Help for sheet metal part

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Plastec835
Posts: 4
Joined: Mon Sep 25, 2017 9:10 pm

Help for sheet metal part

Postby Plastec835 » Wed Jan 02, 2019 4:15 pm

Hi I have attached my file that I have recieved from someone else and i need to flatten this part to be cut out of flat sheets, is there any way to do it?
I tried to use the sheet metal workbench but it comes up with errors and says that if failed.

I tried the sheet metal unfolder macro but it says that I need to start with a flat face as a starter when I try a flat face nothing visibly happens under my part number it says shape and shape 001 but that is it. When I select a flat face and a radius to unbend it says " only one flat face has to be selected!"

Do you have any suggestions?



This my system info:

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.13522 (Git)
Build type: Release
Branch: releases/FreeCAD-0-17
Hash: 3bb5ff4e70c0c526f2d9dd69b1004155b2f527f2
Python version: 2.7.14
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.2.0
Locale: English/UnitedStates (en_US)
Attachments
308160-1 (2).stp
(92.48 KiB) Downloaded 13 times
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NormandC
Posts: 18213
Joined: Sat Feb 06, 2010 9:52 pm
Location: Québec, Canada

Re: Help for sheet metal part

Postby NormandC » Wed Jan 02, 2019 8:26 pm

Hello Plastec835,

You registered on the forum more than a year ago, but since it's your first post here, welcome.

The problem with this model is that it simply cannot be unfolded, there is a sharp corner on one side that I have highlighted in green:
FC_Plastec835_sheetmetal_part_01.png
FC_Plastec835_sheetmetal_part_01.png (21.14 KiB) Viewed 263 times
One other thing that makes it impossible to unfold is the vertical bend at the rear of the part, its top edge is co-planar with the under-face of the main part so the faces are fused together.

Here's what I think: this is actually an item made of two separate sheet metal parts, but because no gap was added between them, it got exported as a single, fused part.

I can explain how to separate both parts and I'm pretty sure it will then be possible to unfold them. But maybe you should check with the person who sent you the STEP file if this is supposed to be two separate parts or a single one. In the latter case, they need to redesign it.

Also,
Plastec835 wrote:
Wed Jan 02, 2019 4:15 pm
OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.17.13522 (Git)
Your version is slightly outdated, the last version with bug fixes is 0.17.13541. On the other hand, we are expecting for v0.18 to be released very soon.

Edit: fix typo
Last edited by NormandC on Wed Jan 02, 2019 8:44 pm, edited 1 time in total.
Plastec835
Posts: 4
Joined: Mon Sep 25, 2017 9:10 pm

Re: Help for sheet metal part

Postby Plastec835 » Wed Jan 02, 2019 8:42 pm

Ok I try that thank-you!
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NormandC
Posts: 18213
Joined: Sat Feb 06, 2010 9:52 pm
Location: Québec, Canada

Re: Help for sheet metal part

Postby NormandC » Wed Jan 02, 2019 8:54 pm

I've successfully split the part into two separate pieces using the new Part Slice apart command that was recently added in v0.18-dev.

But I couldn't unfold the upper part, the SheetMetal addon's unfold tool fails with the info that Face20 is an unsupported type of face.

Face20 happens to be the conical face of the countersunk hole.

I tried to remove it using the new Part Defeaturing tool (requires OCC 7.3.0) but it failed. Will have to do this manually then.

Edit: defeaturing works if I first "defeature" the two small fillets on the corners of the countersunk hole. Unfortunately, I'm getting a new error with Unfold:

Code: Select all

Error Analysis: Sheet thickness invalid for this face! at Face36
Will have to locate Face36...
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NormandC
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Joined: Sat Feb 06, 2010 9:52 pm
Location: Québec, Canada

Re: Help for sheet metal part

Postby NormandC » Wed Jan 02, 2019 9:36 pm

I could unfold the bottom part, but no matter what I try, I can't get the upper part to unfold...
Attachments
FC_308160-1_unfold_01.png
FC_308160-1_unfold_01.png (78.91 KiB) Viewed 241 times
chrisb
Posts: 14108
Joined: Tue Mar 17, 2015 9:14 am

Re: Help for sheet metal part

Postby chrisb » Thu Jan 03, 2019 12:51 am

I had tried a less perfect way and cut the connections away but that failed as well. I think it is due to the fact that that the bends are not circular but B-splines.
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NormandC
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Location: Québec, Canada

Re: Help for sheet metal part

Postby NormandC » Thu Jan 03, 2019 3:26 am

Yeah, I noticed when I created a set of faces to slice the part with. First I created a Draft Facebinder and it worked but there were some residual edges in the slice objects. Then I made a Draft Shape2DView from the Facebinder and extruded it; I noticed many co-planar and overlapping faces. So I converted the Shape2DView to a sketch; while editing the sketch, I discovered B-splines overlapping lines and arcs.

If you look at the tree in my screen capture, you'll see an Offset object - I made it from the Facebinder in an attempt to hopefully get rid of B-spline faces, but I think one of the cylindrical faces from the Facebinder is interpreted as a B-spline face. Anyway, at some point I threw the towel.
chrisb
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Joined: Tue Mar 17, 2015 9:14 am

Re: Help for sheet metal part

Postby chrisb » Thu Jan 03, 2019 7:43 am

I had given up earlier, and I'm glad you answered an open question: It is indeed possible to unfold sheets independent from their build process. Especially it is not necessary having build them with SheetMetal workbench.
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NormandC
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Re: Help for sheet metal part

Postby NormandC » Thu Jan 03, 2019 7:56 am

The Unfold tool in the Sheet Metal workbench is actually taken from ulrich1a's python macro and it has since evolved, so the build process of the part to be flattened has no influence - although, with a part built with the Sheet Metal add-on, you are almost certain that it will unfold.
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meme2704
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Re: Help for sheet metal part

Postby meme2704 » Thu Jan 03, 2019 9:22 am

Hello
I look at your drawing, in addition to what Norman says, I see that the edges are rounded and trim the hinges folding which makes unfolding impossible see my screenshot
I trace in a few minutes the profile of this piece and you provide the blank, for the side, it must redraw too
Attachments
support.FCStd
(98.88 KiB) Not downloaded yet
support.PNG
support.PNG (68.3 KiB) Viewed 193 times