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Alloys promise faster tooling

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Description

A new method for production of injection moulds for prototype and pre-production applications was unveiled at PRW’s Rapid Tooling conference yesterday.The technique has been developed at the UK’s Centre for Rapid Design and Manufacture in High Wycombe.

It uses thin electroformed EDM electrodes created from wax RP models to machine cavity inserts made from controlled expansion (CE) alloys of silicon and aluminium. These, the developers said, are more durable than tooling-grade aluminium but machine much faster.

The process is indirect and uses a Thermojet wax RP negative model created from an STL file as an original. This is then sensitised and electroplated with copper to create a 1mm thick shell. After removal from the model, this is backfilled with a tin/bismuth alloy to produce a durable electrode.

This thin shell electrode is used to cut the cavity in the CE alloy, which EDM machines four times faster than steel. According to process developer Dr David Jacobson, the finished mould inserts are more wear resistant than aluminium and provide thermal expansion rates similar to steel, minimising fitting problems.

Jacobsen said the technique is aimed at detailed electrode applications, which would be lengthy to programme conventionally or require two machining routines. Some mouldmakers at the conference doubted whether the process could produce an electrode faster than conventional high speed machining. However, they showed more interest in the fast machining performance of the CE alloys. These are a spin-off from the electronics industry, especially given their claimed minimal volume price premium over traditional tooling alloys.

Period8/03/2002

A new method for production of injection moulds for prototype and pre-production applications was unveiled at PRW’s Rapid Tooling conference yesterday.The technique has been developed at the UK’s Centre for Rapid Design and Manufacture in High Wycombe.

It uses thin electroformed EDM electrodes created from wax RP models to machine cavity inserts made from controlled expansion (CE) alloys of silicon and aluminium. These, the developers said, are more durable than tooling-grade aluminium but machine much faster.

The process is indirect and uses a Thermojet wax RP negative model created from an STL file as an original. This is then sensitised and electroplated with copper to create a 1mm thick shell. After removal from the model, this is backfilled with a tin/bismuth alloy to produce a durable electrode.

This thin shell electrode is used to cut the cavity in the CE alloy, which EDM machines four times faster than steel. According to process developer Dr David Jacobson, the finished mould inserts are more wear resistant than aluminium and provide thermal expansion rates similar to steel, minimising fitting problems.

Jacobsen said the technique is aimed at detailed electrode applications, which would be lengthy to programme conventionally or require two machining routines. Some mouldmakers at the conference doubted whether the process could produce an electrode faster than conventional high speed machining. However, they showed more interest in the fast machining performance of the CE alloys. These are a spin-off from the electronics industry, especially given their claimed minimal volume price premium over traditional tooling alloys.

References

TitleAlloys promise faster tooling
Media name/outletPlastics & Rubber Weekly
Date8/03/02
PersonsAllan Rennie