Sheet Metal Workbench

[rmu]

hi -- short question on how to use "Material Inside".

Suppose I want to design something like in the first example on the wiki page:


Flanges as defined on the github page here

should be 100mm. Even with Option "Material Inside", it seems I have to manually calculate the length of the bent legs (=flange length - radius - thickness). What am I missing? Thanks.

[FBXL5]

Even with Option "Material Inside", it seems I have to manually calculate the length of the bent legs (=flange length - radius - thickness). What am I missing?

You are right, you have to calculate length manually.

The parameters that control the flange are length and radius which are a leg length and inner radius in the GitHub example. In contrast, as you stated, the flange length equals leg length + outer radius. And so it's the designer's task to handle the thickness properly...

[bleber]

You are right, you have to calculate length manually.

I make some objects with these methot, and it is a tedious task. I thing that it need an easy auto calculated method to work with these.

[rmu]

You are right, you have to calculate length manually.

The parameters that control the flange are length and radius which are a leg length and inner radius in the GitHub example. In contrast, as you stated, the flange length equals leg length + outer radius. And so it's the designer's task to handle the thickness properly...

This manual calulcation becomes very awkward in case you have some non-orthogonal angles and somewhat negates the advantages of CAD I wonder how people use this in reality. In my experience, radius is somewhat determined by bending process and available tools and usually can't be manufactured to arbitrary values. At least with press brakes I'm familiar with.

Even in the 90° case, often times the exact radius is determined by the bending process and can be some arbitrary unwieldy number.

So I wonder how do you go about designing a box with given dimensions with the bend tool? Sure, I can model the box and chamfer/round edges, make a shell und then try to unfold, but that also quickly gets very awkward (corners, relief etc...)

[sfgrayson]

hi -- short question on how to use "Material Inside".

In commercial CAD this problem is handled by the settings Outer Sharp, Inner Sharp, Tangent Bend. Here is a short video showing the functionality.

This, and also a "tangent bend" option are covered in the Solidworks documentation for anyone interested.

Material In, Material Out and Bend Outside are related to the flange position "horizontally" along the material, whereas outer sharp/inner sharp/tangent bend all refer to how flange length is measured. (Shown in video.) So we might say something like - material outwards, flange material inwards, outer virtual sharp to describe this.

Even in Solidworks there is no compensation for material direction of base changing - all of your flanges will turn upside down. So when determining flange length it's important you do not change material in/out on your base wall.

Also: as far as radius changing during manufacturing - if your application requires such precision, you should either decide on an average bend radius across all of your bending tools, or you should optimize your design for whatever it is being bent with. At my job, we use 1mm bend radius standard for all our designs even though the radius on a manual bending break is much larger than on a pressbreak. It isn't big enough to be a problem, but we use thin metal, 24g.

[rmu]

hi -- short question on how to use "Material Inside".

In commercial CAD this problem is handled by the settings Outer Sharp, Inner Sharp, Tangent Bend. Here is a short video showing the functionality.

This, and also a "tangent bend" option are covered in the Solidworks documentation for anyone interested.

That makes perfect sense.

Material In, Material Out and Bend Outside are related to the flange position "horizontally" along the material, whereas outer sharp/inner sharp/tangent bend all refer to how flange length is measured. (Shown in video.) So we might say something like - material outwards, flange material inwards, outer virtual sharp to describe this.

Even in Solidworks there is no compensation for material direction of base changing - all of your flanges will turn upside down. So when determining flange length it's important you do not change material in/out on your base wall.

In FreeCAD there seems to be no way to specify the flange length. That's my main issue. You specify the leg length, but (at least) I don't really care about the length of the leg, I care about the overall flange length. I really don't see a case where you would want so specify a leg length, this quantity is also very difficult to measure in practice. (But then again, I'm no professional).

Also: as far as radius changing during manufacturing - if your application requires such precision, you should either decide on an average bend radius across all of your bending tools, or you should optimize your design for whatever it is being bent with.

That is how i do it, use the (inner) radius that comes out of the press brake CNC control, which typically for my sheet metal thicknesses is around one to two mm. But to me it is kinda strange to have to specify a leg length of 8.8mm given a radius of 1.2mm and flange length of 10mm that should be achieved. It seems more naturally to me to specify the radius in some parameter, and specify flange lengths. (terminology flange/leg as in the drawing linked in my earlier post)

[sfgrayson]

It seems more naturally to me to specify the radius in some parameter, and specify flange lengths ...

I completely agree. I hope that by putting some terms out there, and explaining how things are handled in other CAD, as well information on how this software is used in the industry, we can interest people and developers in implementing some of the things we'd like to see.

[blue0cean]

Corner relief error

can't you use the Corner Relief command on a simple fold?

Error:08:36:30 Traceback (most recent call last):
File "C:\Users\x\AppData\Roaming\FreeCAD\Mod\sheetmetal\.\SheetMetalCornerReliefCmd.py", line 447, in execute
s = smCornerR(reliefsketch = fp.ReliefSketch, ratio = fp.SizeRatio, size = fp.Size.Value, kfactor = fp.kfactor,
File "C:\Users\x\AppData\Roaming\FreeCAD\Mod\sheetmetal\.\SheetMetalCornerReliefCmd.py", line 262, in smCornerR
DetailList = getBendDetail(resultSolid, REdgelist[0], REdgelist[1], kfactor)
File "C:\Users\x\AppData\Roaming\FreeCAD\Mod\sheetmetal\.\SheetMetalCornerReliefCmd.py", line 192, in getBendDetail
cornerPoint = getCornerPoint(edge1,edge2)
File "C:\Users\x\AppData\Roaming\FreeCAD\Mod\sheetmetal\.\SheetMetalCornerReliefCmd.py", line 175, in getCornerPoint
cornerPoint = section.Vertexes[0].Point
<class 'IndexError'>: list index out of range
08:36:31 Recompute failed! Please check report view.

Code: Select all

OS: Windows 10 (10.0)
Word size of FreeCAD: 64-bit
Version: 0.20.28730 (Git)
Build type: Release
Python 3.8.13, Qt 5.12.9, Coin 4.0.0, OCC 7.5.3
Locale: German/Germany (de_DE)
Installed mods: 
  * BOLTSFC
  * Defeaturing
  * DynamicData 2.45.0
  * fasteners 0.3.40
  * fcgear 1.0.0
  * LCInterlocking
  * Manipulator 1.4.3
  * sheetmetal 0.2.49
  * TabBar
  * ThreadProfile 1.81.0

[chrisb]

Corner relief error

I encountered this as well, but perhaps I used it the wrong way. The only helpful documentation is in the icon shorthelp and it is not clear to me which two lines have to be selected before invoking the command (I tried already all I could think of).

[blue0cean]

after reading the manual several times
https://forum.freecadweb.org/viewtopic. ... ef#p549740
I was able to activate Corner Relief like this
Select Edge1 then select Edge4

Screenshot 2022-04-22 102746.jpg (37.18 KiB) Viewed 644 times

Screenshot 2022-04-22 102827.jpg (26.26 KiB) Viewed 644 times