The Influence of SMC Mould Design and Manufacture on Product Precision

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Ⅰ. Commonly used raw materials for SMC moulds

The commonly used raw materials for SMC moulds are resin, methyl ethyl ketone, accelerator, unsaturated polyester resin, curing agent, accelerator, zero-alkali neutral glass fiber cloth, polyvinyl alcohol 17-99 (release agent), special pigment paste for FRP, styrene (thinner).

Ⅱ. The influence of SMC mould on product precision

1. The effect of material shrinkage

When designing SMC moulds, first consider the shrinkage of the materials used and the difference in shrinkage and deformation of different parts of the product, and take necessary remedial measures.

2. Design of product forming parting surface and cutting edge

The product moulding parting surface is generally set at the parts that require less precision, such as the edge of the product, and try to avoid setting it on the front part of the product, so as not to affect the surface accuracy of the processed product in the future. At the same time, try to use vertical parting instead of horizontal parting, because horizontal parting is more likely to cause thickness and precision control problems; the thickness of the cutting edge should be designed to be small, but the material flow filling should be ensured to reduce the amount of burr processing.

3. Surface roughness of SMC mould products

Generally speaking, SMC products show that the roughness is -3 levels lower than that of the mould surface, which needs to be considered when designing the SMC mould.

4. Design of heating system

The surface temperature of the SMC mould and its uniformity will have a direct impact on the curing degree and uniformity of the product, and the benefits of product curing will directly affect the deformation and surface quality of the product. Therefore, in the design and processing of the SMC mould heating system, the best curing temperature for SMC should be realized, and the temperature difference of the mould surface should be controlled within 3-5℃.

5. Consideration of SMC mould manufacturing and mould durability

The accurate selection and processing of SMC mould materials and the correct design of ejection system, guide system, and core pulling system directly affect the service life and movement accuracy of the mould, and to a certain extent also affect the fluctuation of the accuracy of the moulded product.