CIMdata PLM Industry Summary Online Archive
September 2004
Company News
Delcam to Show benefits of Machining and Inspection Integration at JIMTOF
Delcam will demonstrate how closer integration of machining and inspection operations can improve quality and boost productivity at the JIMTOF exhibition to be held at the Big Site in Tokyo from 1st to 8th November. Delcam is the developer of both PowerMILL and PowerINSPECT.
At JIMTOF, the company will demonstrate its latest solutions for adaptive machining and on-machine verification.
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 operations to be completed 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 off-line 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 mis-match 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 un-machined areas, a reduction in air cutting and improved control over the feed rate as the cutter enters and leaves the material.
The most challenging adaptive machining operations are those where the final shape of the component is unknown. This is often the case 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 tooling that has been modified after its initial manufacture, such as press tools that may have been adjusted to compensate for spring back.
The version of PowerINSPECT used for on-machine verification allows off-line programming of the inspection sequence for the machine tool, with fully integrated simulation and collision checking, and so minimizes the time needed for the verification operation on the machine. The most obvious benefit of on-machine verification is to those companies that do not have existing inspection capabilities. Most modern machine tools either come with, or can be retrofitted with, probing capabilities to assist in the set-up of the job. This same equipment can now be used for verification at little extra cost.
On-machine verification can give timesavings by enabling the quality of the component being machined to be monitored at all stages in the manufacturing process. This will allow any errors to be detected earlier, and so corrected more quickly and at lower cost. For example, it will be possible to check that the correct amount of stock has been left on the component after a roughing operation, rather than having to wait until all machining operations have been completed before discovering that an error has been made.
Similarly, the extent of any damage caused, for example, by a tool breakage, can be assessed accurately and a decision made immediately to determine whether the part can still be completed within tolerance or whether it will have to be scrapped.
On-machine verification will also benefit companies with customers that insist on independent inspection of their work. By carrying out an initial verification on the machine, errors can be detected, and corrected, that might otherwise not be found until after the component had been shipped to the inspector.
"Many Japanese companies have already expressed interest in on-machine verification," reported Delcam Japan's General Manager Gordon Moir. "In fact, a number of are already using the system with positive savings becoming apparent."
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