.05 Dev.L

[design-engine]

.05 Dev.L Developed length. How do you folks utilize this in your drawings or designs.

As you guys probably know I've been teaching Sheet Metal classes for years and years but I've never relay questioned anyone about the developed Length. I'm simply wondering how I should explain these when they are shown in the drawing.

 

[dross]

Bart, How can you teach sheetmetal and not know what that is? Oh, I know, you have never actually built a sheet metal part.
This is the amount of material that is required to make a bend taking into account the bend radius and the Y factor. Different Y factors will result in different DLs.

 

[design-engine]

so do you show those specific to each round and change y or k factor specific to those rounds. And is that due to possibly worn out tooling? Is it not common to simply change the y or k factor globally? Is it more common to nail tolerances in each bend?

 

[dross]

so do you show those specific to each round and change y or k factor specific to those rounds. And is that due to possibly worn out tooling? Is it not common to simply change the y or k factor globally? Is it more common to nail tolerances in each bend?

Bart, the factors are a function of the material. Different materials have different factors primarily related to the strength of the material. This matters because when you bend sheetmetal, you are actually stretching it on the outside of bend, and compressing it on the inside. The factor is how much it stretches. You don't want to just change the factor, the length given is correct for a given bend and material.

 

[design-engine]

My question is why are they exposed onto the detail drawing and how do you use them in the drawing? if you want a different stretch on one bend operation than another then you place a different y or k factor at that bend with that note?

When I administer a sheetmetal class I have refereed to bend tables as a way to manage older or worn out tooling. or maybe if grain direction is causing the tolerance to be out.

Maybe you can see Im not questioning the factors or why there is a bend allowance. BTW: My dad started teaching me bend allowances when I was 12 bending up parts for motorcycles from hand calculations from the machinery hand book. of course we didnnt need tolerances.... thats just my dad.

My question is: How do users utilize that .05Dev.L on a drawings?

 

[dross]

Bart, that information is reference and not usually on the drawing. Erase the note, problem solved.
Most sheet metal shops use their own bend factors anyways. If they do, then they will want the formed dimensions rather than the flat dimensions.