Why is my nozzle clogging? Is yours clogged? During dualstrusion?

[Elbot]

I printed out the heart gears keychain and it works. I printed out the key and pins with one extruder and in a 2nd printing did it with the other extruder. However, when I tried to print a large multihour dualstrusion print, the printer jams and air prints. It prints nothing but the print head is moving around. I've been going back and forth with MBI for 2 weeks and they've tried to be helpful (no complaints) BUT problem is not solved. I've printed out the bottle opener personalized with someone's name and it prints fine as a dualstrusion print but that is a small print. I tried to do a large multihour print as a dualstrusion print and it fails.

After it fails, I do the load filamant script and the right nozzle works fine, but the left nozzle is clogged. It will not load itself. So, I give the filament a gentle nudge and it loads fine. The gears are turning, though, so the drive gears aren't broken. The nozzle is heating properly, too. I tried an experiment where I only moved filament with the drive motor without the nozzles and the drive motors did fine. I also fed filament manually with gentle pressure and filament came out without pigtailing as straight filament.

Here's what I suspect happened and there are 2 scenarios so please tell me if either of these are true or if there is a 3rd scenario I am missing (you've got a different theory);

1. short circuit damaged electronics or firmware programmer's error after awhile shuts down nozzle heating mistakenly as part of the shutdown for inactivity for fire safety script. Once nozzle cools down, it clogs.

2. the print is a box of sorts and is layered with left extruder, then right extrusion on top of that, then air (interior of box), then left, and then right. It got through the first layer then on the 2nd layer, it clogs. I suspect that it is trying to print the 3rd layer's support in the same space as the 2nd layer's material, resulting in a jam of the extruder trying to print the 2nd layer (left extruder). As cold plastic from the support material of the 3rd layer enters the nozzle trying to print the 2nd layer, it jams the nozzle trying to print the 2nd layer. My theory here is that I should only use dualstrusion for the first layer, but any layers above that, I should use only one extruder or else this will happen. In the photo, it is the red material that is the support for the 3rd layer. Notice how it is imbedded into the model's material for the 2nd layer.

Please let me know what your experiences are with multilayer dual extrusion models. Thanks.

[Jetty]

There can be a few causes of these types of issues.

1. Heat traveling up to the stepper / pinch wheel

2. Back pressure from the nozzle causing stripping

3. Stripping.


1_ Generally happens when the extruder has been on for a while and not
extruding.
It's also made worse if the fan on the extruder is off (check it's
on). Heat travels into
the stepper / pinch wheel, which also generate their own heat until
the point where the plastic
softens around the pinch wheel area and it doesn't grip the wheel
enough.

This could happen for example if you printed with the left for a
while, and then finished the print
with the right. One solution would be create a sacrificial piece for
the right extruder by the side
of your main piece, so that it's always printing something.

2_ If the nozzle tries to extrude close to the platform and the
filament can't get out because
it's too close, the filament will strip and you have no grip.

3. If you've stripped your filament in the past, then you'll have
filament dust in there which acts
as gets stuck in the pinch wheel and reduces grip. Clean your
extruder as per MBI's instruction.
This is the first thing I check.

Finally, if you're going fast (>60mm/s) and using acceleration, then
poor acceleration settings
can cause filament stripping.

On Oct 8, 10:01 am, Elbot <tomasre...@gmail.com> wrote:
> <https://lh5.googleusercontent.com/-kqV_ZIppAus/UHL40_A3FFI/AAAAAAAAAC...>

[Elbot]

Jetty,

what do you think about drilling a hole into the heat sink on the extruder? Won't that cool down the filament and prevent it from softening from heat and stripping?

BTW, If you're the jetty firmware guy, we all owe you a debt of gratitude we can never repay. if you ever need anything scanned or a replacement part printed to fix your bot, just say the word. thanks.

[Have Blue]

Don't forget #4: Moisture.  Stratasys learned this long long ago, and I'm amazed that so many RepRap/Makerbot users run their filament in the open air where it can suck up moisture.

[Jetty]

> what do you think about drilling a hole into the heat sink on the extruder?
> Won't that cool down the filament and prevent it from softening from heat
> and stripping?

That's an interesting idea, and I don't know if it would help. Some
method of getting air to circulate
on the inside of the extrude assembly, i.e. stepper cooling, pinch
wheel cooling might help. Maybe a bigger heat
sink or fan.

