MATERIALS • PROCESSES
fabrication they tend to have longer fatigue lives and allow more deformation without sudden failure. Switching from fabrications and assemblies to castings can also deliver a number of manufacturing benefits. For most manufactured components, consistency is vitally important. Fabricated assemblies are susceptible to human error; many variables can be introduced, such as missed welds, inadequate weld joining material, pin holes in weld joints and inconsistency in weld beads or process. Cast components have consistency built in: once the pattern is set, every casting is uniform, so human error can be eliminated as a source of inconsistency.
Cast components can reduce weight, cost and wastage compared to fabrications
This contrast becomes even more apparent as
production volumes increase. Achieving economies of scale is difficult with fabricated assemblies as the same process needs to be repeated for each assembly using similar materials and labour. The casting process, however, delivers significant economies of scale once the mould or die has been created. Stripping out many process steps by switching to castings will also speed up the production process. Finally, design is often an important consideration.
More aesthetically pleasing designs are possible using castings as designers can include unique shapes, features and curves. In the past, the realisation of this potential called for outstanding casting geometry design expertise and experience because shape optimisation calls for complex three-dimensional modelling. In more recent years, however, powerful 3D modelling programs and casting simulation software have allowed design engineers to quickly produce solutions featuring continuously varying section geometry that fully utilises material strength while also satisfying stress and deflection requirements. Whether a switch from a fabricated assembly to
Gravity die casting can deliver performance, aesthetic and financial advantages over fabrication
One obvious way to reduce inconsistency is to
improve the training and skill levels of production staff involved in fabrication and welding. Clearly, there is a cost to train, maintain and retain a highly skilled workforce. Casting, by contrast, often requires lower- skilled personnel using more automated production processes.
a single cast component is going to be feasible and whether it will deliver the desired cost, lead time and performance improvements will depend on many considerations, not least of which are the castability of the redesigned component and the production run length. By working closely with foundry engineers experienced in structural geometry, such as NovaCast, it is possible to fully evaluate and fully cost this kind of project and to realise the considerable benefits conversion can deliver. l
Richard Phillips is with NovaCast.
www.novacast.co.uk
www.engineerlive.com 35
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