1、 Causes of black stripes:
1 Thermal Decomposition of materials
2. Screw damage of injection molding machine
Carbonization of materials due to friction and compression of air
2、 Associated knowledge
1. Black bars are most common in the barrel of injection molding machine due to the residue of material decomposition.
In the plunger type injection molding machine, it is easy to leave residue in each part.
3. For the injection molding machine with valve control nozzle, residues are easy to remain in the valve control part.
The air in the barrel is compressed to a high temperature. This high temperature gas plus the shear heat in the gate is easy to form
For the bar.
1 instant: when replacing materials, reduce the injection pressure and the temperature of heating barrel.
2 short term: cleaning of heating barrel (using copper wire brush).
3 long term: repair of barrel.
4、 Due to material differences
1. The pigments, paints, lubricants, UV absorbers and charged preventers in the mixed resin pass through the barrel
The thermal decomposition of these materials is also the cause of black stripes. Especially some kinds of
When the heat resistance of additives is not good, this tendency will be more significant.
When PC is used for molding, black strip is easy to be produced with valve control injection nozzle.
3 the screw with counter current preventing washer is also easy to have scorched residue.
If no special cleaning material is used for material replacement, ordinary soft polystyrene should be used.