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Robotic percussive panel-beater

Percussey.
  (+6, -1)
(+6, -1)
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High-volume car body panels are made using massive hydraulic presses, for which the tooling costs tens of thousands.

For smaller volumes (restoration, or exotic vehicles), metal panels can be made by traditional panel-beating, but this is fearsomely expensive.

I would like to propose an alternative - a method of producing complex bespoke body panels under computer control.

A sheet of steel is held firmly between two frames, leaving it unsupported except at its edges. The business-end of the machine consists of a gun, from which individual ball bearings (say, a few millimetres in diameter) can be fired. The speed of the ball bearings can be controlled precisely, and of course the gun can be moved in the XY plane with a precision of a few microns. Lasers on either side of the gun can be used to measure the displacement of the target (the steel panel) in the Z axis.

Under computer control, the machine plays back and forth over the metal sheet, firing ball bearings with sufficient force to gradually, millimetre by micron, coax the metal into the right form. The used ball bearings are, of course, collected and reused.

For tight or complex curves, it might well be necessary to have guns on both sides of the sheet, independently controlled.

The process would be very slow and very noisy, but useful for producing precisely-shaped one-off panels, with no need to retool between jobs.

MaxwellBuchanan, Jun 13 2014

Father Ted https://www.youtube...watch?v=vcNiYQgsBUU
[spidermother, Jun 14 2014]

deformatation without penetration http://www.bluerhin...ts_test_targets.htm
[not_morrison_rm, Jun 15 2014]

In particular.... http://www.bluerhin...tml_files/10169.jpg
[not_morrison_rm, Jun 15 2014]

[link]






       Pardon? Can't hear you...
not_morrison_rm, Jun 13 2014
  

       "Machine Operated by a young red haired girl in a halter top with a CS degree named Dimples" Rated PG
popbottle, Jun 13 2014
  

       If the pellets are small enough so that their dents can overlap smoothly, then to make them go fast enough to actually dent the sheet of metal, wouldn't you risk puncturing it?
Vernon, Jun 14 2014
  

       I don't think so. Each pellet is only moving the metal by maybe a few tens of microns at most.   

       If you wanted to, you could make the pellets the same size as a panel-beating mallet head, but I think smaller pellets (and many, many more small impacts) will do a better job.
MaxwellBuchanan, Jun 14 2014
  

       May I, as an American who has one, suggest to an Englishman, an English wheel?
cudgel, Jun 14 2014
  

       The English wheel is a great tool in the hands of a skilled craftsman. However, it lacks the ability to automatically produce a given shape from a CAD file in the hands of an unskilled person.
MaxwellBuchanan, Jun 14 2014
  

       This converges on a sandblaster. I think Vernon is right that steel would be too abrasive. Maybe balls of ice?   

       But a sheepish +; mostly for the redhead.
bungston, Jun 14 2014
  

       Well, it's all going to depend on the diameter and speed of the pellets. At some point, it becomes the same as panel-beating, which deforms the metal without abrading it.
MaxwellBuchanan, Jun 14 2014
  

       (+) Pretty sure this would work.
cudgel, Jun 14 2014
  

       I'm guessing that the pellets will at least need to be many times larger than the thickness of the panel. But then it's just a question of optimising; even if the pellets need to be a centimetre or more in diameter for best results, the concept still flies.
spidermother, Jun 14 2014
  

       A bit like shot peening, then, which does not abrade but compresses the surface to reduce stress cracking.
Ling, Jun 15 2014
  

       //the pellets will at least need to be many times larger than the thickness of the panel//   

       I'm not sure if that's the case. Imagine tapping a bluntish nail on a 2mm steel sheet - it will make a small indentation. Hence, a ball with a diameter similar to that of the blunt nail ought to do the same, if fired at a high enough speed, no?
MaxwellBuchanan, Jun 15 2014
  

       It's about mass, as well as contact area. A projectile of small mass cannot transfer much of its energy into moving a large mass; to make a dent (rather than punch a hole) in 2mm steel, you need to move considerably more than 4/3*pi cubic millimetres of steel, so you need a projectile considerably more massive than a 2mm diameter steel pellet.   

       Sand blasting and shot peening have been mentioned; in each case, projectiles which are of relatively low mass mostly have a surface effect.
spidermother, Jun 15 2014
  

       Presumably this could instead be done with a static-mounted hammer and anvil, and a robotically-controlled frame which holds the sheet metal. The hammer bangs away in one fixed place, while the robotism twirls and shiggles the sheet under the hammer.   

