Attached
Nowadays commodities of thermoplastics are often produced to tight dimensional
standardsto facilitate assembly with other components used in electrical, electronic and
mechanical applications such as sockets and adapters. In Sri Lanka variety and quantity
of plastic parts are produced and used for several applications.
A systematic study on the effect of processing conditions on mould shrinkage was
undertaken for some semi crystalline and crystalline plastic materials such as Poly
Properlene (PP), Polyamide (Nylon 6 or PA6), PolyOxymethalene (POM), Poly Butalene
terepthalate (PBT) and PBT with Glass fibre 20% (PBT GF20).
According to this study, it was found that holding pressure and holding time were the
most effective parameters. The effect of the melt temperature and mould temperature
exhibits less important. Injection pressure shows linear effect on shrinkage and cooling
time and Injection speed has small effect on part shrinkage.
GlassFiber filled PBT resin shows anisotropic behaviour. In-flow shrinkage is very less
and cross-flow shrinkage is very much closer to that of unfilled material. Only the
orientationof fiber reduces the shrinkage.
