fcbuilder wrote: ↑Fri Mar 18, 2022 10:18 am
Off topic but if I may ask, which format would you recommend for CNC? STEP or IGES?
When dealing with an outside shop to build your parts, you first need to decide which shop is best suited for the task (data-compatibility, quality, speed, turnaround-time, price).
Only then ... do you ask that shop to tell you which is
the formats that the shop can handle and which they prefer to receive your design data in. That way, you aren't forcing anyone to work "uphill" to get the job done; their internal processes are already streamlined to work with that preferred input (
software for file massaging, creating shop drawings, generating tool paths).
IGES was always problematic as an interface, because the standard never included specific examples of data mappings for the various types, leading to interpretation of the standards by various CAD/CAM software developers. A first step in working with a supplier would be to create a standard drawing with every geometry element type generated by your CAD system, and have that exported from your own system, then imported into the supplier's system, to confirm visually, the quality/acceptability of the transfer, and use that as a starting point for the supplier, NOT the design exporter, to repair/correct the geometry before working with it. (
At times that was tedious, resulting in the industry of "direct translators" converting from one binary CAD format to another.)
STEP evolved from 2 separate but parallel initiatives (PDES in North America; STEP in Europe) and those two merged into one group ... to combine efforts to achieve the same ultimate goal. That was accomplished and is now the more common,
but not the sole, standard for design transfer. The goal of STEP was to separate the "what" info from the "how" info, something that IGES never incorporated given that it was an "Initial Standard".
The other intended advantage of STEP was the use of industry-specific "target profiles", correctly referenced as "
application protocols" or "APs". I have been away from that too long to personally know how well industry "concensus" has worked in documenting and publishing those.
https://en.wikipedia.org/wiki/ISO_10303 includes an extensive list of the APs that had been identified and are being consolidated.
Sadly,
STEP is not immune to some of the "transfer quality" issues that IGES suffered,
so it is important to include data transfer verification for both model transfer formats as one of the critical considerations of the supplier qualification process.
In other words, there is no single "best". "Best" is contextual to each supplier relationship. I hope that helps in your decision-making!
As for choosing a format for
long-term neutral-format storage, allowing for the possibility that you might find yourself forced to migrate to a different CAD system at some future date, STEP might be that "archival" format, because even FreeCAD is evolving geometry such that some feature definitions are not forward compatible, and therefore you could not guarantee the import of the FCstd file into the latest FreeCAD and be guaranteed that those files would come in 100%, to then convert to your target system of migration. It all depends on how long do your designs need to live .. untouched .. before they are likely needed to be resurrected for another application/customization.
As for your original question, is there a difference between the two outputs from the options menu?
- Size-wise: zip container with a compressed coloured STEP file, so it is smaller (where size matters).
- Colour: STEP file, without compression.
Content-wise: no difference. You can confirm this by doing a "diff" on the 2 versions, which will report non-consequential differences (time of generation).
The file also reports data format "schema" for AP214 (geometry along with colors, layering and other info). For reference, that format is a "superset" of the AP203 schema, which would have contained only the plain-vanilla geometry in only one uniform color.