How to Solve the Problem of Color Difference in Injection Products?

There are many factors affecting the color difference of injection molded products, including raw material resin, color masterbatch (or color powder), mixing of color masterbatch with raw material, injection molding process, injection molding machine, mold, etc.

Because of the wide range of factors involved, color difference control technology is also recognized as one of the more difficult techniques to master in injection molding.

In the actual production process, we generally control the color difference from the following six aspects.

Eliminate the influence of injection molding machines and mold factors

To select an injection molding machine with similar problems as showing the main product by BOM, if the machine appears, the equipment must be replaced.

The chromatic aberration caused by mold pouring, changing grooves, etc., can be solved by the maintenance mode of the corresponding part of the injection mold. The complexity of the problem and complexity of the problem can be addressed first to test the problem.

Eliminate the influence of raw resin and color masterbatch

Controlling raw materials is the key to completely solving chromatic aberration. Therefore, especially in the production of light-colored injection molded products, the obvious influence of the thermal stability of the raw material resin on the color fluctuation of the products cannot be ignored.

Given that most injection molding manufacturers do not produce plastic masterbatches or color masterbatches themselves, the focus can therefore be placed on production management and raw material inspection.

That is to strengthen the inspection of raw materials in storage; in production, the same product should be produced by the same manufacturer, the same brand of masterbatch, and color masterbatch as much as possible; for the color masterbatch, we should conduct a random inspection and color testing before mass production.

In this comparison, if the color difference is not big, it can be considered as qualified, just like the batch of color masterbatch has a slight color difference, the color masterbatch can be re-mixed before use to reduce the color difference caused by uneven mixing of the color masterbatch itself.

At the same time, we also need to focus on testing the thermal stability of the raw resin and color masterbatch. For those with poor thermal stability, we recommend that the manufacturer replace them.

Reduce the influence of barrel temperature on color difference

In production, it is often encountered that a heating ring is damaged and failed, or the heating control part is out of control and the mold temperature of the barrel changes drastically, resulting in chromatic aberration. The color difference caused by such reasons is easy to determine.

Generally, the color difference caused by the damage and failure of the heating ring will be accompanied by uneven plasticization, and the uncontrolled long burning of the heating control part is often accompanied by-product gas spots, severe discoloration, and even cooking.

Therefore, it is necessary to check the heating part frequently in production and replace and repair it in time when it is found that the heating part is damaged or out of control, to reduce the probability of such chromatic aberration.

Reduce the influence of injection molding process adjustment

When the injection molding process parameters need to be adjusted for reasons other than a chromatic aberration, the injection production temperature, back pressure, injection cycle and the amount of color masterbatch added should not be changed as much as possible. At the same time, the influence of the process parameter change on the color should be observed.

Avoid using high injection speed, high back pressure, and other injection molding processes that cause strong shearing effects as much as possible to prevent chromatic aberration 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.

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

Before adjusting the color difference, it is also necessary to know the trend of the product color changing with temperature and color masterbatch.

Different color masterbatches vary with the temperature of production or the amount of color masterbatch, and the color change rules of their injection molding products are different. The change rule can be determined through the color test process.

It is impossible to quickly adjust the color difference unless the color change law of the masterbatch is known.

Eliminate the influence of uneven mixing of color masterbatch and masterbatch

Poor mixing of plastic masterbatch with color masterbatch will also make the product color changeable. After the masterbatch and the color masterbatch are mechanically mixed evenly when they are fed into the hopper through the lower suction material.

The color masterbatch is separated from the masterbatch due to electrostatic action and is easily adsorbed on the hopper wall, which will inevitably lead to the change of the color masterbatch in the injection molding cycle. chromatic aberration.

In this case, the raw material can be sucked into the hopper and then manually stirred to solve it. For the production of colored products by adding toner, the most effective way is not to use a suction process injection molding machine, but to use a hot air dryer, and use manual feeding to prevent the factors affecting color difference caused by the separation of the toner and the masterbatch.