Page 117 - Module DMV20173

6.0 POLYMER PROCESSING

11. Cavity meant that the pressure in the mold could be monitored and used to control the

machine.
12. The means that mold filling speed and mold pressure can be controlled to give a better
quality control of the component and ensure density control of the part as well as

ensuring the component does not flash.
13. The use of microprocessors now means that once the parameters are known for the
production of a component the set up operation can be automatically adjusted when the
component is put on the machine again.

6.2.7 MOLDING CYCLE

1. Granules or pallet of plastic powder (Figure 6.3) are poured or fed into a hopper, a large

open bottomed container, which feeds the granules down to the screw.
2. A heater heats up the tube and when it reaches a high temperature a screw thread
starts turning.
3. The screw is turned by hydraulic or electric motor that turns the screw feeding the
pellets up the screw's grooves.

4. As the screw rotates, the granules are move forward along the heater section that melts
then into a liquid.
5. The heated plastic is forced under the pressure of the injection screw to take the shape
of the mold by filling inside mold cavity.

6. Holding time, reduce and maintain the pressure at the hold value while the plastic cools.
The water-cooling channels assists in cooling the mold and the heated plastic solidifies
into the part.
7. The cycle is completed when the mold opens.
8. The part is ejected with the assistance of ejector pins within the mold.

Figure 6.3 Plastic granule.

BPLK 149 DME 1083