3D Printing in Stone, or Copy a Sculpture in Rock

An anonymous reader writes "With all this design your own parts and electronics talk lately here on /., what about creating your own stone sculpture on a PC or Copying a Stone Sculpture? You can do that with an outfit called Studio Roc in CA. The New York Times has an interesting article on this marriage of CAD, laser scanning, and rocks. 'Using a huge Italian-made Omag Mill5 five-axis milling machine equipped with a scanner and 30 interchangeable diamond-tipped bits and blades, the Mill5 can record nearly any object in minutes and carve a duplicate in any stone in a few hours.'"

Re:Nice

[RPI Geek]

If the machine can mill stone, it can mill wood. I've done it before, but you do have to be careful about the feedrate and small features or else you run the risk of splintering the wood.

I don't see how it could restore a wood carving though...

Re:Question on the cutting

[Anonymous Coward]

Laser cutting (or abrasive waterjet) is usually for flat items like sheetmetal where you make the cut all the way through the material. If you need to make a partial cut, a mechanical device is your only choice.

Re:Question on the cutting

[RPI Geek]

There's a few reasons.

Conventional millers are cheaper.

Lasers can't get inside features like hollowed-out areas (they can't control depth as well because they don't know the exact material properties inside the stone, and if it hit an unexpected soft spot, oops! there goes the whole thing.

A laser cutter would use much more energy to burn the material away than a conventional mill uses to just chip it.

Hope this helps.

Re:Question on the cutting

[AKAImBatman]

It seems that Laser Engraving equipment does exist [epiloglaser.com] and can cut Marble without problem. Why would a laser need to perform a plunge cut? (Not that there aren't reasons, I just don't know them.)

This isn't 3D printing, sorry

[panurge]

You need a block of stone in the first place, from which you remove stuff. It's exactly the same as standard sculpture except that instead of apprentices, laborers and great big stone saws, they're using a milling machine to get a high quality rough. And (RTFA) this does produce a rough: hand finishing is required, just as special finishing is required with the output of most machine tools. The comments this is getting suggest to me that too many people nowadays don't have a clue about manufacturing - and we in the West will surely regret this one day.

Printing is a process that involves ADDING material to a substrate, not taking it away.

So yes, it's a nice application of one of those multi-axis machine tools the Italians do so well, but it's basically the same as any die-sinking process.

Of course it would be able to...

[cnelzie]

...you could also get that done at virtually most protoype machine shops across the US.

If they have laser scan capable CMMs (That's Coordinate Measuring Machines), just about any 5-Axis Vertical Milling Machine and some decent machine operators it can be done.

Heck, you could even have that milled out of high-quality Aircraft Aluminum, like a 7000-series. You could also go with tooling steel, like Cold Drawn 1018 Carbon Steel or S-7 Tooling Steel...

None of this is really new. The technology has been around for at least 10 years, from the laser scanning to the 5-Axis Mills.

DIY

[Coupons]

This is lovely, but beyond the means of the average /.er.

With a little ingenuity and, say, $100,000 you can build your own and save a bundle.

McRae and Sons Inc. [mcraeandsons.com], the last US paint brush handle factory, builds their own 4 axis 3D wood carving machines for considerably less. The same principles can be applied to carving stone.

McRae's machines rely on Actek Inc. [actekinc.com] motion controllers, though manufacturers abound. You might be surprised how many are amenable to working with amatures.

Check eBay - no kidding - for cheap machines that can be canibalized or restored.

Re:DIY

[Solder Fumes]

CNC can be had for much, much cheaper than $100,000. I built my own little CNC machine [macetech.com] (bottom of page) from scratch for less than $250. That's not going to mill stone (very fast, anyway) but you can get a full-size Bridgeport or some Japanese mill for under $2,000 in some cases. For another $1,000 or less, and using the mill to build its own parts, you can retrofit the Bridgeport with servo or stepper drives [geckodrive.com], and use an obsolete desktop computer to control it using free [linuxcnc.org] software [dakeng.com]. Shops also turn over equipment like CNC machines pretty often, in order to keep up with everyone else. An expensive machine pays for itself many times over before it becomes obsolete. You may be able to find an older CNC mill, ready to run, for less than $5,000. I happen to know of one that, if I ever get the space, could be had for under $2,000. For all the information you need, try the CAD CAM EDM DRO Yahoo Group [yahoo.com].

Re:Nice

[Wierd Willy]

Jeezuz people, what kind of machinists are you? I have milled wood, alabaster, graphite and other ultra-soft materials with CNC mills and lathes hundreds of times, even soft pine. You need high spindle speeds and low feed rates and razor sharp tools. Milling, you use low angle 2 flute endmills exclusively. Lathe nothing but cobalt steel cutters ground to a knife edge, no greater than 60 degrees.

Typically, most modern mills have factory maximum spindle speed of 10,000 RPM. There are doublers and triplers and beyond that bolt right up to the spindle and its possible to get spindle speeds with these devices up to 100,000 RPM. High pressure air on the cutter keeps the flutes clear as liquid coolant can't be used because it damages the peice. It creates a lot of dust, but a good vaccuum system keeps that down to tolerable levels.

Milling Machines and sculptures

[jrjud]

Duplicating sculptures by methods other than carving directly into stone is nothing new - and milling machines are certainly not a new technology either.

Even Rodin quite often started his work in clay. He sent the original plaster to a person who used a pointing machine invented by Nicolas Gatteaux to do the rudimentary stone carving.

As for milling machines, they have been around forever and come in all sizes and work with all kinds of materials. This one is really good, and the CNC software runs on Linux: http://www.sherline.com/mill.htm

It can be a neat 3D printer, but you need to get versed in machining, which can be very time consuming - especially if you use metal. You can use foam, wood, and lots of different materials.

Re:Question on the cutting

[Wierd Willy]

Diamond cutters are the hardest cutters possible. typically, the diamond tips on the cutting edges will maintain their sharpness with low shear angles in highly friable materials such as stone or graphite. This is why spindle speeds would have to be very high to reduce actual impact pressures on the cutting edges themselves.

Hardness is inversely purportional to shear strength. The harder the material of the peice, the smaller the chipload allowance on the cutter. The harder the cutter, the higher spindle speeds you can run. As long as the cutter stays below its heat tolerance, it will maintain its edge.

Materials like graphite, marble and limestone are easily machined with spindle speeds around 20,000-25,000 RPM with diamond cutters. But the feed rate has to be low in order to get a surface finish within tolerance. Something like Granite, being mostly quartz would have to be machined at over 30,000 RPM with extremely low feed rates. This is extremely difficult as the hardness of the material of the workpeice and the hardness of the material of the cutter are approaching equilibrium. The heat tolerance just isn't there.

Lasers are only really good for cutting blanks out of flat materials, they dont leave a very good surface finish and they tend to change the properties of the material being machined. You can get much better results for this with an abrasive waterjet cutter. Such machine tools are only good for cutting in straight lines.

Other 3D printing firms...

[CoffeeDregs]

Clever.

Also check out:
http://www.precisionlaserart.com - uses lasers to make small fractures in glass;
http://www.prometal.com - uses metal powder to create arbitrary 3D forms;
http://bathsheba.com - artist who uses the above forms;

Note: I've used PrecisionLaserArt for some artwork and had a good experience, so I'm biased...

My crown is made similarly

[duanechamblee]

This is old news AFAIK... I've got a ceramic crown that was created in a machine sitting next to me while I waited. Pretty cool and a practical use of the existing technology. http://www.cereconline.com/ecomaXL/index.php?site= Cerec_PatientInfo