The Werth Tomoscope is the world's first integration of computed tomography into a multi-sensor co-ordinate measurement machine (CMM). Such technology opens up new measurement possibilities for manufacturers by allowing quick, complete and non-destructive inspection of most features with CT, combined with the exact measurements of external dimensions by classical sensors, such as physical probes, plus laser and optical sensors.
Image: Werth Tomoscope
Computed Tomography, an X-Ray process originally used for medical technology, was previously considered insufficient for functional dimension inspection. However, when CT technology is combined with the accuracy of a multi-sensor CMM, it becomes possible to make rapid acquisition of all workpiece measurements by mathematical correction.
HOW DOES IT WORK?
CT works by placing a workpiece on a revolving stage and rotating it through 360°, while 2D X-Ray images are taken at several orientations, measuring the sizes, angles and diameters of the structures inside the part. The scanner processes the CT measurements, and quickly constructs a 3D image of the measuring points depicting the entire workpiece geometry, allowing for subsequent examination of the workpiece.
Image: A model built with the aid of X-rays, using the Werth Tomoscope
This information is combined with exact measurements of tight tolerances, taken with tactile and optical sensors. An image processing sensor enables the operator to make fully automatic, highly accurate measurements of complicated, extremely low-contrast workpieces in the back-lighting and surface-illumination mode. An additional laser sensor allows for the measurement of surface profiles. Tactile sensors, with probe tip diameters down to 20 microns, enable measurements of workpiece characteristics that are inaccessible to optical sensors.
Many multi-sensor CMMs cannot perform complete and accurate recognition of all regular and freeform geometries of a workpiece or internal geometries and inaccessible characteristics, such as hidden edges and undercuts, without destroying the part or requiring pre-treatment of the product. Such systems can also be time-consuming and require considerable experience on the part of the user.
By integrating CT with a multi-sensor CMM, these problems are solved. The different measurements are used to produce a very quick 3D colour image of every feature of the component in the same measurement run, without the need for further checking, so users can rapidly obtain all the information they need.
The Tomoscope itself offers the most accurate industrial CT on the market, integrated into a co-ordinate measuring machine, based on proven software and machine components. The use of patent-pending Werth AutoCorrection to account for the actual properties of the workpiece during the reconstruction process ensures that measurement deviation in tomography can be reduced to just a few microns.
"The benefit to the user is that of increased speed and reduced chance of scrapping good parts or keeping bad parts" says Paul Nash, director of Mantech Sales, the UK agent for the complete Werth range of equipment. "Ultimately, this means less time spent on inspection, without compromising quality. This allows companies to develop products and respond to their customers more quickly. Experience across Europe and the USA shows that these systems represent significant opportunities for cost savings. We are looking forward to seeing similar benefits in the UK."
Such systems have considerable potential for improving any quality programme, particularly where there is a need for inspection of free-form surfaces. Good examples of applications are measurement and digitising of plastic, light metal and graphite parts. Current usage includes inspection of metal automotive parts, as well as plastic parts, such as mobile phone casing, medical inhalators and housing for electrical plugs.
MOULD TOOL BENEFITS
This technology will also bring significant gains to tooling departments and manufacturers of mould tooling. Companies that produce precision, multi-cavity, injection moulds must maintain very tight tolerances to meet the production requirements of their clients. When supplying businesses such as manufacturers of medical equipment, moulds must be reliable enough to produce a huge quantity of the product without a single defect. Even minor variations in a multi-cavity mould can be costly.
The 3D image produced by the Tomoscope, quickly details every feature of moulded components, allowing for the very quick, thorough inspection and proving out of cavities.
Traceability of tomographic measurements can be implemented directly on the measured object using proven CMM sensors that are traceable to the standard of length, the metre, maintained by the UK's national measurement institute, the National Physical Laboratory.
The system uses WinWerth measurement software – graphically interactive, user-friendly software that operates under MS Windows. The interactive graphic instructions are suited for use in a workshop environment, while the software consolidates all data-handling functions that are necessary for the measuring process, from tomography to the final comparison with CAD data.
The high-powered image processing system allows for reliable and automatic measurement of objects, even when there is low contrast and object characteristics fluctuate. Measurements made with a combination of X-ray, optical image processing, 3D tactile –dynamic scanning and touch trigger –and laser sensors extend the flexibility and application range of this new CMM technology.
Mantech Sales is also looking at widening the availability of this technology by introducing a sub-contract service. "There is currently no such service in the UK, as there is in Germany," explains Mr Nash. "Such equipment could be very valuable to a lot of companies and I am very keen to hear from partners or investors who would be interested in working with Mantech to offer such a service to UK manufacturers, who are interested in this technology, on an occasional basis."
First published in Machinery, October 2009