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What are the common methods of plastic molding?

1) Pretreatment (plastic drying or insert preheat treatment)

2) Forming

3) Machining (if needed)

4) Retouching (de-flashing)

5) Assembly (if necessary) Note: The above five processes should be carried out in sequence and cannot be reversed.

Factors affecting the dimensional accuracy of plastic molding:

1) The influence of the shrinkage rate of raw materials

The greater the shrinkage of the raw material, the lower the precision of the product. After the plastic material is reinforced or modified with inorganic filling, its shrinkage rate will be greatly reduced by 1-4 times. Plastic shrinkage processing conditions (cooling rate and injection pressure, processing methods, etc.), product design and mold design and other factors. The forming accuracy of different molding methods is in descending order: injection molding > extrusion > injection blow molding > extrusion blow molding > compression molding > calender molding > vacuum forming

2) The influence of raw material creep (creep is the deformation of the product under stress). General: Plastic materials with good creep resistance: PPO, ABS, PC and reinforced or filled modified plastics. After the plastic material is reinforced or modified with inorganic filling, its creep resistance will be greatly improved.

3) Influence of linear expansion of raw materials: linear expansion coefficient (thermal expansion coefficient)

4) Influence of water absorption rate of raw materials: After absorbing water, the volume will expand, resulting in an increase in size, which seriously affects the dimensional accuracy of the product. (The water absorption of the raw materials will also seriously affect the physical and mechanical properties of the raw materials after they are processed into parts.)

Plastics with high water absorption: such as: PA, PES, PVA, PC, POM, ABS, AS, PET, PMMA, PS, MPPO, PEAK Pay attention to the storage and packaging conditions of these plastics.

5) Influence of swelling of raw materials Caution! ! The solvent resistance of raw materials will seriously affect the dimensional accuracy of the product and the physical and mechanical properties of the product. For plastic products in contact with chemical media, use plastic materials whose media cannot cause them to swell.

6) Influence of filler: After the plastic material is reinforced or modified by inorganic filling, the dimensional accuracy of the plastic product can be improved.