Why Does Plastic Prototypes Have Color Difference ?

During the CNC processing of plastic prototypes, various problems sometimes occur, such as CNC processing defects, uneven color of the prototype, and cracks in the prototype. Today, I will mainly talk about the factors that cause the color of the prototype to suddenly appear during CNC hand-board processing.

The prototype made before was normal, but suddenly the prototype changed color, which is unacceptable. Then the factors that cause the discoloration of the CNC prototype can start from the following aspects:

①Reasons for the mold

1. The mold is not clean, and the dust or other dust deposited on the material causes the material to be polluted and discolored.

2. The thermocouple, thermostat or heating system is out of adjustment, resulting in failure of temperature control. Excessive heat can cause chemical changes, decomposition and discoloration of plastic or pigment components, especially PVC, which is very sensitive to temperature.

3. There are obstacles in the barrel, which can easily promote the degradation of plastics; there are metal foreign objects stuck in the barrel or screw groove, and the continuous grinding will cause the plastic to change color.

②the process reason

1. The screw speed of the CNC lathe is too high, the shear force of the screw is too large, the back pressure of the pre-plastic is too large, and the plastic melting process and the friction of the barrel cause discoloration.

2. The barrel and nozzle temperature are too high, especially for temperature-sensitive materials.

3. The injection pressure is too high, the storage time is too long, and the shutdown time is too long. Plastic materials will decompose and change color, and too fast injection speed will change the color of the product.

③Raw material reasons

1. The material is polluted and mixed with other colors or miscellaneous materials.

2. The raw material has high moisture content and high volatile content, so it should be dried as required.

3. Unreasonable selection of colorants and additives, and discoloration caused by decomposition of temperature-resistant pigments. A reasonable pigment formula should be selected for adjustment.

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