Hey folks, I'm new here but I've gone through a bunch of the backpages in the forum posts and hopefully am not putting forth anything rehashed.
Reading through the State of Dual Extrusion<https://groups.google.com/forum/?fromgroups#!topic/ultimaker/sfAFPqLYEHo> thread the other day, I became more aware of the problems with oozing and retraction. As great as all of the theories for curbing ooze were in that thread, I think maybe there's a much simpler answer. Essentially, we turn the extrusion head into a syringe.
My theory is that making the end portion of the bowden tube air-tight by adding a silicone ring that seals the bowden tube to the filament, when you retract you create negative pressure because the solid filament would act as a syringe piston. This would suck the molten plastic back into the tube. If that seal works properly, considering the small aperture of the nozzle, surface tension should keep the molten plastic from oozing. This would require a retraction length smaller than the amount of solid filament from the seal downwards, but the seal should be as close to the hot end as possible to minimize the air in the chamber.
The problems with this model are that (1) restricting the filament by forcing it through the seal would have dire consequences and, (2) I really don't know enough about fluid dynamics to be sure this will work at all. If thoughts on this forum are encouraging I can try putting together a prototype with some parts from work (I'm a plumber). Let me know what you think.
On a side note: I couldn't be happier with my Ultimaker or the community around it so far. A few minor tweaks from out of the box and I'm getting some pretty excellent prints. Next up, heated bed!
Seems like a good idea to me. One problem I can see is that the
filament is usually deformed by the extruder drives. Some drives are
worse at this than others. The stock extruder drives emboss a knurl
into the filament. This deforming will probably be difficult to seal
around or will destroy the seal. I am using GHagens extruder which
deforms the filament much less than the stock system (V2 anyway I have
no experience with V3).
On Oct 26, 11:48 pm, Mackadoo <machado.m...@gmail.com> wrote:
> Hey folks, I'm new here but I've gone through a bunch of the backpages in
> the forum posts and hopefully am not putting forth anything rehashed.
> Reading through the State of Dual Extrusion<https://groups.google.com/forum/?fromgroups#!topic/ultimaker/sfAFPqLYEHo> thread
> the other day, I became more aware of the problems with oozing and
> retraction. As great as all of the theories for curbing ooze were in that
> thread, I think maybe there's a much simpler answer. Essentially, we turn
> the extrusion head into a syringe.
> My theory is that making the end portion of the bowden tube air-tight by
> adding a silicone ring that seals the bowden tube to the filament, when you
> retract you create negative pressure because the solid filament would act
> as a syringe piston. This would suck the molten plastic back into the
> tube. If that seal works properly, considering the small aperture of the
> nozzle, surface tension should keep the molten plastic from oozing. This
> would require a retraction length smaller than the amount of solid filament
> from the seal downwards, but the seal should be as close to the hot end as
> possible to minimize the air in the chamber.
> The problems with this model are that (1) restricting the filament by
> forcing it through the seal would have dire consequences and, (2) I really
> don't know enough about fluid dynamics to be sure this will work at all.
> If thoughts on this forum are encouraging I can try putting together a
> prototype with some parts from work (I'm a plumber). Let me know what you
> think.
> On a side note: I couldn't be happier with my Ultimaker or the community
> around it so far. A few minor tweaks from out of the box and I'm getting
> some pretty excellent prints. Next up, heated bed!
And what will happen if you put the tube under a permanent light vacuum...?!
Especially with dual extrusion.
The seal doesn't have to be perfect either then.
cheers\joris
Op 27 okt. 2012 14:39 schreef "mastory" <matthew_a_st...@yahoo.com> het
volgende:
> Seems like a good idea to me. One problem I can see is that the
> filament is usually deformed by the extruder drives. Some drives are
> worse at this than others. The stock extruder drives emboss a knurl
> into the filament. This deforming will probably be difficult to seal
> around or will destroy the seal. I am using GHagens extruder which
> deforms the filament much less than the stock system (V2 anyway I have
> no experience with V3).
> On Oct 26, 11:48 pm, Mackadoo <machado.m...@gmail.com> wrote:
> > Hey folks, I'm new here but I've gone through a bunch of the backpages in
> > the forum posts and hopefully am not putting forth anything rehashed.
> > Reading through the State of Dual Extrusion<
> https://groups.google.com/forum/?fromgroups#!topic/ultimaker/sfAFPqLYEHo>
> thread
> > the other day, I became more aware of the problems with oozing and
> > retraction. As great as all of the theories for curbing ooze were in
> that
> > thread, I think maybe there's a much simpler answer. Essentially, we
> turn
> > the extrusion head into a syringe.
