Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
Alloys eliminate toxic hazards in die-proofing
Keywords Mining and Chemical Products, Alloys, Dies, Die casting
According to Mining and Chemical Products, toxic lead can be supplanted as a die-proofing medium by its range of safe fusible alloys. Based chiefly on benign bismuth, the alloys also claim to rid the workplace of the toxicity of lead fuming, and reduce melting times and costs.
Additionally, there is said to be no need for the often lengthy and noisy "hammering-in" necessary to correct for shrinkage when proofing with lead.
The company suggests that with their very low melting points (47°C to 150°C), bismuth proofing alloys can be melted and cast more economically and safely than lead, which melts at 327°C. They reportedly produce more detailed proof castings than wax, which is less penetrative, and can be cast more rapidly than epoxy resin, which takes time to cure.
The low molten viscosity and surface tension enable bismuth alloys to flow freely throughout the die cavity before solidifying. Formulated for stability, they are said to result in dimensionally and geometrically faithful reproductions of the cavities in solid form.
According to the manufacturer, alloys can be used to check at several stages of die production. Half-casts can be taken quickly and easily, even when dies have irregular split lines.
In a typical application, dies are paired, strapped together and exits sealed with plasticine to retain the molten alloy. The die assemblies are pre-heated by gas burner and the alloy is melted by ordinary bench equipment and ladled into the pre-heated cavity.
When the dies and alloy have cooled naturally, the pairing is separated and the casting removed for measurement and inspection. The three alloys in the MCP proofing range include a cadmium-free grade. All three can be melted, cast and recovered repeatedly with little alloy wastage, an economy not available with alternatives such as epoxy.
Details available from: Mining and Chemical Products Ltd. Tel: +44 (0)1256 897200.