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Thread: Thoughts on 3d sand printing...

  1. #1
    Moderator DavidF's Avatar
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    Thoughts on 3d sand printing...

    Well i'm pretty sure everyone on here has seen the videos of the ex1 sand printer making molds and cores with a touch of the button. Its pretty impressive tech (makes me drool) But with a price tag of 1.4M owning one will never happen for me in my life time.
    The past few nights I have been looking over videos on 3d sand printing on YT and ran across a couple things of interest. One video they used a laser to bind the sand. I am assuming that the sand was thermal setting like what is used for making shell cores? And another DIY version that uses a focused halogen lamp to bind the thermo set sand. Ill link videos below.
    Now if that is thermo set sand I saw in the one video and it is possible for a laser to set it, then a diy solution to at home sand printing should be pretty simple Right?? Lasers are pretty cheap, 3d printer parts are cheap, and software is out there that could be used. So why is it that no one on this forum (or that i can locate on the net) working on or offering up one of these printer to the general public?
    Cant be that difficult could it? Looking forward to hearing your thoughts on this subject....

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    Here is the ex1

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    and the open source? printer using the halogen bulb

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    and the laser sintering one.
    A calm sea does not make a skilled sailor....

  2. #2
    Moderator DavidF's Avatar
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    Ill throw this one in too...
    A calm sea does not make a skilled sailor....

  3. #3
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    Pretty cool stuff...

    Being totally na´ve to the whole 3D printing phenomenon, I'd say doing something like this shouldn't be all that more difficult than building a 3D printer to begin with. Without knowing the specifics, I'd say all you would need to do is add a lowering table and a sand dispensary system to a 3D printer. I recall former member PatJ used binder based molding sand. The hardener(catalyst) would be sprayed through an in jet head much like in the last video you linked to.
    FLAME ON...!!!!

  4. #4
    In theory the themo bind sand with a laser is simply as laser cutter with a really tall z axis stage. The z axis stage has a hopper and a spreader to add a layer of sand each time it increments. The hard part is most of these ideas are patented so until the patent runs out we're stuck. Sure you could build your one off unit and not get in trouble. But you can't make money selling them. Until other businesses can make money the costs for the units will not come down.

  5. #5
    I think it is a neat project and a perfect one for you to take on

    I do think the notion of using one of the core sands with heat activated binder is a good idea. I would have thought the problem with a laser would be their focused on a pretty small area and because of the insulative properties of sand would mean you wont get much dispersion nor penetration which could mean very slow build rates but wow, if the video you posted is real time, that laser was kicking out the in2. It did look like they may have a post cure step if that was an oven they plugged it into. I wonder what kind of power that laser was? If high power, that in itself could be prohibitive for DIY or home machine. The finish on the lased part in the video sure looked nice. Would like to see a close up.

    I think most of the hot box resin systems activate between 500-700F. You may not need a laser's heat but you may need the speed at which it can apply that heat.

    I think J hit on one of the challenges for about any approach and that is sand dispersion. In the old SL machines liquids self level, but sand will not, at least not well enough. I would guess laying down layers could be critical due to the cumulative affect of any variation in layer thickness.

    Do you remember the old LOM (laminated Object Modeling) rapid prototypers? They used layers of thin urethane film and paper that got lased and heat rolled. The product looked like 200-ply plywood LOL.

    Being able to adapt an inkjet printer to use a thin resin with depth table and sand dispenser/skimmer or perhaps just a 3D printer with dispensing head sure seems like it would reduce development time. Need to be able to lay down a nice layer of fine sand and bet that could wreak havoc on machine mechanicals after time.

    At my friends foundry, they often cut gates into the thermoset bonded sanded molds with a hand guided router after they hardened. I bet you could 3D machine a resin bonded block of sand with a CNC router duty machine but again, I bet it would play hell with the linear motion surfaces in time.

    I do wonder about quality of casting finishes on any of the above and it seems the niche must be complex shaped prototype's and smaller the better do to mod build time. So when are you starting?

    Best,
    Kelly

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    Moderator DavidF's Avatar
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    20170411_130155.jpg

    All ready have....

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    20170411_130155.jpg

    All ready have....just need to figure out how to deposit the sand layer better, this was a fail but i learned alot from it.
    A calm sea does not make a skilled sailor....

  7. #7
    Hoosier Pattern in indiana has one that was 500k. Got some quotes from them for a 15"L x 6"° casting mold, $900 a pop. Only viable for prototyping or very specific special castings. Those machines will be down to 100K within 5 years and be a pretty common thing in most tool shops.

    https://hoosierpattern.com/


  8. #8
    Moderator DavidF's Avatar
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    1.4 M, 500 K, 100K......still way too much for the hobbiest. I just need to figure out how that ex1 is depositing the sand layer. Looking closely at the sand bed in one video i can see lines in the sand.
    It appears that it has some sort of shut off as well. It only deposits the sand one direction and clears a gap before its park position...

    Dzuari?? Supercharger guy??
    A calm sea does not make a skilled sailor....

  9. #9
    Quote Originally Posted by DavidF View Post
    Dzuari?? Supercharger guy??
    Damn, all these years and you recognize the screen name lol? You from the Hamb or yellowbullet or were my videos posted here?

    Edit:
    I'd think they probably deposite the sand ahead of a rake. To do it right you'd want the rake to be ground from 302 or 304SS so it'd hold up well against sand abrasion. I like the bed drop idea on that one video but it'd be limited in mold size. You'd need a industrial grade serve/ball screw to maintain accuracy and wear with the weight of sand over the years.

  10. #10
    I've seen these videos few weeks ago.
    Best way I can think is like the other powder laser sintering 3d printers (a roller put a layer of sand+binder on the area and then the laser does the curing job.
    There is a company here in Switzerland that sells a kit for a laser sintering 3d printer (it prints with a nylon powder) maybe it can be modified into a sand core printer!
    Here is a video of it in action : https://www.youtube.com/watch?v=3w6JJRAOGsE
    Price for the kit few months ago was around 5k, better but still expansive for a hobbyist...

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