During the use of the Chair Mould, the dimensional accu […]
During the use of the Chair Mould, the dimensional accuracy of the product will be poor, which will lead to production waste and affect the production efficiency of the enterprise. What is the reason for the poor dimensional accuracy of the plastic injection moulded product?
The main reasons for the poor precision of the moulded products are as follows: the design and manufacturing precision of the chair mould products are problematic; the shrinkage of the product caused by the moulding process conditions has changed greatly; the product shrinkage caused by the moulding materials is not balanced; the environmental conditions after moulding cause Time changes.
1. The manufacturing precision of each part of the chair mould will directly affect the dimensional accuracy of the product. Fixed moulds and movable mould parts, the position of the side of the mould structure will lead to product size errors. Long-term use of the mould will cause mould cavity pressure, clamping force and other factors cause the mould to deform or relax. The design of the chair mould must consider the strength and heat treatment of the mould material.
2. The shrinkage of the injection moulded part is caused by the change in melt density from the moulding temperature to the ambient temperature. It is not only related to changes in the forming temperature, but also to the constraints of the part (core and position of the blade). Mould designers must consider the effects of process conditions and material properties shrinkage, especially the design of the cooling system, the geometry of the runners and gates. We should optimize the gating system to ensure balanced flow and avoid overpressure and underpressure caused by uneven shrinkage; optimize multi-cavity cavity layout, ensure heat balance temperature of die water cooling system, optimize design of punch and die, and ensure mould temperature Evenly.
3. The shape change of the product caused by environmental changes is placed in the atmosphere for several days, and the shape of the product changes. Mainly due to the following reasons: ambient temperature, crystallization after forming, residual stress relaxation, etc. The residual stress caused by the above environmental temperature change, crystal change and dimensional change is related to time, generally about 10 days later. Stability, changes in these high-precision size products must be fully considered in the design.