Extruder woes, new hot-end supplier, and re-worked extruder build
Graham Klyne
next-generation Mendel, my hot-end tore itself apart - I think the pressure of
hot plastic in the extruder was too much for the PTFE barrel, which just gave
way. Possibly aided by previous over-tightening of the hot-end onto the PTFE
barrel. Pictures are in the Pif3D Google Code code repository
(http://code.google.com/p/pif3d/source/browse/#hg%2FImages%2F20110625-extruder-woes).
A web search revealed a new supplier of specialist parts, Thingfarm (link aded
to suppliers page in wiki), who appears to be a one-man-band based in Bristol.
As mendel-parts still seem to be in something of a state of disarray, I took a
punt and ordered what he call a "J-head" extruder hot end kit (apparently, an
experimental design) for for about �33. The part arrived very quickly - just a
couple of days, and seems to be well conceived and constructed. The brass
barrel and heater block are machined from a single solid piece of brass, which
looks to me like a fairly complex peiece of machinery. The PTFE barrel is, I
think, made from glass-reinforced PTFE, and has a thick-walled PTFE sleeve for
the filament feed. More pictures in the Google Code project
(http://code.google.com/p/pif3d/source/browse/#hg%2FImages%2F20110625-extruder-woes).
I have today just about finished building a new extruder assembly (printing
replacement plastic parts for this was one of the first things I did when my
Mendel was up and running, as I suspected it might prove a weak point). As I
write, I'm still waiting for some thermal compound around the thermistor to set,
but it does all appear to work. Second time around, I think I've planned the
assembly a bit more cleanly, including:
- using a longer bolt for the filament drive, with the hobbed groove in the
smooth shoulder area (easier to make)
- used washers to space the large gear further away from the extruder body,
leaving more space for the stepper motor retaining screws, and allowing the
small gear to be mounted teeth-out, making it easier to remove the main drive
bolt for servicing.
- better arrangement of the thermistor, with the wires not needing to be taped
to the hot end with Kapton tape (I'm hoping the thermal compound will hold it in
place). If necessary, I might add some epoxy later.
- leading the heater/thermistor wires up through the extruder carriage will, I
hope, make them less prone to snagging and keep them away from other moving parts.
More pictures in the wiki
(http://code.google.com/p/pif3d/source/browse/#hg%2FImages%2F20110626-new-extruder).
#g
--
David F. Flanders
Thanks graham, I yhink ill buy some of those new extruder heads as well. Pics are great ad well. /dff
Graham Klyne
to mount in a Wade extruder in a standard Mendel X-axis carriage. I've emailed
Thingfarm to ask if they can supply longer barrels.
BTW, I just ordered 1m of PTFE tube, 3mm ID, for extruder filament-path sleeving
- I'm pretty convinced that's a good design to use, and may make it easier to
self-fabricate the heat isolating barriers.
#g
--
David F. Flanders wrote:
> Thanks graham, I yhink ill buy some of those new extruder heads as well.
> Pics are great ad well. /dff
>
> On 26 Jun 2011 15:24, "Graham Klyne" <G...@ninebynine.org
David F. Flanders
Good to know!
Graham Klyne
barrel, but may take a little while to make.
I've noticed the Wade extruder design fouls the Mendel A-frame,
limiting the print volume (not a major problem so far, but extra
capacity would be good...) I'm thinking that as soon as I can get my
printer working again, I want to print some alternative extruder body
designs (e.g. Adrian's http://reprap.org/wiki/Adrian's_Geared_Extruder),
so shorter hot-end designs should then be OK.
#g
--
> ).
>
>
>
>
> >> > A web search revealed a new supplier of specialist parts, Thingfarm
> >> (link aded
> >> > to suppliers page in wiki), who appears to be a one-man-band based in
> >> Bristol.
