MOULD
|
To know about |
Assembly of
mould – elements of mould, |
·
Assembly of various plates, function of these plates in
the mould. ·
Elements of moulds are Sprue bush, Locating ring, Runner,
Gate, Fixed halve and moving half, Core and cavity, Ejector pins, Return
pins, Sprue puller, Ejector Plate / rod, Cooling channels, Guide pins,
Locating plugs, Back plate, Spacers. |
Classification and distinction of moulds, |
·
Based on parting lines, ·
Ejection system, ·
Heat exchange system, ·
Transmission of forces |
Feed system in mould - Sprue / runner size balanced type, |
·
Functions of runner system, ·
Circular, series, symemmetrical layout, ·
Factors affecting runner system, Demands on runner
system. |
Gate classification, location,
size and type, |
·
Runners – remain with moulding, ·
Runners – cutoff automatically, ·
Runners –automatically separated from part but remains
with mould. |
Air vent, |
Rate of total air expulsion from the mould due to speeding
melt front in all direction can not be less than injection rate. |
Wall thickness uniform and
capable of promoting balancing of melt flow |
·
Familiarise with plastics PART DESIGN. It has to be
over 90% mouldable shape. ·
Familiarise with MOLDFLOW analysis. |
Balancing
of flow in un-symmetric
part geometry, |
Flow leader or flow deflector techniques are to be used for
balancing of melt flow inside the part geometry so that moulded-in stress is
avoided. |
Mould mechanism |
For split cavity, unscrewing part, etc.
Stripper plate, stripper sleeve etc. |
Mould release. |
·
Surface finish, ejection mechanism, ·
Overpacking in some regions can make it difficult to
eject. |
Mould steel, |
Essential characteristics for mould steel, Heat treatment, Cost of steel is about 20% of cost of mould. |
Cooling system and heating system |
·
Objective of mould cooling, ·
Design of cooling channel, |
Mechanical life of mould – fatigue in mould. |
·
Understanding of FATIGUE in mould. ·
Thickness of plates to be generous so that shut mould
height is with in the specification of machine on which the mould is intended
to run on production. |
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