoid stress in the object. If the object is exposed to extreme force, higher than its set limit, then it will result in breakage.
Through Gas Assist Analysis, the numerical and visual data that it provides allows manufacturers and design engineers to design parts that veer away from the causes of stress. What can the mold maker do to reduce stress in the end product? Just follow these simple design rules to prevent shrinking, warping, residual stress and voids:
The following are the common stresses in objects by injection molding method:
Stress in injection molding manufacturing processcan be avoided by following the manufacturer’s guidelines in using the kind of material for the object.
But it is best to know the varying conditions that will cause the stress in the part and use that information to set varying limits and tolerances to avoid stressful conditions for the part.