> > My theory is that making the end portion of the bowden tube air-tight by
> > adding a silicone ring that seals the bowden tube to the filament, when
> you
> > retract you create negative pressure because the solid filament would act
> > as a syringe piston. This would suck the molten plastic back into the
> > tube. If that seal works properly, considering the small aperture of the
> > nozzle, surface tension should keep the molten plastic from oozing. This
> > would require a retraction length smaller than the amount of solid
> filament
> > from the seal downwards, but the seal should be as close to the hot end
> as
> > possible to minimize the air in the chamber.
> > The problems with this model are that (1) restricting the filament by
> > forcing it through the seal would have dire consequences and, (2) I
> really
> > don't know enough about fluid dynamics to be sure this will work at all.
> > If thoughts on this forum are encouraging I can try putting together a
> > prototype with some parts from work (I'm a plumber). Let me know what
> you
> > think.
> > On a side note: I couldn't be happier with my Ultimaker or the community
> > around it so far. A few minor tweaks from out of the box and I'm getting
> > some pretty excellent prints. Next up, heated bed!
> --
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Great idea Joris. A push-lock tee fitting could be added to the the
bowden tube at any point. Near the extruder drive would keep the
moving mass down. Just need to come up with some kind of seal that
would tolerate the variation of the filament and add it between the
extruder and the tee fitting. A initial test could be done by adding
vacuum orally. If it worked, a compressed air vacuum venturi or a
vacuum pump could supply the negative pressure.
On Oct 27, 1:48 pm, "Joris [van Tubergen]" <rooiejo...@gmail.com>
wrote:
> And what will happen if you put the tube under a permanent light vacuum...?!
> Especially with dual extrusion.
> The seal doesn't have to be perfect either then.
> cheers\joris
> Op 27 okt. 2012 14:39 schreef "mastory" <matthew_a_st...@yahoo.com> het
> volgende:
> > Seems like a good idea to me. One problem I can see is that the
> > filament is usually deformed by the extruder drives. Some drives are
> > worse at this than others. The stock extruder drives emboss a knurl
> > into the filament. This deforming will probably be difficult to seal
> > around or will destroy the seal. I am using GHagens extruder which
> > deforms the filament much less than the stock system (V2 anyway I have
> > no experience with V3).
> > On Oct 26, 11:48 pm, Mackadoo <machado.m...@gmail.com> wrote:
> > > Hey folks, I'm new here but I've gone through a bunch of the backpages in
> > > the forum posts and hopefully am not putting forth anything rehashed.
> > > Reading through the State of Dual Extrusion<
> >https://groups.google.com/forum/?fromgroups#!topic/ultimaker/sfAFPqLYEHo>
> > thread
> > > the other day, I became more aware of the problems with oozing and
> > > retraction. As great as all of the theories for curbing ooze were in
> > that
> > > thread, I think maybe there's a much simpler answer. Essentially, we
> > turn
> > > the extrusion head into a syringe.
> > > My theory is that making the end portion of the bowden tube air-tight by
> > > adding a silicone ring that seals the bowden tube to the filament, when
> > you
> > > retract you create negative pressure because the solid filament would act
> > > as a syringe piston. This would suck the molten plastic back into the
> > > tube. If that seal works properly, considering the small aperture of the
> > > nozzle, surface tension should keep the molten plastic from oozing. This
> > > would require a retraction length smaller than the amount of solid
> > filament
> > > from the seal downwards, but the seal should be as close to the hot end
> > as
> > > possible to minimize the air in the chamber.
> > > The problems with this model are that (1) restricting the filament by
> > > forcing it through the seal would have dire consequences and, (2) I
> > really
> > > don't know enough about fluid dynamics to be sure this will work at all.
> > > If thoughts on this forum are encouraging I can try putting together a
> > > prototype with some parts from work (I'm a plumber). Let me know what
> > you
> > > think.
> > > On a side note: I couldn't be happier with my Ultimaker or the community
> > > around it so far. A few minor tweaks from out of the box and I'm getting
> > > some pretty excellent prints. Next up, heated bed!
> > --
> > You received this message because you are subscribed to the Google Groups
> > "Ultimaker" group.
> > There are also forums, which are the official gathering place for
> > Ultimaker operators:
> >http://forum.ultimaker.com/
> > If you still want to post to this group, send email to
> > ultimaker@googlegroups.com
> > To unsubscribe from this group, send email to
> > ultimaker+unsubscribe@googlegroups.com
> > For more options, visit this group at
> >http://groups.google.com/group/ultimaker?hl=en
Agreed. If the tee is in accessible place like over the extruder drive,
replacing the seal regularly from wear would be easy.