       A contraption like a daisy-wheel printer rotates different shapes of anvil under the work point. Perhaps a number of different shaped hammers could be used, typewriter-style as well. That gives the robot lots of options for shaping convex, concave and other types of surface.
pocmloc, Jun 15 2014
  

       //so you need a projectile considerably more massive than a 2mm diameter steel pellet.//   

       Hmmm. I'm not sure. WIth a high enough velocity, the pellet will punch a hole through the sheet. With a low enough velocity, it will just rebound without permanently deforming the sheet.   

       Are you saying that there is no velocity between those extremes, whereby the pellet will dent the steel, even by a few microns?
MaxwellBuchanan, Jun 15 2014
  

       //Are you saying that there is no velocity between those extremes, whereby the pellet will dent the steel, even by a few microns?   

       Yes. But only to be annoying.   

       Falling back on empirical evidence (the last resort of the scoundrel, I know) it seems our transatlantic cousins, in the drive to use something other than lead in shooting, have done quite a few ad hoc tests of steel shot/plate steel interactions, see linky, Not to mention road signs et al.
not_morrison_rm, Jun 15 2014
  

       Something like a rapidly-repeating captive-bolt gun might work better - or even the 'hammer' action from a hammer drill
hippo, Jun 16 2014
  

       It might well. On the other hand, it lacks the machine-gun-esque charm of the original.
MaxwellBuchanan, Jun 16 2014
  

       Very true. Another approach might be to use a high-pressure jet of water. High-pressure water jets can be used to cut all sorts of materials, so they should be able to do a bit of gentle panel-beating.
hippo, Jun 16 2014
  

       A constant jet might have difficulty to control the plastic yield. But a pulsing jet might be better.   

       Edit: like a high powered ink jet...
Ling, Jun 16 2014
  

       OK, I confess I like the water-jet method, even though it lacks explosions.   

       So, a water jet that can be moved in the X, Y and (probably) Z directions, with control over force and jet diameter. We might as well add pitch and yaw (useful if you're making a steep curve, as the jet can be tilted to remain at right-angles to the metal as the curve forms). And jets on both sides of the sheet will allow reflex curves etc.   

       The whole thing is looking frighteningly plausible. I don't see it working for mass production, but more like a 3D printer for low-volume work. The advantage over a 3D printer, however, is the ability to work in cheap sheet steel or aluminium. If the thing were scaled up, it would also make aircraft skin panels.
MaxwellBuchanan, Jun 16 2014
  

       Not only would a water jet be useful for shaping the material but it could also cleverly control the thickness. If you are making a car body panel for example, you only need thickness (and strength) in certain areas. By having the water jet mixed (under conputer control) with a fine sand as it shapes certain parts of the panel it would be able to abrade away the surface to a pre-defined pattern.

Explosions will be just outside the manufacturing plant, in the form of massive fireworks celebrating the succesful IPO of Water-Jet Shaping Technologies Inc.
hippo, Jun 16 2014
  

       Another idea for a 3D dimpler would be to use multiple focussed laser beams and immerse the sheet in water. This would provide the gratification of an explosion of steam at every pulse.
Ling, Jun 16 2014
  

       I'm liking the lasers.   

       Also, I wonder if the intertia of the water would work rather like the shot-bag that panel-beaters use. As I understand it, when shaping a panel with a mallet, the beater will use either a solid dolly or a shot-bag behind the work piece, allowing local deformation whilst supporting the metal overall.   

       The water might work rather like that, if the laser- generated steam pockets were formed instantaneously.
MaxwellBuchanan, Jun 16 2014
  

       Another approach would be to use actual explosions. Something like a fuel injector from a car engine would be scanned across the metal surface at a distance of a few milimetres, spraying jets of vapourised fuel into a minature spark generator hundreds of times a second. The shockwave of the explosions, perhaps focussed by a suitable shielding, would be used to deform the metal. This approach has the advantage that fuel-injector technology is cheap and reliably produces explosions.
hippo, Jun 16 2014
  

       (hippo) Sorry but gasoline burns in an engine.
cudgel, Jun 16 2014
  

       What about a shaped charge? It shouldn't take unfeasibly too much computing power to calculate from the desired final shape, how the explosive should be arranged. The robot sculpts the explosive charge, you lay the flat sheet of metal on top, and then press the big red button. There is a deafening flash and your perfectly shaped panel tumbles back down beside you.
pocmloc, Jun 16 2014
  

       I suspect that the use of high explosives might put this out of the reach of the average hobbyist.
MaxwellBuchanan, Jun 16 2014
  

       ...and suicide bombers would have rather a large order backlog after the first production trial.
Ling, Jun 16 2014
  
      
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