THINGS to know about MOULD

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.