Acrylic thick plate manufacturers tell you the injection molding process of the plate

Acrylic thick plate manufacturers tell you the injection molding process of the plate

1. Processing of plastic

PMMA has a certain water absorption, water absorption rate of 0.3-0.4%, and injection molding humidity should be below 0.1%, generally 0.04%. The presence of water causes bubbles, gas lines, and reduced transparency in the melt. Therefore, it should be dried. The drying temperature is 80-90 ° C, and the drying time is 3 hours or more. Recycled materials can be used 100% in some cases. The actual weight depends on the quality requirements. Usually can exceed 30%. Recycled materials should be protected from contamination, which would otherwise affect the transparency and performance of the product.

2. Selection of injection molding machine

PMMA has no special requirements for injection molding machines. Due to its high melt viscosity, deeper grooves and larger diameter perforations are required. If the strength requirements of the product are high, the long-diameter screw should be used for low-temperature plasticization. In addition, PMMA must be stored in a dry funnel.

3. Mold and gate design

The mold temperature can be between 60-80 ° C, and the main groove diameter should match the inner taper. The best angle is 5~7 degrees. For injection molding of 4 mm and above, the angle is 7 degrees, the main groove diameter is 8 to 10 mm, and the total gate length is not more than 50 mm. For products with a wall thickness of less than 4 mm, the diameter of the runner should be 6-8 mm.

For products with a wall thickness greater than 4 mm, the runner diameter should be 8-12 mm, the gate depth should be 0.7-0.9 t (t is the product wall thickness), the needle diameter should be 0.8-2 mm, the low viscosity should be selected Smaller size.

Generally, the vent hole has a depth of 0.05 and a width of 6 mm, and the draft angle is between 35'-1 and 30~130.

4. Melting temperature

It can be measured by air jet method. According to the information provided by the supplier, the range is 210 270. The rear seat is withdrawn, leaving the injection molding machine nozzle away from the main channel bushing and then manual plastic injection, ie air injection.

5. Injection temperature

Rapid injection can be used, but in order to avoid high internal stress, multi-stage injection should be used when injecting thick parts, such as slow, fast, slow injection.

6. Residence time

When the temperature is 260 ° C, the residence time is no more than 10 minutes, and when the temperature is 270 ° C, the residence time is not more than 8 minutes.