On Oct 27, 2012 2:06 PM, "mastory" <matthew_a_st...@yahoo.com> wrote:
> Great idea Joris. A push-lock tee fitting could be added to the the
> bowden tube at any point. Near the extruder drive would keep the
> moving mass down. Just need to come up with some kind of seal that
> would tolerate the variation of the filament and add it between the
> extruder and the tee fitting. A initial test could be done by adding
> vacuum orally. If it worked, a compressed air vacuum venturi or a
> vacuum pump could supply the negative pressure.
> On Oct 27, 1:48 pm, "Joris [van Tubergen]" <rooiejo...@gmail.com>
> wrote:
> > And what will happen if you put the tube under a permanent light
> vacuum...?!
> > Especially with dual extrusion.
> > The seal doesn't have to be perfect either then.
> > cheers\joris
> > Op 27 okt. 2012 14:39 schreef "mastory" <matthew_a_st...@yahoo.com> het
> > volgende:
> > > Seems like a good idea to me. One problem I can see is that the
> > > filament is usually deformed by the extruder drives. Some drives are
> > > worse at this than others. The stock extruder drives emboss a knurl
> > > into the filament. This deforming will probably be difficult to seal
> > > around or will destroy the seal. I am using GHagens extruder which
> > > deforms the filament much less than the stock system (V2 anyway I have
> > > no experience with V3).
> > > On Oct 26, 11:48 pm, Mackadoo <machado.m...@gmail.com> wrote:
> > > > Hey folks, I'm new here but I've gone through a bunch of the
> backpages in
> > > > the forum posts and hopefully am not putting forth anything rehashed.
> > > > Reading through the State of Dual Extrusion<
> https://groups.google.com/forum/?fromgroups#!topic/ultimaker/sfAFPqLYEHo>
> > > thread
> > > > the other day, I became more aware of the problems with oozing and
> > > > retraction. As great as all of the theories for curbing ooze were in
> > > that
> > > > thread, I think maybe there's a much simpler answer. Essentially, we
> > > turn
> > > > the extrusion head into a syringe.
> > > > My theory is that making the end portion of the bowden tube
> air-tight by
> > > > adding a silicone ring that seals the bowden tube to the filament,
> when
> > > you
> > > > retract you create negative pressure because the solid filament
> would act
> > > > as a syringe piston. This would suck the molten plastic back into
> the
> > > > tube. If that seal works properly, considering the small aperture
> of the
> > > > nozzle, surface tension should keep the molten plastic from oozing.
> This
> > > > would require a retraction length smaller than the amount of solid
> > > filament
> > > > from the seal downwards, but the seal should be as close to the hot
> end
> > > as
> > > > possible to minimize the air in the chamber.
> > > > The problems with this model are that (1) restricting the filament by
> > > > forcing it through the seal would have dire consequences and, (2) I
> > > really
> > > > don't know enough about fluid dynamics to be sure this will work at
> all.
> > > > If thoughts on this forum are encouraging I can try putting
> together a
> > > > prototype with some parts from work (I'm a plumber). Let me know
> what
> > > you
> > > > think.
> > > > On a side note: I couldn't be happier with my Ultimaker or the
> community
> > > > around it so far. A few minor tweaks from out of the box and I'm
> getting
> > > > some pretty excellent prints. Next up, heated bed!
> > > --
> > > You received this message because you are subscribed to the Google
> Groups
> > > "Ultimaker" group.
> > > There are also forums, which are the official gathering place for
> > > Ultimaker operators:
> > >http://forum.ultimaker.com/
> > > If you still want to post to this group, send email to
> > > ultimaker@googlegroups.com
> > > To unsubscribe from this group, send email to
> > > ultimaker+unsubscribe@googlegroups.com
> > > For more options, visit this group at
> > >http://groups.google.com/group/ultimaker?hl=en
> --
> You received this message because you are subscribed to the Google Groups
> "Ultimaker" group.
> There are also forums, which are the official gathering place for
> Ultimaker operators:
> http://forum.ultimaker.com/
> If you still want to post to this group, send email to
> ultimaker@googlegroups.com
> To unsubscribe from this group, send email to
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On Saturday, October 27, 2012 1:16:40 PM UTC-5, Mackadoo wrote:
> Agreed. If the tee is in accessible place like over the extruder drive, > replacing the seal regularly from wear would be easy. > On Oct 27, 2012 2:06 PM, "mastory" <matthew...@yahoo.com <javascript:>> > wrote:
>> Great idea Joris. A push-lock tee fitting could be added to the the >> bowden tube at any point. Near the extruder drive would keep the >> moving mass down. Just need to come up with some kind of seal that >> would tolerate the variation of the filament and add it between the >> extruder and the tee fitting. A initial test could be done by adding >> vacuum orally. If it worked, a compressed air vacuum venturi or a >> vacuum pump could supply the negative pressure.
