How to solve the problem of black bars in injection molded products?
Reasons for black bars in injection molded products
1. Thermal decomposition of materials
2. Damage to the screw of the injection molding machine
3. Carbonization of materials due to friction and compression of air
Related knowledge
1. The most common black streaks produced by the residue of material decomposition remaining in the barrel of the injection molding machine.
2. In the plunger injection molding machine, residues tend to remain in various parts.
3. Injection molding machines with valve-controlled nozzles are prone to residue residues in the valve-controlled part.
4. The air in the barrel is compressed to a high temperature. This high-temperature gas combined with the shear heat at the gate can easily form black bars.
Solution
1. Immediately: When replacing materials, reduce the injection pressure and reduce the temperature of the heating barrel.
2. Short term: cleaning of heating barrel (use copper wire brush).
3. Long term: barrel repair.
Due to differences in materials
1. The pigments, paints, lubricants, ultraviolet absorbers, antistatic agents, etc. in the mixed resin are overheated in the barrel. Thermal decomposition of these materials when retained for a long time is also the cause of black streaks. Especially when certain types of additives have poor heat resistance, this tendency will become more obvious.
2. When molding with polycarbonate (PC), it is easy to produce black streaks with a valve-controlled nozzle.
3. Screws with backflow prevention washers are also prone to burnt residue.
HUATAO provides blow molding equipment. Including:
Plastic Mold Equipment
Automatic Blow Molding Machine
Semi-automatic Blow Molding Machine
PS Foaming Machine
EPE Foaming Machine
PU Foaming Molded Machine
Horizontal lnjection Molding Machine
vertical lnjection Molding Machine
All-electric Injection Molding Machine
Thick Sheet Blister Machine
Thin Sheet Blister Machine
Color Plastic Masterbatch
Plastic Recycle Machine
Whether you need help with equipment selection, process optimization, or design customization, our team can help. We have the expertise and knowledge to analyze your project needs, identify challenges and develop innovative solutions.