In the process of using plastic Injection mould, poor dimensional accuracy will occur, which will lead to the production of waste products and affect the production efficiency of the enterprise. So what are the reasons for the poor dimensional accuracy of plastic Injection mould?
The main reasons for the poor dimensional accuracy of plastic Injection mould are: there are problems in mold design and manufacturing accuracy, molding process conditions cause large changes in product shrinkage, unbalanced product shrinkage caused by molding materials, and changes over time caused by environmental conditions after molding Wait.
1. The manufacturing accuracy of each part of the mold will directly affect the dimensional accuracy of the product. The fitting of the fixed mold and the movable mold, the position of the parting surface, the structure of the side male mold, etc. will cause the product size error. Long-term use of molds will cause mold deformation or relaxation due to factors such as cavity pressure and clamping force. The strength of the mold material and heat treatment must be considered when designing the mold.
2. The shrinkage of plastic Injection mould is caused by the change of the melt density when the plastic is cooled from the molding temperature to the ambient temperature. It is not only related to the change of the molding temperature, but also related to the constraints of the part (the position of the core and the insert, etc.) ). Plastic mold designers must comprehensively consider the effects of process conditions and material behavior shrinkage when designing molds, especially cooling system design, runner and gate geometry, etc. The gating system should be optimized to ensure flow balance to avoid uneven shrinkage caused by overpressure and underpressure; for multi-cavity molds, the cavity layout should also be optimized to ensure the thermal balance of the mold system temperature, and optimize the cooling of the punch and die The waterway is designed to ensure uniform mold temperature.
3. The change over time caused by environmental conditions is the change in the size and shape of the molded product after it is placed in the atmosphere for several days. Mainly caused by the following reasons: ambient temperature, crystallization after molding, relaxation of residual stress, etc. The above-mentioned environmental temperature changes, crystalline changes and dimensional changes caused by residual stress are all related to time, and are generally stable after about 10 days. These changes must be fully considered in the design of high-precision dimensional products.