>> On Oct 27, 1:48 pm, "Joris [van Tubergen]" <rooiejo...@gmail.com> >> wrote: >> > And what will happen if you put the tube under a permanent light >> vacuum...?! >> > Especially with dual extrusion. >> > The seal doesn't have to be perfect either then.
>> > cheers\joris >> > Op 27 okt. 2012 14:39 schreef "mastory" <matthew_a_st...@yahoo.com> het >> > volgende:
>> > > Seems like a good idea to me. One problem I can see is that the >> > > filament is usually deformed by the extruder drives. Some drives are >> > > worse at this than others. The stock extruder drives emboss a knurl >> > > into the filament. This deforming will probably be difficult to seal >> > > around or will destroy the seal. I am using GHagens extruder which >> > > deforms the filament much less than the stock system (V2 anyway I have >> > > no experience with V3).
>> > > On Oct 26, 11:48 pm, Mackadoo <machado.m...@gmail.com> wrote: >> > > > Hey folks, I'm new here but I've gone through a bunch of the >> backpages in >> > > > the forum posts and hopefully am not putting forth anything >> rehashed.
>> > > > Reading through the State of Dual Extrusion<
>> https://groups.google.com/forum/?fromgroups#!topic/ultimaker/sfAFPqLYEHo> >> > > thread >> > > > the other day, I became more aware of the problems with oozing and >> > > > retraction. As great as all of the theories for curbing ooze were >> in >> > > that >> > > > thread, I think maybe there's a much simpler answer. Essentially, >> we >> > > turn >> > > > the extrusion head into a syringe.
>> > > > My theory is that making the end portion of the bowden tube >> air-tight by >> > > > adding a silicone ring that seals the bowden tube to the filament, >> when >> > > you >> > > > retract you create negative pressure because the solid filament >> would act >> > > > as a syringe piston. This would suck the molten plastic back into >> the >> > > > tube. If that seal works properly, considering the small aperture >> of the >> > > > nozzle, surface tension should keep the molten plastic from oozing. >> This >> > > > would require a retraction length smaller than the amount of solid >> > > filament >> > > > from the seal downwards, but the seal should be as close to the hot >> end >> > > as >> > > > possible to minimize the air in the chamber.
>> > > > The problems with this model are that (1) restricting the filament >> by >> > > > forcing it through the seal would have dire consequences and, (2) I >> > > really >> > > > don't know enough about fluid dynamics to be sure this will work at >> all. >> > > > If thoughts on this forum are encouraging I can try putting >> together a >> > > > prototype with some parts from work (I'm a plumber). Let me know >> what >> > > you >> > > > think.
>> > > > On a side note: I couldn't be happier with my Ultimaker or the >> community >> > > > around it so far. A few minor tweaks from out of the box and I'm >> getting >> > > > some pretty excellent prints. Next up, heated bed!
>> > > -- >> > > You received this message because you are subscribed to the Google >> Groups >> > > "Ultimaker" group.
>> > > There are also forums, which are the official gathering place for >> > > Ultimaker operators: >> > >http://forum.ultimaker.com/
>> > > If you still want to post to this group, send email to >> > > ulti...@googlegroups.com <javascript:> >> > > To unsubscribe from this group, send email to >> > > ultimaker+...@googlegroups.com <javascript:> >> > > For more options, visit this group at >> > >http://groups.google.com/group/ultimaker?hl=en
>> -- >> You received this message because you are subscribed to the Google Groups >> "Ultimaker" group.
>> There are also forums, which are the official gathering place for >> Ultimaker operators: >> http://forum.ultimaker.com/
>> If you still want to post to this group, send email to >> ulti...@googlegroups.com <javascript:> >> To unsubscribe from this group, send email to >> ultimaker+...@googlegroups.com <javascript:> >> For more options, visit this group at >> http://groups.google.com/group/ultimaker?hl=en
If a seal/vacuum is made back at the drive, you need to worry about sealing
at all the different joints all the way up to the nozzle tip (where the
vacuum actually matters). From experience I can tell you this would be a
headache. It's much better to try and make it as close to the nozzle as
possible, the ideal case being Mastory's idea.
While the marks left on the filament by the drive bolt would impact the
vacuum in the nozzle a bit, you can easily implement this using a high-wear
o-ring (technically this is a dynamic radial seal or piston seal. Google
for more info). To get a decent seal you need a minimum squeeze
(diametrical compression) of 0.125 mm, a target squeeze of 15% and a
maximum of 30%. So, as you can see, they can handle quite a range. For us
the ideal O-ring would be a* Metric O-Ring 1.5 mm Width, 2.5 mm ID* or, if
you're one of them goofy imperial people (or the even more f'd up
imperial/metric mix like me), use a *AS568A-103*. Ideally you'd want to use
a hard o-ring for abrasion resistance (like A90) but will add more
resistance to the filament. A soft o-ring (like A50 or 55) will conform
much better and give lower resistance but at the expense of being chewed up
faster. Personally I'd go with the later. If you rub the o-ring with
mineral oil when it's first installed, it will help with abrasion and
resistance. No idea if this will impact printing though.
