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State of pelletd plastic printing.

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  • Dave
    Hi folks. My first post here. I m one of the pre-release buyers of the still-a-prototype Makibox
    Message 1 of 6 , Jun 13, 2012
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      Hi folks.  My first post here.

      I'm one of the pre-release buyers of the still-a-prototype Makibox.     In spite of the delays, the builder and his team have me convinced that they know what they're doing, and will soon be shipping a well designed exceptionally low cost printer.  Frankly, I'm in awe of what they've accomplished so far.

      But recently, the project has taken a turn that has me a bit puzzled.  They've switched from a filament spool in the back, to a hopper full of ABS pellets and filament making extruder system.  What was a nice clean well planned and tested design seems to have suddenly taken on a bunch of unnecessary complications.

      Seems to me that a pellet to filament system is something of a holy grail.  There's a competition,  and at least one funded kickstarter campaign for a pellet to filament system.  Not to mention a few posts and articles from people who've tried it before.  But the only example of a pelleted print system  I've been able to find leaves me somewhat unimpressed.

      I still believe in this project.  And if anybody can bring home a pellet to print system, it's Jon Buford.  I figure there MUST be something out there that I'm missing.  Does anyone know of a successful or at least promising pelleted print system?

    • Graham Stabler
      I can t see any reason why a screw based pellet plasticiser system shouldn t work and work well. It may well be an easier problem to solve than the extrusion
      Message 2 of 6 , Jun 13, 2012
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        I can't see any reason why a screw based pellet plasticiser system shouldn't work and work well. It may well be an easier problem to solve than the extrusion of filament I suspect. Screw based systems are commonly used to dispense glues and solder and if he intends to heat the screw and can ensure it is always supplied with pellets I think it could work.

        If not then it won't be hard to go back to the usual filament design.

        Graham



        On Wed, Jun 13, 2012 at 10:57 PM, Dave <danceswithrobots@...> wrote:
         

        Hi folks.  My first post here.

        I'm one of the pre-release buyers of the still-a-prototype Makibox.     In spite of the delays, the builder and his team have me convinced that they know what they're doing, and will soon be shipping a well designed exceptionally low cost printer.  Frankly, I'm in awe of what they've accomplished so far.

        But recently, the project has taken a turn that has me a bit puzzled.  They've switched from a filament spool in the back, to a hopper full of ABS pellets and filament making extruder system.  What was a nice clean well planned and tested design seems to have suddenly taken on a bunch of unnecessary complications.

        Seems to me that a pellet to filament system is something of a holy grail.  There's a competition,  and at least one funded kickstarter campaign for a pellet to filament system.  Not to mention a few posts and articles from people who've tried it before.  But the only example of a pelleted print system  I've been able to find leaves me somewhat unimpressed.

        I still believe in this project.  And if anybody can bring home a pellet to print system, it's Jon Buford.  I figure there MUST be something out there that I'm missing.  Does anyone know of a successful or at least promising pelleted print system?

      • Terence Tam
        From what I understand, there s a lot of issues with trapped air causing the extruder to burp when it comes to feeding it pellets. This is OK for injection
        Message 3 of 6 , Jun 13, 2012
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          From what I understand, there's a lot of issues with trapped air causing the extruder to "burp" when it comes to feeding it pellets.  This is OK for injection molding as the tool has air vents built into it to relief the air pressure inside the tool, and the immense amount of pressures that an injection molding press puts behind the charge tends to take care of the problem.

          But in a RapRep / FFF extruder, the air trapped causes the filament to break, and as far as I know this is an unsolved problem.  Putting the extruder screw in a horizontal axis configuration and venting the top will help, but I don't know if it will fully eliminate it.

          The cost savings are huge if someone can do it and do it well.  It's currently about US$20/lb for PLA ($50/kg).  Most commodity ABSes are less than $5/kg.

          -=- Terence

          --
          --

          Terence Tak-Shing Tam (譚德成)   |  ttstam@...   |   http://www.TerenceTam.com

        • Graham Stabler
          That s very interesting Terence and makes total sense. I wonder if the plastic could enter a zone made from something like porous carbon to vent (assuming you
          Message 4 of 6 , Jun 13, 2012
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            That's very interesting Terence and makes total sense.

            I wonder if the plastic could enter a zone made from something like porous carbon to vent (assuming you it is porous to air not plastic), this chamber could be pressurised by the back pressure from the output nozzle. But I suppose the molten would make a great seal.

            Sorry, taking this off topic, I've shown my ignorance. Carry on!

            Graham



            On Wed, Jun 13, 2012 at 11:42 PM, Terence Tam <ttstam@...> wrote:
             

            From what I understand, there's a lot of issues with trapped air causing the extruder to "burp" when it comes to feeding it pellets.  This is OK for injection molding as the tool has air vents built into it to relief the air pressure inside the tool, and the immense amount of pressures that an injection molding press puts behind the charge tends to take care of the problem.


            But in a RapRep / FFF extruder, the air trapped causes the filament to break, and as far as I know this is an unsolved problem.  Putting the extruder screw in a horizontal axis configuration and venting the top will help, but I don't know if it will fully eliminate it.

            The cost savings are huge if someone can do it and do it well.  It's currently about US$20/lb for PLA ($50/kg).  Most commodity ABSes are less than $5/kg.

            -=- Terence

            --
            --

            Terence Tak-Shing Tam (譚德成)   |  ttstam@...   |   http://www.TerenceTam.com


          • Dave
            To me, it looks like something that would be relatively easy to do and should work. But it s been tried a number of times and in spite of quartering the cost
            Message 5 of 6 , Jun 13, 2012
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              To me, it looks like something that would be relatively easy to do and
              should work. But it's been tried a number of times and in spite of
              quartering the cost of material, (as mentioned in another post in this
              thread.) But no one seems to have accomplished it yet. I just hate to
              see the project suffer another delay.

