How does injection molding work?
A plastic filling granulate mixture (plastic pellets, colorant or recycled material) is fed into the hopper. The hopper is a tank that supplies the injection molding machine with the pellets, while also ensuring plastic material is moisture free.
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Next the pellets flow from the hopper to the barrel, where the heating elements and the reciprocating screw are found. The pellets are caught within the flights of the screw and are pushed forward as the screw rotates. The screw also pushes the pellets along the sides of the barrel, which creates the friction needed to melt the plastic. Additional heat is supplied by the heater bands.
The molten mixture is then pushed to the front of the screw through flutes, which are indentations on the screws tip. The front of the screw also acts as a plunger. When there is enough plastic in front of the screw, the screw pushes forward forcing the molten material into the molds. The molten plastic cannot flow backwards through the flutes, as a check ring acts as a one-way valve.
The molten material then fills the mold, forcing air out. The air escapes through tiny vents which are too small for the plastic to escape.
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The plastic material cools (with help of coolant or water) and the mold is opened. Ejector pins then push the plastic unit out of the mold.
Any excessive plastic is then ground down to complete a full closed loop solution to minimize waste. This computer controlled system automatically repeats to produce large unit quantities at high speeds and accuracy.
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