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

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

Choose an injection molding machine with the same capacity as the main injection molding product. If the injection molding machine has problems such as material dead corners, it is best to replace the equipment. The color difference caused by the pouring system and the mold exhaust groove can be solved by repairing the mold at the corresponding part of the mold; before organizing production, the problems of the injection molding machine and the mold must be solved to reduce the complexity of the problem.

2. Reduce the influence of injection molding process adjustment

When the injection molding process parameters need to be adjusted for non-color difference reasons, the injection molding temperature, back pressure, injection molding cycle and masterbatch dosage should not be changed as much as possible. At the same time, it is necessary to observe the effect of changes in process parameters on color; if color difference is found, it should be adjusted in time.

Try to avoid using injection molding processes with strong shearing effects caused by high injection speed and high back pressure to prevent local overheating or thermal decomposition from causing color difference. Strictly control the temperature of each heating section of the barrel, especially the temperature of the nozzle and the heating part near the nozzle.

3. Reduce the influence of barrel temperature on color difference

In production, it is often encountered that the barrel temperature changes sharply and produces color difference due to damage and failure of the heating ring or long-term uncontrolled burning of the heating control element. The color difference caused by this reason is easy to judge; generally speaking, the color difference caused by damage and failure of the heating ring will be accompanied by uneven plasticization.

However, the heating control part that burns out of control for a long time is often accompanied by gas spots, severe discoloration, and even product coking. Therefore, in production, the heating element should be checked frequently. If the heating element is damaged or out of control, it should be replaced and repaired in time to reduce the occurrence of such color difference.

4. Eliminate the influence of raw material resin and masterbatch

Controlling raw materials is the key to completely solve the color difference. Therefore, especially in the production of light-colored products, the obvious influence of different thermal stability of resin raw materials on product color fluctuations cannot be ignored. Given that most injection molding manufacturers do not produce plastic masterbatches or color masterbatches, you can pay attention to production management and raw material inspection.

That is, strengthen the inspection of raw materials entering the warehouse; use the same manufacturer and the same brand of masterbatch and masterbatch to produce the same product as much as possible; for masterbatch, sampling and color testing should be carried out before mass production, and compared with the last time and this time. If the color difference is not large, it can be considered qualified, just like the masterbatch has a slight color difference.

The masterbatch can be remixed before use to reduce the color difference caused by the uneven mixing of the masterbatch itself. At the same time, we also need to focus on testing the thermal stability of the raw resin and masterbatch. For products with poor thermal stability, we recommend that manufacturers replace them.

V. Master the influence of barrel temperature and masterbatch on product color change

Before adjusting the color difference, we must also understand the trend of the color change of the injection molding machine product with temperature and masterbatch; with the change of production temperature or masterbatch dosage, the color change law of the product is also different; the change rule can be determined by the color testing process; unless the color change law of the masterbatch is known, it is impossible to adjust the color difference quickly.