How to solve the wire drawing problem in injection molding process?

In the process of injection molding, wire drawing is a common and thorny problem. It is usually manifested as the surface of the plastic parts appear thin plastic filaments, affecting the appearance of the product quality and subsequent coating, printing and other processes.

So, how to effectively solve the problem of wire drawing in the injection molding process?

1. Optimization of mold design

Reasonable mold design is a prerequisite to avoid wire drawing. Designers need to carefully consider the shape and size of the runners to ensure that the melt can fill the mold cavity evenly. In addition, the choice of gate location is also critical, should try to avoid the melt directly impact to the core or cavity edges, to reduce the shear force caused by the wire drawing problem. At the same time, a reasonable arrangement of the cooling water circuit can ensure that the mold temperature is balanced to prevent local overheating.

2. Adjustment of injection parameters

Injection parameters, including injection speed, pressure, back pressure, barrel temperature, etc., have a significant impact on the melt flow performance. Reducing the injection speed can reduce the shear force generated when the melt flows, thus reducing the drawing. Appropriate increase of back pressure helps to improve the density of the melt and reduce the defects caused by gas entrapment. And the appropriate barrel temperature ensures the homogeneity and stability of the melt.

3. Material selection and drying treatment

Selection of suitable plastic materials is equally important for the prevention of wire drawing. Different resins have different rheological properties, and the selection of appropriate materials can reduce the adhesion of the melt and reduce the tendency of wire drawing.

4. Mold surface treatment

Special treatment of the mold surface, such as plating or spraying release agents, can reduce the coefficient of friction between the plastic and the mold, and help to eliminate drawing due to excessive adhesion.

5. Use of dynamic pressure holding and cooling techniques

The use of advanced dynamic pressure holding technology can automatically adjust the pressure holding pressure according to the thickness of the plastic part, so that the force on all parts of the plastic part is more uniform. Combined with efficient cooling technology, the plastic parts can be quickly cooled down to the demolding temperature, preventing wire drawing caused by melt flow.

6. Application of post-processing technology

If it is still difficult to avoid wire drawing completely by the above methods, the appearance of the product can be improved by post-treatment processes such as grinding, sandblasting and brushing. These methods can effectively cover the slight wire drawing traces without affecting the overall quality of the product.