Loading ...
Sorry, an error occurred while loading the content.

Re: Greetings, and extrusion

Expand Messages
  • ttelmah
    ... The pressurised syringe pushed by a linear stepper, was the first thing that other people have tried. Suffers from dripping... They switched to using
    Message 1 of 20 , Jan 31, 2011
    • 0 Attachment
      --- In diy_3d_printing_and_fabrication@yahoogroups.com, "Boman33" <boman33@...> wrote:
      >
      > Welcome!
      >
      > How about a rigid oversized syringe with the plunger CNC controlled. All
      > metal or other stiff material. No pipes or hoses to flex. Nozzle directly
      > attached.
      >
      >
      >
      > When low, it could be automatically refilled from a side port with
      > pressurized material to avoid any air pockets.
      >
      > Bertho
      >
      The pressurised syringe pushed by a linear stepper, was the first thing that other people have tried. Suffers from dripping...
      They switched to using pressurised syringes (this is what is commonly used for things like epoxies), better, but still drips. Hence the need for a positive cutoff close to the needle.

      Best Wishes
    • Lino
      screw pump http://upload.wikimedia.org/wikipedia/commons/d/d8/Screw_pump.png On Mon, 31 Jan 2011 19:08:53 -0800, Jon Elson ... --
      Message 2 of 20 , Jan 31, 2011
      • 0 Attachment

        screw pump

        http://upload.wikimedia.org/wikipedia/commons/d/d8/Screw_pump.png


        On Mon, 31 Jan 2011 19:08:53 -0800, Jon Elson <elson@...> wrote:


         

        Fernando wrote:
        >
        >
        > Is that as in one screw feeding the other from a vat?
        > How would that be mounted, at a 90º angle to eachother?
        No, one is left-hand, one is right-hand, they lie parallel and
        interlock, in a housing with a figure-eight cross-section.
        They rotate in opposite directions.
        This pinches off regions in the outer part of each screw, while the
        overlap prevents any flow
        backwards. Each pinched-off region moves from the inlet side to the
        outlet side.

        See http://impeller.net/magazine/news_en/doc3413x.asp for a mediocre
        picture, but the best one
        I could find.

        Unlike an Archimedes screw, these are positive displacement pumps, they
        can stop and the fluid
        will not flow backwards.

        Jon




        --
        Using Opera's revolutionary email client: http://www.opera.com/mail/
      • ttelmah
        ... Yes, peristaltic makes a lot of sense, in view of what I said, since you can treat the pipe as a disposable item. Thanks for the archive link. I m sure
        Message 3 of 20 , Feb 1, 2011
        • 0 Attachment
          --- In diy_3d_printing_and_fabrication@yahoogroups.com, Jack Coats <jack@...> wrote:
          >
          > The concrete industry regularly pumps 'hard to pump' fluids, and the
          > plastics injection molding industry uses a screw pump that works in
          > stages (all on one axis) to get the pressure higher as it flows
          > through the heating chamber.
          >
          > I did not find 'monnow' pump (Seems to be a "C'mon now" music/dance
          > with racy lyrics going around in some circles) ... any reference would
          > be a appreciated.
          >
          > http://www.plasticstech.info/equipment/injection-molding-machine/ has
          > a schematic images, but the details of the compression screw isn't
          > show very well.
          >
          > Monolithic.com uses a peristaltic pump for pumping concrete to shoot
          > onto the inside of their domes. That concrete is very viscous since
          > it needs to be quite 'dry' to stick overhead without forms. This is
          > also what is used in hospitals (on a different scale) for pumping
          > blood so the blood doesn't come in contact with the pump directly.
          > Monolithic uses replaceable flexible lines inside their pump due to
          > the erosion of the fluids.
          >
          > http://www.monolithic.com/topics/concrete-pumps
          > http://monolithic.myshopify.com/collections/all/products/peristalticpumpline
          >
          > I am pretty sure this is similar to what other companies use too.
          >
          > http://blog.makezine.com/archive/2008/12/make_a_a_peristaltic_pump.html
          > is one from Make: Magazine ... Ok for pumping some things, but shows
          > the principle anyway!
          >
          Yes, peristaltic makes a lot of sense, in view of what I said, since you can treat the pipe as a 'disposable' item.
          Thanks for the archive link.

          I'm sure the name was something like monnow. It was two spiral helixes running inter-twinned with each other, and could pump things like sewage, cement etc., without stones hurting the pump. I think it was patented probably in the early 20th century, and the patent expired a few years ago. The name was I think the company that held the patent, and certainly forty years ago, you could still buy them with this name, but on the web, can't see anything resembling the name. I'll dig out some of my old Victorian engineering encyclopediae, and see if I can get the name right.

