I'm trying to get some bent sheet metal parts made by SendCutSend, but can't get their site to accept my 3D STEP file. With the attached 3D model I get an error "This STEP/STP file contains a non-sheet metal part and cannot be manufactured."

I used a material thickness of 0.119" and a bend radius of R.063" taken from their bend calculator output for A36 steel.

https://sendcutsend.com/bending-calculator/

I've never designed bent sheet metal parts. What else do I need to do in MoI to create an acceptable 3D model?

- Peer

hi PEER
have you take a look on the next post , perhaps it could help you !


MO script

https://moi3d.com/forum/index.php?webtag=MOI&msg=11523.13

chri

Hi Peer, this is just a guess but maybe it wants simplified planes.

Is it happier with either of these?

- Michael

Hi Michael,

Decent hunches on the analytic planes and coplanar surfaces, but the same error is thrown for both these new versions.

Poking around it almost sounds like there's a kind of BRep called a "sheet metal body" and the vendor is particular about "Your STEP/STP file should contain a single, solid sheet metal body. Files with multiple bodies stitched together or assemblies will not upload successfully."

I tried a zero-thickness surface, but that doesn't work either. I guess a sheet metal body must have thickness since one of the links below says "Parts designed with a thickness greater than 0.500″ may not upload successfully."

Is there such a thing as a "sheet metal body" in the STEP standard, or are they talking loosely about sheet metal bodies that have attached parametric bend data in a CAD system's internal representation, but become standard-issue solids when exported? I'm surprised by the prohibition on solid bodies being stitched together since I didn't think that was a thing in the first place.

https://help.autodesk.com/view/fusion360/ENU/?guid=GUID-F26CB5C7-A011-4C13-A2E9-F58790B8FC1D
https://sendcutsend.com/guidelines/3d-files/
https://sendcutsend.com/blog/how-to-export-a-step-file-from-solidworks/

- Peer

Thanks for the link Christian. Have you successfully uploaded a 3D .STEP file to SendCutSend using that plugin?

- Peer

Hi Peer,

re:
> Is there such a thing as a "sheet metal body" in the STEP standard

Not that I know of. Maybe when SolidWorks has an object in sheet metal mode it writes out some particular attributes that their importer is looking for.

Is there any example STEP file that works?

- Michael

Hi Peer,

re this part:
> I'm surprised by the prohibition on solid bodies being stitched together since I didn't think that was a thing in the first place.

Yeah that's kind of a strange thing to say. Usually that term "stitched" means surfaces being attached to each other along a shared edge.

I think they just mean that they don't want multiple solids to be packaged together in a single STEP file.

- Michael

Hi Michael,
Yes, programs like 360 and solidwrks have a "Sheet metal Mode or workbench". The STEP file will contain other info like bend data and flattened entities.

Hi Michael,

good.stp works, but MoI.stp fails

MoI.stp is the result of opening good.stp with MoI and then saving as .stp

The MoI header is ok: the problem is in the Data section. I created a hybrid file with the MoI header and the good data and that works, but using the good header and the MoI data fails.

- Peer

Hi Peer, what do you have set in moi.ini under:

[NURBS Export]
WriteAnalyticCurves=n
WriteAnalyticSurfaces=n

Do you get any different behavior if those are set to =y ?

Does "good.stp" come from sheet metal mode in SolidWorks?

- Michael

hi PEER


" Have you successfully uploaded a 3D .STEP file to SendCutSend using that plugin ?"

No I didn't do it

What is important for me is not to unfold but to provide the manufacturer a correct 3D part
I let the supplier unfold

( the "losses" when folding and the unflattening parts depend from the folding tools witch will be used and the material quality ).

Excuse me for my bad english, i'm french

christian

Hi Michael,

Now we're getting somewhere. The washer works if it's exported with analytic surfaces:

WriteAnalyticCurves=n
WriteAnalyticSurfaces=n
- fail

WriteAnalyticCurves=y
WriteAnalyticSurfaces=y
- success

WriteAnalyticCurves=y
WriteAnalyticSurfaces=n
- fail

WriteAnalyticCurves=n
WriteAnalyticSurfaces=y
- success

But, going back to the bent part we started with, .stp files of your "119 R063 sendcutsend3.3dm" and "119 R063 sendcutsend2.3dm" exported from MoI with WriteAnalyticCurves=y and WriteAnalyticSurfaces=y fail with the same error when uploaded to SendCutSend.

If I try uploading a .stp exported from "119 R063 sendcutsend.3dm" that I originally posted with the non-analytic planes generated by Sweep, but now exported with WriteAnalyticCurves=y and WriteAnalyticSurfaces=y, I get a new error "This STEP/STP file has an inconsistent thickness and cannot be manufactured."

Re:
> Does "good.stp" come from sheet metal mode in SolidWorks?

I downloaded it from McMaster-Carr. No idea of the software origin beyond what's in the header.

- Peer

Hi Christian,

Re:
> the "losses" when folding and the unflattening parts depend from the
> folding tools witch will be used and the material quality

Yes that's exactly why I want to send the manufacturer a 3D model. I want the manufacturer to calculate the bending losses for me.

- Peer

OK I got to the bottom of the problem. Surfaces generated by Sweep are non-analytic. Not just planar faces, but also the cylindrical faces at the bend.

Attached is a model made with Extrude and Revolve that works. Should have thought of this earlier since it's not the first time that a non-analytic result from Sweep has tripped me up.

- Peer

That's great Peer! It would be cool to see some of the metal parts when you get them made.

- Michael

Hi Peer,

Does full analytic bend.3dm and full analytic bend.stp exported with this NURBS Export settings?
WriteAnalyticCurves=y
WriteAnalyticSurfaces=y

Hi Michael,

I would like to deeply understand of NURBS Export settings, may I ask you for your explanation in which case we should use "y" or "n" parameter in MoI ini file?

Thank you very much.
Mik

Hi Mik,

re:
> I would like to deeply understand of NURBS Export settings, may I ask you for your explanation
> in which case we should use "y" or "n" parameter in MoI ini file?

The case where you could benefit from switching it is if a receiving application works better with one or the other.

It depends on the behavior of the application you're sending it to.

When WriteAnalyticSurfaces=n then surfaces will be written to STEP format as a general B_SPLINE_SURFACE entity. When WriteAnalyticSurfaces=y then surfaces that are planes, cylinders, cones, or spheres will be written as a specialized entity type like PLANE, CYLINDER_SURFACE, etc...

Most of the time if the receiving app cares about analytic geometry they will examine general surfaces and automatically detect if they are actually planes, cylinders, cones, or spheres so it doesn't make any difference. But in certain cases (as Peer encountered here) that might not be how the importer works.

- Michael

Hi Michael,

Re:
> It would be cool to see some of the metal parts when you get them made.

Sure here's a pair of sheet metal brackets I made by hand using MoI dimensioned drawings.

- Peer

Hi Michael,

OK, I understand.

Thank you.
Mik