Frequently Asked Questions

Questions about Possible Technical Issues

Does STEP-NC require feature recognition?
No, the first two conformance classes of AP-238 (CC1 and CC2) can be implemented without defining any features at all because these two conformance classes manufacture the part from the tool path data. The more sophisticated conformance classes (CC3 and CC4) can take advantage of feature information to do some path planning on the control. Feature recognition is one way to get this information, but CAM tools and design-by-feature CAD systems can also produce AP-238 feature data.

Can I use STEP-NC with tooling databases?
Yes. A STEP-NC driven manufacturing process can be defined to including the definition of explicit or implicit cutting tools. If the definition is explicit then the control is expected to select the tool listed in the program. If the definition is implicit then the control can select the best-fit tool available in the database and generate tool paths dynamically for that tool.

How much does STEP-NC depend on tolerances?
The optimal process plan can only be computed when the required tolerances are known. The STEP-NC AP-238 specification makes use of the same inspection quality tolerances as AP-203 ed2 and AP-219. In the early years of STEP-NC deployment the CAM or CNC operator will read these tolerances and decide on the best speeds and feeds using their experience with the machine. In the longer term, CAM and CNC vendors will include algorithms to generate optimal speeds and feeds using the supplied tolerances and the known characteristics of the machine.

What about geometry healing?
If the geometry defined by a CAD system is bad, then none of the downstream systems will be able to process that data. There are two possible fixes. The first is to use geometry healing to repair the data. The second is to measure the file against the validation properties that should also be in the file, and use that information to demand delivery of better STEP files.