Injection molding machine products shrink, how to solve?
Injection pressure, holding pressure, speed, back pressure, temperature, glue content, inlet and die temperature
The working principle of injection molding machine and injection syringe with similar, it is the use of screw (or piston) thrust, the plasticizing good molten state (i.e. viscous flow) plastic injected into the mold cavity closed good after curing stereotypesmade the process of the products. Injection molding is a cycle process, each cycle mainly includes: quantitative feeding - melt plasticization - pressure injection - mold cooling - die opening pieces. Take out the plastic parts and then close the die for the next cycle. Action procedure: die, pre molding, pour, retract, nozzle (nozzle forward), injection, pressure protection, nozzle (back of nozzle), cooling, mold opening, ejecting, opening, taking the workpiece, closing the door, closing the mould, closing the mould, closing the mould, closing the door, closing the mould and closing the mould.Product shrinkage problem, if it does not involve other reasons, only injection molding process, the holding pressure is the most critical factor. Is the purpose of holding pressure when the screw after the injection, and exert a certain strength to the screw is held in place for a period of time, namely after injection and then squeeze some material into the cavity and prevent plastic reflux is not solidified completely to shrink. Keep the pressure big, the density of the plastic in the cavity is big, the surface is smooth and full. Shrinkage is positively related to size. Position, pressure, speed, the relationship between the three is connected, and in the adjustment of the machine should be based on the size of the product, the location of glue points, methods, raw materials, types and so on. For example, PC material, poor liquidity, injection molding must use high speed, high pressure, or easy to fight. And nylon or PP, the speed is too fast, the lack of mold exhaust, it is easy to generate coke.
