Plastic container shrinkage problem

Update:08 Jun 2018
Summary:

The problem of shrinkage is a defect that often occurs […]

The problem of shrinkage is a defect that often occurs in the processing of plastic containers. In particular, for large-scale plastic products with high surface quality requirements, shrinkage is a chronic illness. Therefore, people have developed various technologies to minimize the shrinkage problem and improve the product quality of packaging containers.

Plastic container shrinkage issues:
Shrinkage problems are often found in thicker parts of injection molded plastic parts, such as ribs or protrusions, which are more severe than adjacent locations. This type of defect severely limits the design and molding of plastic products, especially large-scale thick-walled products, such as The TV's bevelled case and display case etc. In China, for products such as household electrical appliances, which require strict quality, contraction marks must be eliminated, and for products such as toys that do not require high surface quality, shrink marks are allowed to exist.

There may be one or more reasons for the formation of shrink marks, including processing methods, part geometry, choice of materials, and mold design. The choice of geometry and material is usually determined by the raw material supplier and is not easy to control.

For molding workers, adjusting the processing conditions is one way to solve the shrinkage problem of plastic containers. Fill pressure and time significantly affect shrinkage. After the part is filled, excess material continues to fill the cavity to compensate for shrinkage of the material. This method may not be able to control the shrinkage marks to standard levels, but the shaper can adjust the filling conditions and improve the shrinkage marks.

In addition, there is a way to reduce the occurrence of shrinkage by modifying the molds by modifying the regular core holes. However, this method is currently not suitable for all resins. In addition, gas assist methods are also worthwhile.

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