          Best Wishes
        • ttelmah
          ... It s funny, but another posted has talked about a two helix design, the Wikipedia article shows a three helix design. Mono, do a two rotor design, but it
          Message 4 of 20 , Feb 1, 2011
          • 0 Attachment
            --- In diy_3d_printing_and_fabrication@yahoogroups.com, Lino <creaturemaker@...> wrote:
            >
            > screw pump
            >
            > http://upload.wikimedia.org/wikipedia/commons/d/d8/Screw_pump.png
            >
            >
            >
            > On Mon, 31 Jan 2011 19:08:53 -0800, Jon Elson <elson@...>
            > wrote:
            >
            > >
            > > Fernando wrote:
            > > >
            > > >
            > > > Is that as in one screw feeding the other from a vat?
            > > > How would that be mounted, at a 90º angle to eachother?
            > > No, one is left-hand, one is right-hand, they lie parallel andinterlock,
            > > in a housing with a figure-eight cross-section.
            > > They rotate in opposite directions.
            > > This pinches off regions in the outer part of each screw, while the
            > > overlap prevents any flow
            > > backwards. Each pinched-off region moves from the inlet side to the
            > > outlet side.
            > >
            > > See http://impeller.net/magazine/news_en/doc3413x.asp for a mediocre
            > > picture, but the best one
            > > I could find.
            > >
            > > Unlike an Archimedes screw, these are positive displacement pumps, they
            > > can stop and the fluid
            > > will not flow backwards.
            > >
            > > Jon
            > >
            >
            >
            >
            > --
            > Using Opera's revolutionary email client: http://www.opera.com/mail/
            >
            It's funny, but another posted has talked about a two helix design, the Wikipedia article shows a three helix design.

            Mono, do a two 'rotor' design, but it is not the pump I remember, which is like a spiral version of the same idea. It has now 'got me annoyed', since I used one of these something like forty years ago, submerged in a well. I'm sure the name was pronounced like 'mono', but was a couple of characters longer...

            I suspect all these designs would be too complex, and think peristaltic, with a stepper and a bit of 'intelligence' to give automatic drip control, may be the nicest solution in terms of easy maintenance, reasonably low cost, and achieving the required operation.

            Have to sit down and think if the basic parts for this could be extruded in ABS, if so will have to build an extrusion head for this (thousands of designs for this online), and try this as an 'intro' experiment, to see how things go.

            Off to do some drawing/thinking again.

            Best Wishes
          • Fernando Muñiz
            A peristaltic pump is a simple and therefore dependable device. What you would need to figure out is how to make the flow continuous and not pulsed though.
            Message 5 of 20 , Feb 1, 2011
            • 0 Attachment
              A peristaltic pump is a simple and therefore dependable device.
              What you would need to figure out is how to make the flow continuous and not pulsed though.
              I'll be looking forward for what you come up with!

              On Tue, 2011-02-01 at 09:16 +0000, ttelmah wrote:
               


              --- In diy_3d_printing_and_fabrication@yahoogroups.com, Jack Coats <jack@...> wrote:
              >
              > The concrete industry regularly pumps 'hard to pump' fluids, and the
              > plastics injection molding industry uses a screw pump that works in
              > stages (all on one axis) to get the pressure higher as it flows
              > through the heating chamber.
              >
              > I did not find 'monnow' pump (Seems to be a "C'mon now" music/dance
              > with racy lyrics going around in some circles) ... any reference would
              > be a appreciated.
              >
              > http://www.plasticstech.info/equipment/injection-molding-machine/ has
              > a schematic images, but the details of the compression screw isn't
              > show very well.
              >
              > Monolithic.com uses a peristaltic pump for pumping concrete to shoot
              > onto the inside of their domes. That concrete is very viscous since
              > it needs to be quite 'dry' to stick overhead without forms. This is
              > also what is used in hospitals (on a different scale) for pumping
              > blood so the blood doesn't come in contact with the pump directly.
              > Monolithic uses replaceable flexible lines inside their pump due to
              > the erosion of the fluids.
              >
              > http://www.monolithic.com/topics/concrete-pumps
              > http://monolithic.myshopify.com/collections/all/products/peristalticpumpline
              >
              > I am pretty sure this is similar to what other companies use too.
              >
              > http://blog.makezine.com/archive/2008/12/make_a_a_peristaltic_pump.html
              > is one from Make: Magazine ... Ok for pumping some things, but shows
              > the principle anyway!
              >
              Yes, peristaltic makes a lot of sense, in view of what I said, since you can treat the pipe as a 'disposable' item.
              Thanks for the archive link.