> >> > As mendel-parts still seem to be in something of a state of disarray,
> >> I took a
> >> > punt and ordered what he call a "J-head" extruder hot end kit
> >> (apparently, an
> >> > experimental design) for for about £33. The part arrived very quickly
> >> - just a
> >> > couple of days, and seems to be well conceived and constructed. The
> >> brass
> >> > barrel and heater block are machined from a single solid piece of
> >> brass, which
> >> > looks to me like a fairly complex peiece of machinery. The PTFE
> >> barrel is, I
> >> > think, made from glass-reinforced PTFE, and has a thick-walled PTFE
> >> sleeve for
> >> > the filament feed. More pictures in the Google Code project
>
> >> (
>
> ).
> ).
>
>
>
>
>
> >> > #g
> >> > --
David F. Flanders
We need a lathe...
Graham Klyne
> We need a lathe...
>
I've considered this, but actually I think it probably wouldn't be good use of
resources. It's not just the lathe (e.g. £500-1000), but the skills to use it
appropriately. The extruder hot-end is the only part that has caused problems
in this way.
Personally, I'm more interested in alternative designs that avoid the need
altogether. E.g. I noticed someone was experimenting with gas burner nozzles
for extruders. I think with a redesign of RP parts, it might be able to build a
hot end that can be made using just stock PEEK and PTFE tube using just a drill
and standard hand tools - if that could be mated with an off-the-shelf nozzle
part, we could have an easy supply of replacement hot-ends.
Now, if someone came up with a good open source build-it-yourself lathe design,
that would be a different matter...
On this topic, I heard the phrase "Afgan Lathe" applied to this technique:
http://staff.bath.ac.uk/ensab/replicator/Downloads/Afghan_lathe/Afghan_Lathe.html
(I didn't realize previously that name is used in the link. He goes on to say:
"Why an 'Afghan Lathe'? Because I first saw this kind of technique being used by
Afghan gunsmiths to produce counterfeit firearms with remarkable precision.")
Also saw:
http://reprap.org/wiki/Extruder_Nozzle_Variations#No_Lathe_-_Variation
#g
--
> On 4 Jul 2011 15:37, "Graham Klyne" <gk-g...@ninebynine.org
> <mailto:gk-g...@ninebynine.org>> wrote:
> > I had a response from Thingfarm - they say they will supply a longer
> > barrel, but may take a little while to make.
> >
> > I've noticed the Wade extruder design fouls the Mendel A-frame,
> > limiting the print volume (not a major problem so far, but extra
> > capacity would be good...) I'm thinking that as soon as I can get my
> > printer working again, I want to print some alternative extruder body
> > designs (e.g. Adrian's
> http://reprap.org/wiki/Adrian's_Geared_Extruder
> <http://reprap.org/wiki/Adrian's_Geared_Extruder>),
> > so shorter hot-end designs should then be OK.
> >
> > #g
> > --
> >
> > On Jul 1, 5:21 pm, "David F. Flanders" <d.fland...@jisc.ac.uk
> <mailto:d.fland...@jisc.ac.uk>> wrote:
> >> Good to know!
> >> On 30 Jun 2011 14:48, "Graham Klyne" <G...@ninebynine.org
> <mailto:G...@ninebynine.org>> wrote:
> >>
> >>
> >>
> >> > BEWARE: I discovered yesterday the Thingfarm hot-emnd assemblies
> are too
> >> short
> >> > to mount in a Wade extruder in a standard Mendel X-axis carriage. I've
> >> emailed
> >> > Thingfarm to ask if they can supply longer barrels.
> >>
> >> > BTW, I just ordered 1m of PTFE tube, 3mm ID, for extruder
> filament-path
> >> sleeving
> >> > - I'm pretty convinced that's a good design to use, and may make
> it easier
> >> to
> >> > self-fabricate the heat isolating barriers.
> >>
> >> > #g
> >> > --
> >>
> >> > David F. Flanders wrote:
> >> >> Thanks graham, I yhink ill buy some of those new extruder heads
> as well.
