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Use of plastic shrinkage of injection molding

Plastic mold factory small make up today to introduce the injection molding of plastics used in the contractility, molded parts after cooling to room temperature, out of the mold plastic parts of every part size than the original size has shrunk in the mold, this performance is called contractility. So what is called molding shrinkage, called molding contraction after molding plastic parts.

The formation of the molding shrinkage:

(1) the size of the plastic shrinkage: due to the heat bilges cold shrink and demoulding elastic recovery of plastic parts and plastic deformation causes such as plastic parts mold release its size shrinkage after cooling to room temperature.

(2) contraction direction: plastic parts in the process of forming molecules arranged in a certain direction, present anisotropic plastic, contraction along the direction of material flow, the intensity is high, and material flow vertical direction were narrow and low strength. In addition, the plastic parts in molding due to uneven distribution of the density of each part and packing, so that contraction is not uniform, causing shrinkage is poor, prone to plastic buckling, deformation, cracks.

Contraction after (3) : when molding plastic parts, due to the molding pressure, shear stress, anisotropy, uneven density, packing, distribution, uneven mold temperature and hardening not divide evenly, plastic deformation, caused a series of stress, because of the stress in the plastic stick when flow cannot disappear, so the plastic molding after curing residual stresses are present. After demoulding because of the influence of the stress into balance and storage conditions, to make plastic parts happen again after called contraction.

(4) post-processing contraction: sometimes parts in accordance with the requirements of performance and process after molding need to heat , after processing will also result in changes of parts size or contraction called post-processing hand search.

The factors affecting shrinkage rate:

(1) plastic varieties

(2) plastic parts characteristics

(3) the mold structure

(4) the molding process

This is Jiezheng mould of small make up to introduce the use of injection molding plastic shrinkage, mainly the formation of the molding shrinkage is introduced and the factors affecting shrinkage rate.

Note: the above information by dongguan jiezheng mold products co., LTD on the Internet, welcome to reprint, indicate the source!

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