sheet metal, bend allowance

[bengee5454]

Hi

I've have not had that much experience of working with sheet metal. I have been asked to draw a simple bracket (see attached). I have used 2mm thk aluminium.

I have been asked to supply the overall length of the flat pattern (which is no problem), and the bend allowance. How do I get this????

I've looked online and found a formula:  bend allowance = (bend angle (in radians))(bend radius+K*thickness), which i calculate as 4.5mm.

(pi/2)*(2+0.44*2)

Is there a way of calculating this in IV? I have used the default K factor value.

[bengee5454]

obviously it helps if I attach what I said was attached!

[CCarreiras]

Hi!

You can set the flat pattern calculation based in the K Factor, or bend allowance.

Check it there.

Tip: if you want always to flat parts based in Bend allowance method, just change the specification (by default, is the K factor method active) and save the file "as template".

[Thomas_Savage]

Hello,

If you measure the bend extents like in the printscreen, you will get bend allowance. I find this the easiest way.

Which is the same as what you got from the equation. 

Hope this helps?

Thomas.

[bengee5454]

Thanks.

If I use the K factor route, is it wise to use the default 0.44?

In the examples I've seen, they've used 0.33. Which to use???

[Thomas_Savage · Accepted solution]

Hello,

Yes use the .44 K-Factor. 

There is an equation to calculate K-Factor. But makes such little difference it is not really worth it.

And most people use .44 as K-Factor.

Thomas.

[CCarreiras]

Hi!

You have to measure the parts in the shop floor and compare what you have in the program with what you have in reallity.

If you are happy with the results, don't change anything, if not, you can change the Kfactor, or even better create a bend table to fit exactly your machine needs to achieve the real part equal to the one you design.

[Thomas_Savage]

Hello @CCarreiras,

Another way i usually do it is, bend a piece of metal on our press brake, scan it in, then in Inventor i can get an accurate Bend allowance, Bend Radius, and K_Factor.

Like in the prinscreen below.

Thomas.

 

[johnsonshiue]

Hi! To add to Thomas' reply, k-factor is merely a ratio defining the neutral layer. This layer is where the sheet metal unfold length is equal to the folded length. 0.44 means the layer is 44% of thickness from the inner side.

Please let me know if more information is needed.

Many thanks!