Cast aluminium is still the most cost-effective method for complex mouldings
Reasons to use
- Still the most cost-effective method for complex mouldings
- Suitable for small- to large-sized mouldings
- Ideal for higher volume applications as multiple cavities can be produced at lower cost
- Can provide a range of surface finishes produced by shot peening, photo-etching, or cast in
- Tools can be modified to accommodate design changes.
Method of manufacture
A model of the product is made (with casting contraction and moulding shrinkage added) onto which epoxy resin is laid-up by hand, to become a reverse pattern. The resulting pattern is then transferred to a foundry where aluminium castings, similar in shape to the pattern, are produced. These castings are subject to machining and other engineering process, to create the finished tool.
There are a number of variations on this theme, such as the direct CNC machining of the patterns, the use of flexible patterns to allow undercuts in the tool, and the use of plaster instead of the usual foundry sand.
Where the quantity of the required rotomouldings suggests that multiple cavities, or moulds are required, the cost of second and subsequent moulds is significantly lower than the original mould.