茂名How to control the color difference of injection molding medical devices in Dalian

Color difference is a common defect in injection molding medical device products in Dalian. There are many factors affecting color difference, including raw resin, color masterbatch, mixing of color masterbatch with raw material, injection molding process, injection molding machine, etc. In the actual production process, we generally control color difference from the following five aspects.

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

Select the 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 recommended to replace the equipment. For the color difference caused by the mold pouring system and exhaust slot, it can be solved by the maintenance mold of the corresponding part of the mold. The problems of injection molding machines and molds must be solved before production can be organized to reduce the complexity of the problem.

2. Eliminate the influence of raw resin and color masterbatch

Control of 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 raw resin on the color fluctuation of products cannot be ignored. Since most injection molding manufacturers do not produce plastic masterbatch or color masterbatch, attention can be focused on production management and raw material inspection. That is to strengthen the inspection of raw materials warehousing; The same product shall be produced by the same manufacturer, the same brand masterbatch and color masterbatch as far as possible; For color masterbatch, we should carry out spot check and color test before batch production, which should be checked with the last time and compared with this time. If the color difference is not large, it can be considered as qualified, just as the batch color masterbatch has slight color difference, it can be re-mixed and reused to reduce the color difference caused by uneven mixing of the color masterbatch itself. At the same time, we also need to focus on the thermal stability of raw resin and color masterbatch. For those with poor thermal stability, we recommend the manufacturer to replace them.

3. Reduce the influence of barrel temperature on color difference

In production, it is often encountered that a heating ring is damaged and invalid, or the heating control part is out of control and burnt for a long time, resulting in a drastic change in the barrel temperature, resulting in color difference. It is easy to determine the color difference caused by such reasons. Generally, the color difference caused by the damage and failure of the heating ring will be accompanied by the uneven plasticization, while the uncontrolled long burning of the heating control part will often be accompanied by the product gas spot, serious discoloration and even coking. Therefore, it is necessary to check the heating part frequently during production, and timely replace and repair the heating part if it is found to be damaged or out of control, so as to reduce the probability of such color difference.

4. Reduce the impact of injection molding process adjustment

When it is necessary to adjust the injection molding process parameters for reasons other than color difference, try not to change the injection temperature, back pressure, injection cycle and color masterbatch addition amount as much as possible. At the same time, observe the effect of the change of process parameters on the color. If color difference is found, timely adjust it. Try to avoid the use of injection molding processes with high injection speed, high back pressure and other factors that cause strong shear, and prevent color difference caused by local overheating or thermal decomposition. Strictly control the temperature of each heating section of the barrel, especially the nozzle and the heating part close to the nozzle.

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

Before color difference adjustment, it is also necessary to know the change trend of product color with temperature and masterbatch quantity. With the change of production temperature or masterbatch quantity, the change rule of product color is different. The change rule can be determined through the color test process. It is impossible to adjust the color difference quickly unless the change rule of this color master is known.