Re: Sheet metal Cad

Ballendo,

I'm a novice at sheet metal design so the "K" factor is new to me.
Is that term widely used in the sheet metal fabrication trade?
Another term I saw recently on a CAD drawing was "mold line"
referring to the bend line.

Roughly paraphrasing here from an old D&K press brake book..the
neutral plane of a metal part (10 to 24 gage) lies 20% of the
thickness from the inside face of a 90 degree bend and 80% of the
thickness from outside face of the bend....the neutral plane is one
where no stretching of the metal takes place........the length of the
formed part along the neutral plane will be the correct length, or
cutting size, of the sheet.

Exact location of the bend lines can be figured from this also. This
applies to steel sheet and has served me well so far, not sure if it
applies to other materials like aluminum.

For other novices here's an example of how important it is to take
into account the material thickness.....for a simple "U" shape with
sharp 90 degree bends in 16 ga (.060") steel, the blank length will
have a 1/4" difference depending on whether the measurement is taken
inside the legs or outside. This is where simple "unfolding"
software could get you into trouble.

thanks,

Doug

--- In CAD_CAM_EDM_DRO@y..., ballendo@y... wrote:
> Tom,
>
> Nearly any high school drafting textbook will have the techniques
for
> drawing this sort of sheet metal work. Done manually, it is fast
and
> interesting. The "K" factor (which takes into account the metal
> thickness. The amount the metal "grows" or "shrinks" as it makes
> bends) may be overlooked in these texts, but IS found online. Try a
> search on "sheet metal layout" or "K factor".
>
> Also, a few of the woodworking magazines have published plans for
> cyclone type collectors, which have the sheet metal already worked
> out. Try Fine Woodworking and American Woodworker and WOOD for a
> start.
>
> Hope this helps.
>
> Ballendo
>
> P.S. BTW, the K factor for .063 alum, with relatively tight bends
of
> 90° is .100 . Using an import 3 in 1 press brake, this has worked
> well for me.