Sheet metal forming on a CNC mill...

[BobWarfield]

Can someone tell me more about what's being shown here:

http://www.youtube.com/watch?v=GxysBla3NyI

Looks really cool. Seems like that sheet metal has to be moving down in Z each trip around or a forming piece underneath is moving up somehow.

The sheet metal appears to be gripped in a frame that's riding on some kind of linear shaft system?

Best,

BW

[Geof]

Inside out Metal Spinning .

Have you ever seen Metal Spinning done on a lathe? This seems just the same but kind of inverted; tool spins and moves around and work is stationary. I guess the purpose of spinning the tool rather than just moving a stationary tool around could be threefold; first the spindle bearing can handle a much larger load safely when spinning, second the friction may heat and anneal the copper in the region of contact preventing work hardening and three many CNC mills will not run the axes under feed unless the spindle is turning.

I would expect there is a form under the shape that is being generated and the corner supports for the copper sheet could simply be spring loaded so as the tool works the copper down over the form the supports pull the surrounding area down also.

I have to thank you for the link because I intend to get into this type of work. Have you ever seen the embossed copper ceilings and wall panels in fancy offices and restaurants? These are expensive. A couple of years ago I bought a Haas GR510 with the intent of developing a retirement business doing large embossed copper panels. My idea was to have the sheets of thin copper held down by vacuum on low density MDF and then use a program something like Photo Vcarve but instead of cutting just deform the copper; hoping the soft MDF would just crush out of the way. I would only be deforming a few hundred thou deep so I thought this seemed reasonable to expect.

So far this project is just a gleam in my eye; the GR machine spends a lot of its time doing routine production for my existing business and I have spent most of my time during the past two years on new product development for my existing companies. Ah, futile dreams of retirement.

[DareBee]

Geof

Try red Urethane instead of the MDF

[Geof]

Originally Posted by DareBee Geof Try red Urethane instead of the MDF

But the urethane is non-porous and an elastomer, correct?

I could not suck a vacuum through the urethane to hold the sheet down and it would rebound after the tool has passed even if I could suck it down. I want the metal deformed down into the MDF to stay down.

Sorry for the hijack Bob; when (if) I get this project off the ground you can send me a picture to process into a plaque you can put on your wall...machine time gratis if you pay the material cost.

[BobWarfield]

I was able to discover a bit more after looking through Google. This is a relatively new process called Asymmetric Sheet Incremental Forming (ASIF). The "Asymmetric" clues you to a fourth advantage which is the ability to do things that aren't symmetrical in the way they'd have to be with a lathe.

It appears the form underneath does rise up or the sheet can come down either way. I could envision driving leadscrews as a 4th axis to move the sheet/form.

One other thing I learned in my web prowling is that this technique does not involve a die. It's hard to find info--apparently its a very new technique. You have to buy mechanical engineering research papers to learn much.

Best,

BW

[Geof]

The shape was very deep so I think progressive dies would be needed. Also it is quite possible the form could simply be a rigid plastic because it is taking very little if any load. I suspect the form is largely responsible for holding back the already formed material from moving deforming further; the tool is stretching and deforming to match the form but the form is not really contributing to the shape in the region it is being made. Metal spinning uses a similar technique in that the metal is deformed down onto a form while regions that are yet to be spun are held and stabilized against a movable spinning disc equivalent to the moving supports.

Even though the process is slow the overall cost of producing just a few examples could be considerably cheaper than pressing if all that is needed is a low cost plastic plug.

Thinking a bit further I realise you could machine the plug and then use the same program for doing the forming. The tool used for machining would need a nose radius larger than the forming ball by an amount equal to the thickness of the metal being formed. It may also be possible to get an acceptable smooth finish on the formed part even using a plug that was made with a large stepover because the part shape could come primarily from the forming tool action rather than closely replicating the plug.

[DareBee]

Hijack some more.

Geof

I here what you are saying about the vacuum - I agree.
As for as deformation goes red urethane is great. We use it all the time for embossing into. It is flexible enough to give and it is stiff enough to form really well and you can do it for a million hits without needing replacement.

[Geof]

Originally Posted by BobWarfield ..It appears the form underneath does rise up or the sheet can come down either way. I could envision driving leadscrews as a 4th axis to move the sheet/form. One other thing I learned in my web prowling is that this technique does not involve a die. It's hard to find info--apparently its a very new technique. You have to buy mechanical engineering research papers to learn much...Best, BW

It may be possible to do the sheet moving down fairly easily by having a mechanical link to the head. The flat surface of the sheet stays in more or less the same place relative to the tool.

