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  • Forming sheet metal

    I was thinking the other day about how CAD and CNC machines have revolutionalized things that we can machine and the speed with which we can do it.

    It seems however that with custom sheetmetal work, many of the operations are done manually. Is there a CNC equivalent machine for sheet metal? Something that automates the combined process of hammering, english wheel, and other manual sheetmetal operations.


  • #2
    Well...

    My failures are numerous.

    Problem is I don't have enough money to throw at it properly.



    ------------------
    David Cofer, Of:
    Tunnel Hill, North Georgia

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    • #3
      CNC bending and forming? Yep.

      See here:

      http://www.finnpower.com/html/bending_automation.html
      Free software for calculating bolt circles and similar: Click Here

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      • #4
        Thank Evan. I've seen those machines but they are really only suited for doing regular shaped operations, unless you use specialized or custom dies but then you're back to doing custom work.

        I was think of a machine which will produces parts like car fender, customer gas tank, etc. In other words, any curves and shapes that you can draw on CAD.

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        • #5
          A piece of metal does different things at different times.

          Pressure such as a hardwood stick while spinning builds heat to anneal the metal. Pressure under a english wheel anvil does too. A hammer well that is much quicker but stretches the metal pretty bad.

          Tubing, it does not act the same way twice. The spring-back of identical pieces thou close is not the same.

          My english wheel was automated with a gearbox, for/back limits. I was really scratching my head at times.. Different results with same input..

          Nothing beats the "human" eye for coordination and estimates on what to do next.. (fuzzy logic?)


          ------------------
          David Cofer, Of:
          Tunnel Hill, North Georgia

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          • #6
            Oh yea Evan; bolt one of those examples to the rear quarter of a 39 Dodge. That would look dandy. The CNC benders make great straight lines but you can't "form" complex shapes with them. (Curves and compound curves.)

            There's no subsitute for the press but not many home or small shops can't afford the $50,000+ for ONE set of DIES. Much less the press. You need one set of dies for each part you make.

            In comes the hand made parts. Just like they used to be made. With a modest investment and some skill, you can fabricate just about any panel for any car. Where a press might make a floor pan in one process, the hand made piece may take five or six steps and involve ten tools. But... those tools can turn around and make a splash apron or firewall in a few minutes. Changing out dies in a large press can take days.

            Production is one thing; a one-off reproduction or repair is another. Custom work is just that and it usually needs to be done now. Would you pay $150,000 for a 1925 Ford fender? Counting the overhead, that's what you'd pay for ONE stamped fender. And certainly no CNC folding machine can make it either.

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            • #7
              <font face="Verdana, Arial" size="2">Originally posted by ibewgypsie:
              A piece of metal does different things at different times.
              ...

              Nothing beats the "human" eye for coordination and estimates on what to do next.. (fuzzy logic?)
              </font>
              Surely the dynamics of sheetmetal deformation is a well understood science.

              [This message has been edited by rotate (edited 09-17-2004).]

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              • #8
                I missed the part about english wheel etc. You want to see the ultimate home project in hand forming? Check out this guy.

                http://members.aol.com/COUPECHUCK/
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  I think a cnc'ed english wheel is entirely possible. Even for a home shop.

                  My last attempt caused me to push the whole mess outside. I just now bit my lip and moved it back in.

                  Frustrating. Scanners are needed to compensate for bending metal. Yes, if you did it like that it will work.

                  I made several motorcycle fenders, problems.. too much metal,, I need some way to shrink added to my stretching. I am still learning. If you live and pay attention you can't help from it.

                  I throwed them out, a friend picked them up and used them w/much bondo.. I don't like adding bondo do you?

                  A rotating die type press arrangement is possible too. but you still need the hand/eye to fix it.

                  Nothing beats a good eye. be it hitting the mark shooting a gun or bending metal. Automation is still years behind.

                  ------------------
                  David Cofer, Of:
                  Tunnel Hill, North Georgia

                  Comment


                  • #10
                    Rotate,

                    Is this more what you have in mind?

                    http://www.irishscientist.ie/2002/co...=is02pages.xsl
                    Free software for calculating bolt circles and similar: Click Here

                    Comment


                    • #11
                      Hey- its not fair if you ask about what the sheet metal equivalent of $100,000 CNC VMC's are, then say, oh, yeah, they have to cost lest than a grand.
                      There are lots of 3d sheetmetal parts being formed on cnc machines- but the costs are enormous. There are CNC bending brakes, rolls, turret punches with lasers and plasma like evan linked to, and then there are CNC presses.
                      One interesting CNC trick these days is hydroforming- do a google and see-

                      But so far no one has made a CNC press that will shape sheet metal in 3D, without dedicated tooling, as well as a phillipino guy with a hammer and a hole in the ground. No reason it couldnt be done, though- its just that industry doesnt need the ability to make one ferrari fender. They need to make 100,000 chevy fenders a month. So the cost of fixed tooling is easily amortized.
                      I would imagine that the intermediate step will be 3D printers making tooling for big presses, and the final stage could be a variation on the way they do embossing on a turret punch- lots of little taps, with a nylon tipped die, computer controlled table moving the metal around.

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                      • #12
                        <font face="Verdana, Arial" size="2">Originally posted by Evan:
                        Rotate,

                        Is this more what you have in mind?

                        http://www.irishscientist.ie/2002/contents.asp?contentxml=02p133b.xml&contentxsl =is02pages.xsl
                        </font>
                        Yes. I think if they had "hemispherical" tool both on the top and the bottom of the sheet metal, they could work in unison to create contours that would not be possible with one tool. I think having pods which can locally apply clamping and holding would be necessary, since as other have noted, pulling, stretching, and contracting can cause finished part of the sheet metal to deform.

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                        • #13
                          On the discovery channel there was a show on building the Queen Mary 2. They were building it in sections and I seem to remember hearing that the sheets of steel that made up the ships hull were precisely formed on a computer controlled forming machine. Unfortunately they didn't show the machine

                          Come to think of it, those sheets are pretty thick, so how did they use to form those huge sheets. I don't think it was done with a hammer and an english wheel, and I doubt they would build a die for each one of them.

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                          • #14
                            I worked at one time at a place that made specialty electrical boxes, the kind that they put in the floor of ballrooms for Audio and Power. I was the only machinist in the shop as most of the work their was with "tin". Anyway, they had a big CNC turret punch that would bang out the box, then it would go to the CNC press brake and folded into shape. The advantage of the Turret punch is that 99% of the time, you can use off the shelf dies, which are changed in minutes, plus they're relatively cheap and easy to replace. The machine wasn't: $400K. Turret punches aren't really suitable to drawing. That is still the realm of big presses. Of course, nowadays, a CNC machining center cuts the wait for a new die down to days, where it used to be weeks or months in "the bad old days". As for the bender debate, you should see a CNC mandrel bender at work. most can rotate the tube so that bends can be done on a different radial plane. They are fast and accurate, and expensive as hell. I believe Gray Machinery usually has them in stock.

                            HTRN
                            EGO partum , proinde EGO sum

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                            • #15
                              Incremental forming, we've been doing it for a couple years.

                              Toyota in Japan makes prototype panels that way.

                              The link Evan posted shows only the simplest shape.

                              The downside is unless you do some tricks before the CNC formng part of the operation the forming is pure stretching/thinning of the metal. Also there's some limits to steepness of the walls of part, ie. you can't do a tin can shape.

                              Ries, it doesn't take a $100K machine.

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