Causes discoloration is multifaceted, it is:

Equipment:
(1) The equipment is not clean. Dust or other dust deposited on the hopper so that contaminated material discoloration.
(2) thermocouples, temperature control device or heating system disorder caused by the temperature control failure.
(3) barrel obstructions, easy to promote degradation of the plastic; cylinder or screw slot card metallic foreign body, constantly grinding the plastic color.

Molds:
(1) mold venting is bad, the plastic is adiabatic compression, at high temperature react violently with oxygen, burn plastics.
(2) mold gate too small.
(3) feed or in-mold lubricants, release agents too. Necessary regular cleaning cartridge, remove the plastic heat resistance worse than antistatic additives.
(4) the nozzle orifice, sprue and runner size is too small.

Technological aspects:
(1) screw speed is too high, pre-plastic backpressure too.
(2) the barrel, the nozzle temperature is too high.
(3) injection pressure is too high, too long, the injection speed is too fast for the products and discoloration.

Raw materials:
(1) the material is contaminated.
(2) moisture and volatile matter content.
(3) a coloring agent, additive decomposition.

Spots or liquor

The main reason for this defect in equipment and raw materials:
Equipment
(1) barrel has charred material.
(2) barrel cracks.
(3) a screw or plunger wear.
(4) near the hopper dirty.

Molds:
(1) oil cavity.
(2) penetrate the oil from the top of the device.
Raw materials:
(1) raw material dirty.
(2) lack of lubricant.


Charred Obscure
Equipment: After injection of heat-sensitive plastic, barrel or nozzle not clean material mat have resulted in poor exhaust injection begins.

Molds:
(1) Exhaust poor.
(2) improper or small gate gate location.
(3) of the cavity local resistance, so that the exhaust gas stream resulting slow convergence difficulties.

Technological aspects:
(1) barrel, the nozzle temperature is too high.
(2) pre-plastic injection pressure or back pressure is too high.
(3) injection injection period is too long or too fast.

Raw materials:
(1) uniform particles, and containing the powder.
(2) high volatile content of the feedstock.
(3) lubricants, release excessive amount.