Feb 24, 2010

Delcam to demonstrate more accurate composite machining at JEC

Delcam will show how its NC-PartLocator software can improve accuracy and consistency when machining composite components, at the JEC exhibition to be held in Paris from 13th to 15th April. NC-PartLocator, which has been developed in association with metrology specialists MSP, gives the ability to adjust toolpaths to the actual position of the part, rather than having to ensure that the component is in exactly the nominal location specified in the CAM system.

To ensure accurate trimming and profiling, NC-PartLocator first gathers the necessary data using a probe fitted onto the machine tool. A probing sequence is created within the software to collect a series of points from the component. This data is then used by best-fit routines within the software to determine the part’s exact position. Any mismatch between the nominal position used in the CAM system to generate the toolpaths and the actual position of the component on its fixture can be calculated. The software then feeds the results to the machine tool control as a datum shift or rotation to compensate for the differences in location and alignment. This adjustment can be made much more quickly and easily than placing, and holding, the part in exactly the specified position, especially with large, flexible components.

NC-PartLocator can also help to tackle localised problems that can result from variations in material thickness across the part, or from distortion within the part caused by differing cure rates or cooling rates in different areas. For example, the software can ensure that fixing holes are drilled to the correct depth. The actual surface of the component can be mapped with NC-PartLocator and this surface used to calculate the drilling routine. This will give more reliable results than using the nominal data from the CAD model of the part.

A second problem that can occur when drilling composites is that the part can distort as the reinforcement is cut. This can be overcome with NC-PartLocator by using 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 in a second drilling routine with the correct size of tool. Any distortion of the part will be picked up by the scan and the centres for the second series of holes can be adjusted accordingly.

NC-PartLocator can also save time that could be wasted in machining and inspecting parts that are already scrap. The process can discover, during the set-up phase, that the component is so distorted that no realignment will give a satisfactory part. While obviously not good news, at least this is better than machining the part anyway and only finding out during the final inspection that it was beyond redemption.