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.