injection molding machine manufacturers | Hisson Plastic Machinery Co., Ltd. 

PMMA for injection molding machines

by:Hisson     2020-01-08

1. PMMA treated with plastic has certain water absorption, and its water absorption rate reaches 0. 3-0. 4%, while injection molding must be at 0. The degree of deviation below 1% is usually 0. 04%. The presence of water causes bubbles, Air Lines and transparency in the melt to decrease. Therefore, it is necessary to carry out drying treatment. Drying temperature 80-90 ° C, the time is more than 3 hours. The recycled material can be used 100% under certain circumstances.  The actual weight depends on the quality requirements, usually over 30%.  The recycled material should avoid pollution, otherwise it will affect the transparency and the nature of the finished product. 2. PMMA for injection molding machines has no special requirements for injection molding machines. Because of its high melt viscosity, a deeper screw groove and a larger diameter nozzle hole are required. If the strength of the product is required to be high, the screw with a larger aspect ratio shall be plasticized at low temperature. In addition, PMMA must be stored in a dry hopper. 3. Mold and gate design, Mold temperature can be 60 ° C- 80 ° C, the diameter of the main channel should be matched with the inner taper, the best angle is 5 ° to 7 °, if you want to inject 4mm or more products, the angle should be 7 °, the diameter of the main channel is 8 to 10mm, and the overall length of the gate should not exceed 50mm. For products with wall thickness less than 4mm, the diameter of the runner should be 6- 8mm for products with wall thickness greater than 4mm, the diameter of the runner should be 8- The depth of 12mm opposite edge, fan and vertical gate should be 0. 7/to 0. 9t (T is the wall thickness of the product)The diameter of the needle gate should be 0. 8 to 2mm; Low viscosity should choose smaller size. Common vent holes are 0. 05 to 0. 6mm deep, wide demoulding slope is 30 ′-1 ° cavity part 35 ′-Between 1 ° and 30 °. 4. Melt temperature can be measured by empty injection: from 210 ℃ ~ 270 ℃, depending on the information provided by the supplier. Withdraw the back seat, make the injection molding machine nozzle leave the main channel bushing, and then manually carry out plastic injection molding, which is air injection molding. 5. The injection temperature can be quickly injected, but to avoid high internal stress, multi-stage injection, such as slow-Quick-Slow, etc. , when injecting thick parts, slow is used. 6. Retention time: if the temperature is 260 ℃, the retention time shall not exceed 10 minutes at most;  if the temperature is 270 ℃, the retention time shall not exceed 8 minutes.                                

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