This question needs to be considered from two aspects: physical and mechanical properties of plastic and plastic molding process:
Influence of plastic physical and mechanical properties:
1. Temperature of injection molding equipment is not well controlled, color masterbatch cannot be fully mixed with resin after entering mixing chamber.
2. Injection molding machine does not add a certain amount of back pressure, mixing effect of screw is not good.
3. Dispersion of color masterbatch is not good or resin plasticization is not good.
Process can be debugged as follows:
1. Slightly increase temperature of part of mixing cavity near discharge port.
2. Apply a certain back pressure to injection molding machine.
If it is still not good after above debugging, it may be a problem of dispersion or matching of color masterbatch and resin, masterbatch manufacturer should be contacted to solve it.

This may be due to poor diffusion and mutual solubility caused by poor quality of dispersant or auxiliary selected by manufacturer, which affects physical and mechanical properties of product.

Although this problem is simple, there are many possibilities, specifically:
1. Color masterbatch has not been tested carefully, and pigment is too little or too much.
2. Measurement is inaccurate when in use, and there are a lot of random measurement by domestic enterprises, especially small and medium-sized enterprises.
3. There is a problem with matching of color masterbatch and resin. This may be caused by improper selection of carrier of color masterbatch, or manufacturer may change resin variety at will.
4. Temperature of machine is improper, and color masterbatch stays in machine for too long.
Processing procedure: Firstly, check whether resin type matches color masterbatch and whether measurement is accurate. Secondly, adjust temperature or speed of machine. If there are still problems, contact masterbatch manufacturer.

This is often caused by injection molding machine. Different injection molding machines have different mechanical conditions due to different manufacturing, use time or maintenance conditions, especially difference in the degree of close contact between heating element and barrel, which makes dispersion state of color masterbatch in barrel different, and above phenomenon will be appear.

Density and melt index of different grades of resin will be different, so performance of resin will be different, compatibility with color masterbatch will also be different, resulting in a color change. Generally speaking, as long as density and melt index are not much different, color difference will not be too large. You can correct color by adjusting amount of color masterbatch.

Some color masterbatches have high pigment content (or dyes). In this case, migration is normal. Especially color masterbatches added with dyes will cause serious migration. But this does not affect quality of product, because after color masterbatch is injected into product, pigment is in normal color concentration in product.

There are many possibilities:
1. Nozzle temperature of injection molding machine is too low.
2. Mold finish of injection molding machine is not good.
3. Product molding cycle is too long.
4. Too much titanium dioxide contained in color masterbatch.
5. Dispersion of color masterbatch is not good.

Basic pigments used by manufacturer are of poor quality and drifting occurs.

Different brands of ABS produced in various countries have a large color difference, even if same brand of ABS, each batch number may exist. However, this chromatic aberration is generally not serious. When using ABS color masterbatch, users must pay attention to this characteristic of ABS.

 

It is necessary to choose an injection molding machine with same capacity as main injection molding product. If injection molding machine has problems such as material dead ends, it is best to replace equipment. Chromatic aberration caused by mold gating system, exhaust groove, etc. can be solved by repairing corresponding part of mold. Problem of injection molding machine and mold must be solved first before production can be organized to reduce complexity of problem.

Controlling raw materials is key to completely solving chromatic aberration. Therefore, especially when producing light-colored products, obvious influence of different thermal stability of raw material resin on color fluctuation of product cannot be ignored. In view of fact that most injection molding manufacturers do not produce plastic masterbatch or color masterbatch themselves, focus of attention can be placed on production management and raw material inspection. That is to strengthen inspection of raw materials storage; same product in the production is produced with same manufacturer, same brand of masterbatch, and color masterbatches as much as possible; for color masterbatches, we have to conduct random inspections before mass production, both same proofreading and comparison in this time. If color difference is not large, it can be considered qualified. If batch of color masterbatch has a slight color difference, color masterbatch can be re-mixed before using it to reduce color difference caused by uneven mixing of color masterbatch itself. At the same time, we also need to focus on testing thermal stability of raw resin and color masterbatch. For those with poor thermal stability, we recommend that manufacturer replace them.

In the production, it is often encountered that a certain heating ring is damaged or failed, or heating control part is out of control and burns, which causes temperature of barrel to change drastically, resulting in color difference. Chromatic aberration caused by this kind of reason is easy to determine. Generally, chromatic aberration caused by failure of heating ring will be accompanied by uneven plasticization, out-of-control heating of heating control part is often accompanied by product air spots, severe discoloration and even coking. Therefore, it is necessary to check heating part frequently during production, replace and repair it in time when heating part is found to be damaged or out of control, so as to reduce chance of this kind of color difference.

When injection molding process parameters need to be adjusted for non-chromatic aberration reasons, do not change injection temperature, back pressure, injection cycle and amount of masterbatch added as much as possible. Adjustment also needs to observe effect of process parameter changes on color and luster. If color aberration is found, it should be adjusted in time. Try to avoid use of injection molding processes that cause strong shearing effects such as high injection speed and high back pressure as much as possible to prevent color difference caused by local overheating or thermal decomposition. Strictly control temperature of each heating section of barrel, especially nozzle and heating part close to nozzle.

Before adjusting color difference, it is necessary to know trend of product color with temperature and amount of color masterbatch. With change of production temperature or amount of color masterbatch, color change law of product is different. Color test process can be used to determine its changing law. Unless color change law of this masterbatch is known, it is impossible to adjust color difference quickly.