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Home > Forums > Industrial / Manufacturing Engineers > Activities > Industrial/Mfg engineering other topics Forum

Steel plate bend & unbend

thread301-242534
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z1 (Industrial)
12 Apr 09 19:16
Hi,

If for example, a steel plate of 1.5mm is bent 30 degrees with an internal radius of 2mm, when we flatten it again, it's lenght will increase, how much? How to calculate this?


Thanks,

Rjl
  
looslib (Mechanical)
13 Apr 09 16:39
Does your company use any type of CAD system? They can all calculate the flat pattern length.

Some links to help:
http://www.ciri.org.nz/bendworks/bending.pdf
http://www.sheetmetaldesign.com/WhitePapers/BendAllowance/SheetMetal-BendAllowance.pdf
http://www.mechengcalculations.com/jmm/metw004_process.jsp
 

"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

MikeHalloran (Mechanical)
13 Apr 09 21:20
That's the easy part.

The hard part is modeling, and then executing, the process of reversing the bend, which has to include a little overbend to get the part flat again, dealing with the change in K factor because of work hardening, and getting the reverse bend tooling precisely aligned with the initial bend.  ... and then there's the cracking.

Just out of morbid curiosity... couldn't you just leave it flat in the first place?

 

Mike Halloran
Pembroke Pines, FL, USA

ajack1 (Automotive)
14 Apr 09 13:00
If you calculate the developed length to the formed stage as described by looslib it will alter very little when you re-flatten it.

I am guessing this is for a lace in a progression tool where you need to tip the lace in order to "get at" an area that would otherwise be undercut or need awkward cams and is then re-flattened for further operations, this is fairly common practice.
 
z1 (Industrial)
15 Apr 09 13:26
I'm using this, as ajack1 mentioned, for a progressive tool, I need to rotate the part, and then rotate it again for it's initial position.
At the moment I'm considering this will not alter, but I know that it will (very little), so if I could just know how much, it was easy to compensate.
I guess there isn't a direct formula for this.

Thank's.
ajack1 (Automotive)
15 Apr 09 15:47
Z1 I would expect it to "grow" in the region of 0.05 to 0.1mm I would doubt this will matter. You could do two things firstly actually form and re-form a sample part of material or secondly depending on the final limits move everything as if it were to grow say .1 as it will defiantly grow this will decrease any possible errors.

I assume you will do as many critical stages (piercings, swaging etc) as possible after it has been re-flattened.
 
z1 (Industrial)
16 Apr 09 18:04
You're assuming correctly ajack1, I'm rotating the part to better form a corner, and following, after being flatened, piercing. I've thought also of making some tests in a probe, but also, de deviation values are meaningless for the part.
I was just wondering if there was a formula to calculate it.
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