QMT Features: March 2007
Investing in 3D excellence
The Wolfson School laboratory is one of very few centres of excellence for metrology in British universities. Dr Jon Petzing believes his department has one of the most accurate measuring facilities of any UK university.

Dr Jon Petzing , senior lecturer in metrology at the Wolfson School of Mechanical & Manufacturing Engineering, Loughborough University. Left: Metrology Laboratory manager, Jagpal Singh.

Metrology kicks off
An undergraduate sports project, involving reverse engineering of a football to test for sphericity, being carried out on the Metris LK Ultra 10.7.6 CMM at Loughborough University.

In collaboration with the National Physical Laboratory, tungsten carbide pistons are manufactured by the Wolfson School to within one micron cylindricity, circularity and straightness, which the Ultra CMM is able to measure.
Recent Government funding has boosted Loughborough University’s engineering research and furthered its international reputation for engineering excellence.  £160,000 was allocated to the university’s Wolfson School to upgrade the UKAS-standard dimensional metrology laboratory, with only two thirds of that amount  needed to buy a Metris LK Ultra co-ordinate measuring machine (CMM) from Metris UK.

 Dr Jon Petzing, Senior Lecturer in Metrology,  explains, “We could easily have spent the entire budget and more on a CMM, as we wanted a bridge-type machine capable of sub-micron accuracy.

“However, the Ultra’s price allowed us to buy a dedicated, non-contact CMM as well, and spend several thousand pounds on improving laboratory infrastructure.”

The British-built CMM has a 0.7 micron accuracy statement, although Dr Petzing indicated that 0.5 micron can be achieved in reality. 

The Metris CMM has a small footprint, and while space is currently not at a premium in the laboratory, economising on floor area means there is room to install more equipment.

One application in which the Ultra’s precision is proving useful is in the manufacture of tungsten carbide pistons used in collaboration with the National Physical Laboratory’s primary pressure standard. The Wolfson School is the only academic centre investigating manufacturing, surface characteristics and performance issues of such devices.

Cylindricity, circularity and straightness have to be within one micron, which the previous best in-house CMM was unable to inspect as it was capable of only 3-micron accuracy. In practice, therefore, matched pistons and cylinders were paired by trial and error. Now, full 3D geometrical analysis on the Ultra enables a batch of ten pistons to be machined and inspected so that they are fully interchangeable with three cylinders to a repeatable clearance of less than one micron – an achievement that has not previously been demonstrated.

The main purpose of the metrology equipment in the Wolfson School laboratory is to assist with undergraduate coursework during term time and the research activities of 13 groups throughout the year. Research supported includes automotive and aeronautical manufacture, chemical and electronic manufacturing engineering, sports technology and optical engineering.  The Wolfson School is currently home to two Innovative Manufacturing Research Centres with a combined budget of approximately £20 million.

Most of the Wolfson School engineering degree programmes involve metrology modules that are taught by Dr Petzing and other members of staff.  CAD modelling is an integral part of five undergraduate programmes – Innovative Manufacturing Technology, Manufacturing Engineering & Management, Mechanical Engineering, Product Design & Manufacture, and Sports Technology.  Advantage is taken of the CAMIO CMM software from Metris, which interfaces directly with the Wolfson School’s AutoCad, SolidEdge and UGS NX4 CAD systems.

Once the CAD data is downloaded, it can be used immediately to program the Ultra CMM to inspect the physical component even before it has been manufactured. CAMIO also supports the reverse process, ie analogue scanning as well as discrete point digitising of freeform surfaces to create a design file, if one is not available.  Reverse engineering is also used to acquire information on manufactured components for which electronic data does exist, but where there are issues of consistency in the manufacturing process.

Dr Petzing is considering buying a Metris laser scanning head for non-contact point cloud generation to extend further the CMM’s capabilities.  Irrespective of how the measurement data has been acquired, its analysis is ably supported by the statistical process control package within CAMIO.

The Wolfson School laboratory is one of very few centres of excellence for metrology in British universities and Dr Petzing believes that, with the Ultra, his department has one of the most accurate measuring facilities of any UK university. All the equipment, including articulated-arm measuring machines, non-contact CMMs and a range of surface texture measurement instruments, are available to manufacturing and industrial companies looking to subcontract their inspection. Annual calibration by recognised UKAS bodies, including Metris, ensures traceability and confidence in results.

Dr Petzing concludes, “The LK Ultra CMM covers all of our degree course metrology requirements and over 90 percent of the Wolfson School’s dimensional co-ordinate measurement and inspection requirement in support of research, whereas previously only two-thirds of our needs were catered for in-house.

“Now, only a few activities such as tissue engineering work carried out by the Healthcare group and nano technology projects below the 1 nm scale involve metrology assistance outside of the Wolfson School, although it is often provided elsewhere in the University.” l

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