Bend/Corner Relief's & other Sheet Metal Details.

[womble]

Hi All,

I am currently writing a Design Manual for my employers. The chapter I am writing at the moment is on sheet metal design.
There is some discussion at work as to what the correct sizes for relief's are in relation to material thickness and in some cases material type.
We have also been discussing if circlular type relief's are better than rectangular relief's or if it's just down to what tooling you have.
Basically I am looking for what other sheet metal workers think on this subject. What other tips may you also have?
Lastly, has any on this info been documented before in a 'standardised' fashion?
Any referance books on this subject?

Cheers,

Womble

 

[twentywinks]

Hi Womble,
was interested to read your article referring to corner bend relief.have to say my personal preference is to use a circular relief as opposed to a rectangular one,mainly because I feel it looks tidier if it is required that the relief is left as is after any welding or indeed if no weld is required.I also tend to use a practice of the diameter being twice the material thickness which usually looks quite neat and tidy.I hope my views are of some help.
Kind regards AEK

 

[MadMango]

There are less stress concentrations when using circular reliefs over rectangular reliefs. "The attempt and not the deed confounds us."

 

[ornerynorsk]

Ditto. You'll develop cracks less quickly with circular reliefs if the fabrication is subject to vibration and deflection.

 

[womble]

Hi all,

Thankyou for your replies.
Yes, I agree with your views on the improvement in fatique life with the circular reliefs. We use them on our thicker parts all the time.

Sometimes though when we manufacture parts for other people they like to have squared reliefs, mostly on very thin gauge material eg. 0.5mm. I have asked why, their reply was that it was what everyone else did in their market. Not a particually satisfying answer!

Cheers.

 

[MarkZE]

In one of my previous jobs I did a lot of work with service body designs. I always used round reliefs generally because we had round punch tools in various sizes. I awalys tried to use the smallest relief possible and increased it if the resulting part was difficult to fold or was creating a high spot on the corners. Generally a hole of about double the metal thickness is a good start on thin stuff. When getting thicker the internal bend radius starts becoming more significant hence a bigger relief is needed.

It is sometimes a good idea to use a very small relief especially if the part is not being welded. The distortion of the metal in the corner has the effect of nicely closing the corner if you get it right. I always found trial and error was the best method.

I had the benefit of being able to see the result of the corner notch in solidworks before I released the drawings for cutting. Solidworks is a very powerful tool for any sheetmetal designer.

 

[smcadman]

We use circular reliefs. Easy to weld and looks good if not welded.

Flores