Plastic mold forming shrinkage in the form of the following are: plastic parts of the size of contraction, post-contraction and post-treatment shrink these types. Today, Dongguan Plastic mold factory editor with everyone to take a look at the form of plastic mold shrinkage.
Size of plastic parts shrink:
Due to thermal expansion and contraction and plastic parts when the elastic recovery, plastic deformation and other reasons, resulting in plastic parts from the cooling to room temperature after its size reduced. Direction of contraction:
Plastic in the molding process due to the role of molecular orientation of the plastic parts show anisotropy, along the flow direction (ie, parallel direction) shrinkage, high strength, and the vertical direction of the shrinkage is small, low strength.
When the plastic parts are molded, the residual stress exists in the plastic parts due to the factors such as molding pressure, shear stress, anisotropy, uneven density, uneven distribution of packing, inconsistent mold temperature, unevenness of hardening and plastic deformation. When the stripping, due to stress balance and storage conditions, so that plastic parts shrink again, this contraction
Called post-contraction. General plastic parts in the demoulding within 10h after the largest change, after 24 hours the basic shape, but the final stability to go through 30 to 60 days. Usually the post-shrinkage of thermoplastics is greater than that of thermosetting plastics, and extrusion and injection shrinkage after compression molding.
In some cases, the plastic parts according to their performance and process requirements, after forming heat treatment, treatment will lead to shrinkage of plastic parts, this contraction called post-processing contraction. In the mold design, the high-precision plastic parts should be considered after the contraction and post-processing shrinkage of the deviation and be compensated.
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