CNC STEP file type

[MisterMaker]

It’s Time to Get Over IGES (from GrabCAD Blog)
https://blog.grabcad.com/blog/2014/10/14/get-over-iges/

Just use Freecad format instead of these stupid translation files.
But it's not up to us sadly.

[eajmarceau]

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.

[chrisb]

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.

I dare to disagree. It is completely useless to have an excellent best price shop next door if they cannot handle one of the formats you can deliver. So the first filter would be to rule those out.

[MisterMaker]

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.

At least you can always install an older Freecad version. You could even write your own update script to update files to newer versions.
This issue is kinda of a big deal if you actually use those expensive big corp CAD packages, but just a minor issue if you have access to all the data you need to fix it.

[eajmarceau]

I dare to disagree. ... (snip)

... Then we will have to agree to disagree. Different experience drives different perspectives on what is important.

[eajmarceau]

At least you can always install an older Freecad version. You could even write your own update script to update files to newer versions.
This issue is kinda of a big deal if you actually use those expensive big corp CAD packages, but just a minor issue if you have access to all the data you need to fix it.

I grant you that someone ... who has mastered the start-to-finish process of downloading source-code from the GitHub repo and building his own compiled version ... could indeed access those older versions, and build those specific version images ... if they also have access to all the old version libraries for those older languages for the various OSs in question. But is that a realistic expectation of someone who is not so adept, limiting themselves to the usage of pre-built WorlBenches and a few personal macros? I am not sure that would be the case. And these latter individuals may not be able to afford the consultants who could to that for them. Hence, the suggestion that people need to consider how long the models will be stored, and what would be the best format if such storage is for an extended period of time.

... and if every model is a throwaway after each job is done, the problem will never be faced.

As you said, for a FreeCAD guru, that may be a non-issue. For others who might need to ramp-up on the FreeCAD APIs (because the staff keener/expert has left to start his own enterprise), that lead-time and complexity may be too steep a hill to climb if there is a deadline on the table. It is a matter of context and needs sober consideration to identify what is best for the individual context.

As for the availability of older images, has there been any consideration of the possible value of having a repository of AppImages of the final build for each version (for the supported platforms for each of those), for just such an eventuality. I don't see such a list offered on https://wiki.freecadweb.org/Developer_hub, nor on https://github.com/FreeCAD/FreeCAD/branches, nor where I would l logically see those offered, onhttps://wiki.freecadweb.org/AppImage. But that raises the additional question of issues encountered with some WorkBenches (as documented in some Forum postings) when AppImages are involved, instead of compiled on the target machine. Truly humbly, I suggest that is a can of worms best avoided with early planning for business continuity.

[MisterMaker]

You can hire someone to write a script that can probably be done in Python or regex as fcstd is editable in simple text editor. You can download Freecad versions here without the need to compile https://github.com/FreeCAD/FreeCAD/releases
You cannot hire someone to reverse engineer a propietory file format, well you can but that is going to be more expensive than re-doing a lot of engineering work.
Basically for non-multinational companies if you loose acces to your expensive CAD program you loose your CAD data or it turns into stone.
If your old Freecad data won't rebuild correct you have options.

[eajmarceau]

You can hire someone ...

I am aware of all you have said.
I have no disagreement with anything you said.
I was simply pointing out, from experience, that people need to think it thru.

Just as a point of clarification ... I looked a the URL reference that you provided. I believe I have reviewed that before.

For FreeCAD 0.19.3 and earlier, I do see binaries provided the 3 OSs.
But I noticed that for FreeCAD 0.15 or earlier, there is no Applimage for Linux or Mac or both of those.
Again, from a standpoint of business continuity, maybe I am expecting something different, but I do not see (for the release at the top, FreeCAD 0.19.4, a precompiled AppImage provided in the same way that has been provided for the Windows environment.

So while I understand the rationale for dedicating manpower to the finalizing of FreeCAD 0.20 release (Important Note for FreeCAD 0.19.4), and I recognize that judgement call is justified given the scope of potential benefits that it will reap.

However, to keep it simple where someone might need to "recover" older data formats, it would seem a good idea to eventually have those added at a later date, to maintain the uniformity of "long-term" support across all versions. Just offering feedback in line with your guidance that those earlier builds would be available to enable the data recovery step. Thank you for hearing me out.

[fcbuilder]

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.

Thanks for explaining! Really helpful. Learnt a lot here

[MisterMaker]

Ok here is an idea, why not just save a static 3D model like step in the Freecad file? You can always open the Freecad file outside Freecad, since it is just a zip file.
I would say this wouldn't be too hard to implement, having a setting that saves a step file when you press save in Freecad and maybe a setting to retrieve the step within Freecad. You don't need any file managing, you get automatic backups in the file. Could even do revisions saving.
Something like this: