20 March 2009
20 March 2009
Delcam will be showing its latest developments for the machining and inspection of composites at the JEC exhibition.
These will include the new releases of its PowerMILL machining software for high-speed and five-axis machining and of the PowerINSPECT inspection software, plus a range of adaptive machining solutions to allow more accurate manufacture of composite components.
PowerMILL is used by many composites manufacturers for the production of master models, moulds, jigs and fixtures, as well as for the trimming and drilling of components. The latest release offers a more complete solution for complex machining operations, together with more control for experienced machinists that know exactly how they wish to machine a particular part. The program also includes a range of enhancements to existing functionality to enable both faster programming and faster machining.
Version 5 of Delcam’s PowerINSPECT software includes support for five-axis scanning with Renishaw’s REVO probe. This new release of the world’s most successful hardware-independent inspection software also features the ability to use multiple alignments within parts or assemblies, additional GD&T features, more flexible best-fit algorithms, improved CMM connectivity and more versatile report generation.
Delcam will also demonstrate new ways in which machining and inspection can be integrated to give adaptive machining. One example of this integration is electronic fixturing. With this technique, toolpaths are adjusted to match the actual position of the surface of the workpiece, rather than trying to align the part into exactly the nominal position specified in the CAM system. It can overcome the problems caused when machining large, flexible composite panels.
The first stage in this approach is to create a probing sequence in the inspection software, preferably using off-line programming so there is no interruption to the machine tool’s cutting time. This sequence is used to collect a series of points from the workpiece, which can be used map the surface of the part. Any mismatch can then be calculated between the nominal position used in the CAM system to generate the toolpaths and the actual position of the workpiece surface in relation to the machine-tool bed. A modified set of toolpaths can then be created within the CAM system. This approach can ensure that any pockets cut into the surface of a composite part will be in the correct positions. Similarly, by using a map of the actual surface, the user can ensure that any holes and counter-bores are drilled to the correct depth, relative to that surface.
Another problem in the machining of composites is that the materials tend to relax as the composite fibers are cut. This is not as serious as might be thought since any pockets tend to be undersize and so can be corrected with an extra machining operation. However, the effect is difficult to predict because the fibers will not lie in the same orientation when they are cut. This means that the degree of distortion will vary in different directions. To overcome this problem, the initial machining operation should be followed by an inspection on the machine tool with a probe fitted where the cutting tool would normally be. This shows how much more material needs to be removed and enables the required extra toolpaths to be generated in the company’s CAM system. For more complex components, with twenty or more pockets, a further cycle of inspection and machining may well be needed to produce all the dimensions to the required tolerance. However, for subsequent parts in a series, the complete machining sequence can be repeated and the results checked with a final inspection.
A similar problem can arise when drilling holes as the relaxation of the surface can alter their final positions. One solution is to use a two-stage drilling operation. The first sequence is done using an under-size drill, typically half of the size required for the final hole. The surface of the part is then scanned and the results used to create a second drilling routine with the correct size of tool. Any distortion of the part will be picked up by the scan and the centers of the second series of holes can be adjusted accordingly.