Quote:
Originally Posted by 1885.Blake
I am a novice at this; but what I have read/heard is that STEP files basically define the shape of an object by modeling it's skin as zillions of small triangles, and they don't convey important information about things like the radius of a circular arc, or the density of a material being modeled, or that a couple of concentric circles/holes are supposed to stay concentric (as opposed to just happing to be concentric because of random luck), etc.
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What you are describing sounds more like an .stl file than a STEP file. STLs are used by additive fabrication (sometimes called Rapid Prototyping) machines to generate build files. STLs are a standard format used by all RP machines I am aware of including stereolithography, selective laser sintering, fused deposition modeling, e-beam melting, fab@home (a DIY RP machine for approx $3K!), and a couple of others that are rare and difficult to find. They can also be used to generate a conventional CNC tape if you have the right software.
STEP on the other hand does contain true geometry information. STEP is the 3D version of IGES, a 2D standard for graphics data transfer. IGES has been expanded in later versions to handle 3D data. Today either can be used for transfering complex surface information from one CAD system to another. Neither is entirely bullet proof and when I have to transfer parts from one system to another I will typically request both a STEP and an IGES version. I'll typically start working with the STEP file because it is a true solid model but if it doesn't translate properly I can always go back to the IGES and work from the surfaces there. IGES always works, within its inherent limitations, but is generally more work for me in overcoming thse limitations.
Both STEP and IGES will loose some of the additional data like density, drawing notes, colors, etc. This has more to do with the lack of standards in how such information is treated by the CAD systems than technical capability.