              I'm sure the name was something like monnow. It was two spiral helixes running inter-twinned with each other, and could pump things like sewage, cement etc., without stones hurting the pump. I think it was patented probably in the early 20th century, and the patent expired a few years ago. The name was I think the company that held the patent, and certainly forty years ago, you could still buy them with this name, but on the web, can't see anything resembling the name. I'll dig out some of my old Victorian engineering encyclopediae, and see if I can get the name right.

              Best Wishes





            • Boman33
              The syringes pressurized by air are hard to accurately control. The rigid syringe ought to be able to control the dripping by slightly backing up the plunger
              Message 6 of 20 , Feb 1, 2011
              • 0 Attachment
                The syringes pressurized by air are hard to accurately control. The rigid
                syringe ought to be able to control the dripping by slightly backing up the
                plunger but obviously there cannot be any slop or play in the system.
                Bertho
                =================================

                From: telmah Sent: Monday, January 31, 2011 17:01
                --- <boman33@...> wrote:
                >
                > Welcome!
                > How about a rigid oversized syringe with the plunger CNC controlled. All
                metal or other stiff material. No pipes or hoses to flex. Nozzle directly
                attached.
                > When low, it could be automatically refilled from a side port with
                > pressurized material to avoid any air pockets.
                > Bertho
                =====================================
                The pressurised syringe pushed by a linear stepper, was the first thing that
                other people have tried. Suffers from dripping...
                They switched to using pressurised syringes (this is what is commonly used
                for things like epoxies), better, but still drips. Hence the need for a
                positive cutoff close to the needle.
                Best Wishes
              • Fernando Muñiz
                Heterogeneous fluids (as in suspensions and pastes) are usually non-Newtonian fluids so there will be a certain elastic tendency. Pneumatic control must be
                Message 7 of 20 , Feb 1, 2011
                • 0 Attachment
                  Heterogeneous fluids (as in suspensions and pastes) are usually non-Newtonian fluids so there will be a certain "elastic" tendency.
                  Pneumatic control must be quite a difficult design to implement. In any case I would rather use oil pressure rather than air to actuate it.
                  Screw drive plungers are more reliable and solid, also quicker to revert direction.

                  On Tue, 2011-02-01 at 07:56 -0500, Boman33 wrote:
                   
                  The syringes pressurized by air are hard to accurately control. The rigid
                  syringe ought to be able to control the dripping by slightly backing up the
                  plunger but obviously there cannot be any slop or play in the system.
                  Bertho
                  =================================

                  From: telmah Sent: Monday, January 31, 2011 17:01
                  --- <boman33@...> wrote:
                  >
                  > Welcome!
                  > How about a rigid oversized syringe with the plunger CNC controlled. All
                  metal or other stiff material. No pipes or hoses to flex. Nozzle directly
                  attached.
                  > When low, it could be automatically refilled from a side port with
                  > pressurized material to avoid any air pockets.
                  > Bertho
                  =====================================
                  The pressurised syringe pushed by a linear stepper, was the first thing that
                  other people have tried. Suffers from dripping...
                  They switched to using pressurised syringes (this is what is commonly used
                  for things like epoxies), better, but still drips. Hence the need for a
                  positive cutoff close to the needle.
                  Best Wishes





                • Roger Hamlett
                  ... Problem is that you are going to need a soft seal at the tip of the syringe plunger (polyethylene probably), and you will be pulling at the top of a
                  Message 8 of 20 , Feb 3, 2011
                  • 0 Attachment
                    > In principle it would work with the extra air plunger but I think you are
                    > unnecessarily making it more complex, creating several new variables and
                    > making it harder to control. For example, the flexible hose will flex and
                    > it will vary with temperature, consistency of the medium and so on. It will
                    > affect both the dispensing cycle and the off cycle.
                    >
                    > Why not just use the rigid syringe and plunger as I suggested. Today it is
                    > easy to get a backlash free linear actuator that in software can accurately
                    > be controlled and if needed also reversed.
                    > Bertho
                    > =============================
                    >
                    > From: Roger Hamlett Sent: Wednesday, February 02, 2011 11:50
                    >
                    Problem is that you are going to need a soft seal at the tip of the
                    syringe plunger (polyethylene probably), and you will be pulling at the
                    'top' of a variable length (and hence variable stiction) column of clay.
                    If you take a syringe of clay, and try pulling back on a nearly empty
                    one, it works. But on a nearly full one, you just create a vacuum, and
                    the plunger pulls away from the clay leaving a cavity (I tried...).
                    It looks as if the 'pull back' really has to be done near the nozzle.

