Extrusion not working right

[Shawn]

I'm using a Replicator with Dual extruders. Last night the left
extruder stopped working right. Midway through a print it stopped
feeding plastic. I unloaded the plastic and it was pretty beat up - the
wheel was obviously turning but just stripped away a notch in the plastic.

So, I cut away the damaged part, and reloaded. It loaded fine, but
immediately when it started extruding it would curl up towards the back
of the Replicator like one side wasn't flowing right. After a second or
two of this the motor would start clicking as it missed feeding the
filament properly.

I then unloaded and loaded the filament a bunch of times, this happens
every time.

I disassembled the extruder and cleaned up the plastic shavings, checked
my plunger (can see a line, but not notched yet) and generally cleaned
everything up. Couldn't see anything obviously wrong. I reassembled
the extruder and loaded filament - and got the exact same problem.

I soaked a paper towel in acetone and used that to try to clean up the
nozzles. Some of the surface gunk game off, but it doesn't look like it
affected whatever is causing this issue. Still curling up when extruding.

So, what next? Has anyone else seen this? Is it a simple fix? Do I
need to pull off the nozzle and soak it in acetone? Do I need a new
nozzle? (only had the replicator a month and don't have THAT much time
printing...) Or is this an oddball thing I should talk to MBI support on?

Thanks for any tips.

[Rob Giseburt]

Watch the temperature on the display. It looks to me like it's loosing
it's temperature.

Tip: Connect to the Replicatir from RepG, an open the control panel.
Then start the print from the SD card using the keypad, and you'll get
a graph of the temperatures over time.

-Rob

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[Joseph Chiu]

When that happens to me on the ToM Mk7, I sometimes find it helpful to
heat up the extruder and let it extude for about 30 seconds
continuously. In a few cases, the stripping also gathers plastic dust
in between the teeth, lessening the extruder's ability to chomp down
on the filament -- that is solved by taking the extruder apart and
cleaning the teeth.

[Shawn]

I've tried feeding plastic for a minute or so, with me applying pressure
to the filament to keep it feeding. It just curls up to the back and
causes the motor to mis-feed. It *seems* like a partial blockage. I've
also cleaned out the plastic dust already with no improvements.

Will try RobG's suggestion to monitor the temperature.

[Shawn]

Hooked up the laptop and pulled up the machine monitor. Then used the
LCD panel to load the filament. Watched the temperature raise to 224,
then ease off to 218 then stabilize around 220 (give or take a degree or
two). Then loaded the filament. Immediately saw the curling when the
extrusion started. Force fed the plastic when it started to mis-feed
for about a minute. The mis-feed became more and more pronounced and
required more force to push the plastic through. Temperature stayed
stabled at 220(ish) for all of this.

Unloaded the filament, and again the temperature stayed stable.

Is this just a blockage of some sort? How do I go about determining
that/cleaning it out?

Thanks for the suggestion Rob.

Shawn

[Joseph Chiu]

Perhaps your temperature reading is low? If you feed, then pause, and
then feed again, does it get better before it starts to slow again?
It might be that it's not heating up fast enough either because of low
thermistor reading, or possibly a bad heater (or bad heater mounting)
not replacing heat sufficiently fast enough?

[Rob Giseburt]

I just had a similar problem. It turned out that the set screw on the
filament feeder had come loose. It was hard to tell because it fits
tight anyway.

There's a hex key for it in the bag that came with the replicator, btw.

-Rob

[Greg Thorstad]

If you wanted you could also crank up the temp 10 degrees or so and see what
happens if you are suspecting the temperature readings are wrong.

I think you probably have a blockage, maybe a chunk of fuzz got in the
extruder or something. I would be tempted to pop off the nozzle and have a
look/clean it out.



Greg Thorstad, B. Comm.
Thorstad Computer/Thor3d.ca/Canadian Makerbot Distributor
Box 268
Outlook, SK
S0L 2N0
306 867-9596

[66tbird]

I've just had both problems, the nozzle partial clog and the set screw slippage. One issue on each extruder. The partial clog was an easy fix by just lifting a small thimble size dish of acetone up into the tip and letting it soak. (filament removed and extruder removed for cleaning)  A small syringe for final irrigation and the increased flow of acetone through the nozzle was noticeable.

  The set screw issue on the other extruder was easy to spot because I could pull and push filament through.to the tip without the load/unload script. Not hard to figure out there. Close inspect showed the flat on the stepper shaft had not been machined far enough along the shaft. Some careful Dremal action fixed that. IMHO only use blue loc-tite on the set screws to keep then on the flat.  Minimal twist on those because mine didn't feel to good on the wrench.

[Shawn]

Just did that - the temp thing. Used the control panel in RepG to set
230. When it was at temp, I fed the filament through, with the same
results. So I think I can cross off a faulty temperature reading.