In terms of operation, if you dial in the retract to only suck back enough
without pulling in an air bubble, this will work well. We could actually
figure out the amount of pressure needed if we can measure the surface
tension and contact angle of liquid PLA on brass. This is similar to how
some of the older inject printers used to work. The only issue I see is if
the PTFE tube is a bit bigger than the filament there will be a bit of
buckle before the filament pushes through the o-ring when repriming. This
leads to a bit of a lag and possible over pressure when re-priming, but
that could be ironed out with some fancy retraction.
On Sat, Oct 27, 2012 at 11:43 AM, Dan Newman <dan.new...@mtbaldy.us> wrote:
> On 27 Oct 2012 , at 11:41 AM, Billy Zelsnack wrote:
> > Isn't the part of the filament just above the molten section effectively
> > already a plunger that conforms perfectly to the tube?
> It's molten just below it -- pulling on it just elongates/draws out a
> molten
> thread and doesn't pull back much (if at all) on the melt itself.
> Dan
> --
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> There are also forums, which are the official gathering place for
> Ultimaker operators:
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> If you still want to post to this group, send email to
> ultimaker@googlegroups.com
> To unsubscribe from this group, send email to
> ultimaker+unsubscribe@googlegroups.com
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How about reversing this idea, instead of putting a vacuum on the nozzle, which would be problematic with leakage, how about having a small pump which can put quite a bit of air pressure on the bowdentube. This way you could blow the nozzle empty.
My latest dual extrusion with V2 hotends at 210C only had a tiny bit of oozing compared to the earlier experiment. I think if you blow the nozzle empty at a known location you might have solved the issue. (My previous dual extrusion experiments where with V1 hotends)
On Saturday, October 27, 2012 5:48:01 AM UTC+2, Mackadoo wrote:
> Hey folks, I'm new here but I've gone through a bunch of the backpages in > the forum posts and hopefully am not putting forth anything rehashed.
> Reading through the State of Dual Extrusion<https://groups.google.com/forum/?fromgroups#!topic/ultimaker/sfAFPqLYEHo> thread > the other day, I became more aware of the problems with oozing and > retraction. As great as all of the theories for curbing ooze were in that > thread, I think maybe there's a much simpler answer. Essentially, we turn > the extrusion head into a syringe.
> My theory is that making the end portion of the bowden tube air-tight by > adding a silicone ring that seals the bowden tube to the filament, when you > retract you create negative pressure because the solid filament would act > as a syringe piston. This would suck the molten plastic back into the > tube. If that seal works properly, considering the small aperture of the > nozzle, surface tension should keep the molten plastic from oozing. This > would require a retraction length smaller than the amount of solid filament > from the seal downwards, but the seal should be as close to the hot end as > possible to minimize the air in the chamber.
> The problems with this model are that (1) restricting the filament by > forcing it through the seal would have dire consequences and, (2) I really > don't know enough about fluid dynamics to be sure this will work at all. > If thoughts on this forum are encouraging I can try putting together a > prototype with some parts from work (I'm a plumber). Let me know what you > think.
> On a side note: I couldn't be happier with my Ultimaker or the community > around it so far. A few minor tweaks from out of the box and I'm getting > some pretty excellent prints. Next up, heated bed!
The melt interface zone already conforms to the inside wall, making it a
perfect plunger. The problem with oozing is not the initial retraction as
we know that works well. The problem is what happens after the retraction
when the PLA flows down the sides of the cylinder back to the nozzle.
But I do have another solution: fibres! This problem of oozing/dripping
viscous fluid from a small orifice has already been fixed for fineliners
etc. They add a bunch of fibres into the tip, making sure the
adhesion/capilary action keeps it from dripping. Just adding a few glass
fibres cut of at the nozzle end will help a lot I think. Basically it
transforms the nozzle in a bunch of smaller nozzles. No idea how these
fibres should be attached inside the nozzle, that is still to be
determined. Melting them to a small glass ring might work?
On Sat, Oct 27, 2012 at 9:44 PM, Daid <daid...@gmail.com> wrote:
> How about reversing this idea, instead of putting a vacuum on the nozzle,
> which would be problematic with leakage, how about having a small pump
> which can put quite a bit of air pressure on the bowdentube. This way you
> could blow the nozzle empty.
> My latest dual extrusion with V2 hotends at 210C only had a tiny bit of
> oozing compared to the earlier experiment. I think if you blow the nozzle
> empty at a known location you might have solved the issue.