                    The variability of the hose should be small in a 'room temperature'
                    environment.
                    I'm going to try to reduce the variability in the medium, by making some
                    form of viscosity 'tester', and working to a standard on this.

                    I was going to use a linear driver of some form, to give constant feed
                    rates, but the idea was to give a tiny amount of suck back right behind
                    the nozzle. I might think about a little brass assembly, with an O-ring
                    sealed plunger that just moves a small amount (perhaps adjustable with a
                    couple of screw stops), and see what the life of this is like in the
                    abrasive environment, to avoid the elasticity of the pipe idea. However
                    the pipe has the big advantage of being cheap, and a replaceable part. I
                    was visualising it being in a shaped hole, to limit it's stretch, and
                    just compressing the one section, so the variability should be small.
                    This is where a few experiments are now needed.

                    Best Wishes


                    > Heterogeneous fluids (as in suspensions and pastes) are usually
                    > non-Newtonian fluids so there will be a certain "elastic" tendency.

                    >> Pneumatic control must be quite a difficult design to implement. In any
                    >> case I would rather use oil pressure rather than air to actuate it.
                    >> Screw drive plungers are more reliable and solid, also quicker to revert
                    >> direction.
                    >>
                    >> On Tue, 2011-02-01 at 07:56 -0500, Boman33 wrote:
                    >>
                    > Yes,
                    > I'd begun to suspect this was the case. So you actually need not just
                    > 'removal' of pressure, but positive _subtraction_ at the tip, to prevent
                    > ooze.
                    > So if you have a 'pushed' syringe, feeding to a simple nozzle, with
                    > control of the feed, but then have a short length of pipe between the
                    > syringe and the nozzle, that is slightly squeezed at the side by an air
                    > piston, when the feed is on. Cut the feed, and at the same time, the
                    > feed piston stops pushing, the side pressure is relaxed (spring),
                    > actually creating a small suction at the nozzle, and 'pull back'.
                    > Not too complex, and seems to handle the likely problems.
                    > Have ordered some pipe, nozzles, and syringes, and going to play with this.
                    >
                    > Best Wishes
                    >
                  • Roger Hamlett
                    ... How are you going to projector form, solid gold, bronze, copper or silver?. The clay extrusion method allows these to be produced (after firing), with
                    Message 9 of 20 , Feb 4, 2011
                    • 0 Attachment
                      > All of this discussion seems to be the hard way when one considers the ease and accuracy of the projector forming a whole plane on each step. Why would you still be working with this method?
                      >
                      > Michael Couch
                      >
                      > --- In diy_3d_printing_and_fabrication@yahoogroups.com, "Boman33"<boman33@...> wrote:
                      How are you going to projector form, solid gold, bronze, copper or silver?.
                      The clay extrusion method allows these to be produced (after firing),
                      with polymer clay forms of all of these available.
                      No 'projector' solution available for these materials....


                      Best Wishes

                      >> In principle it would work with the extra air plunger but I think you are
                      >> unnecessarily making it more complex, creating several new variables and
                      >> making it harder to control. For example, the flexible hose will flex and
                      >> it will vary with temperature, consistency of the medium and so on. It will
                      >> affect both the dispensing cycle and the off cycle.
                      >>
                      >> Why not just use the rigid syringe and plunger as I suggested. Today it is
                      >> easy to get a backlash free linear actuator that in software can accurately
                      >> be controlled and if needed also reversed.
                      >> Bertho
                      >> =============================
                      >>
                      >> From: Roger Hamlett Sent: Wednesday, February 02, 2011 11:50
                      >>
                      >>> Heterogeneous fluids (as in suspensions and pastes) are usually
                      >>> non-Newtonian fluids so there will be a certain "elastic" tendency.
                      >>> Pneumatic control must be quite a difficult design to implement. In any
                      >>> case I would rather use oil pressure rather than air to actuate it.
                      >>> Screw drive plungers are more reliable and solid, also quicker to revert
                      >>> direction.
                      >>>
                      >>> On Tue, 2011-02-01 at 07:56 -0500, Boman33 wrote:
                      >>>
                      >> Yes,
                      >> I'd begun to suspect this was the case. So you actually need not just
                      >> 'removal' of pressure, but positive _subtraction_ at the tip, to prevent
                      >> ooze.
                      >> So if you have a 'pushed' syringe, feeding to a simple nozzle, with
                      >> control of the feed, but then have a short length of pipe between the
                      >> syringe and the nozzle, that is slightly squeezed at the side by an air
                      >> piston, when the feed is on. Cut the feed, and at the same time, the
                      >> feed piston stops pushing, the side pressure is relaxed (spring),
                      >> actually creating a small suction at the nozzle, and 'pull back'.
                      >> Not too complex, and seems to handle the likely problems.
                      >> Have ordered some pipe, nozzles, and syringes, and going to play with this.
                      >>
                      >> Best Wishes
                    • Jon Elson
                      ... You could use the LCD projection item to make a wax pattern or investment form for casting the part in metal. Admittedly, a multi-step process. Jon
                      Message 10 of 20 , Feb 4, 2011
                      • 0 Attachment
                        Roger Hamlett wrote:
                        >> All of this discussion seems to be the hard way when one considers the ease and accuracy of the projector forming a whole plane on each step. Why would you still be working with this method?
                        >>
                        >> Michael Couch
                        >>
                        >> --- In diy_3d_printing_and_fabrication@yahoogroups.com, "Boman33"<boman33@...> wrote:
                        >>
                        > How are you going to projector form, solid gold, bronze, copper or silver?.
                        > The clay extrusion method allows these to be produced (after firing),
                        > with polymer clay forms of all of these available.
                        > No 'projector' solution available for these materials....
                        >
                        You could use the LCD projection item to make a wax pattern or
                        investment form for casting the part in metal.
                        Admittedly, a multi-step process.

