Beginner Sheetmetal question 2

[a0r0t]

Beginner Question:

I have a piece of sheet metal .010 thick and need to add a bend, what's a good Rule of Thumb to figure out your inside & outside radius?

Thanks!

-Art

 

[desertfox]

Hi nofear

I would use an inside bend radius of two or three times the material thickness.

regards

desertfox

 

[Dennyd]

The inside bend radius is a function of the tool used to make it. In general, you should use an inside bend radius at least 1.5 * material thickness. However, what you specify may not be what is available. Check the radii of the available tools and select from those. You might want a .045" radius but you'll likely not find it. The tools we used had nose radii of .030, .060, .090, etc.

- - -Dennyd, P.E.

 

[mloew]

nofear,

This topic has been covered before. Please see the thread Sheet metal design (thread404-65458).

Best regards,

Matthew Ian Loew


Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[pennpoint]

nofear
Aluminum or steel?

 

[drawoh]

nofear,

The optimal sheet metal bending radius depends on the thickness and the material. Brittle materials require a larger radius. Take at look at the following table.

http://www.engineersedge.com/sheet_metal.htm

This information might also be in a sheet metal catalogue. Do a Google search.

JHG

 

[profengmen]

No no no no no.

Talk to your fabricator and find out what his bend deduction is...all tools are different (like dennyd tried to tell you)

Then remember to cut the bend deduction in half if you are dimensioning the bend line on a flat layout.

Only the guy that bends the metal can tell you what the bend deduction is.

 

[drawoh]

profengmen,

I believe that nofear asked what the inside and outside bend radii are. The bend deductions should be left to the sheet metal fabricator. The fabricator we work with seems to trust SolidWorks, if that is any help to anyone.

My old Atlas Alloys catalogue has a table showing the forming characteristics for a ninety degree cold bend of aluminium sheet. For a thickness of .065" to .128", you multiply the thickness by the following numbers to get the inside bend radius.

Alloy Bend factor
1100-0 0
1100-H14 0
1100-H16 2
1100-H18 3
2024-0 1
2024-T3 6
2024-T4 6
2024-T6 7
5052-0 0
5052-H32 1/2
5052-H34 1
5052-H36 3
5052-H38 4
6061-0 1/2
6061-T4 2
6062-T6 3

This table is partial, and I have _not_ checked to see if it agrees with the web link above.

One of the morals of this is that there are certain grades of aluminium that are very good for sheet metal fabrication, and others that are not. 6061-T6 is a popular machining grade, but it cracks when the sheet metal guys try to bend it. Sometimes it cracks afterwards, after delivery to the customer.

The outside radius is the inside radius plus the thickness.

JHG

 

[liberty]

Remember, Solidworks' bend deductions are only as good as the bend table on your hard drive. Be careful!

But of course, this thread is about bend radius. And drawoh hit it on the head.

 

[aamoroso]

The best modern way to be sure is to cut a sample of material. Measure the exact dimensions, have forming put a few 90 degree bends and then measure all of the legs. You can get your bend radius and k factor by doing this. The tooling used, method used (coining vs air bend) these will all impact the amount of stretch to the material so run some tests and you will be suprised how accurate you can get it.