DELCAM, represented in Australia by Camplex , has launched a new range of adaptive machining solutions to overcome a variety of manufacturing challenges in both toolmaking and production machining operations.
The new techniques are based on Delcam's expertise in software for both machining and inspection, which has been built up over the development of the PowerMILL CAM system, and PowerINSPECT hardware-independent inspection software.
The programming of most machining operations is based around knowing three things: the position of the workpiece on the machine, the starting shape of the material to be machined, and the final shape that needs to be achieved at the end of the operation. Adaptive machining techniques allow successful machining when at least one of those elements is unknown, by using in-process measurement to close the information gaps in the process chain.
The most common case is that where the exact position of the workpiece is unknown. With larger components, such as aerospace structures, moulds for bigger parts like automotive dashboards, or press tools for car body panels, achieving the correct position and orientation of the stock on the machine is a major challenge, taking many hours of checking and adjustment. It is often easier to adjust the datum for the toolpaths to match the position of the workpiece, than it is to align the stock in exactly the desired position. This approach has been used in the machining of geometric features for some time. Delcam now offers an equivalent solution for the manufacture of complex shapes and surfaces that gives the same benefits of shorter set-up times and improved accuracy.
The Delcam process in these cases uses PowerINSPECT, together with a new program, PS-Fixture. First, a probing sequence is created for PowerINSPECT using the software's offline programming capabilities. This sequence is used to collect a series of points from the workpiece, which can be used by a range of best-fit routines to determine its exact position. Any mismatch between the nominal position used in PowerMILL to generate the toolpaths and the actual position of the workpiece can be calculated in PS-Fixture. The software can then feed the results to the machine tool control as a datum shift or rotation to compensate for the alignment differences.
Examples where the exact starting shape is unknown can result from near net shape manufacturing processes, like casting and forging, or from imprecise repair techniques, such as welding. The main requirement here is to allow an even distribution of material to be removed around the stock to avoid over-machining in some areas and under-machining in others. Other benefits include the ability to give a smooth transition between machined and unmachined areas, a reduction in air cutting and improved control over the feed rate as the cutter enters and leaves the material.
Depending on the degree of uncertainty of the shape, a probing solution or a reverse engineering solution can be used. Typically, machining of near net shape preforms will use a probing path created with PowerINSPECT to determine the form of the stock. The final shape to be achieved can then be orientated within this envelope to give an even thickness of material on the surfaces to be machined.
When there is greater uncertainty over the starting shape, which can result from component or tooling repair, Delcam's CopyCAD reverse engineering software can be used to create a complete model of the areas to be machined. This can then be used within PowerMILL to create toolpaths specific to that component.
The most challenging adaptive machining operations are those where the final shape of the component is unknown. This usually is needed when undertaking repairs to components that have been changed from their nominal CAD shape during service, for example, turbine blades that have been distorted by the high temperatures in aircraft engines. A similar problem can arise when repairing tools that have been modified after their initial manufacture, such as press tools that may have been adjusted to compensate for spring back.
The initial stage in these cases is to probe the component to determine the extent of its deviation from the nominal CAD data. Then, the morphing functionality in Delcam's PowerSHAPE hybrid modeller can be used to bring the CAD model into line with the actual geometry. Finally, toolpaths can be generated for the required areas with PowerMILL.
A similar approach can be used when repairing older parts or tooling for which no CAD data exists. For these components, it is often only necessary to machine the repaired areas into the surrounding surfaces with a smooth blend, rather than to create a precise region of known geometry.
Companies wanting to use adaptive machining processes must understand that they tend to be much more complex and process-specific than conventional CAM programming. Most adaptive machining projects will require some specific consultancy and customisation work by Delcam as part of their implementation.