The ISO T24 STEP-Manufacturing team met at the Boeing Renton plant on October 12 and 13, 2010. The meeting featured a demonstration of closed loop machining using a FARO arm and the Okuma machine tool. The part machined was the Boxy part machined at previous meetings but in this demonstration the orientation of the part in X, Y and Z was deliberately offset using shims.
In the demonstration the orientation of the part was determined by using the FARO arm to measure three faces. The geometry of the three faces was then delivered to the STEP-NC environment as a STEP file. In the STEP-NC file, two workingsteps were used to process these measurements. The first workingstep registered the coordinates of the fixture using the geometry defined by machining the first setup. The second workingstep computed the coordinates of each setup by measuring the coordinates of the part as setup against the coordinates as defined in CAD and determining the difference using the coordinates of the fixture.
The demonstration was a success. We showed that the orientation of the part can change in three dimensions and three directions and that minor issues such as changes to the size of the fixture spacer will be non-issues in STEP-NC. The next priority is to extend the compensation to the measurement of hole sizes so that the system can compensate for changes to the diameter of a drill during machining and STEP-NC can be applied to the problem of drilling holes in hard flexible materials. Other issues that can be explored include restricting compensations to one or two dimensions when variations in the other dimensions cannot be allowed (for example when machining in three axes), and error control so that machining is stopped when the error in one of the fixed or unfixed dimensions exceeds predefined limits.
After the demonstration, the meeting discussed how to develop a second edition of the standard so that the CAD, CAM and CNC vendors can be required to support the interfaces necessary for machining compensation in five axes, and how to implement a next generation machining simulation service for STEP-NC. The latter is being funded by a DARPA SBIR program and the proposal is to build a simulation service that can be used to link manufacturing operations across the country and across the globe.