Quality Scan: Integrate Probing/Toolpath Generation
Most modern machine tools either come or can be retrofitted with probing capabilities to simplify and speed job setup.The same probing equipment can be used at little extra cost for in-process quality checks or even final part inspection and buy-off. On-machine probing enables faster, leaner part processing, a high degree of process control, and makes 100% good parts achievable objectives.
New probing software aids the move to one-stop processing by allowing parts inspection to be programmed and simulated offline on CAD/CAM systems in the same manner, by the same people, and at the same time as toolpath generation. Machine-tool probing for process control and inspection becomes a natural part of the application engineering task, using the probe just like any other tool in the magazine.
The new software makes available the full spectrum of probing capabilities, allowing the generation of probing routines to:
- Set tool length and diameter,
- Perform workpiece identification,
- Do workpiece setup,
- Make in-process checks and apply offset control, and
- Conduct final part buy-off inspection.
Inspection is programmed in concert with toolpath generation. Intuitive menus in the probing software remove the need for specialist knowledge of probing macro commands. Such commands vary by machine controller, and are a time-consuming way to produce probe routines. The instructions required to control the probe are automatically included in the same postprocessed files as the toolpath. Some programming software can be used to develop probing routines for both contact touch probes and noncontact laser probes.
Besides new program generation, existing programs can be reprocessed to include probing. The machining programs can be read, and probing routines added at the desired points in the program, removing the need for cutting and pasting into text editors or on-machine editing.
Features can also be selected directly from an imported CAD model, simplifying the generation of probing cycles. A part feature can be selected with a single click. A drag-and-drop interface uses the part data to update machine parameters. Software allows point-and-click automatic programming of surface normals, saving time and reducing manual-input errors.
For users without an existing CAD system, our company offers software that allows the design of probing cycles using dialog-based feature selection.The software provides feedback throughout to ensure that the program is right the first time.
Once programs are completed, they can be fully simulated to identify errors and detect potential crashes. The software protects against stylus and probe collisions by flagging a warning if any move will violate the part being inspected. Once simulation delivers a clean routine, programs can be postprocessed for a wide variety of control systems. Users can program and prove-out even complex probing operations, eliminating accidents that can arise with macro programming.
The software can be used with high-accuracy spindle probes, such as our MP700 or compact OMP400, to collect data for in-process quality checks. Neither probe needs to be calibrated in all the intended vectors.This capability reduces the number of points required to measure a given part, and shortens measurement-cycle times.
Data can be collected to check surface accuracy or to measure features such as circles, cylinders, cones, spheres, and planes to a high level of precision. The automated accuracy checks can then determine cutting compensations for closed-loop process control.
Software can compare the data to minimum/maximum tolerance bands for the part, and generate best-fit compensations based on least-squares averaging. Data can be displayed graphically against the CAD part model, and views rotated to various orientations.
On-machine monitoring at stages of the machining process allows errors to be detected earlier and corrected more quickly at lower cost. Similarly, the extent of any damage—such as from a tool breakage—can be assessed accurately and a decision made immediately to determine whether the part can still be completed within tolerance, or must be scrapped.
Using probes to perform final inspection, while the part is still fixtured, eliminates the added costs and time for CMM and other post-process inspection. Integrating metalcutting and probing allows programmed actions to be taken by the machine tool based on data collected, giving confidence for lights-out untended operation.
This article was first published in the September 2006 edition of Manufacturing Engineering magazine.