> BTW, If you're the jetty firmware guy, we all owe you a debt of gratitude
> we can never repay. if you ever need anything scanned or a replacement part
> printed to fix your bot, just say the word. thanks.

Thanks. It's not just me though, Dan's equal on it, and of course
it's based on the backs
of others too.

[Elbot]

Sorry, moisture? How can that clog stuff up? Please explain. I was a very poor physics student.

[simongeist]

 

 

Hi,

I just yesterday had the same problem with my Replicator1 dual extrusion: Nozzle Clog, working for smaller prints, failing on larger prints at the left extruder.

Here is what I figured out: I disassembled the extruders to clean them, also took out the nozzle where ABS was stuck inside and cleaned with a heat gun and acetone. What made me wonder was that it worked afterwards – but only if I pushed the filament gently by hand inside. It did not properly worked without helping hands.

So I disassembled everything again and found out that the Ring with the grip of the left extruder that sits on the shaft of the stepper motor was lose. The nozzle was ok, the stepper motor was ok, but there was  just no filament pushed into the nozzle.

I think now that this is a design problem of the extruder (see my nice drawing): the ring has a hex-screw to connect it to the shaft of the stepper Motor (BTW: I think this at all is not a good solution). The shaft of the stepper motor has a bevel that is not big enough so that the screw’s bottom cannot press on the bevel but on the blank shaft, the ring can come loose from the shaft, the filament is not pushed into the nozzle and the nozzle gets clogged. Puhh.

I tightend the screw and It worked again, but its only a matter of time when it will come loose again. 

Why is it only happening on the left extruder? The right one seems to be build differently: The ring sits properly on the bevel of the shaft. I can take some photos if needed. Has anyone experienced the same or more information?

Cheers,

Moritz

[Doogiekr]

Yes, I know many have had the same issue, and some people have even resorted to taking a dremel tool to flatten the shaft all the way to the base so the grub screw has a correct surface to sit on ( I do not suggest you do this unless you really know what your doing )

[MacGyver]

I've run at least 15 lbs of plastic (probably more) through my machine and haven't had any sort of real clog.  I believe it is because I have my filament running through a sponge right before it goes into the extruder.  You wouldn't believe the dust that my sponge has stopped it gathers a LOT of dust.  I change out the sponge every couple of months.  

Below is a pic of my bot from several months ago.  You'll notice that the thing I'm using to hold my sponge is a spool holder that I never ended up using or its original purpose.  If you zoom in you can see quite a bit of dust.  The sponge is dark gray in color so dust is quite easy to see.

http://thingiverse-production.s3.amazonaws.com/renders/df/38/8a/1a/3a/100_6007_display_medium.jpg

[Have Blue]

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6268999

[sylefeb]

Hi - I had the exact same issue on my left extruder. Right extruder seems fine. I also had the issue on the Y axis stepper. In all cases the gear went loose (but only progressively). In the case of the extruder the main symptom was that I could freely push the filament by hand. In the case of the Y axis it actually seemed to work fine, only in rare cases the motor would step and nothing moved! After fixing all that ... I got much better prints! In both cases I simply made sure the hex screw was lying on the flat part of the motor axis. For the extruder I had to move the gear a bit forward since the bevel does not start close enough to the motor (as on your drawing). This seems fine however.

[gth]

Definitely a similar problem with my left extruder.  I haven't got to the bottom of why just yet (the right extruder is very busy in the meantime  :)

My symptoms are -

* Problem first exhibits as no material coming from nozzle after previously working okay

* Attempts to feed during printing just sound like 'clicking' from the stepper drive - cannot feed at all

* Cannot unload filament "normally" ...I have to disassemble the head (i.e. silver heatsink/fan/stepper drive) and get some serious effort with pliers + 230' pre-heat to remove the remaining filament from the nozzle/heater unit.

* I can then load filament again, after which the issue returns after a few hours of printing.

Originally thought it was due to non-MBI filament being used, but that filament is working fine in right extruder.  Putting MBI filament in left extruder now exhibits the same problem as when it had 3rd-party-supplied filament in it.  

Will try the acetone + heat clean of the nozzle next...

- G.

[Shawn]

The clicking noise is likely one of two things. It is either the
retraction happening, or it is your filament trying to feed but being
blocked in some manner and then stripping/skipping.