                        Jon
                      • Michael Couch
                        Project a form cast a mold and mold it? Michael
                        Message 11 of 20 , Feb 5, 2011
                        • 0 Attachment
                          Project a form cast a mold and mold it?

                          Michael

                          --- In diy_3d_printing_and_fabrication@yahoogroups.com, Roger Hamlett <ttelmah@...> wrote:
                          >
                          >
                          > > All of this discussion seems to be the hard way when one considers the ease and accuracy of the projector forming a whole plane on each step. Why would you still be working with this method?
                          > >
                          > > Michael Couch
                          > >
                          > > --- In diy_3d_printing_and_fabrication@yahoogroups.com, "Boman33"<boman33@> wrote:
                          > How are you going to projector form, solid gold, bronze, copper or silver?.
                          > The clay extrusion method allows these to be produced (after firing),
                          > with polymer clay forms of all of these available.
                          > No 'projector' solution available for these materials....
                          >
                          >
                          > Best Wishes
                          >
                          > >> In principle it would work with the extra air plunger but I think you are
                          > >> unnecessarily making it more complex, creating several new variables and
                          > >> making it harder to control. For example, the flexible hose will flex and
                          > >> it will vary with temperature, consistency of the medium and so on. It will
                          > >> affect both the dispensing cycle and the off cycle.
                          > >>
                          > >> Why not just use the rigid syringe and plunger as I suggested. Today it is
                          > >> easy to get a backlash free linear actuator that in software can accurately
                          > >> be controlled and if needed also reversed.
                          > >> Bertho
                          > >> =============================
                          > >>
                          > >> From: Roger Hamlett Sent: Wednesday, February 02, 2011 11:50
                          > >>
                          > >>> Heterogeneous fluids (as in suspensions and pastes) are usually
                          > >>> non-Newtonian fluids so there will be a certain "elastic" tendency.
                          > >>> Pneumatic control must be quite a difficult design to implement. In any
                          > >>> case I would rather use oil pressure rather than air to actuate it.
                          > >>> Screw drive plungers are more reliable and solid, also quicker to revert
                          > >>> direction.
                          > >>>
                          > >>> On Tue, 2011-02-01 at 07:56 -0500, Boman33 wrote:
                          > >>>
                          > >> Yes,
                          > >> I'd begun to suspect this was the case. So you actually need not just
                          > >> 'removal' of pressure, but positive _subtraction_ at the tip, to prevent
                          > >> ooze.
                          > >> So if you have a 'pushed' syringe, feeding to a simple nozzle, with
                          > >> control of the feed, but then have a short length of pipe between the
                          > >> syringe and the nozzle, that is slightly squeezed at the side by an air
                          > >> piston, when the feed is on. Cut the feed, and at the same time, the
                          > >> feed piston stops pushing, the side pressure is relaxed (spring),
                          > >> actually creating a small suction at the nozzle, and 'pull back'.
                          > >> Not too complex, and seems to handle the likely problems.
                          > >> Have ordered some pipe, nozzles, and syringes, and going to play with this.
                          > >>
                          > >> Best Wishes
                          >
                        Your message has been successfully submitted and would be delivered to recipients shortly.