Analysis of Reasons of Black Spots in White Injection Molded Parts
The occurrence of black spots in white injection molded parts is a common quality issue that significantly affects the appearance and overall quality of the products. The causes of black spots are diverse and can generally be categorized into the following types:
1. Raw Material Issues
Impurities in Raw Material: Contaminants or foreign particles mixed into the raw material can result in black spots during the injection molding.
Moisture or Oxidation in Raw Material: Undried raw materials are prone to decomposition or oxidation at high temperatures, leading to the formation of black substances.
Uneven Mixing: Inconsistent mixing of materials may cause localized overheating, leading to decomposition byproducts.
2. Equipment Issues
Aging or Worn Screw and Barrel: Prolonged use of equipment can result in oxidation layers or residues on the surfaces, which may flake off during processing and form black spots.
Abnormal Heating System Temperatures: Excessively high or low temperatures in localized areas can cause raw materials to decompose or adhere to the barrel walls, eventually forming black spots.
Mold Contamination or Wear: Dirt, oxidation, or damage inside the mold cavity can also lead to black spots.
3. Process Issues
Excessive Processing Temperature: Overly high temperatures can cause raw materials to decompose, resulting in black residues.
Prolonged Downtime: Materials left heated in the barrel for extended periods will likely decompose and form carbonized residues.
Unstable Injection Cycles: Fluctuating injection cycles may result in inconsistent material heating, leading to prolonged or uneven heat exposure and the formation of black spots.
4. Environmental and Operational Issues
Environmental Contamination: Dust or foreign particles from the processing environment may enter the mold or raw materials, causing black spots.
Incomplete Cleaning of Equipment: Residual old material or contaminants left in the equipment during material changes or cleaning processes can pollute new raw materials and result in black spots.
