length of sheetmetal

[d.evans]

I have a thin strip of sheetmetal, .0235" thick, that is bent twice forming "half" of a surround for a door opening. I can measure height, width, length, corner radius. What I DON't know how to do is measure the overall linear length of the part if it were "unbent" or straightened out. In my mind this is basically figuring out the circumference. Anyone know how to do this?

[george frick]

no this would not be the circumference. you have to figure the bend deduction allowance. i haven't worked in sheetmetal in years but the fomula for a 90 degree bend deduction is: 1.27 X T+.45 X R = BD. hope this helps.

[Matthew D. Hoedeman]

Well, have you tried a tape measure?

No seriously, depending on the tolerance, why not a tape measure? Are you looking for the length needed for the 'blank' of the part?

[craiger_ny]

Any measurement you derive from the formed part is not going to be the actual size of the "pre-formed" part. It can be done however. Do you want to include the radii, or do the length of each leg where they intersect each other then add them (the latter would be the easiest)?

[d.evans]

tape measure

or something like one, will probably be what we'll end up using. This project is full of these types of weird parts. They all have to be laser beam welded, so the tolerances are tight, even on extremely non-rigid parts like this one.

The print for this part has an overall width and overall height, corner radius callout, thickness of material and part depth...but it has no note for fixturing. There is enough springback in this part to make the corner radii out-tol, unless they are fixtured against a nominal size radius block. Yet, it gets left to me to come up with such a device on no budget.

[Aguayo]

yes the formula is C=2PIR THEN DIVIDE BY FOUR OR C=PiR DIVIDE BY TWO.
SUPPOSE THAT YOU NEED TO DETERMINE THE TOTAL LENGTH OF STEEL ROD.
FORMED AT 90º WITH A RADIUS OF 2" AND A DISTANCE FROM THE EDGE TO THE TANGENT RADIUS TO BE 8" AND THE OTHER SIDE DISTANCE TO THE TAGENT RADIUS 6" AND THEN WITH A THICKNESS OF 1". YOU WILL NEED TO ADD 8IN + 6 IN OR 14IN TOTAL.WHEN THE ROD IS BENT THE MATERIAL IS STRETCHED AND THE MATERIAL IN THE INSIDE COMPRESSED.THEN ADD HALF OF THE THICKNESS TO YOUR RADIUS.YOU HAVE IS THIS SAMPLE THE ANSWER IS.

3.1416 X 2.5RADIUS=7.854/2=3.927 + 14IN=17.927IN TOTAL LAYOUT.

I TRIED TO SEND YOU INF,BUT I'M HAVING PROBLEMS WHEN I INSERT A DOCUMENT,I HOPE THIS HELPS.

[Underspec]

Get a part that has not been bent and measure that one??

[Aguayo]

Yes,agree is better to measure one part before is bent.

[d.evans]

thanks for the responses

unfortunately, these were done by an outside vendor, and I have no access to the pre-bent parts.