Re: [rp-ml] algorithm&implementation for STL slicing-SplineScan

From: Charles Overy <>
Date: Fri Aug 25 2006 - 20:51:53 EEST

I keep wondering why someone does not adapt a project like this to make
a non contact scanning head for CNC machines. Off the cuff it would
seem that you could create a hardware head that would sit in a collet
holder and software that would output generic G-code to scan an
arbitrary sized area. Is it more difficult to patch meshes where the
scanner is moving rather than the part?


Sebastien Bailard wrote:
> On Thursday 17 August 2006 19:01, you wrote:
>> At 4:25 PM -0400 8/17/06, Sebastien Bailard wrote:
>>> For raw 3D structured light scan to stl , there is some open source
>>> software called . (This is the opposite of what
>>> you are asking for, as far as I can tell.) It is GPL'ed python code.
>> Hi Sebastien,
>> Thanks for all the info! Splinescan looks interesting and fun - I may have
>> to give that a try.
> Do. If you need support, you'll have to get it through the splinescan mailing
> list. The lead developer's working on development, not documentation just
> now, but someone should answer. I have no idea when they're going to publish
> their next release.
> They've got some interesting tweaks in the pipeline - they're going to publish
> a hardware package that you can RP, so all you have to do is assemble it,
> bolt on a camera, laser pointer diode, cylindrical lens (glass rod), and
> you've got the scanning unit. For the turntable, just go scrounge a
> turntable and have your laser printer print out a paper encoding strip*,
> paste it on, and you're good to go. The camera/python code figures out where
> the turntable is by looking for the encoder strip.
> I've been daydreaming that all you need is a sheet of paper printed with
> artoolkit tags and a camera, and you could put an object on the sheet, take
> loads of photos, and then dump them into gpl'ed code that figures out all the
> computational geometry and spits out your point cloud/simplical surface/.stl
> file. It would take some keen programming and computational geometry, but it
> would be so useful.
> If you happen to be interested in the computational geometry background for
> all this, look at "Surface Reconstruction from Unorganized Points" by
> H. Hoppe 903 citations, and fairly readable,
>>> Roy - what materials are you working in? You may be able to use our
>>> extrusion head along with the control software:
>>> nHead
>> I've been aware of Reprap but didn't realize or look closely at the
>> software part of the project. have to take a closer look. My materials?
>> Well... this is a 'for art' project so I have been looking at various
>> materials which flow and then harden - slurries of clay, etc. I was
>> thinking about wax but wanted to avoid the complexity of a heating element.
> I would go with kaolin slurry or store bought "earth clay" slurry or slip as
> well in that case, or cncmill/RP a reprap extruder head and use
> thermoplastic. It'd be a lot easier to set up.
> Waxes can be nasty - one tuft of cat hair in your feedstock, it clogs, and
> unless you've got a thermostat or thermal-overload detector and hard shutdown
> circuit, it all goes up like a candle and you kiss your studio goodbye. So
> many artists die just because they forgot to use a double boiler, crockpot,
> or soup warmer to heat their wax, so they just put it directly in a pot on
> the heating element, maybe go and answer the phone, the bottom layer
> liquefies and starts to boil even though when the top's solid, then you get a
> big cloud of vaporized wax and poof! Wax is the main reason art foundries
> and studios burn down, so you'd want to trouble shoot the hell out of any
> autonomous 24/7 mechanism you're building that uses wax. A slurry printer
> screws up, and all you've got to clean up is a puddle.
> One thing to realize is whatever earth clay you go with is possibly going lose
> all its plasticity if you run it through a feed system - it depends how happy
> the bacterial colony is in the clay, after it's been extruded. (Bacteria
> makes the gel that lets the clay platelets slip past each other.) But a
> couple spritzes with dilute vinegar could perk it up again/
> If you're not going to work the clay after extruding it, this doesn't matter.
> You might be able to use a good oilclay (aka plasticine, modeling clay)
> instead of wax. Oilclays liquefy when heated, but I don't think they can
> burn.
> One problem with oilclay is you can't sell it as a finished piece without
> going through the casting/moldmaking steps. Wax or thermoplastic you can do
> lost wax casting with, slurries you can fire in a kiln.
>> For a 'print head' I have been tinkering with building a peristaltic pump -
>> the idea being that with that I can deposit a measured amount of material
>> that is fairly viscous and it seemed a simple way to do it. It's all in the
>> testing/failing stages now.
> Sounds fun. Did you see
> Think you can clip one onto your 'Drip Painter' machine?
> Apropos of nothing, we're using wood filler for a test material. It's pretty
> much wood glue (polyvinylacetate) and marble dust.
>> I'm assuming (and hoping) that this will be a functional "expressive" 3
>> printer - along the lines of Giacometti type forms. I think I can get a
>> fair degree of precision in placing the material- and the material will
>> slump and distort in unpredictable ways. The art/sculpture "part" of this
>> is both the machine as it's working and the forms it creates.
>> --Roy
> It's an interesting approach. Sort of like manipulating the hell out of the
> negative in the darkroom, where I'm stuck on photorealism/toolmaking - I want
> to image an oilclay model or broken machine part, work up the virtual image,
> print it, and have a perfect duplicate.
> How are you planning on creating your input code - c code that bit bangs the
> printer port and the motors do their thing, traditional cad cam -> g code ->
> emc (linux machining controller - ), or something esoteric
> whipped up in processing? (algorithmic art / data analysis tool with thriving
> community - ,
> )
> Regards,
> -Sebastien Bailard
Received on Fri Aug 25 20:12:31 2006

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