> (My previous dual extrusion experiments where with V1 hotends)
> On Saturday, October 27, 2012 5:48:01 AM UTC+2, Mackadoo wrote:
>> Hey folks, I'm new here but I've gone through a bunch of the backpages in
>> the forum posts and hopefully am not putting forth anything rehashed.
>> Reading through the State of Dual Extrusion<https://groups.google.com/forum/?fromgroups#!topic/ultimaker/sfAFPqLYEHo> thread
>> the other day, I became more aware of the problems with oozing and
>> retraction. As great as all of the theories for curbing ooze were in that
>> thread, I think maybe there's a much simpler answer. Essentially, we turn
>> the extrusion head into a syringe.
>> My theory is that making the end portion of the bowden tube air-tight by
>> adding a silicone ring that seals the bowden tube to the filament, when you
>> retract you create negative pressure because the solid filament would act
>> as a syringe piston. This would suck the molten plastic back into the
>> tube. If that seal works properly, considering the small aperture of the
>> nozzle, surface tension should keep the molten plastic from oozing. This
>> would require a retraction length smaller than the amount of solid filament
>> from the seal downwards, but the seal should be as close to the hot end as
>> possible to minimize the air in the chamber.
>> The problems with this model are that (1) restricting the filament by
>> forcing it through the seal would have dire consequences and, (2) I really
>> don't know enough about fluid dynamics to be sure this will work at all.
>> If thoughts on this forum are encouraging I can try putting together a
>> prototype with some parts from work (I'm a plumber). Let me know what you
>> think.
>> On a side note: I couldn't be happier with my Ultimaker or the community
>> around it so far. A few minor tweaks from out of the box and I'm getting
>> some pretty excellent prints. Next up, heated bed!
> --
> You received this message because you are subscribed to the Google Groups
> "Ultimaker" group.
> There are also forums, which are the official gathering place for
> Ultimaker operators:
> http://forum.ultimaker.com/
> If you still want to post to this group, send email to
> ultimaker@googlegroups.com
> To unsubscribe from this group, send email to
> ultimaker+unsubscribe@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/ultimaker?hl=en
Another way is to have a single wire made of stainless steel, slightly
smaller than the nozzle diameter. This wire could be attached so it
hangs down right above the nozzle orifice from the inside. It should
act in the same way as the glass fibres you mention, but potentially
be easier to build. The wire could be simply screwed into the junction
between the nozzle and heater barrel (the junction that occurs inside
the heater block!) I'm tempted to try this, but I don't have a v2 hot
end...
Maybe it doesn't even have to be smaller than the nozzle diameter, as
long as there is a very small boundary between the wire and the nozzle
orifice, which would act to hold surface tension much better than the
nozzle orifice itself. Or instead of one wire it could be like a wire
brush.
On Sat, Oct 27, 2012 at 4:10 PM, Jelle Boomstra <je...@protospace.nl> wrote:
> The melt interface zone already conforms to the inside wall, making it a
> perfect plunger. The problem with oozing is not the initial retraction as we
> know that works well. The problem is what happens after the retraction when
> the PLA flows down the sides of the cylinder back to the nozzle.
> But I do have another solution: fibres! This problem of oozing/dripping
> viscous fluid from a small orifice has already been fixed for fineliners
> etc. They add a bunch of fibres into the tip, making sure the
> adhesion/capilary action keeps it from dripping. Just adding a few glass
> fibres cut of at the nozzle end will help a lot I think. Basically it
> transforms the nozzle in a bunch of smaller nozzles. No idea how these
> fibres should be attached inside the nozzle, that is still to be determined.
> Melting them to a small glass ring might work?
> On Sat, Oct 27, 2012 at 9:44 PM, Daid <daid...@gmail.com> wrote:
>> How about reversing this idea, instead of putting a vacuum on the nozzle,
>> which would be problematic with leakage, how about having a small pump which
>> can put quite a bit of air pressure on the bowdentube. This way you could
>> blow the nozzle empty.
>> My latest dual extrusion with V2 hotends at 210C only had a tiny bit of
>> oozing compared to the earlier experiment. I think if you blow the nozzle
>> empty at a known location you might have solved the issue.
>> (My previous dual extrusion experiments where with V1 hotends)
>> On Saturday, October 27, 2012 5:48:01 AM UTC+2, Mackadoo wrote:
>>> Hey folks, I'm new here but I've gone through a bunch of the backpages in
>>> the forum posts and hopefully am not putting forth anything rehashed.
>>> Reading through the State of Dual Extrusion thread the other day, I
>>> became more aware of the problems with oozing and retraction. As great as
>>> all of the theories for curbing ooze were in that thread, I think maybe
>>> there's a much simpler answer. Essentially, we turn the extrusion head into
>>> a syringe.