The blocks are easy. But first you need to determine what the block is.
When it starts clicking, reach behind the printer and apply gentle
pressure on the filament to encourage it to feed. If this overcomes the
clicking and starts spitting out plastic, then I'd bet your platform is
too close to the nozzle. Back it off a little (1/8th turn of the screws
or less should be fine). If that doesn't do it and the clicking
continues regardless how much pressure you have on the filament, then
chances are your nozzle is clogged.

Cleaning a clogged nozzle depends on the plastic you used. Using flame
(from a blow torch) to burn out the plastic in the nozzle will work with
ABS and PLA. Just don't do it too much - it is possible to
inadvertently melt your nozzle. (I know a guy... lol) If you are only
using ABS, an acetone bath overnight with periodic cleanings (get rid of
the melted gunk) will likely do the trick. If you go through that and
you STILL get the same behavior, either your bed is not properly
levelled/trammed or you have a different problem going on.

You may be seeing different behaviors from the different nozzles if they
are not at the same height. This is easy to fix as well - raise your
(relatively level) platform until it makes contact with the nozzle.
Watch closely - it should contact both nozzles at the same time. If
not, use a wrench to tighten/loosen the nozzles a little until both
touch at the same time. Then re-level your platform. Do not do this
approach unless you are fairly confident you are already levelled, or
you can throw out the platform/nozzle bit and just make more work for
yourself. (i.e. it may be level at one point and at the right distance,
but nowhere else on the platform....) Still, it is a simple thing to
fix this, just time consuming.

Oh, and this thread says the problem only happens after some time
printing. This says to me the temperature is finding it's way up the
filament faster than it it being fed into the nozzle, resulting in the
toothed gear working against soft plastic and stripping it. Reduce your
nozzle temperature by 10 degrees and the problem should go away.
Combine that with the other tips here and hopefully things are much better.

Use common sense if you attempt any of the above. I claim no
responsibility! :) But can say these processes have worked for me.

Shawn

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[Shawn]

Oh, and the dual strusion bit - I had my second extruder blocking itself
and burning the plastic before it got to print anything. I edited the
merged gcode file and dropped the second extruder by 10 degrees and
everything worked fine after that.

[Ted Larson]

I have been following this thread with great interest….I have had ALL these problems.  I have made 100’s of prints without trouble….I have also had some clogs….usually a clog would happen right out of the gate…on the first layer because the nozzle was adjusted too close to the build platform.  It was solved quickly.  Stop the print, retract the HBP, reload the nozzle….re-adjust the height and print again.

 

However….a few weeks ago…..I started having clogs all the time….even mid-print.  I finally had a clog so bad I couldn’t unclog it.  I had to remove the nozzle and do the acetone soak…things got up and going again….and were good for like a week….then the problems started again.  I couldn’t figure it out.  I was like…what is different….what has changed…..then I took my nozzle which loved to clog the most, put it under a microscope and compared it to a brand-new nozzle, fresh out of the bag.   WHOA!  Somewhere along the way, my nozzle had made contact with the HPB….the opening was ever so slightly flattened…just so slightly….just enough to change the shape and size of the extrusion filament.

 

Swapped it out with a new nozzle….VOILA!  Never clogged since!   Beautiful printing again!

 

Maybe this wasn’t the reason…but, I think it was, because no more clogging.

 

Hope this helps,

 

-Ted

--

[Elbot]

looks like i'll have to buy a de-humidifier. The big spool of plastic just sits in the open on my makerbot replicator. didn't know that moisture will affect my prints.

GUYS, I've fixed my replicator! Try this mod by Emmett:
http://www.thingiverse.com/thing:28241

It is guaranteed to get you printing again.

[Have Blue]

Best to just keep the filament in a dry box packed with desiccant and feed it out to the print head via plastic pneumatic tubing.  The drier the filament, the better it will print for you (less absorbed moisture means less ooze).

[gth]

Thanks to Shawn for the detail, in particular the temperature warning.  

I also noticed while cooking my nozzle (thanks andrewoutandabout for that) some klapton on my heatsink was folded onto the back of it and reducing contact with the aluminium bar behind the heater elements. 

Also I noticed the non-stock filament only feeds when I'm pushing it during the load process, so I'm guessing that's a worn plunger/filament diameter problem - i.e. the clogging is a secondary symptom.  Hopefully printing thing:32315 will help.

- G.

[Doogiekr]

"Hopefully printing thing:32315 will help."

 

 

I have had a few requests for different versions to accomodate on hand bearings, etc... its pretty easy for me to change the bearing size if you let me know what bearing you have

 

Anyway, let me know if you want a modified version and I will see what I can do for ya...