Correct Method for Fusing Sheet Metal Part to Itself

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whoneyc
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Correct Method for Fusing Sheet Metal Part to Itself

Post by whoneyc »

I am creating a part using the sheet metal workbench, and I want to make a loop with the extend. What is the correct way to fuse an extension to the part?

Image

In the picture above, I have made two extensions of the base sheet metal at the top right of the highlighted part using extends and bends. I want to now close the loop by creating an extension in the magenta box, thus creating a sort of "O" shape. However, using an extension by itself does not fuse when extended to the other side. This is acceptable if I am laying it out flat for cutting. The challenge, is that I want to create a fillet at internal corners so it is not a 90\deg connection for CAM later.

Is there a way to do this with an extension?

Other options I have tried include: boolean base part (doesn't fit correctly because of weird fractional dimensions).

I am aware of the canonically correct method from this thread (https://forum.freecadweb.org/viewtopic. ... e&start=40) which suggests using an extruded path to form the sheet metal from the profile prior to performing a subtraction operation. In the future, for more complicated examples, I would like to know the answer to my question above.
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papyblaise
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Re: Correct Method for Fusing Sheet Metal Part to Itself

Post by papyblaise »

you make a fold on this face as for the others by informing Gap1 and Gap2 to have the width sufficient to fill the free space
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Shalmeneser
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Re: Correct Method for Fusing Sheet Metal Part to Itself

Post by Shalmeneser »

:idea:
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ShetMetalHole_SHALM.FCStd
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papyblaise
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Re: Correct Method for Fusing Sheet Metal Part to Itself

Post by papyblaise »

for fun: in a single sheet of metal, not sure if it's the most economical
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whoneyc
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Re: Correct Method for Fusing Sheet Metal Part to Itself

Post by whoneyc »

Thanks to all the folks more skilled than myself for answering.

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papyblaise wrote: Sat Aug 06, 2022 8:23 am you make a fold on this face as for the others by informing Gap1 and Gap2 to have the width sufficient to fill the free space
Good thought papyblaise; it is actually what I tried first when exploring my options. But there are some problems which arise from using US units (the preference of the shop I want to send this to) and curved edges. Radii introduce values to the system which are dependent on trigonometry, requiring loads of digits. Since the base of this part is constructed to fit the needs of other curved parts, it has a bizarre length, something like 23.1233333". When I attempt to adjust the gap, I cannot set it to a length which matches this value, as the fractional US inches do not play nice.

This means that practically, I can cover the gap and just assume that the part is connected. BUT, if I send this to my waterjet cutting guy, I will need to manually patch this spot or else the part is not continuous. Of course, for a single bad spot, this is trivial, but I would still like to know a "correct" way to deal with this for the future.

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Shalmeneser wrote: Sat Aug 06, 2022 9:50 am:idea:
and
papyblaise wrote: Sat Aug 06, 2022 11:55 am for fun: in a single sheet of metal, not sure if it's the most economical
Shalmeneser and papyblaise have both demonstrated the "canonically correct" method I mentioned in the last paragraph of the OP. Both are correct that the best way is to design a part which avoids the need to bridge and fuse. But this does not answer the question posed. Clearly, I am the type who designs himself into awkward places like this. I would like to know how to do something like a bridge+fuse in case I am, hypothetically, 1000 hours into a project and don't want to Undo steps back to hour 3.
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papyblaise
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Re: Correct Method for Fusing Sheet Metal Part to Itself

Post by papyblaise »

you would tell me about +/-1micrometer for an F1 engine part I would understand
but 23.123333......333mm rounded to 23.12mm for a sheet metal part is about acceptable, more precise is frog hair or fly's leg
whoneyc
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Re: Correct Method for Fusing Sheet Metal Part to Itself

Post by whoneyc »

papyblaise wrote: Sat Aug 06, 2022 6:47 pm you would tell me about +/-1micrometer for an F1 engine part I would understand
but 23.123333......333mm rounded to 23.12mm for a sheet metal part is about acceptable, more precise is frog hair or fly's leg
Oh absolutely, +/- 1 mm would be more than acceptable for this part. If I could round the value properly to a fractional inch, that would be great. But if there is not a proper corner because of some infinitesimal gap or overlap, how do I add a fillet so the part can be manufactured?

I've done plenty of work with fabrication in nm and Angstroms, but that certainly wasn't done with sheet metal! :lol:
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papyblaise
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Re: Correct Method for Fusing Sheet Metal Part to Itself

Post by papyblaise »

where do you want to add a fillet, all the functional ones are already
as you are stingy with your file, we cannot help you more
whoneyc
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Re: Correct Method for Fusing Sheet Metal Part to Itself

Post by whoneyc »

papyblaise wrote: Sun Aug 07, 2022 2:51 pm where do you want to add a fillet, all the functional ones are already
as you are stingy with your file, we cannot help you more
I need to fillet the interior corners of the opening in this shape. See updated version of the original picture below. The topmost fillets are easy, and if I create the bridge part, one of the fillets will be easy as well. The fourth will be challenging.

Image

This is updated in the new picture below:

Image


Getting that last fillet eludes me. Sorry for not attaching the file, the original was too large. I have removed all other bodies from the part in the attached file.
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papyblaise
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Re: Correct Method for Fusing Sheet Metal Part to Itself

Post by papyblaise »

Extend does not join the 2 sides, there remains a line in contact
I added a small square for welding, the 4 fillets are done but the unfold no longer works
Try Schlm's method it's what will work best
Note that unfold does the welding, you can make the last fillet on the blank before wearing it to the Lasercut
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bridge fuse.JPG
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bridge fuse2.JPG
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