Several issues needing attention in the design of precision injection moulds
① Avoid the design of precision injection moulds The same design as ordinary injection precision injection moulds Avoid ambiguity in the concepts of precision injection moulding and precision injection moulds. As the name implies, precision injection moulding is the injection moulding of plastic products with high moulding size and shape accuracy and low surface roughness.
② Avoid whether the processing method of the mould can make the parts meet the accuracy requirements. Consider that most of the mould cavities are manufactured by sharp cutting, grinding or electrical processing methods. The highest precision and practical economic precision that these processing methods can achieve. In order to achieve higher accuracy, the mould cavity must be ground or CNC milled with extremely high precision. Because the shape of the mould cavity is generally very complex, it is often a very difficult job to grind the whole. In order to solve this problem, the cavity is often designed as a mosaic structure. To make the manufacturing tolerance of the mould exceed IT5 ~ IT6 level.
① To avoid that the quality of precision moulds can not reach the production of parts, and the drawings have no tolerances, and the dimension accuracy of the mould parts must be marked correctly and reasonably, which can meet the needs of the production of parts. 0.02, this is wrong. According to the fitting type, precision requirements and nominal size of the parts.
② The materials used for the production of precision moulds should be high-quality alloy steels with high mechanical strength, and the materials used for cavity runners should be heat-treated materials with high hardness, good wear resistance and strong corrosion resistance. The part manufacturing process should consider the generation and elimination of internal stress of parts processing and heat treatment, as well as the difficulty of mechanical processing. The designed sprue system can be modified after trial mould.
Common defects and causes of injection moulded products
① The most common defects of injection moulded parts
Insufficient filling, dents, shrinkage holes, air holes, flow lines, dark spots, dark lines, silver lines, weld marks, whitening, delamination, whitening, scorching, warpage, no gloss, uneven color, gate cracks , Lack of material, broken feet, top braces, poor surface roughness, surface cracks and flash burrs, etc.
② Understand the causes of moulding defects
If the mould designer has a good understanding of the complex causes of common defects in moulded products, he can fully consider the corresponding preventive measures when designing the mould structure to avoid problems with the quality of the moulded products due to the design of the mould. At the same time, to avoid common product defects due to the injection moulding process,
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Such a mould is the first plastic part to be moulded among various types of moulds. Relatively speaking, they are placed directly in the relevant plastic barrels for compression, and they are placed at a certain temperature. Open the mould cavity, and then close all of these moulds. Under the action of heat and pressure, basically the plastic melting state can be changed into a flowing state, because of its physical and chemical effects, all plastics are hardened Slowly become a normal temperature plastic component with a certain shape and size. Compression moulding can basically be applied to the processing of thermosetting plastics and other plastics. It can also be used to process unsaturated plastic clusters and other things. In order to carry out joint processing, under normal circumstances, often press the plastic mould, so as to have a variety of cooperation.