> >> >> Pics are great ad well. /dff
> >>
> >> >> On 26 Jun 2011 15:24, "Graham Klyne" <G...@ninebynine.org
> <mailto:G...@ninebynine.org>
Graham Klyne
shop: http://thingfarm.org/product.php?id_product=47
#g
--
Gray, Steven
We have just ordered this long barrelled extruder for our Mendel. I think we have dropped the ball and I need to get back up to speed and get printing.
Any suggestions with the build Graham?
Steve
------------------------------------------------------------
Steven J. Gray
Research Associate
Centre for Advanced Spacial Analysis
T: +44(0)20 3108 3886
E: steve...@ucl.ac.uk
Current Project:
National e-Infrastructure for Social Simulation (NeISS)
Centre for Advanced Spacial Analysis
(CASA)
University College London (UCL)
Gower Street
London, WC1E 6BT
------------------------------------------------------------
CASA's MRes course starts in 2011:
http://casa.ucl.ac.uk/courses/CASA-MRes-ASAV.pdf
Graham Klyne
Assuming a Wade extruder:
1. The quality of the hobbed bolt can affect print quality: my first attempt
slipped a bit at some positions of its rotation, leading to intermittent
reduction of extrusion flow rates, hence poorer quality printing. At least, I
think that was what was happening. It's when I swapped in a more deeply knurled
hobbed bolt that my extruder broke - more pressure, I guess.
2. I use high-temperature heat-shrink to protect the wiring, especially for the
thermistor. I also try to attach the wiring run to the carriage, to protect
where it connects to the heating block.
3. I haven't yet finalized how I want to do it, but I was considering drilling
out the filament run in the extruder block so the filament feeds directly into
the PTFE sleeving ... but check the length of the sleeving if you consider this.
When printing, you'll want to be able to insert new filament from the top
preferably without disassembling the pinch wheel assembly.
4. You'll need to reload the Gen6 firmware with calibration for your particular
extruder setup, assuming you use the most recent Skeinforge to generate GCode.
I've put some notes in the wiki. Before finalizing the wiring, check the
extruder drive direction: I haven't yet figured exactly how to change the
direction in the firmware (the other axes are easy to change in firmware).
...
When I get my printer running again (soon now, I hope) I intend to look at
alternative extruder designs as a priority, preferable choosing one for which
the hot end is actually retained by more than just the thermal isolation barrel
(e.g. I think Adrian's design does this).
#g
--
Graham Klyne
How are you getting on with this?
I'm writing mainly to warn you of a problem I've experienced with both
this *and* the Mendel-parts hot-end.
After several hours of printing, plastic starts to leak out of the
barrel and onto the outside of the hot-end, especially when higher
temperatures are used (when the plastic becomes very liquid). You see
iot oozing out where the brass hot-end crews into the PEEK thermal
isolator. IO was hoping the PTFE sleeve would stop this happening,
but apparently not.
I don't have a sure-fire fix yet, but I'm going to try using plumbers
PTFE tape (you should get a free roll with the J-head hot-end) both to
improve the seal between the PTFE sleeve and the brass hot-end, and
also between the threads on the brass hot-end where it screws into the
PEEK thermal isolator barrel. You might want to consider doing
something like this before you get runny goo all over the outside of
your hot end and on your print jobs :)
(If you do suffer runny goo, don't panic, it's fairly easy to remove
by bringing the hot-end up to about 60-80C. To unscrew the brass from
the barrel, I brought the temperature up to about 140C.)
#g
--
On Jul 14, 10:09 am, "Gray, Steven" <steven.g...@ucl.ac.uk> wrote:
> Hey,
>
> We have just ordered this long barrelled extruder for our Mendel. I think we have dropped the ball and I need to get back up to speed and get printing.
> Any suggestions with the build Graham?
>
> Steve
>
> On 14 Jul 2011, at 08:27, Graham Klyne wrote:
>
>
>
>
>
> > UPDATE: ThingFarm have now added a longer-barreled hot end assembly to their web shop: http://thingfarm.org/product.php?id_product=47
>
> > #g
> > --
>
> > Graham Klyne wrote:
> >> BEWARE: I discovered yesterday the Thingfarm hot-emnd assemblies are too short to mount in a Wade extruder in a standard Mendel X-axis carriage. I've emailed Thingfarm to ask if they can supply longer barrels.
