Page 125 - Module DMV20173

6.0 POLYMER PROCESSING

2. The method of operation of a compression molding process is as follows:

 Into the bottom half of a die is placed a measured amount of material.
 There has to be a slight excess of material required to make the product, to
ensure complete filling of the mold.

 This gives rise to a certain amount of flash or excess material that squeezes out
of the die closing line.
 The two half molds are then closed and the heated molds cause the plastic resin
to polymerise.

 Once the crosslinking ("curing") is completed the component is solid and can be
ejected whilst still hot.
 The mold opens and the component is ejected and removed from the mold.

 The mold is then cleaned to remove the flash and spilt plastic resin by
compressed air, ensuring a clean mold ready for the next plastic resin charge.
 Normally the patterns are heated by electric heaters, although steam has been
used.

6.5 TRANSFER MOLDING

(a)

(b)
Figure 6.10 (a)Transfer mould (b) Sequence of transfer moulding process.

BPLK 157 DME 1083