>>> My theory is that making the end portion of the bowden tube air-tight by
>>> adding a silicone ring that seals the bowden tube to the filament, when you
>>> retract you create negative pressure because the solid filament would act as
>>> a syringe piston. This would suck the molten plastic back into the tube.
>>> If that seal works properly, considering the small aperture of the nozzle,
>>> surface tension should keep the molten plastic from oozing. This would
>>> require a retraction length smaller than the amount of solid filament from
>>> the seal downwards, but the seal should be as close to the hot end as
>>> possible to minimize the air in the chamber.
>>> The problems with this model are that (1) restricting the filament by
>>> forcing it through the seal would have dire consequences and, (2) I really
>>> don't know enough about fluid dynamics to be sure this will work at all. If
>>> thoughts on this forum are encouraging I can try putting together a
>>> prototype with some parts from work (I'm a plumber). Let me know what you
>>> think.
>>> On a side note: I couldn't be happier with my Ultimaker or the community
>>> around it so far. A few minor tweaks from out of the box and I'm getting
>>> some pretty excellent prints. Next up, heated bed!
>> --
>> You received this message because you are subscribed to the Google Groups
>> "Ultimaker" group.
>> There are also forums, which are the official gathering place for
>> Ultimaker operators:
>> http://forum.ultimaker.com/
>> If you still want to post to this group, send email to
>> ultimaker@googlegroups.com
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> Bezoekadres: Nijverheidsweg 16B, Utrecht
> Postadres: Postbus 10152, 3505 AC Utrecht
> T +31 (0)30 223 08 75 | E je...@protospace.nl | W www.protospace.nl > open inloop: dinsdag middag + donderdag
> --
> You received this message because you are subscribed to the Google Groups
> "Ultimaker" group.
> There are also forums, which are the official gathering place for Ultimaker
> operators:
> http://forum.ultimaker.com/
> If you still want to post to this group, send email to
> ultimaker@googlegroups.com
> To unsubscribe from this group, send email to
> ultimaker+unsubscribe@googlegroups.com
> For more options, visit this group at
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Yes, metal wires might work too. A coating of some sort on the nozzle might
be needed too if the metal surface is too hydrophilic.
A coating would be better as that does not restrict the flow like a
capillary would.
On Sun, Oct 28, 2012 at 4:56 AM, Andrey Shur <as...@hmc.edu> wrote:
> Another way is to have a single wire made of stainless steel, slightly
> smaller than the nozzle diameter. This wire could be attached so it
> hangs down right above the nozzle orifice from the inside. It should
> act in the same way as the glass fibres you mention, but potentially
> be easier to build. The wire could be simply screwed into the junction
> between the nozzle and heater barrel (the junction that occurs inside
> the heater block!) I'm tempted to try this, but I don't have a v2 hot
> end...
> Maybe it doesn't even have to be smaller than the nozzle diameter, as
> long as there is a very small boundary between the wire and the nozzle
> orifice, which would act to hold surface tension much better than the
> nozzle orifice itself. Or instead of one wire it could be like a wire
> brush.
> On Sat, Oct 27, 2012 at 4:10 PM, Jelle Boomstra <je...@protospace.nl>
> wrote:
> > The melt interface zone already conforms to the inside wall, making it a
> > perfect plunger. The problem with oozing is not the initial retraction
> as we
> > know that works well. The problem is what happens after the retraction
> when
> > the PLA flows down the sides of the cylinder back to the nozzle.
> > But I do have another solution: fibres! This problem of oozing/dripping
> > viscous fluid from a small orifice has already been fixed for fineliners
> > etc. They add a bunch of fibres into the tip, making sure the
> > adhesion/capilary action keeps it from dripping. Just adding a few glass
> > fibres cut of at the nozzle end will help a lot I think. Basically it
> > transforms the nozzle in a bunch of smaller nozzles. No idea how these
> > fibres should be attached inside the nozzle, that is still to be
> determined.
> > Melting them to a small glass ring might work?
> > On Sat, Oct 27, 2012 at 9:44 PM, Daid <daid...@gmail.com> wrote:
> >> How about reversing this idea, instead of putting a vacuum on the
> nozzle,
> >> which would be problematic with leakage, how about having a small pump
> which
> >> can put quite a bit of air pressure on the bowdentube. This way you
> could
> >> blow the nozzle empty.
> >> My latest dual extrusion with V2 hotends at 210C only had a tiny bit of
> >> oozing compared to the earlier experiment. I think if you blow the
> nozzle
> >> empty at a known location you might have solved the issue.
> >> (My previous dual extrusion experiments where with V1 hotends)
> >> On Saturday, October 27, 2012 5:48:01 AM UTC+2, Mackadoo wrote:
> >>> Hey folks, I'm new here but I've gone through a bunch of the backpages
> in
> >>> the forum posts and hopefully am not putting forth anything rehashed.