> >> BTW, I just ordered 1m of PTFE tube, 3mm ID, for extruder filament-path sleeving - I'm pretty convinced that's a good design to use, and may make it easier to self-fabricate the heat isolating barriers.
> >> #g
> >> --
> >> David F. Flanders wrote:
> >>> Thanks graham, I yhink ill buy some of those new extruder heads as well. Pics are great ad well. /dff
>
> >>> On 26 Jun 2011 15:24, "Graham Klyne" <G...@ninebynine.org <mailto:G...@ninebynine.org>> wrote:
> >>> > Last week, as I was about 2/3 way through printing a set of parts for a
> >>> > next-generation Mendel, my hot-end tore itself apart - I think the pressure of
> >>> > hot plastic in the extruder was too much for the PTFE barrel, which just gave
> >>> > way. Possibly aided by previous over-tightening of the hot-end onto the PTFE
> >>> > barrel. Pictures are in the Pif3D Google Code code repository
> >>> > A web search revealed a new supplier of specialist parts, Thingfarm (link aded
> >>> > to suppliers page in wiki), who appears to be a one-man-band based in Bristol.
> >>> > As mendel-parts still seem to be in something of a state of disarray, I took a
> >>> > punt and ordered what he call a "J-head" extruder hot end kit (apparently, an
> >>> > experimental design) for for about £33. The part arrived very quickly - just a
> >>> > couple of days, and seems to be well conceived and constructed. The brass
> >>> > barrel and heater block are machined from a single solid piece of brass, which
> >>> > looks to me like a fairly complex peiece of machinery. The PTFE barrel is, I
> >>> > think, made from glass-reinforced PTFE, and has a thick-walled PTFE sleeve for
> >>> > the filament feed. More pictures in the Google Code project
> >>> > I have today just about finished building a new extruder assembly (printing
> >>> > replacement plastic parts for this was one of the first things I did when my
> >>> > Mendel was up and running, as I suspected it might prove a weak point). As I
> >>> > write, I'm still waiting for some thermal compound around the thermistor to set,
> >>> > but it does all appear to work. Second time around, I think I've planned the
> >>> > assembly a bit more cleanly, including:
> >>> > - using a longer bolt for the filament drive, with the hobbed groove in the
> >>> > smooth shoulder area (easier to make)
> >>> > - used washers to space the large gear further away from the extruder body,
> >>> > leaving more space for the stepper motor retaining screws, and allowing the
> >>> > small gear to be mounted teeth-out, making it easier to remove the main drive
> >>> > bolt for servicing.
> >>> > - better arrangement of the thermistor, with the wires not needing to be taped
> >>> > to the hot end with Kapton tape (I'm hoping the thermal compound will hold it in
> >>> > place). If necessary, I might add some epoxy later.
> >>> > - leading the heater/thermistor wires up through the extruder carriage will, I
> >>> > hope, make them less prone to snagging and keep them away from other moving parts.
> >>> > More pictures in the wiki
> >>> > #g
> >>> > --
>
> ------------------------------------------------------------
> Steven J. Gray
> Research Associate
> Centre for Advanced Spacial Analysis
> T: +44(0)20 3108 3886
Graham Klyne
the filament jams while the extruder is driving (e.g. driving filament
when the end is too cool to allow extrusion). The drive grooves in
hobbed bolt can become partially clogged with plastic, resulting in an
intermittent slowdown in the extrudate supply, in turn leading to thin
extruded filamanent that doesn't stick down properly.
The fix that seems to work for me so far is to remove the hobbed bolt
and lightly repeat the hobbing process to clean the clogging plastic
from the drive grooves.
#g
--
David F. Flanders
Cheers graham, the hot end really is the bottleneck in the build :/