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The Influence Of Shrink Belt On The Machining Of Plastic Mould
May 18, 2017

1, after processing shrinkage: plastic shrinkage can be divided into molding processing shrinkage and shrinkage after two types. After processing shrinkage is the product demoulding after a period of time contraction, compared with the molding shrinkage, the shrinkage is generally smaller. The first reason for the subsequent contraction is the relaxation of the internal stresses of the products. For a rigid polymer with a molecule chain, the latter shrinkage of the products is larger; this is mainly due to the slow movement of rigid molecular chains, the transition from one state to another, requiring a longer time reordering process, resulting in a longer contraction time and a larger posterior contraction rate. On the other hand, rigid molecular chains are prone to internal stress, and slowly stress relaxation will occur after molding. The second reason for the subsequent contraction is the continuation of crystallization. For the crystallization of polymer, plastic processing molding, did not achieve complete crystallization, at room temperature can continue to crystallization, resulting in the micro-shrinkage of products. 2, the average shrinkage rate: due to the plastic injection molding shrinkage size affected by the conditions of the larger, thus the shrinkage rate is not a fixed value, but a range, in the specific processing process, various processing conditions can increase the molding shrinkage rate, can choose 4% for the specific shrinkage rate; If the molding conditions are conducive to the reduction of molding shrinkage, you can select 2.5% for the specific shrinkage rate. Of course, the latter method is more difficult to choose.

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