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It should be noted plastics material shrinkage
2018-05-05

Yuyao a nebulizer production export to Egypt a grant worth more than 20,000 US dollars a plastic hand pump due to the pressing of the parts come off easily, but unfortunately returned back home rework finishing.

 

Yuyao, Ningbo Inspection and Quarantine Bureau immediately in accordance with the entry of goods repair process requirements, the goods were investigating the case. The field investigation found that the specific reasons for the return of enterprises in manufacturing plastic hand pump injection molding process is not carefully taken into account shrinkage of the plastic material, resulting in the product does not match the size of the parts, the upper and lower part of the product separation bounce, the impact of product use. Shrinkage plastic is the percentage difference between the cooled to room temperature and the size of the size of the plastic parts removed from the mold at the molding temperature. It reflects the degree of cooling after removal of plastic parts from the mold size reduction. Any plastic products have a certain size requirements, with the requirements of the plastics in use or installation, its high dimensional accuracy requirements. Fluctuations in the value of the shrinkage difference when designing and manufacturing products plastic mold shrinkage estimated and actual shrinkage will affect the dimensional accuracy of plastic products.

 

Secondly, plastic shrinkage and also the shape of the complexity of the internal structure of plastic parts, whether there are inserts, etc. have a great relationship. In addition, the mold cavity in the course of constant wear and tear, so that the same mold in new and old, when the production of the product size varies.

 

Molding parts dimensions, with changes in the gap, which will affect the plastic parts tolerance. For this reason, we recommend that the relevant export enterprises: If the extrusion or injection molding shrinkage problem, it should be a corresponding increase in margin from molds; if it is large shrinkage of raw materials, can be used to join fiberglass modified to reduce the raw material of its own shrinkage big problem; if it is affecting the appearance of uneven shrinkage products, you should consider addressing the thickness distribution in terms of the structure of products. It must be taken for heating or cooling the mold temperature control measures in the mold design and mold in order to make the temperature difference between the cavities to minimize, and must pay attention to the temperature cooling circuit design.

 


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