ONLY a select few engineering firms today have the finishing and analysis capabilities to create the ultra tight tolerance parts required by many high-tech industries.
Where parts must fit extremely close, even very slight changes in a component’s surface finish can significantly affect performance. Achieving the right surface requires not only high calibre finishing equipment, but test equipment able to confirm geometry and roughness to the angstrom level (one angstrom is equal to 0.1 nanometers). Such equipment can cost tens of thousands of dollars.
Surface finish requirements have become increasingly stringent in recent years, leaving a wide range of manufacturing opportunities available to just a limited number of capable companies. Graeme Foulds is area sales manager for one of the world’s leading surface analysis equipment providers, Taylor Hobson, and explained some of the reasons for the tightening requirements.
“Possibly the one demand which impacts us most at the moment is the drive to lower CO2 emissions. In order to lower emissions, engines need to run more efficiently. One important factor in their efficiency is the fuel supply system. Suppliers of fuel systems, from pumps through to injector nozzles, are thus demanding tighter tolerances and more accurate measurements,” Foulds told FEN.
The optics industry has also driven surface finish requirements to new levels, Foulds reported.
“Applications include head-up displays and infra red sensors. The form accuracy and low surface finish values required to manufacture good quality optics has driven the need for larger range, improved form accuracy and very low noise metrology instruments.”
State-of-the-art surface analysis instruments today are able to measure both large and small components with equal accuracy, using a measuring head with a large Z range and typically, resolution of less than 1nm. They come with traverse units up to 200mm in length, featuring straightness values less than 150nm over the full traverse length. To enable the measurement of very smooth surfaces, a quality machine keeps residual mechanical and electronic noise in the region of 1nm. It is also able to accurately calibrate a majority of the gauge range, ensuring linearity. Foulds recommended the first choice for a laboratory surface finish instrument should encompass all of these features.
Melbourne firm, Rosebank Engineering, is one company to have invested in state-of-the-art Taylor Hobson surface analysis equipment. The equipment is critical to Rosebank’s work in the aerospace industry, according to general manager Craig Butler.
“In aerospace we typically deal with a lot of close tolerance requirements. Although you can measure a part with a micrometer or some similar device and it will give you a size, that size doesn’t take into account the roughness of the surface and how much that varies. When you’ve got parts that are fitting closely together, you need a good mating surface so that there aren’t a lot of peaks that wear off, or so that the surface isn’t so rough it starts to wear parts and cause them to fail early. It’s important to have a finish which aligns with the designer’s intent for the functioning part,” Butler told FEN.
There was a time when Rosebank only used handheld shop floor devices for surface measurement, but as requirements became more stringent it became necessary to invest in higher level laboratory machines. Butler explained the difference.
“Our laboratory machines can measure to a much higher resolution. A lot of the new surface analysis machines from the likes of Taylor Hobson have resolutions down to the angstrom level, so you can pick up much more detail on a part. Typically they can measure bigger features. For example, the standard handheld shop floor instrument probably only has a measuring range length of 20mm, whereas laboratory instruments can have anywhere up to 200mm of travel. You can also measure in 3D and look at a part’s complete form, including radiuses and heights and a lot of geometric features you can’t measure with a handheld instrument,” Butler said.
It was Rosebank’s combination of precision finishing and surface analysis equipment that recently put it in top spot to manufacture piston rods for the JSF project, according to Butler.
“The particular JSF part was previously ground and measured in the UK, however their measurement equipment wasn’t good enough to measure all of the parameters the designer required. The work came to us because we had the measuring equipment combined with the grinding machines to develop the process to finish these particular piston rods. If not for our capability the work would have gone offshore,” Butler said
Rosebank is in the unique position of not only being a user of Taylor Hobson equipment, but also the brand’s representative in Australia. In theory, the arrangement means Rosebank could be selling to its competitors the very equipment on which it has built its own advantage. Butler however, sees no direct threats to Rosebank’s own niche capability. He emphasised the tremendous advantage such equipment could bring to Australian industry as a whole.
“If we want to stay competitive and differentiate ourselves from the mass producers of the world, we need to understand this kind of technology and the advantages it can bring. If we want the industry to be stronger we’ve got to have this capability in our country,” he said.
While the cost of a laboratory surface finish instrument may seem high, a number of leading international high-tech manufacturers can testify to its value. Graeme Foulds explained their reasoning.
“The cost of this equipment can be easily justified when considering the implications of producing scrap components, especially where the raw material or high labour content makes the components very high value. In the case of suppliers, many of the purchasing companies demand proof that components meet the stated surface finish specifications,” Foulds said.
If Australian industry and government are indeed serious when they talk about building a large part of the nation’s manufacturing future on high-tech industries, surface analysis capability will be critical. This is still something Australian manufacturers are yet to realise, according to Butler.
“One of the things we’ve found is that people don’t appreciate what they need to do to comply with a lot of the surface finish requirements in today’s designs and they don’t look at that in advance when doing quotes or establishing capability. The parameters we see in drawings today differ from standard practice years ago when people could assess surface finish much more simply. Companies need to be aware of what the technology is now doing in this area,” Butler said.
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