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  1. #1
    Staff Engineer
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    Gigabot starting work on a large pellet-fed printer

    https://www.kickstarter.com/projects...on-3d-printer/

    I don't usually believe in anything that launches on Kickstarter, but Gigabot actually knows how to build 3D printers has a fairly solid track record of producing them. Using pellets (or failed prints, ground up into pellet-sized pieces) makes a whole lot of sense to me. For one thing, it's a lot (10x) cheaper to buy plastic in the form of pellets, and you can get all sorts of different materials that aren't usually offered in filament form. It also makes it possible to extrude a lot faster, with a nozzle that doesn't need to be sized to the common filament diameters.

    When I asked about that here, I was told it wouldn't work, because the plastic needs to retract as well as extrude, so it's not dribbling material all the time. I guess the Gigabot folks have figured out a workaround for that. The auger-extruder they show looks a lot like what I had in mind. They don't show the feed chute and hopper that will also be necessary, though. Their first machine will have a volume of 24" cubed, but there's no reason they can't go even bigger, if the nozzle size is also increased. After seeing so many copy-cat machines launch, it's good to see some actual innovation.

    Andrew Werby
    computersculpture.com

  2. #2
    Technologist
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    It's a common misconception that filament retraction results in the filament being pulled back any appreciable distance. The reason for retraction is to provide a reduction or removal of feed pressure to the nozzle, reducing or preventing drips and dribbles. There's reason to believe that a manufacturer can incorporate a pressure reduction process in a pellet feeder design.

  3. #3
    Super Moderator curious aardvark's Avatar
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    the pellet thing versus filament rolls isn't quite as simple as 'it's 10x cheaper'.
    Only in bulk. And as for materials you can't get in filament form - hardly.
    Plus you'll mostly need to colour your own to keep the costs right down.
    So while for mass prints it can be cheaper, for most users it complicates matters.

    Also it's only really cheaper if you buy it by the pallet load.
    I have searched for companies selling pellts over here in the uk, never yet found anyone selling them cheaply in less that 100kg batches.

    Okay given the machine will cost well over $10,000 (it's 9.5 on kickstarter and prices usually go up by at least 1.5x once normal retail starts)- it's clearly a commercial system aimed more at low voilume factory production than desktop. So pallet loads of pellets are a more realistic option.

    My biggest concern wouldn't be retraction, you could simply use a cut off valve for a clean transition and back off the pressure at the same time.
    Air in the system would be my biggest issue.
    Not sure how you can cram pellets into hot tube and completely eliminate the air gaps between them. The material is too viscous for all the air to rise to the surface in time. PLus it's heated from the outside in, so the pellets in the centre will be sealed in with the air before they melt.
    Curious to see how they've dealt with that.

    If you leave a miniscule gap at the edges of the auger, air could get out there, but then you'd lose compression. Can't see anything in the design that specifically allows for air to escape:


    None of the videos work on this machine, so will have another look later.
    Last edited by curious aardvark; 03-14-2018 at 07:14 AM.

  4. #4
    Staff Engineer Davo's Avatar
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    We're working on a similar project.

  5. #5
    Staff Engineer
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    Quote Originally Posted by Davo View Post
    We're working on a similar project.
    And funding it yourselves? How's it going? Are you running into any problems with stopping the flow, or entraining air? Has someone already patented the idea of a pellet-fed printer, so they can pounce on anyone who actually builds one?

  6. #6
    Super Moderator curious aardvark's Avatar
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    what he said :-)

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