How to chose correct injection mould?

plastic mold
plastic mold

How to choose correct injection mould?

Injection mould design types and configurations vary enormously due to the many technical requirements of the moulded components to be produced.

For this reason, the categorisation of mould tool type can only be generally applied.

Of all the mould configurations employed, the two- plate and three-plate mould designs are the most easily recognisable in appearance.

The two- and three-plate designs owe their names to the number of split or parting lines employed within the tool design. Figure 1. illustrates the significance of split line position with respect to the individual mould designs.

The two- and three-plate designs form the basis for many variations on their basic design format. The following are examples to illustrate how they may be employed:

Figure 1. The significance of split line position with respect to individual mould designs.

plastic mold structure
plastic mold structure


fig 1.

  • Runnerless moulds

more frequently referred to as hot runner moulds, in which the material feed system remains molten throughout the entire moulding cycle,only freezing off at the gate of the moulding prior to ejection from the mould.

  • Undercut moulds

which produce components whose features undercut the mould cavity or core components in such a manner as to require core pulling or feature removal prior to mould opening or ejection.

  • Family moulds

in which many different components are manufactured within the same tool, e.g. model kits, kitchen utensils, etc. Family moulds are often employed on short run,relatively low volume ranges of components to reduce tooling costs.

  • Stack moulds

Stack moulds in which the impressions are stacked either side of the mould centre plates, often used on vertical moulding machines for compression moulding purposes, e.g. the manufacture of insert loaded components,records, sinter moulded components made in PTFE, etc

Choosing the correct mould

Choice of mould design and construction method is determined by the number of factors and requirements imposed on the tool designer. Mistakes can easily be made if all the relevant factors and requirements are not obtained and considered beforehand. A good mould designer will obtain
as much information as possible about the following:

  • Component:

obtain the final signed-off drawing issue from the prospective customer. Obtain commercial information regarding the component, e.g. component cost,size of required production batches, the estimate of production cycle time acceptable to the customer,mould life requirement, etc.

  •  Material to be processed:

obtain information on material properties, e.g. shrinkage,cooling requirement,rheological features ,thermal stability, etc.

  •  Machine data:

obtain a machine specification

Mould specification

The use of a mould specification has a number of advantages to the mould designer in terms of reducing the likelihood of unnecessary mistakes occurring and building up the designer’s background knowledge of related subjects.

A good mould specification also provides the mould designer with the basis for a quality control system for customer auditor approval requirement thus increasing customer confidence, a factor of importance with respect to further order placements.

The easiest way of compiling a mould specification is by the use of a standard formatted form with all the required information laid out in a logical sequence.