              --- In diy_3d_printing_and_fabrication@yahoogroups.com, Graham Stabler
              <grezmos@...> wrote:
              >
              > I can't see any reason why a screw based pellet plasticiser system
              > shouldn't work and work well. It may well be an easier problem to
              solve
              > than the extrusion of filament I suspect. Screw based systems are
              commonly
              > used to dispense glues and solder and if he intends to heat the screw
              and
              > can ensure it is always supplied with pellets I think it could work.
              >
              > If not then it won't be hard to go back to the usual filament design.
              >
              > Graham
              >
              >
              >
              > On Wed, Jun 13, 2012 at 10:57 PM, Dave danceswithrobots@... wrote:
              >
              > > **
              > >
              > >
              > > Hi folks. My first post here.
              > >
              > > I'm one of the pre-release buyers of the still-a-prototype
              > > <http://makibox.com> <http://makibox.com>Makibox
              <http://makibox.com>.
              > > In spite of the delays, the builder and his team have me convinced
              that
              > > they know what they're doing, and will soon be shipping a well
              designed
              > > exceptionally low cost printer. Frankly, I'm in awe of what they've
              > > accomplished so far.
              > >
              > > But recently, the project has taken a turn that has me a bit
              puzzled.
              > > They've switched from a filament spool in the back, to a hopper full
              of ABS
              > > pellets and filament making extruder system. What was a nice clean
              well
              > > planned and tested design seems to have suddenly taken on a bunch of
              > > unnecessary complications.
              > >
              > > Seems to me that a pellet to filament system is something of a holy
              > > grail. There's a competition
              <http://desktopfactory2012.istart.org/>,
              > > and at least one funded kickstarter campaign for a pellet to
              filament
              > > system. <http://filabot.com> Not to mention a few posts and
              articles
              > > from people who've tried it before. But the only example of a
              pelleted
              > > print system <http://www.youtube.com/watch?v=0l-8UpCbK2A> I've been
              able
              > > to find leaves me somewhat unimpressed.
              > >
              > > I still believe in this project. And if anybody can bring home a
              pellet
              > > to print system, it's Jon Buford. I figure there MUST be something
              out
              > > there that I'm missing. Does anyone know of a successful or at
              least
              > > promising pelleted print system?
              > >
              >
            • Chris Marion
              I m currently working on a plastic extrusion system - I ll be sure to post back with any results I have. I have a few ideas on how to solve many of these
              Message 6 of 6 , Jun 15, 2012
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                I'm currently working on a plastic extrusion system - I'll be sure to post back with any results I have. I have a few ideas on how to solve many of these mentioned issues, but it will be a few weeks as I'm probably going to some parts CNC'ed to take care of the issue. There's only so much you can do with hacked-together plumbing fittings and nichrome ;)

                -Chris

                On 6/13/2012 8:24 PM, Dave wrote:
                 

                To me, it looks like something that would be relatively easy to do and
                should work. But it's been tried a number of times and in spite of
                quartering the cost of material, (as mentioned in another post in this
                thread.) But no one seems to have accomplished it yet. I just hate to
                see the project suffer another delay.

                --- In diy_3d_printing_and_fabrication@yahoogroups.com, Graham Stabler
                <grezmos@...> wrote:
                >
                > I can't see any reason why a screw based pellet plasticiser system
                > shouldn't work and work well. It may well be an easier problem to
                solve
                > than the extrusion of filament I suspect. Screw based systems are
                commonly
                > used to dispense glues and solder and if he intends to heat the screw
                and
                > can ensure it is always supplied with pellets I think it could work.
                >
                > If not then it won't be hard to go back to the usual filament design.
                >
                > Graham
                >
                >
                >
                > On Wed, Jun 13, 2012 at 10:57 PM, Dave danceswithrobots@... wrote:
                >
                > > **
                > >
                > >
                > > Hi folks. My first post here.
                > >
                > > I'm one of the pre-release buyers of the still-a-prototype
                > > <http://makibox.com> <http://makibox.com>Makibox
                <http://makibox.com>.
                > > In spite of the delays, the builder and his team have me convinced
                that
                > > they know what they're doing, and will soon be shipping a well
                designed
                > > exceptionally low cost printer. Frankly, I'm in awe of what they've
                > > accomplished so far.
                > >
                > > But recently, the project has taken a turn that has me a bit
                puzzled.
                > > They've switched from a filament spool in the back, to a hopper full
                of ABS
                > > pellets and filament making extruder system. What was a nice clean
                well
                > > planned and tested design seems to have suddenly taken on a bunch of
                > > unnecessary complications.
                > >
                > > Seems to me that a pellet to filament system is something of a holy
                > > grail. There's a competition
                <http://desktopfactory2012.istart.org/>,
                > > and at least one funded kickstarter campaign for a pellet to
                filament
                > > system. <http://filabot.com> Not to mention a few posts and
                articles
                > > from people who've tried it before. But the only example of a
                pelleted
                > > print system <http://www.youtube.com/watch?v=0l-8UpCbK2A> I've been
                able
                > > to find leaves me somewhat unimpressed.
                > >
                > > I still believe in this project. And if anybody can bring home a
                pellet
                > > to print system, it's Jon Buford. I figure there MUST be something
                out
                > > there that I'm missing. Does anyone know of a successful or at
                least
                > > promising pelleted print system?
                > >
                >


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