The uncured rubber is fed into the machine in the form of a continuous strip.
The uncured rubber is worked and warmed by an auger screw in a temperature controlled barrel.
As the rubber stock accumulates in the front of the screw, the screw is forced backwards. When the screw has moved back a specified amount, the machine is ready to make a shot.
With the mold held closed under hydraulic pressure, the screw is pushed forward. This forces the rubber into the mold, similar to the action of a hypodermic syringe.
While the rubber cures in the heated mold, the screw turns again to refill.
The mold opens and the part can be removed. The machine is ready to make the next shot, as soon as the mold closes.
Advantages of Injection Molding
- Provides the maximum product consistency
- Allows the most control of flash
- Because the rubber is warmed before going into the mold, fastest cycle times
- Not suited for all compounds
- Most expensive molds
- Typically has some runners or other "throw away" portion in each shot