> >>> Reading through the State of Dual Extrusion thread the other day, I
> >>> became more aware of the problems with oozing and retraction. As
> great as
> >>> all of the theories for curbing ooze were in that thread, I think maybe
> >>> there's a much simpler answer. Essentially, we turn the extrusion
> head into
> >>> a syringe.
> >>> My theory is that making the end portion of the bowden tube air-tight
> by
> >>> adding a silicone ring that seals the bowden tube to the filament,
> when you
> >>> retract you create negative pressure because the solid filament would
> act as
> >>> a syringe piston. This would suck the molten plastic back into the
> tube.
> >>> If that seal works properly, considering the small aperture of the
> nozzle,
> >>> surface tension should keep the molten plastic from oozing. This would
> >>> require a retraction length smaller than the amount of solid filament
> from
> >>> the seal downwards, but the seal should be as close to the hot end as
> >>> possible to minimize the air in the chamber.
> >>> The problems with this model are that (1) restricting the filament by
> >>> forcing it through the seal would have dire consequences and, (2) I
> really
> >>> don't know enough about fluid dynamics to be sure this will work at
> all. If
> >>> thoughts on this forum are encouraging I can try putting together a
> >>> prototype with some parts from work (I'm a plumber). Let me know what
> you
> >>> think.
> >>> On a side note: I couldn't be happier with my Ultimaker or the
> community
> >>> around it so far. A few minor tweaks from out of the box and I'm
> getting
> >>> some pretty excellent prints. Next up, heated bed!
> >> --
> >> You received this message because you are subscribed to the Google
> Groups
> >> "Ultimaker" group.
> >> There are also forums, which are the official gathering place for
> >> Ultimaker operators:
> >> http://forum.ultimaker.com/
> >> If you still want to post to this group, send email to
> >> ultimaker@googlegroups.com
> >> To unsubscribe from this group, send email to
> >> ultimaker+unsubscribe@googlegroups.com
> >> For more options, visit this group at
> >> http://groups.google.com/group/ultimaker?hl=en
> > Bezoekadres: Nijverheidsweg 16B, Utrecht
> > Postadres: Postbus 10152, 3505 AC Utrecht
> > T +31 (0)30 223 08 75 | E je...@protospace.nl | W www.protospace.nl > > open inloop: dinsdag middag + donderdag
> > --
> > You received this message because you are subscribed to the Google Groups
> > "Ultimaker" group.
> > There are also forums, which are the official gathering place for
> Ultimaker
> > operators:
> > http://forum.ultimaker.com/
> > If you still want to post to this group, send email to
> > ultimaker@googlegroups.com
> > To unsubscribe from this group, send email to
> > ultimaker+unsubscribe@googlegroups.com
> > For more options, visit this group at
> > http://groups.google.com/group/ultimaker?hl=en
> --
> You received this message because you are subscribed to the Google Groups
> "Ultimaker" group.
> There are also forums, which are the official gathering place for
> Ultimaker operators:
> http://forum.ultimaker.com/
> If you still want to post to this group, send email to
> ultimaker@googlegroups.com
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On Saturday 27 October 2012 05:48:01 Mackadoo wrote:
> My theory is that making the end portion of the bowden tube air-tight by
> adding a silicone ring that seals the bowden tube to the filament, when you
> retract you create negative pressure because the solid filament would act
> as a syringe piston.
Apart from the mentioned "blow it empty" and the "use fibres", I got an idea that might be impractical as well, seeing there are some bowden-related issues mentioned on the list: using a double bowden, the inner being air tight to the outer and preferably not to much airflow around the filament as well. I thoght so, because the filament does not have enough volume to displace a lot of air, creating less of a vacuum. By pulling back the bowden, inside another bowden, the (extra) motor can be static as well.
It is more complex than other mentioned ideas, but might bring about some inspiration :-)
I ran the various issues we have with stringn to my ME dad, and he suggested a small peltier chip right on the nozzle. Send some electricty to it a few ms before a travel operation, just enough to plug/lower the viscosity, then turn it off as it approaches the destination.
Has anyone tried anything like this before?
Some nice specs on the commercially available modules can be found here. It doesn't look like they test at the temps we are talking, but may be worth some R&D dollars to check it out?
I've done some air purge tests tonight using a rough o-ring system to seal around the filament after the extruder, by retracting 20mm & then purging the nozzle it does seem to eliminate oozing, However purging takes around 30 seconds(roughly around 50 PSI) and a wiper station would be needed. It's a very rough test but the oring around the filament is working well, but suspect it will wear fast. I will try get some proper fittings and if it looks promising may hook up a solenoid to automate the process from the gcode.
