Teach you how to control the color difference of injection products

Release time: 2021-06-16

Color difference is a common defect in injection molding. It is not uncommon that the injection molding machines are scrapped in batches due to the color difference of parts. There are many factors affecting color difference, including raw resin, color masterbatch (or color powder), mixing of color masterbatch with raw materials, injection molding process, injection molding machine, mold, etc. Because of the wide range of pulling surface, the color difference control technology is also recognized as one of the difficult technologies in injection molding. In the actual production process, we generally control the color difference from the following six aspects.


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


To select the injection molding machine with the same capacity as the injection molding product, if the injection molding machine is in the dead corner of the material and other problems, * replace the equipment. For the color difference caused by the mold pouring system, exhaust groove, etc., it can be solved by the maintenance of the corresponding part of the mold*** First of all, to solve the problem of injection molding machine and mold can organize production, in order to reduce the complexity of the problem


2. Reduce the impact of injection molding process adjustment


When the injection molding process parameters need to be adjusted for non color difference reasons, the injection temperature, back pressure, injection cycle and the amount of Color Masterbatch should not be changed as much as possible. At the same time, it is necessary to observe the influence of process parameters change on the color. If color difference is found, it should be adjusted in time.


Avoid the use of high injection speed, high back pressure and other strong shear effect of injection molding process as far as possible, prevent the color difference caused by local overheating or thermal decomposition and other factors, strictly control the temperature of each heating section of the barrel, especially the nozzle and the heating part only relying on the nozzle.


3. Eliminate the influence of uneven mixing of masterbatch and masterbatch


The poor mixing of plastic masterbatch and masterbatch will also make the color of the product changeable. When the masterbatch and masterbatch are mechanically mixed evenly and fed into the hopper through the lower suction, the masterbatch and masterbatch are separated due to electrostatic action, so as to be adsorbed on the hopper wall, which is bound to cause the change of the amount of masterbatch in the injection molding cycle, resulting in color difference.


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


Before adjusting the color difference, we should also know the change trend of product color with temperature and color masterbatch. With the change of temperature or amount of Color Masterbatch, the color change law of products is different. It can be determined by the color test process


It is impossible to adjust the color difference quickly, especially when the new color masterbatch is used.


5. Reduce the influence of barrel temperature on color difference


In the production, it is often encountered that the temperature of the barrel changes dramatically due to the damage and failure of a heating ring or the runaway long burning of the heating control part, resulting in color difference. It is easy to judge the color difference caused by this kind of reason. Generally, the color difference caused by the damage and failure of the heating ring will be accompanied by the influence of uneven plasticization. The uncontrolled long burning of the heating control part is often accompanied by the product color spots, serious discoloration and even coking. Therefore, the heating part is often checked in production, and the heating part is replaced and repaired in time when it is found that the heating part is lost or out of control, In order to reduce the probability of this kind of color difference


6. 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 color products, the obvious influence of different thermal stability of raw resin on the color fluctuation of products should not be ignored.


Copyright:Henan JinXin 2021