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How to control the color of injection molding machine products?

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

Select 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 angle, it is better to replace the equipment. The color difference caused by the gating 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 impact of injection molding process adjustment

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

Try to avoid using the injection molding process with strong shear effect caused by high injection speed and high back pressure to prevent color difference caused by local overheating or thermal decomposition. 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 heating ring is damaged or the heating control element is out of control and burns for a long time, which leads to the sharp change of the barrel temperature and the color difference. The color difference caused by this reason is easy to judge. Generally speaking, the color difference caused by the damage and failure of the heating ring will be accompanied by uneven plasticization.

However, the heating control part of long-term combustion out of control is often accompanied by gas spots, serious 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 this color difference.

4. Eliminate the influence of raw material resin and masterbatch

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

That is to strengthen the warehousing inspection of raw materials, as far as possible, use the same manufacturer, the same brand of color masterbatch and color masterbatch to produce the same product. For color 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 color 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 color masterbatch. For products with poor thermal stability, we recommend manufacturers to replace them.

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

Before adjusting the color difference, we must also understand the change trend of the color of the injection molding machine product with the temperature and the masterbatch. With the change of the production temperature or the amount of masterbatch, the color change rule of the product is also different. The change rule can be determined by the color test process. Unless we know the change rule of the masterbatch color, it is impossible to adjust the color difference quickly.