bent sheet metal manufacturability problem

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Internet4ever
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Joined: Sun Oct 25, 2020 3:41 pm

bent sheet metal manufacturability problem

Post by Internet4ever »

Hi all,

the following problem has been bothering me for a long time. I'd really appreciate it if someone could take a look at it.

Short version for quick readers:

Attached is an STL file of a simple bent piece of metal. If you look at the bend a bit closer, you can see that it is made out of faces.
Is there a tool within FreeCAD that converts my split-up bends into smooth bends that appear as radiuses in a STEP file?

Long version:

I regularly order laser-cut sheet metal from simple 2d drawings without any problems. The manufacturer also offers sheet metal bending. My bent metal 3d drawings in STEP format cannot be processed. Customer services says my bends consist of multiple adjacent faces instead of just a perfect radius. This is true. It is because I work with openSCAD. In openSCAD, I export an STL file, open that file with Freecad and then use Freecad to export a STEP file.

I'v gotten quite far in learning openSCAD. Thanks to corona, mostly. It would be a bit sad for me to have to start all over again trying to get used to the user interface of a different 3d drawing software, just because openSCAD doesn't do radiuses.

Thank you very much in advance.
Attachments
bent sheet metal that cannot be manufactured.stl
(59.9 KiB) Downloaded 31 times
chrisb
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Re: bent sheet metal manufacturability problem

Post by chrisb »

STL is quite usefuly as output format, yet I wish it had never been invented, because it is frequently used as input format. It is a lossy format where you just loose information. Almost every other format is better suited to transport geometry from one program to the other, very common is the STEP format.

You are right, that a smart program could guess some smoothing, but this is not implemented in FreeCAD yet (to anser your question). Your sheet metal looks rather easy, so I would always recommend to re-model it from scratch.
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papyblaise
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Re: bent sheet metal manufacturability problem

Post by papyblaise »

Fc does not have an export platform to other software allowing to use drawings and transform them for example: in sheet metal part file and to obtain the unfolded blank for use on laser cut
you have to learn Sheetmetal Wb and make your part with it, unfold the blank and ask your laser-cut contractor for the format compatible with his hardware and software
Internet4ever
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Re: bent sheet metal manufacturability problem

Post by Internet4ever »

@ papyblaise: Thanx for your answer. I'm aware of the 'sheet metal' workbench but the manufacturer I work with, needs 3d drawings to be able to assure manufacturability. I do not have to transform 3d bent sheet into unfolded 2d blank sheet metal in this case. The manufactuerer does that.
@ chrisb: If I get you right, there is no 'smoothing' function of the kind I would need, implemented in FreeCAD at the moment, like you say. The file I attached (thanx for watching, all of you, truly) was of course very simple. The sheet metal I really want to have laser-cut and bent in reality, is a little more complicated. I still haven't lost hope that someone knows how to create radiuses from [bends that look exactly like radiuses but are made out of faces]. Thank you all for your quick replies, still!
Regards,
internet4ever
chrisb
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Re: bent sheet metal manufacturability problem

Post by chrisb »

I see, as SheetMetal examples aren't the typical stl files found somewhere in the internet: No chance to get a STEP file instead?
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Internet4ever
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Re: bent sheet metal manufacturability problem

Post by Internet4ever »

Hi Chrisb,

thanks for your quick answer. I would love to give you a STEP file, like you reasonably asked for, because that's also the file format that the manufacturer wants. When I want to export such an STEP file, FreeCAD says 'please select first the objects you want to export'. I reckon that I do not understand something important here. The object looks perfect to me. It is the same, simple, bent sheet that I created and attached to/for my first post. I attached an FCstd file of the same object to this message for your reference.

I was able to export STEP files in the past that weren't useful to the manufacturer because of the faceted-curve problem discussed. The files back then were viewable in Step-viewer software. I'm quite sure it was about the adjacent-faces / radiuses thing.

If the attached FCstd file is of no use for you/for us to try and understand the problem, I'll create a STEP with facetted bends to emphasize my problem. I would rather know for sure that I can't create radiusus from openSCAD before I learn how to create them in FreeCAD, as was suggested. Still I would of course do so, if the latter is true.

Thank you again and in advance,
internet4ever
Attachments
bent sheet metal that cannot be manufactured.FCStd
this time in FCstd
(1.04 KiB) Downloaded 43 times
Internet4ever
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Re: bent sheet metal manufacturability problem

Post by Internet4ever »

Sorry I did not read between the lines.
There is no design from the internet.
Attached are two identical drawings, in different formats, that represent the lower part of a sheet metal enclosure that I drew. The enclosure will probably not fit but that's not the point. All the bends are not manufacturable as they are, because of the problem discussed in previous posts.
Converting those drawings to STEP is still a big problem because the many 'faces' that result in lots of Megabytes and consume a lot of time (several hours on a two-core computer, for example).
The attached drawings just indicate the problem. The simple bent sheet from my previous posts was just a simplification to be able to concentrate on the curve / facette problem. The drawing was not from the internet, it was mine.
I'm accepting if this is something that can't be solved through the openSCAD--FreeCAD route, still I would be very, very grateful if there's some way to just smooth the bends a bit and get corresponding STEP files.
Many thanks in advance,
internet4ever
Attachments
Rack Panel halbfertig 26-10-2020.scad
(21.03 KiB) Downloaded 26 times
Rack Panel halbfertig 26-10-2020.stl
(478.74 KiB) Downloaded 43 times
chrisb
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Re: bent sheet metal manufacturability problem

Post by chrisb »

I am not at all familiar with OpenSCAD, but there is an import format *.csg for OpenSCAD files. Can you export into that format? Hopeully it is not lossy as stl is.
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papyblaise
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Re: bent sheet metal manufacturability problem

Post by papyblaise »

I still haven't lost hope that someone knows how to create radiuses from
Very simply , this is " squaring the circle "
good luck
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papyblaise
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Re: bent sheet metal manufacturability problem

Post by papyblaise »

This here a drawing of your rack panel , made whith Sheetmetal , and a unfolding + bending lines
Ask your contractor for the right export file he need
Attachments
rack panel.FCStd
(216.81 KiB) Downloaded 16 times
rack panel.PNG
rack panel.PNG (23.58 KiB) Viewed 968 times
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