How to reduce plastic mold, injection mold shrinkage?

2021-3-18
The problem is that all products shrink plastic mold, injection mold suppliers face the enemy, especially for high surface quality home appliances and precision plastic mold products, contraction is a chronic illness. Therefore, various techniques have been developed to minimize shrinkage and improve product quality.   

In the plastic mold, injection mold member thicker location, such as shrinkage than the adjacent positions of ribs or protrusions formed at the more serious, because the cooling rate is much slower than the thicker region surrounding area. Cooling at different speeds lead to the formation of the connecting surface depression, ie the familiar scar contraction. This deficiency severely limits appliances precision plastic mold design and molding products, especially large thick-walled products such as televisions and monitors slant cabinet shell. In fact, this type of requirement for household electrical appliances must eliminate sink marks on the strict product, and for less demanding surface quality toys and some other products to allow the presence of scar contraction.   

Reasons for the formation of scar contraction may have one or more, including processing methods, part geometry, material selection, and mold design. Geometry and material selection which is usually determined by raw material suppliers, and not easy to change. But there is still a lot of mold makers about mold design factors that may affect the contraction. Cooling channel design, gate type, gate size may produce a variety of effects. For example, the small gate as tube gates cooling much faster than the tapered gate. The gate will reduce premature cooling cavity fill time, thereby increasing the probability of contraction resulting scar. For molding workers adjust processing conditions is one way to solve the shrinkage problem. Filling pressure and time significantly affect shrinkage. After filling member, the excess material continues to fill the cavity to compensate for shrinkage of the material. Filling stage is too short will cause contractions intensified, eventually will produce more or larger contraction marks. This approach may not be able to shrink scar itself reduced to a satisfactory level, but workers can adjust the fill molding conditions improve shrink marks.