What are crack and albino injection defects?
Cracking is a common defect of plastic products, which is mainly caused by stress deformation. There are mainly residual stress, external stress and stress deformation caused by external environment. As shown in the figure
Analysis and elimination of crack and whiten injection defects
1) The surface residual stress is too large
Excessive residual stress is the main cause of surface cracking of plastic parts. In the process operation, the process parameters should be set according to the requirements of reducing residual stress of plastic parts. Especially when the temperature of molten material and mold is high and the melt flow performance is good, the injection pressure should be reduced as much as possible. When removing the cracking fault, the methods of eliminating cracks and cracking fault can be referred to.
If there are cracks on the surface of the plastic parts, annealing can be considered to eliminate them. The annealing treatment is to heat the plastic parts fully for about 1 hour at a temperature about 5 degrees lower than the hot deformation temperature of the plastic parts, and then cool them slowly. It is better to anneal the cracked plastic parts immediately after forming, which is conducive to completely eliminating the cracks. However, it is difficult to eliminate cracks by annealing in mass production, so it is generally not suitable.
In addition, due to the residual stress in the crack, if the plastic parts with crack defects are sprayed, the flux in the coating is easy to cause the crack to dissolve and develop into a crack. In this case, special attention should be paid to the selection of coatings and diluents that will not cause crack.
2) The surface of plastic parts is affected by concentrated external force
External force is the main cause of surface whitening of plastic parts. In most cases, the whitening part is always located in the ejection part of the plastic part. For example, in the demoulding process of plastic parts, due to poor demoulding, when the demoulding force on the surface of plastic parts is close to the elastic limit of resin, whitening will occur.
After whitening, the injection pressure should be reduced and the demoulding angle should be increased appropriately, especially the chamfer should be prevented near the stiffener and boss. The ejection device of the demoulding mechanism should be set at the wall thickness of the plastic part or the thickness of the ejection part of the plastic part should be increased appropriately.
In addition, the surface finish of the cavity should be improved to reduce the demoulding force, and a small amount of demoulding agent can be used if necessary.
About JasonMould Industrial Company Limited
Jasonmould is a China mold maker of plastic molds- injection mold, die casting moulds, plastic blow molding, rotational molding, medical plastic injection molding, two shot plastic injection molding, insert molding, overmolding, metal injection molding, micro injection molding, powder injection molding, ceramic injection molding, liquid injection molding, husky injection molding, household mold, casting mold, die mold tool, custom molds, china moulds, rapid prototyping tooling, plastic prototyping tooling, punch press tooling, die and tooling for mobile/ cell phone parts, automotive parts, vacuum cleaners, rechargeable tools, telephones, copiers, computers, multimedia speakers, and many other electronic products and household appliances. And also a plastic product manufacturer, mold manufacturer China– plastic parts, plastic water tank, plastic balls, plastic containers, plastic buckle, plastic anchor, plastic hanger, plastic spoon, plastic pipe fitting, plastic tumble, plastic tableware, plastic cups, plastic bottles, plastic tray, plastic cosmetic container, plastic case, plastic food container, plastic chairs, plastic caps, plastic cap closure, plastic tubes, plastic water pipes, plastic knobs, plastic tubing, plastic utility boxes, plastic racks and so on.
Person: James Yuan
Company: JasonMould Industrial Company Limited
Add: LongGang Village,LongXi Town,BoLuo County,HuiZhou City,GuangDong Province, China
Email: [email protected]