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Emerald Group Publishing Limited
Copyright © 1998, MCB UP Limited
EdgeDMIS programming optimises CMM performance
Software solutions for aerospace
EdgeDMIS programming optimises CMM performance
There are two schools of thought as to the best way to program CNC machine tools. While on-machine programming has its followers, off-line CAM-based systems are now proving to be by far the most popular method of creating tool path data. And, with coordinate measuring machines (CMM) now becoming more integrated into the manufacturing equation and their ability for immediate acceptance of CAD data, off-line CMM programming is rapidly following the metal cutting fraternity.
One company endorsing this trend is MBM Technology in East Sussex. Manufacturing a wide range of actuation and control systems for aerospace and defence equipment including inflight entertainment systems, flexible circuits, motors and endcoders, MBM now generates all its part programs on an EdgeDMIS off-line programming system.
Kaimet's EdgeDMIS off-line programming software
The EdgeDMIS system, previously marketed as EdgeCAM CMM was recently supplied by Kaimet Systems of Reading, the metrology-based off-line programming sister company of the Truline Technology Group's Pathtrace Engineering Systems.
As well as meeting all its multi-axis production requirements, the fully integrated CAM system also uses the EdgeDMIS module to program two different CMMs at the company's Portslade works using CAD design data.
MBM was keen to optimise programming routines on its DEA and Mitutoyo CMMs and increase machine utilisation levels in order to meet increasing workloads and the need for 100 per cent three dimensional inspection on certain defence industry components.
Dedicated inspection type programming software was quickly discounted as this would have meant buying two separate systems and there would have been inevitable compatibility problems. However, by investing in the fully integrated EdgeDMIS system, the company effectively killed four birds with just one stone.
Malcolm Bennett, MBM's chief inspector explained:
"As well as covering 90 per cent of our inspection requirements, the Kaimet system can be used to program both our CMMs as well as meeting the turning and milling demands of our production engineering department."
The EdgeDMIS programming system is DNC linked to ten CNC machine tools on the shopfloor and there are two workstations in the office one for production and the other for inspection. A major benefit has also been realised in that measuring programs can be quickly swapped at will between the DEA and Mitutoyo as required.
Operating under Microsoft Windows 95 and Windows NT, EdgeDMIS can be used on any CMM control system that is able to accept the generic dimensional measuring interface standard DMIS. Third party CAD system data can also be directly imported using the industry standards IGES, VDA, DXF, SAT, DWG and other files. The programming system clearly shows the probe positions and paths on screen, by highlighting them in a separate colour, while its macro library of inspection routines and cycles speeds the measurement of standard features such as: pitch circle diameters, holes, surfaces, profiles, cylinders and planes.
Having previously programmed both CMMs by teach/repeat and off-line manual programming methods, MBM is now able to readily appreciate the all-round performance and power of the new measurement system. "Providing CAD data are available, when compared with teach routines, EdgeDMIS is twice as quick, does not require a component and it produces a perfect probe path which requires no further editing," says Malcolm Bennett. While even on short, simple programs, the system is some 25 per cent faster than manual off-line programming and this increases progressively to over 50 per cent on more complex inspection routines.
This increase in programming efficiency has enabled the company to cut inspection lead times by up to a fifth and virtually eliminate program prove-out. The software also enables suitable fixtures for measuring routines to be dropped in, as required, and allows any changes in the number of measuring points specified to be quickly and easily incorporated into the program.
Up to three quarters of MBM's work is related to the aerospace sector. The company produces heavy duty ejector release systems for weapons and fuel tanks on the Tornado and is a key manufacturing partner in the Paveway III laser guided bomb as fitted to Jaguar, Harrier and Tornado aircraft. For civil aviation MBM produces aileron-style control systems for Saab and anti-icing valves and solenoids for actuators and control functions on the European Airbus.
As part of the Paveway III project, MBM makes the weapons release system which comprises two mace saddles, a hardback air smoothing device, various lugs and lug adaptors. It also manufactures the four control fins on the front of the laser controlled device which enable the bomb to fly.
Inspection is crucial in the production programme and both the DEA and Mitutoyo CMMs are used extensively. Some components are checked on a sample SPC type basis, others require 100 per cent inspection on key features. A number of parts such as control fins, which have over 30 features, are all individually inspected as soon as they have been machined on the horizontal machining centres.
Around 35 separate components are inspected on the weapons release system by one or other of the CMMs and typical inspection routines include measuring: diameters, positional tolerances, squareness, hole centres and concentricity. Setting-up for the different components has proven to be the longest part of the inspection process.
Now with the speed and efficiency of the EdgeDMIS programming system, MBM regularly checks all machine operations on some components even though only six main features actually require 100 per cent inspection. For very little extra, the company knows it has a detailed and complete manufacturing record.
Both the DEA and Mitutoyo are also used to produce detailed first off article inspection reports on all new components. The DEA machine tends to be used for the Paveway III work due to its close location to the production area, while the Mitutoyo CMM has the task to check heavy duty components. On average, the DEA unit is used for 16 hours a day while the Mitutoyo usually runs for between eight to ten hours each day.
As a guide to size, the hardback unit, a semi-circular component, measures 1.2m long × 250mm wide and 200mm deep. The mace saddle units, which fit into the hardback, are 150mm square. Such components are measured on both CMMs to an accuracy of ten microns on key features and between 18 and 20 microns for other elements.
Whenever possible, CAD data are used as the basis for the CMM programming routines. Sometimes traditional engineering drawings are used as the starting point from which to create the necessary probe paths. However, occasionally the CAD element with Kaimet's EdgeDMIS is used to create surface details from scratch.
MBM does not make use of the CAM programs generated for its CNC machine tools, in the inspection process, as the relevant geometry and features are not really suitable. "It's much quicker with the system to work from the basic CAD data and build up probe cycle accordingly," says Malcolm Bennett.
"We have very successfully implemented a policy of operators checking their own work which involves extensive use of our CMM technology," says Malcolm Bennett. "The ability to produce programs much quicker now using Kaimet's EdgeDMIS package ensures that the time available for operators to inspect their work 'in cycle' is maximised," he maintains.
Details from Kaimet Systems (a division of the Truline Technology Group). Tel: +44 (0) 118 931 4177.