As most of you may know, in a Sheet Metal part, flat pattern feature can also be configured like any other feature:
There are a few options there that I normally would have left as default, but recently I got involved with more SM designs and I am wondering about whether leave Corner Treatment Option On or Off (it’s on in SW default templates).
This is how I interpret it after researching about it: (though there aren’t many topics about this) it manipulates the flat pattern where bends meet (presumably for manufacturing purposes? to create a clean profile) but at the cost of flat pattern not matching 3D model, which to me is a very bad practice. My confusion is why then it’s left as default and is there really any benefit to it when it comes to manufacturing?
Can I ask you to please create a sample model, experiment with this and let me know your findings? (all it takes is a part with two flanges)
Here’s a sample example:
Corner Treatment On:
Corner Treatment Off: (More realistic? Folding this actually produces the 3D Model)
Flat Pattern Overlapped with 3D with Corner Treatment On: (Doesn’t make sense to me):
Flat Pattern Overlapped with 3D with Corner Treatment Off:
There’s a video in MySolidworks training catalog that basically advocates leaving it on, so I am now confused whether leaving it on is the way to go and I am missing something here.
https://my.solidworks.com/training/master/308/flat-patterns-in-sheet-metal
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ON, 100%.
Correct flat pattern is more important.
SM model is never 100% correct because of geometry limit.
But to me ON is way too off, bending would be affected.
You don’t usually want the result with Treatment Off. Well, I didn’t have any reason to want that in the pass 30 years.
This is what most will want:
Seems to me it’s getting rid of the relief which is desirable to have at corners, but if those parts came okay then I guess somehow fabricator make it work 
Edit: https://youtu.be/9hdFZR5722s?si=XdR7CiWIQ2XF_GpR
Found this link.
My guess is that for thin material it doesn’t matter but have to confirm.
It depends on how you want the corner.
Will they be welded? On outside? Inside?
You add corner treatment to get what you want.
It’s not about material thickness. I’ve done the same with 0.5 in plate.
It depends on how you want the relief in the corner.
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I know we are deviating a bit from SW related topic, but what I meant about depending on material thickness is that for thick gauges or plates not having any corner relief (corner treatment on) is not recommended.
In my case I don’t have any welding - in cases that I have welding I probably also go with “Corner Treatment” on to keep the gap as small as possible so welding can easily be done.
All I can say is that corner treatment is getting rid of the relief. It should be noted that if you actually have a corner relief feature added then corner treatment on or off doesn’t affect the flat pattern.
This is a 3mm sheet with 3mm inner radius, pretty typical.
Corner treatment is on, how can this be bent without tearing material. Only way that’s possible is going with smaller inner radius.
Here the inner radius was changed from 3mm to only 0.03125mm, this one at least can be bent without tearing material.
Turning off corner treatment for the 3mm inner radius example, modified the pattern so it has relief, so bends won’t tear through material.
What I’ve shown is the first one.
Material didn’t “tear”. They did get pushed up a bit.
Material will tear if bend in opposite direction.
I don’t know man, to me you can’t get the formed shape from the yellow (flat) without tearing that corner, it’s physically not possible.
I don’t dispute you got your parts well and good but I have to think maybe fabricators adjust things as needed to make it work or add slight reliefs (so long as final formed shape OAL size etc. is maintained), or using smaller inner radius. I’m very curious about this and will reach out to some fab shops to get their opinion on this as well.
To me corner treatment is altering the model by getting rid of the corner relief, somehow similar to to the simplify bend which alters the curved edges to straight ones only in your flat so one can be sure the bent real life version won’t be curved (again I think to ease the cutting with laser, etc. easier as it works better on just a straight edge).
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I work in fab shop, not magic shop.
No magic on making good part.
Do you want corner relief or corner treatment? Pick one, can’t use both.
Got photo of the part you want to make?
Another part in the shop:
No magic, no cheating. Tooling mark is on the part. Air bend, no corning.
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Took a closer look at the “Corner Treatment” option.
Looks like it “cheat” on the flat pattern without changing 3D model.
It’s a quick fix without modeling.
If it give you what you want, use it.
If it’s doesn’t then model it properly.
And there are other way to “fix” or “cheat” flat pattern.
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Hi Frederick,
Thanks for the info and the last picture, I think this was a fruitful conversation and will be helpful for future visitors considering there aren’t many info on this on the web, I appreciate it.
I want 3D model to match the flat pattern so no corner treatment for me.
Edit: In fact @David_Matula already added this to 3DS forum under tips - we made the news.
Thanks!
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It was to good of a post not to let some of them guys that always ask how to convert to sheet metal on how to achieve good results.
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Sheetmetal is always tricky. Never straight forward.
Try not to fight with the software. Just get a usable result.
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Regarding corners, usually this isn’t necessary unless you are doing 3d renders and just need the formed part to look exactly how it will look.
The flat needs to be whatever it needs to be for your manufacturing process and environment. We sometimes have to add features just for flat to get it the way mfg wants it. They are looking for the simpliest and most cost effective way to fabricate the part. We have many examples like @Frederick_Law has shown. Thin gauge parts with closed corners and no corner relief. They are thin enough that the corner deformation isn’t too pronounced and material cracking it not a concern.
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