University of Nottingham's Metrology department to take over TCT Show Tech stage for special metrology focus.
On day two of TCT Show 2019, 25th September, the University of Nottingham's Metrology department will take over the Tech stage for a session on metrology. Professor Richard Leach and members of his team will present the latest on technologies and practices. Here, Professor Leach discusses the latest trends.
From a metrology point of view, the extra level of design freedom offered by additive manufacturing (AM) with respect to subtractive techniques, results in an extra level of complexity in geometries to be measured; this is why there are so many developments in geometrical metrology for AM and why there are still unsolved measurement issues. These developments are the focus of this session.
Right now, the integrity of metal AM parts essentially made of fused powders is not equivalent to that achievable using more traditional subtractive manufacturing techniques. AM parts made from metal powders are commonly characterised by high surface roughness values and can suffer from undesired material characteristics. Also, where a part would not be manufactured with subtractive techniques without a dimensional tolerance scheme, it is still not clear exactly how to apply tolerance principles to AM parts. AM does not currently have the benefit of the over one hundred years of research into the production of components that is the hallmark of precision subtractive techniques.
The following reasons to measure part geometry remind us why so much effort is devoted to measuring manufactured components – all of these also apply to AM, although in many cases, AM can avoid assembly processes:
- To know whether a part is fit-for-purpose; for example, to determine whether or not a shaft will fit within a hole, but still give enough clearance to allow the flow of lubricating fluids?
- To allow assembly of complex components; without understanding the dimensions of parts and their associated tolerances, it becomes almost impossible to determine whether a part will fit to another – this is an especially relevant point when assembling parts that have been manufactured at different companies or different parts of a company.
- To allow control of a manufacturing process; for example, to change the intensity of a laser depending on the surface texture that it is producing – the texture (or something from which texture can be inferred) needs to be measured during the production process.
- To avoid unnecessary scrap material and redundant processing time; metrology is essential for quality control which allows things such as net-shape manufacturing – getting it right first time.
- To improve energy-efficiency; the fewer repeat manufacturing processes that are required, the lower the energy required to produce a product.
- To give customers confidence in a product; “customers” in this context could be another manufacturing concern that needs to use your components – without tolerances and quality control, there will be a lack of confidence in the assembly processes down the line.
From the metrology standpoint, AM is no different to subtractive manufacturing. But, a lack of integrated metrology in current AM machines and processes is hindering the commercialisation of the resulting products. The last bullet point above is especially relevant in this context. For example, an aerospace manufacturer is not going to “fly” a turbine blade made using AM without the high degree of confidence that metrology can supply.
TCT Show will take place on 24-26th September at NEC, Birmingham. Registration is now open.
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