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Sheet Metal Question.... Something to ponder...

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  • Sheet Metal Question.... Something to ponder...

    While at work... I was given a basket of parts off the laser center and told to run them in the new press-brake. Only two people currently are experts on this thing... I am still at the OMG IT CAN DO THAT?! stage of my training.

    Anyway I do have a background in bend-fu... but on older presses. This new press uses "frigging lasers" and other methods to measure the part as it bends... and adapts on the fly. Or you can feed it a drawing and it will construct three-D models on the fly and tell you how to bend said part...

    Very high tech.

    So I feed the basket of parts through the Timesaver... this is an underwater belt-sander that puts a fine finish on the parts... think "brush finish."

    I start running... first 60 parts are good... next part is 3 degrees under-bent. Next part after correction is three degrees over-bent.

    I put my corrections into the machine, and ended up with the over-over-under-under thing happening over the span of ten parts.

    Long story short... I figured it out but it only took me 20 pieces... when they nested the parts for the laser they had some going across the grain of the sheet and some with the grain of the sheet.


    Now it's too late, they've been removed from the sheet and brushed... You can't tell from looking at them which way they were nested. If I knew that, I could compensate.


    This is my question to you folks here: Does anyone know a method for determining grain direction in a sheet-metal part once it has been laser cut and removed from the sheet? Is there perhaps a trick or a SCIENCE! I could pull to figure this out?

    ...boss authorized a recut and scolded the laser operator. Going forward parts will be nested in one direction only... but I would like to at least attempt to save what we cut.
    "The Administration does not support blowing up planets." --- Finally some SENSIBLE policy from the Gov!

  • #2
    Anyway you could magnitize a portion and drop some filings on there and see what happens?
    Opportunity knocks once, temptation leans on the doorbell.....

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    • #3
      If it is aluminum then there is very fine grain lines that would indicate the direction of rolling. This applies to any 3003, 5052,2024, and 6061 that I have seen. On cold or hot rolled steel or 2B stainless sheet I think you would have no way of knowing without polishing, etching and a microscope. Much easier to learn the lesson and prevent in the future

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      • #4
        Originally posted by Grind Bastard
        Does anyone know a method for determining grain direction in a sheet-metal part once it has been laser cut and removed from the sheet?
        Yes, bend a few and then sort into "with grain" and "across grain" piles.

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        • #5
          Originally posted by Boostinjdm
          Yes, bend a few and then sort into "with grain" and "across grain" piles.
          That was my thought as to the easiest way. Set the press for the lesser bend so some will be OK and others will not be bent enough. Bend them all. Sort them into piles. Re-bend the "bad" ones to make them good.

          And do send a note to "them" about the problem and the need to keep the grain the same in all blanks.
          Paul A.
          SE Texas

          Make it fit.
          You can't win and there is a penalty for trying!

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          • #6
            Check if the press can tell how much force is required for the bend. The across grain parts will take more. Perhaps the press can be programmed to take that into account during the bend and compensate.
            Free software for calculating bolt circles and similar: Click Here

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            • #7
              I will suggest underbending everything and rehitting them to bring them into spec.
              "The Administration does not support blowing up planets." --- Finally some SENSIBLE policy from the Gov!

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              • #8
                without going for an etch and a microscope, without having the edges to work off its a bit tricky, you can use the thickness, when steel is temper or finish rolled it has a profile, this is the wedge and crown, the strip is thicker in the centre than the edge, a necessity to get the strip to track through the mill without a cobble as it must pass through the 6 or 7 rolling stands without going mad at up to 60Kmh hence the profile.
                you can measure it, its not much but if one side of the peice is thicker than the other the thick bit was at the middle of the strip so rolling was perpendicular to this if you see what i mean, its not going to be bang on but its a guide.
                also the mechanical properties and chemistry of a coil of steel are known to vary from one end to the other and from one side to the other as the coil is made from a continuously cast slab which usually varies in composition from the outside to the inside [due to solidification processes] and from one end to the other[ due to the nature of a ladle of steel] possibly even 2 different analysis are present as each succcessive ladle is always different.
                i have left a lot out as i'm trying not to get too boring!
                regards
                mark

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                • #9
                  you're discovering why pressbrake work can be so much fun (cough, cough)

                  You are apparently trying to air bend these parts using little pressure. Material thickness does have an influence in how well bending goes, as well as how one moves from air bending to bottom bending and then beating the crap out of the part.

                  Good luck. I really don't want to say any more.
                  gvasale

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                  • #10
                    Instead of running them in the ubertron-300 I ran them in the cranky old Niagara and bent the out of 'em. You know when you bottom-bend something SO HARD the die explodes... then you back the wheel off 1/8th turn? Yeah. THAT old trick. Coining I think they call it. :P

                    They are good enough.

                    Next batch is oriented properly and should bend "just fine" in the ubertron.
                    "The Administration does not support blowing up planets." --- Finally some SENSIBLE policy from the Gov!

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