I'm going to disassemble/clean the extruder again, and check the set
screw next. If that still doesn't work, I'll try the acetone soak.
(just need to find a suitable container... hmm I *might* have a thimble
kicking around..).

Then if that all fails, I'll take the extruder off. I'm hoping to avoid
that though as I've not done it yet and suspect I may have difficulty
lining it up right again. But I have to do it sooner or later anyways...

Thanks for the tips everyone.

Shawn

[Shawn]

So I took apart the extruder again. The set screw does seem to have
slipped some and was about 20 degrees off from the flat part of the
shaft. I removed the set screw and lined things up properly and noticed
that when the gear is in correct position, the flattened part of the
shaft does not extend far enough back. So I'll break out my dremel
later (if I can find it) and flatten that out. For now I tightened down
the set screw and reassembled.

This did NOT resolve the problem. Removing the nozzle is the next step
then.

So now I have to do a shopping trip. Turns out my wrenches are much too
large for the nozzle, and I need to get some blue locktight. Oh and I
just might get a good corded dremel while I'm at it (my other is a
cordless that is 5+ years old and I'm sure the battery is near it's end
of life..).

Progress. Still not fixed, but now have a few things crossed off...
Thanks for the tips.

Shawn

[AKron]

My corded Dremel is almost 20 years old, and still Dreming!
Good luck, and let us know what we need to do when this happens to us
Replicator owners!

[Dan Newman]

On 16 May 2012 , at 2:23 PM, Shawn wrote:

> So I took apart the extruder again. The set screw does seem to have slipped some and was about 20 degrees off from the flat part of the shaft. I removed the set screw and lined things up properly and noticed that when the gear is in correct position, the flattened part of the shaft does not extend far enough back. So I'll break out my dremel later (if I can find it) and flatten that out. For now I tightened down the set screw and reassembled.
>
> This did NOT resolve the problem. Removing the nozzle is the next step then.
>
> So now I have to do a shopping trip. Turns out my wrenches are much too large for the nozzle, and I need to get some blue locktight.

You'll want Blue 246 loctite which is good to ~234C (450F). The typical loctite is
only rated to 149C (300F). And, when overheated, it can become a bit of a pain to
undo.

Dan

[Rob Giseburt]

One important note, may or may not apply:

If there is any PLA in the nozzle, you do not want to use acetone to clean it. The PLA will harden and become an even worse clog. 

  -Rob

[Shawn]

No PLA has gone through my extruders - yet. I do have a roll I'm
waiting to play with, but have some other projects first.

So I pulled the nozzle off tonight. This is after unloading the
filament earlier. There was about 2mm of plastic stuck in the end, with
some lighter spots on it (possibly from unloading the filament and
stretching it to breaking?). The nozzle is soaking in Acetone right now
- hopefully after an hour or so there it will be all fixed up. I'm
hoping it is just a dust thing, and will be building a dust solution
eventually (seen some on thingiverse).

I *am* taking pics along the way and will blog about the experience when
fixed.

BTW, Home Depot and Lowes both suck at finding the tools for this sort
of work... Good thing I have good dealings with the local hobby shop,
will visit there tomorrow.

On 12-05-16 05:09 PM, Rob Giseburt wrote:
> One important note, may or may not apply:
>

> If there is any PLA in the nozzle, you do *not* want to use acetone to

[Shawn]

Whoo Hoo!! I'm printing again.

The nozzle soaked in acetone overnight. I used some tin wire I had
laying around to help clear out the chunkies (gently of course!). Then
a small paintbrush to finish up and make sure the hole was clear.
When it seemed that it was 100% clear, and I could actually see through
the hole (held up to light) without seeing chunks, then I remounted the
nozzle.

I loaded my filament and it worked perfectly with a long straight noodle
coming out of the nozzle. I did a quick print of a tramming square to
help me determine if the nozzle was loaded to the right height. When I
ripped up the kapton I knew I wasn't quite there. Some more turns of
the nozzle and the test print seemed to come out fine.

My second print is running now. The first layer is way too close, so
still need some adjustments. But, it's far enough away that it is not
scoring the kapton (just mostly blocking the noodle on layer one). I'll
do a few more tests and tuning after this print, and re-tram/level if
needed.

The interesting thing is that I never found what was actually causing
the issue. I'm going to write it off to dust on the filament getting
into the nozzle though. The acetone bath did have a number of specs in
there - I assumed it was all the dark scorching marks on the outside,
but now I don't know.

Still, it is all fixed and I can print with both nozzles again! After
this, I won't be so hesitant to take the nozzle off - it's not as bad an
experience as I thought it'd be.

Thanks everyone for the support!

Shawn