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Bottle defects and solutions?
The preform is yellow
Reason: Resin thermal degradation or oxidative degradation, but not to the carbonization point
1. Reduce the drying temperature, the maximum drying temperature is 175°C; 2. Check whether the raw material specifications meet the requirements; 3. Confirm that the drying parameters range from 160°C (6h) to 175°C (4h); 4. Reduce the melting temperature to 280°C ± 10 °C; 5. Minimize the % control, because the % control has no feedback; 6. Reduce extrusion back pressure, large extrusion back pressure can make the liquid mix evenly, too small will produce bubbles, ranging from 15 to 20bar; 7. Confirm The screw buffer is not excessive, at least 25mm; 8. Confirm whether the thermocouple and its mechanism are damaged.
Black spots on the preform
Reason: Raw material degrades to carbonization point
1. Reduce melting temperature to 280°C±10°C; 2. Minimize % control as % control does not feedback; 3. Reduce injection speed, range is controlled at 10~12g/s/cavity; 4. Reduce extrusion back pressure, Extrusion back pressure in the range of 15-20 bar; 5. Reduce the screw speed to reduce the shear force, but within the cycle; 6. Confirm the raw material specifications meet the requirements; 7. Check the head for impurities, there is Then remove it; 8. Make sure the thermocouple and its mechanism are damaged.
 
Bubbles on the head of the preform
Cause: Gas trapped in molten material cannot be excluded
1. Reduce the dew point or increase the drying temperature. 2. Verify that the drying parameters range from 160°C (6h) to 175°C (4h). 3. Verify that the melting temperature is within 280°C±10°C; 4. Make sure the melt does not exceed the extrusion screw If exceeding, increase the extrusion temperature or increase the cycle time; 5. Improve the head cooling temperature (minimum 160 °C) 6. Make sure the cylinder is not blocked; 7. Increase the extrusion back pressure; 8. Increase the screw buffer, the screw Buffer at least 25mm; 9. Reduce the return time and position, time = -1s, distance = -10mm; 10. If the use of recycled materials, particles can not be too much; 11. Check the nose for impurities, and then remove it ;
Inside the bottle slightly sunken
Cause: Due to the fact that the preform is still inside the mold, the cooling of the cavity is faster than the cooling of the core, resulting in internal shrinkage after external curing.
1. Make sure that the cooling water temperature is between 7°C and 10°C; 2. Make sure that the cooling water is flowing properly; 3. Make sure the stem is open properly; 4. Make sure that the pressure is enough to open the valve and the pressure range is 8 to 10bar; 5. Reduce the cooling time. Cooling time 1s ~ 3s, determined by the wall thickness; 6. Increase the pressure holding time; 7. Increase the holding pressure; 8. Increase the melting temperature to 280 °C ± 10 °C; 9. Reduce the return time and position, time = -1s , Distance = -10mm; 10. Make sure that the mouth of the mold is clean and tidy, and the exhaust can be smooth; 11. Make sure that there is no condensation water and the dew point needs to be cooler than the cooling water temperature.