As a result of the use of this software, there is no need for custom fixturing to hold the part in a precise location and orientation. The machine uses its probe to find where the part sits, and the software ensures that even a complex program with contoured five-axis moves will match the part’s position.
How well the software does its transformations is directly determined by the accuracy of the probe measurements. The GKN facility uses the MP700E probe from Renishaw (Hoffman Estates, Illinois), a probe that improves accuracy by employing strain gage technology to detect triggers instead of using moving parts. The accuracy of probing measurements is particularly important in this application, because some probed features already have a layer of uncertainty. Part of the ingenuity of the process, and part of what allows the weldment to be machined in two setups, is that unreachable datums of the part are referenced to datum spheres that are added in accessible places. Both features are measured on a CMM before machining. The probe therefore does not measure the critical features themselves, but instead measures the spheres that refer to them.
The software used in this application works with the posted NC program. It rewrites five-axis tool paths line by line to match the location and orientation of the part.
Speed And Quality
The NC Transformer software was developed and proven in the course of developing the aft boom weldment machining process. Initially, watching the software begin to work in this application was scary to those involved. Although custom fixturing may be cumbersome and demanding, a process that involves setting up the part more casually, along with rewriting posted lines of code, can seem as though it doesn’t have enough reassuring “hardness” in it.
However, the process works. It delivers the aft boom part faster and more reliably than the previous process could. And because the process does not rely on any hard tooling, it can be applied to other large and complex five-axis parts in the shop. In fact, now that the facility can perform five-axis machining to a level of effectiveness and quality that rivals that of many machining houses, the Thermal Joining Center has already applied the process to other machining jobs that it previously would have outsourced. ( |
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