The profile of the sheet aluminium component is inspected against the CAD model
from which cutter paths were created to rout the part. Out of tolerance areas are
shown in red, while other colours denote different tolerance bands
One of the few aluminium alloy routing specialists in the UK, Whitwam Precision Components, has installed an optical, non-contact measuring machine that allows inspection of flat components up to 1,350 mm x 900 mm against the original CAD file much more quickly than using a traditional laser system.
Called Planar P120.50, the machine was supplied in January 2008 by Press & Shear Machinery, UK agent for the Irish manufacturer, InspecVision. Chris Whitwam owns and runs the aerospace subcontract firm in Colne, Lancashire, together with wife Judith and their four children. Before establishing the business in 2004, he was for many years the technical director of Wadkin, responsible for designing and building high-speed routing machines.
His long experience in the sector had left him with the impression that there was only one viable solution for inspecting two-dimensional components. Based on laser scanning of the profile in two planes, the system works well enough but is time consuming and sensitive to swarf and scratches on the glass table, which the laser often sees as part of the profile.
"The InspecVision measuring process is between two and three times faster than the laser system, irrespective of component complexity," said Mr Whitwam. "Results are just as accurate and are unaffected by foreign matter on the table."
He pointed out that the digital camera-based system costs less than two-thirds the price of a laser scanner. An added bonus is that the Planar machine is also able to inspect 3D parts using a line laser measuring option, which Mr Whitwam added to his machine's specification at the time of order.
In addition to inspecting aerospace components that Whitwam produces, the Planar is available for reverse engineering parts for which drawings or electronic data are no longer available. CAD files can be created for a customer, from which further parts can be made. This service is being actively marketed, both within the aerospace industry and in other sectors as well.
The Colne company works mainly for a tier 1 suppliers to commercial aircraft manufacturers in Europe and the USA, notably Airbus, Boeing, Hawker Siddeley and Embraer. The tier 1s supply to Whitwam the CAD files from which cutter paths are created for three high-speed (24,000 rpm spindle : 3 m/min profiling) routers on the Colne site.
Measured results from the Planar machine are obtained in about 15 seconds and correlated back to the original CAD file already loaded into the machine's control. Graphically on screen, the measured profile is displayed against a trace of the CAD model, with any out-of-tolerance areas shown in red. Results may be printed out as required and supplied with the parts to the customer.
Until 2007, the tier 1s that Whitwam supplied were happy to inspect components on arrival, or provide a calibrated master so that the subcontractor could inspect parts by eye. The latter, although satisfactory, was not ideal as there was a risk of human error, which could lead to a batch of parts being scrapped.
Around of the middle of last year, Whitwam won a contract from Generation Metals International to supply aluminium parts for the range of business jets being built in the US by Eclipse Aviation. Components include empennage parts, wing-to-body fairings, keel beams and sundry items such as supports for the pilot's sun visor.
The contract stipulated that all parts had to be inspected and certified before delivery, after having been routed using CNC cutting cycles created from IGES files originating from Eclipse. Whitwam's manual methods were not adequate for inspection, necessitating the purchase of a computerised measuring system. Components are checked on the Planar machine after they have been routed and the tags securing the nested parts to the skeleton have been removed by hand.
The largest router at Colne accepts sheet up to 4 m by 1.5 m, sufficient to machine the tail fin of a Hawker Siddeley 125 in one operation. Sheet size generally used is 3,660 mm by 1,220 mm and gauge ranges from 0.4 mm to 3.5 mm. Parts are nested automatically using software within Whitwam's AlphaCam CADCAM system. Some cycles take up to four hours if the sheet contains a lot of small, complex shapes.
Many components are subsequently formed, painted and incorporated into sub-assemblies, operations that Whitwam's customers often undertake, although the subcontractor offers the same services through partner companies.
Expected to more than double within the next two years, the Eclipse contract now accounts for a large part of the Colne factory's output. To cope with increasing demand, Whitwam will be purchasing another CNC router and adding a night shift to supplement the current 6.00 am to 6.00 pm working.