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What are the reasons for the poor precision of injection molded parts?

 Monday, 09 August 2021

Common injection defects are unqualified in size. The main reasons for analysis are: mold design and manufacturing accuracy problems, molding process conditions cause obvious changes in product shrinkage, uneven product shrinkage caused by molding materials, continuous changes caused by environmental conditions after molding, etc. .

1.The machining accuracy of each part of the mold directly affects the dimensional accuracy of the product. The core and cavity assembly, the position of the parting surface, the design of the side slider, etc. will cause dimensional errors. The long-term use of the mold will be affected by the cavity pressure. , Clamping force and other factors cause mold deformation or relaxation, the strength of the mold material and heat treatment must be considered when designing the mold.
2.The shrinkage of injection molded parts is caused by the change of melt density when the plastic is cooled from the molding temperature to the ambient temperature. It is not only related to the change of molding temperature, but also related to the constraints of the product. When designing the mold, the injection mold, the designer, The influence of process conditions and material shrinkage must be considered comprehensively, as well as the cooling water circuit design, the geometry of runners and gates, etc. For multi-cavity molds, the cavity layout should also be optimized to ensure the thermal balance of the mold system temperature, and the cooling water circuit design of the core and cavity should be optimized to ensure uniform mold temperature.

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