The melt viscosity of the PVC pipe production line is high, so a higher injection pressure is adopted.
1. For large and thin-walled ones, the injection pressure should be large;
2. For the parts to be electroplated, sprayed or decorated, the injection pressure should be moderate;
3. For small and thick-walled ones, the injection pressure should be lower.
If too fast, it is easy to cause B particles to burn or decompose and precipitate vapor. This can lead to obvious fusion joints, poor gloss, and redness in the sprue area. For injection molding of large thin-walled parts, it is important to ensure a high enough speed.
The mold temperature is individually 75 to 85°C. When molding plastic parts with a large projection area, the temperature of the fixed mould should be about 20°C higher than the temperature of the moving mould.
Gates for PVC production line parts should not be needle-shaped gates, especially if high quality is required. For plastic parts that need to be plated, the gate should be round, not trapezoidal or semi-circular.
A stress test should be done on the plastic part before plating. This is usually done by immersing the plastic part in glacial acetic acid for 30 seconds or 2 minutes, removing it, and rinsing it with clean water to see if white spots appear; if white spots or even white lines appear, this indicates the presence of stress. Such a plastic part may be solved by heat treatment.
Heat treatment standard: heating to 75-85°C, 2-4 hours, air cooling. If the stress is not removed, the plating layer will blister and peel.
In actual use, sometimes some larger shells also produce deformation or cracking, either because of structural design problems, the mould has been manufactured and it is very difficult to modify, or because of the improper opening of the gate, or because of excessive injection pressure.
To weigh up the pros and cons, due to factors such as schedule and cost, the stress of the plastic parts of the PVC pipe production line can also be solved by adopting the heat treatment standard of electroplating plastic parts.
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