Color difference problem and control of barrel screw products?

Screws are mostly used in plastic molding equipment, such as extruder barrel screw applications, plastic profile extruders, injection molding machines, and so on. The screw and barrel are the core parts of plastic molding equipment. It is the part of heating extrusion plasticizing. It is the core of plastic machinery. Widely used in machining centers, CNC machines, CNC lathes, injection molding machines, wire cutting, grinding machines, milling machines, slow walking wire, fast walking wire, PCB drilling machines, precision engraving machines, engraving and milling machines, spark discharge machines, biting machines, planing machines, large-scale vertical lathe gantry milling machines and so on.

Chromatic aberration is a common problem in screws. Chromatic aberration is also known as discoloration and poor luster. Chromatic aberration is a common defect in the barrel screw, and the impact of barrel screw chromatic aberration factors are more than, which involves the material resin, injection molding machine, injection molding process, masterbatch, masterbatch with the mixing of the material, and so on. Color difference is a common defect in injection molding, color difference affects many factors. So can the color difference of the barrel screw products be controlled within the prescribed range, how to control it? See the following explanation.

In the actual operation process, barrel screw color difference we can generally go from five directions to the control, the specific mode of operation:

  1、Cut the impact of injection molding process adjustment

Non-color difference reasons need to adjust the injection molding process parameters, as far as possible, do not change the injection temperature, back pressure, injection cycle, and masterbatch addition, in the adjustment at the same time also needs to investigate the impact of changes in process parameters on the color, such as the discovery of the color difference should be adjusted promptly. As far as possible avoid the use of high injection speed, high back pressure, and other causes of the strong shear effect of the injection molding process, to avoid part of the overheating or thermal differentiation and other elements of the formation of the color difference. Strictly control the temperature of each heating section of the barrel, especially the nozzle and the heating part immediately adjacent to the nozzle.
  2、Eliminate the influence of injection molding machines and mold elements

Select the appropriate specifications of the injection molding machine, injection molding machine to solve the existence of material dead space and other issues; production needs to be frequently checked in the heating part of the damage or out of control promptly to replace the heating element to reduce the chances of color difference; to ensure that the injection molding workshop, the injection machine, the mold is clean; to adjust the appropriate screw plasticizing speed.

Through the corresponding part of the mold maintenance, to solve the mold casting system, exhaust tanks, and other problems caused by chromatic aberration;

  3、Cutting the influence of barrel temperature on color difference

Production is often encountered due to a heating ring damage failure, or heating control part of the runaway long burn formed cylinder temperature drastic changes and then color difference. This type of reason for the color difference is easy to determine, general damage to the heating ring failure occurs at the same time the color difference will be accompanied by the phenomenon of uneven plasticization, while the heating control part of the uncontrolled long burning is often accompanied by the product gas spot, serious discoloration, and even coking phenomenon. Therefore, the production needs to often check the heating part, and find that the heating part is damaged or out of control in timely replacement and repair, to reduce the incidence of such color differences.

  4、Eliminate the influence of material resin, color masterbatch
Control of raw materials is the key to completely solving the color difference. Therefore, especially in the production of light-colored products, we can not ignore the thermal stability of the material resin and different color fluctuations on the products brought about by the significant impact. Given the majority of injection molding manufacturers do not produce their plastic masterbatch or masterbatch, the focus of attention can be placed on production management and raw materials inspection.

That is, to strengthen the inspection of raw materials in the warehouse; production of the same product as far as possible to use the same manufacturer, the same trademark masterbatch, and masterbatch production; on the color masterbatch, we have to carry out sampling before the batch production test color, both with the previous calibration, but also in the comparison, if the color difference is not too big, it can be regarded as qualified, such as the same batch of masterbatch color difference is slight, can be masterbatch from the beginning of the mixing and then used to cut down on the masterbatch itself mixed unevenly The color difference is formed by the uneven mixing of the masterbatch itself. In addition, we also need to focus on checking the thermal stability of the material resin and color masterbatch, on the bad thermal stability, we suggest the manufacturer change.

  5、Master the molding process to reduce the color difference

Master the barrel temperature, the amount of masterbatch on the product color changes, through the color process to determine the pattern of change; to avoid local overheating and decomposition of the material caused by the color difference, strict control of the barrel temperature of the heating section, especially the nozzle and the nozzle immediately adjacent to the heating part; injection speed is too high, reduce the injection speed: the use of multi-stage injection: fast - slow; reduce the injection pressure and the back pressure of the screw pre-molding, to prevent overheating of the shear.