October 25, 2020

What are the “culprits” that cause discoloration of injection molded products? How should this problem be solved?

Equipment aspect

(1) The equipment is not clean. Dust or other dust deposits on the hopper to contaminate the material.

(2) Temperature control failure due to thermocouple, temperature controller or heating system imbalance.

(3) There are obstacles in the barrel, which tends to promote the degradation of plastics; metal foreign objects are stuck in the barrel or the screw groove, and the plastic is continuously ground to discolor the plastic.

Mold aspect

(1) The mold is poorly exhausted, the plastic is adiabatically compressed, reacts with oxygen at high temperature and high pressure, and burns the plastic.

(2) The mold gate is too small.

(3) Too much lubricant or mold release agent in the material or in the mold. If necessary, the cylinder should be cleaned regularly to remove additives such as antistatic properties that are inferior to the heat resistance of plastics.

(4) The size of the nozzle hole, the main flow path and the branch passage are too small.

Process aspect

(1) The screw speed is too high and the pre-plastic back pressure is too large.

(2) The temperature of the barrel and nozzle is too high.

(3) The injection pressure is too high, the time is too long, and the injection speed is too fast to cause discoloration of the product.

Raw material

(1) The material is contaminated.

(2) High moisture and volatile matter content.

(3) Decomposition of coloring agents and additives.

Black spot or black liquor

The main reasons for this defect are in equipment and raw materials:

Equipment aspect

(1) There is a blackened material in the barrel.

(2) The barrel has cracks.

(3) The screw or plunger is worn.

(4) The vicinity of the hopper is not clean.

Mold aspect

(1) There is oil in the cavity.

(2) Infiltration of oil from the ejector.

Raw materials:

(1) The raw materials are not clean.

(2) Insufficient lubricant.

Burnt dark lines


After the injection of heat sensitive plastic, the barrel is not cleaned or there is a mat at the nozzle that causes the exhaust to be poor at the beginning of the injection.

Mold aspect:

(1) Poor exhaust.

(2) The gate is small or the gate is not in the proper position.

(3) The local resistance of the cavity is large, which makes the exhaust of the flow slower and makes the exhaust difficult.

Process aspect:

(1) The temperature of the barrel and nozzle is too high.

(2) The injection pressure or pre-plastic back pressure is too high.

(3) The injection speed is too fast or the injection cycle is too long.

Raw materials:

(1) The particles are uneven and contain a powder.

(2) The volatile content of the raw material is high.

(3) Too much amount of lubricant and mold release agent.

Scomi Prima 3g Shaker Screen

Steel Frame Shaker Screen for Scomi Prima 3G Shale Shaker

SJ-Scomi Prima Shaker Screen, also commonly called Scomi prima 3G/4G/5G screen, refers to the replacement screen for Scomi Prima series shale shakers. The main shaker models are including SCM-PrimaG 3P/4P/5P linear motion shale shaker and SCM-PrimaG 4PDD cascading shale shaker. Screen quantity correspondingly varies by the different shaker models. The whole screen cloth is divided into independent small surfaces by rectangle perforated holes to prevent the part excessive expansive damaged.

Technical Parameter

  • Mesh Material: stainless steel 304/316/316 L.
  • Frame Material: Q235 steel.
  • Screen Type: XL, XR.
  • API RP 13C Designation: API 20 – API 325.
  • Package: packed in paper carton, shipped by wooden case

Adaptable Shale Shaker Model

SJ-Scomi Prima 3G Shaker Screen are used as the substitute screen for

  • SCM-PrimaG 3P linear motion shale shaker (3-panel).
  • SCM-PrimaG 4P linear motion shale shaker (4-panel).
  • SCM-PrimaG 4PDD cascading shale shaker (4-panel).
  • SCM-PrimaG 5P linear motion shale shaker (5-panel).

Competitive Advantage

  • 100% interchangeable with OEM brands screen panel size.
  • SS 304/316 wire mesh cloth, triple layered sandwich construction.
  • Bonded to perforated panel, rugged structural support.
  • Manufactured according to the API RP 13C (ISO 13501).
  • Scientific & reasonable cost control system for competitive price.
  • Adequate inventory in the shortest time to meet customers' demand.


Scomi, SCM-PrimaG 3P, 4P, 4PDD, 5P are marks of Scomi equipment INC.

ShengJia only produces the replacement screens but not original from Scomi.


Scomi Prima 3g Shaker Screen

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