Mating a part with an imported STEP File

Normally when I need to interact with step files in an assembly, I will open the step files in Creo and then immediately save them as Creo parts or assemblies, usually with file names that indicate to me that these are external files. Then when I assemble them, for instance to check for fit-up or interference, they assemble just like any other part or assembly, provided they do not have any geometry issues.

When a part imports, it also creates a coordinate system (Csys).

If you pull the "insert here" above the import, you can place the default datums (you can also manage this in which import template you use).

Bottom line, if the file is a true STEP file (not an converted polygon file), it knows circles, it knows flat planes... those you should be able to use.  if nothing else, you can add axes and datum planes to known feature of the imports.

Another good thing to use for these types of files, files difficult to mate, is to pre-define the mating features for when you put them in the next level assembly.  That will provide only the logical mating elements.  I wish I knew more about these but know I don't feel the need in my normal way of working.

There are two camps in software development. One is to try to work with broken parts and give the impression that all is well and hide the defects and the other is to reject broken parts so they do not later cause unexpected failures. PTC is generally in the latter camp.

The most frequent failure for mating parts is that the features involved are not precise; for example mating the end of a nominal cylinder when the end is not actually perpendicular to the axis of the cylinder to a blind hole where the surfaces are perpendicular. You can use vertex on surface and pick a vertex on the edge of the cylinder for cases like that.