A significant increase in orders for the supply of prototype pressings and bracketry, notably to Jaguar Land Rover (JLR), has prompted Birmingham Prototypes to install two multi-sensor co-ordinate measuring machines (CMMs).
The goal was not only to measure the sheet metal parts more quickly but, more importantly, to shorten the time needed for generating subsequent reports. The investment has also resulted in the establishment of a new sub-contract service offering laser scanning and inspection.
Based in Redditch, Birmingham Prototypes (birminghamprototypes.co.uk) started working directly for JLR two years ago. To receive its supplier’s code, the sub-contractor needed to satisfy the automotive manufacturer’s stringent quality control requirements in respect of first article inspection reporting and PPAP (production part approval process) documentation. These required an increase in the number of reports that had to be produced, as well as more detail on component accuracy and repeatability than is requested by other customers in the automotive, aerospace and other sectors.
Birmingham Prototypes’ managing director, Mick Adams, says: “Using the former manual CMM at Redditch, report generation was a laborious process requiring entry of data and drawings by hand into Microsoft Office applications. A single report took anything from an hour to half a day, depending on its complexity.” In 2013 he decided to install a Nikon Metrology LK V 15.10.8 ceramic bridge co-ordinate measuring machine (
www.nikonmetrology.com) to automate and speed up the reporting process. It also allows inspection cycles to be completed in a shorter time — and without operator attendance after components have been fixtured. This saves further time, especially when measuring a batch of identical components.
The use of a Nikon Metrology LC15Dx laser scanner is the default method of inspecting pressings at Birmingham Prototypes. It allows high-accuracy resolution of freeform surfaces and geometry. For measuring tight dimensional tolerances, and sometimes for initial job set-up, a touch probe is picked up automatically from the stylus changer on the LK V 15.10.8 by a Renishaw PH10M motorised indexing head.
Most drawing tolerances on pressed parts at Redditch are fairly open, ±0.25mm being typical on surfaces and ±1mm for trim edges. Only hole positions are measured to within tens of microns. The LK CMM is capable of measuring to an accuracy that is at least an order of magnitude better than is required for these applications. Nikon Metrology’s multi-sensor Camio V8 software in use at Redditch produces industry-standard DMIS programs that support both laser scanning and touch probing. The software applies the optimum measurement strategy based on the feature and sensor selected.
For measuring complex surfaces, it automatically generates scan paths that result in fast and smooth laser scanning that closely follows the part surface, with full machine simulation and collision detection. Camio also has instant, highly productive reporting functionality based on standard templates. Tabulated tables, graphics and form plots derived from scanned point clouds and touch probing are combined in a single, concise report.
It is Nikon Metrology Focus 10 software that manages the point clouds acquired during laser scanning and allows inspection data to be compared against the customer’s original CAD model. A typical pressing at the Redditch factory, such as a prototype aluminium engine bay mounting plate for a Jaguar car, comprises seven to eight million points. Focus software produces annotated, colour deviation maps showing how the 3-D scanned model correlates with — and deviates from — the original CAD file. For such global comparisons, a 0.1mm grid is generally selected.
Early in 2015, Birmingham Prototypes installed a Trumpf five-axis laser profiling machine so that it could bring in-house the laser cutting work it was sub-contracting at a cost of £350,000 per year. Mr Adams says: “Practically every job that comes off the machine is a unique prototype that needs to be inspected, a job that was previously done by the laser cutting sub-contractors before parts were delivered to us. As our CNC CMM needs to be programmed for each new part, making it more suited to our low-volume pre-production runs, it made sense for us to invest in a manual measuring system to check the output from the Trumpf laser. Rather than choose another static CMM, we decided to install a portable co-ordinate measuring arm, an MCAx from Nikon. It is twice as fast at producing inspection results for a one-off part.”
The facility is used in-house on a dedicated steel table in the quality control room. It often inspects or reverse engineers components and fixtures for other manufacturers that have requested sub-contract measuring to be carried out, a service that was introduced two years ago when the CNC CMM arrived. The measuring arm has extended the scope of the service by allowing off-site inspection at customers’ premises of fabrications that are too bulky to be transported easily. The MCAx — a seven-axis counterbalanced-arm unit with continuous rotation — is used mainly with a digital laser scanner at Redditch, together with Focus 10 hand-held scanning and inspection software. Occasionally a touch-trigger probe is employed if additional accuracy is needed. The equipment can reliably scan steep-sided and reflective components; moreover, it is thermally stable and has a zero warm-up time.
The Nikon CMMs have greatly enhanced the quality control of sheet metal parts at Birmingham Prototypes and allowed the firm to increase turnover by launching sub-contract inspection and reverse engineering. They are backed by ISO 9001:2008 quality management accreditation, which has been held for over 10 years. The move to laser scanning has improved not only the firm’s sheet metal-working activities, but also its additive manufacturing service using a Dimension 1200es 3-D printer.
The laser scanner generates a CAD model of components for which there is no drawing or electronic data. It is altered as necessary, STL files are exported for printing the plastic part layer by layer and the customer is given both the component and the CAD file in any appropriate format.