Regarding it being a new technique I would mildy disagree, not with you Bob but any engineer making this claim. It is an old technique being performed with a new assembly of tools. Surely you have seen beaten copper and bronze bowls in all manner of shapes with intricate decoration in museums. These were done on a wool packed leather form or against a block of lead with different shaped punches and a whole lot of skill. And they were done several thousand years ago.

[BobWarfield]

Originally Posted by Geof It may be possible to do the sheet moving down fairly easily by having a mechanical link to the head. The flat surface of the sheet stays in more or less the same place relative to the tool.

I thought of having some sort of support underneath tracking the head. It's an interesting thought, though potentially awkward to implement. There are some pictures that show a sort of probe underneath that tracks the head. It reminded me of an English wheel that can move in XYZ.

Regarding your red urethane, it seems like an ideal material would deform right under the probe, but would resist deformation extremely well away from the probe, and would spring back after the probe moves on. This sort of thing could underlay the sheet metal and while the whole assembly moves downward, the tool could spiral out as the video shows. Is this what you're thinking of with the urethane?

A lot of the pictures I see on the web have the head pushing down so part forms downward rather than pushing the sheet down as the video does.

All of this seems to imply that some kind of support is needed when you are leaving enough sheet metal hanging that pressure in the middle is overly deforming the areas that are not supported but are sufficiently far away from the probe.

Regarding it being a new technique I would mildy disagree, not with you Bob but any engineer making this claim. It is an old technique being performed with a new assembly of tools. Surely you have seen beaten copper and bronze bowls in all manner of shapes with intricate decoration in museums. These were done on a wool packed leather form or against a block of lead with different shaped punches and a whole lot of skill. And they were done several thousand years ago.

Geof, I can't see that as a valid comparison. May as well say CNC is not really anything new because manual lathes work on essentially the same principles as a CNC lathe. If you generalize, that's true, but it isn't a useful comparison. In this case, it is a new technique relative to manufacturing techniques available in the past. This is a plastic deforming process, but there are an awful lot of them, and it seems to me this one has a lot of novel features.

Since reading this, my favorite thought has been the "Boyd Coddington" CNC machine. Imagine a big gantry machine that can do this. You feed it a CAD model of a new body panel and it shapes the panel out of aluminum. Imagine the potential for one-off cars like Boyd's hot rods and the like. The custom car guys would go crazy for it. In that respect, it really does get to be a CNC English wheel.

I think if one wants to pursue this, it would pay to purchase 3 or 4 of those research papers you find under Google. I could find very little else about this technique. What little I could read was clear you didn't need a die specific to the part being made.

Best,

BW

[jerryrig]

Originally Posted by Geof Inside out Metal SpHave you ever seen the embossed copper ceilings and wall panels in fancy offices and restaurants? These are expensive. A couple of years ago I bought a Haas GR510 with the intent of developing a retirement business doing large embossed copper panels. My idea was to have the sheets of thin copper held down by vacuum on low density MDF and then use a program something like Photo Vcarve but instead of cutting just deform the copper; hoping the soft MDF would just crush out of the way. I would only be deforming a few hundred thou deep so I thought this seemed reasonable to expect. So far this project is just a gleam in my eye; the GR machine spends a lot of its time doing routine production for my existing business and I have spent most of my time during the past two years on new product development for my existing companies. Ah, futile dreams of retirement.

Geoff,

if you machine can handle that size why not cut into the MDF, suck the copper down and then explosively hydro form into it? you might even get more than one go with the MDF

Jerry

[Geof]

Originally Posted by BobWarfield ...Regarding your red urethane, it seems like an ideal material would deform right under the probe, but would resist deformation extremely well away from the probe, and would spring back after the probe moves on.......

The urethane was mentioned by Darebee in the context of my plans for CNC embossing large sheets. For this my expectation is that the spring back would be undesirable; I want to deform the metal down immediately at the probe but not spring back. This is why I think I will need a material that is both porous, for the vacuum hold down, and crushable underneath so the embossed parts do not come back up and in doing so lift the surrounding unembossed sheet.

Regarding my 'not a new technique' claim it depends which side of a potential patent dispute one could be on. The side that claims it is new and unique or the side that claims it is an obvious extension of prior art.

[Geof]

Originally Posted by jerryrig Geoff, if you machine can handle that size why not cut into the MDF, suck the copper down and then explosively hydro form into it? you might even get more than one go with the MDF Jerry

Explosively hydroforming over an area 5 feet by 10 feet boggles my mind even if it doesn't boggle anyone elses mind. That is the area I can and hope to handle.

I did think of explosive hydroforming when I viewed the video. I think it can produce items comparable to what was shown in the video. But it requires a fairly complex setup.