How to control the color difference of the screw products of the injection molding machine

Update:09 Jul 2021

There are many requirements for the material of the injection screw, which we have introduced before. The color difference is a common defect in the screw of an injection molding machine. There are many factors that affect the color difference, involving raw material resin, color masterbatch, color masterbatch mixing of the same material, injection molding process, injection molding machine, etc.

In the actual production process, we generally control the color difference from the following five aspects. The specific methods are as follows:

1. Eliminate the influence of injection molding machine and mold elements

It is necessary to select an injection molding machine with an appropriate capacity for the main injection molding products. If the screw of the injection molding machine has problems such as material dead ends, it is best to replace the equipment. Nitriding screw barrel
Regarding the formation of chromatic aberrations in the mold pouring system, exhaust grooves, etc., it can be dealt with by repairing the corresponding part of the mold. It is necessary to deal with the injection molding machine and mold problems first to be able to organize production to reduce the complexity of the problem.

2. Eliminate the influence of material resin and color masterbatch

Controlling raw materials is the key to completely solving chromatic aberration. Therefore, especially in the production of light-colored products, the significant impact of different thermal stability of the material resin on the color fluctuation of the product cannot be ignored. In view of the fact that most injection molding manufacturers do not produce plastic masterbatch or color masterbatch themselves, the focus of attention can be placed on production management and raw material inspection.

That is to strengthen the inspection of raw materials storage; in production, the same product should be produced from the same manufacturer, the same trademark masterbatch, and color masterbatches; for color masterbatches, we must conduct random inspections and test colors before mass production, which is the same as the previous calibration. Also in this comparison, if the color difference is not large, it can be considered qualified. Just as the batch of color masterbatch has slight color difference, the color masterbatch can be mixed from the beginning and then used to reduce the color difference caused by uneven mixing of the color masterbatch itself. In addition, we also need to focus on checking the thermal stability of the material resin and color masterbatch. Regarding the poor thermal stability, we recommend that the manufacturer replace it.