Causes and solutions of top white in injection molding

We need to understand the definition of top white. Top white refers to the fact that in the process of injection molding, the plastic melt fails to completely fill the mold cavity when it reaches the surface of the injection mold, forming a blank area. This phenomenon will affect the quality of products and production efficiency, so it is necessary to take measures to prevent and solve.

We need to understand the causes of top white. The causes of top white mainly include the following aspects:

1. Unreasonable design of injection mold: Unreasonable design of mold, such as uneven surface of mold cavity and uneven wall thickness of mold cavity, will lead to melt cannot completely fill mold cavity when it reaches the surface of injection mold, forming top white.

2. Improper material selection: the selection of materials not suitable for injection molding, such as too high or too low melting point, shrinkage rate is too large or too small, will also lead to the production of top white.

3. Improper process control: in the process of injection molding, improper process control, such as unreasonable setting of temperature, pressure, time and other parameters, will also lead to the production of top white.

Reasons related to injection molding processing parameters and improvement measures:

1, the pressure is too high to reduce the pressure

2, the pressure holding time is too long to shorten the pressure holding time

3. The voltage holding time is changed too late, and the voltage holding time is changed in advance

4. The cooling time is too short to extend the cooling time

Reasons related to injection mold design and improvement measures:

1, release inclination is not enough according to the specifications of the selection of release inclination

2. The surface on the demoulding direction is rough, and the injection mold on the demoulding direction is polished

3. The vacuum core is filled with gas on the ejecting side

If the necessary release force of the injection mold is too high or the surface of the ejector rod is relatively small, the surface pressure here will be high, and the deformation will eventually cause the ejector part to be white. The phenomenon of stress whitening and stress rise was found at the side of the product facing the nozzle, that is, where the ejector rod was located on the ejector side of the die.