Ye Olde extruder clicking  

RE: Ye Olde extruder clicking

Does the cold pull give you a clean smooth internal imprint of the nozzle, including the nozzle opening itself, the bevel between the nozzle and the heatbreak and the accumulation of filament just above the heatbreak?

RE: Ye Olde extruder clicking

Attached is a picture of the last pull of PLA filament; there is still some ASA attached to one side: I take it that's not good enough?

RE: Ye Olde extruder clicking

This is what a clean cold pull looks like: 

However yours seems to be complete, too, if somewhat stretched. What worries me slightly is the shape of the nozzle cone, in your case rather round.

To get better cold pull results I recommend using Nylon or a specialized cleaning filament (typically HDPE based), and always let the nozzle fully cool down to room temperature before starting to heat it up again and then starting pulling at about 80 °C. This ensures that the core of the filament is as cold as possible to prevent stretching, while the walls are already heating up and letting go of the walls of the nozzle and heatbreak.

Disassembling the print head, extruder and hot-end isn't hard. It can be done without much printer disassembly, even the X carriage and wiring can stay intact, so that's what I'd try next and make sure there are no blockages throughout. It's basically removing three screws from the back of the X carriage and the whole thing pops off. Just keep in mind that if you want to take a look inside the pre-assembled hot end, then the hot-end disassembly needs to be done at 285°C, otherwise you damage it. That's hard to achieve on a disassembled printer, so either remove the nozzle in advance, or have a heat gun ready.

RE: Ye Olde extruder clicking

One more comment. While I've never printed with ASA, I have printed with Nylon, which is also a hygroscopic material. Wet Nylon causes clicking. Make sure your ASA is dry.

RE: Ye Olde extruder clicking

OK, I'll do some more cold pulls with the material I have, following your detailed instructions and, if that doesn't work, I'll buy a sample of nylon and have another go.  If I lose patience with that I'll pop the nozzle off and stick it in some acetone.

Thanks for the swift and detailed advice.

RE: Ye Olde extruder clicking

I've now taken the nozzle off and cleaned it in acetone: definitely nothing blocking the way.  But I still get the clicking.  I've also shoved a 1.5 mm rod down the entire extruder.  Still clicks.  And I've tried PLA instead of ASA.  Still clicks.  Here's a video of everything I've done, just to prove it:

Does anyone have any other suggestions?

RE: Ye Olde extruder clicking

I'm out of good suggestions, but I'll add a few thoughts: A Gauge 10 string has a 0.25mm diameter, much less than the nozzle that comes with the Mk2/Mk3 (0.4mm). Carbon deposits from ABS/ASA  printing aren't necessarily soluble in acetone. Clicking happens when the extruder gears aren't able to push the filament through at the speed they try. The springs compress, the filament slips back by one or more teeth of the hobbed groove and makes a click. I assume you'd notice your spool tangling and/or not turning smoothly. Since your filament obviously makes it all the way to the nozzle and the path through the extruder is thus likely clear, the nozzle would still be my prime suspect. The extrusion doesn't look good, the stream of filament should be nice and thick (~0.5-0.6mm, expanding as it flows out of the nozzle) and go down straight without curling upwards if the nozzle is clean. Any curling indicates obstacles in the flow.

RE: Ye Olde extruder clicking

• Does dialing back to 50% using the front knob make any difference?
• Does the clicking occur when printing any particular feature (e.g. infill)?
• Have you checked the extruder idler to be sure it turns freely and is seated well in the door?
• Have you tried adjusting the extruder tension screws on the left? Mine typically protrude < 1mm from the left side cover. You want it tight enough, but not too tight (which is annoying vague I realize).

RE: Ye Olde extruder clicking

Most likely: Have you verified the idler gear shaft is properly fitted into the two door ears?  If the idler gear flexes, the shaft is probably not in both sides (the shaft it short, and if assembled so it's flush on one side, it is NOT properly installed.

Less likely: Have you lost the idler door spacers?  If they aren't installed the door will jam.

RE: Ye Olde extruder clicking

Excellent suggestions/points, thanks guys.  I've removed the nozzle again and used a .013 guitar string (0.33 mm) this time but the next size I have is 0.17 (.43 mm) and so won't fit anyway.  This hasn't helped unfortunately.

The clicking first began when the machine was 12 hours into a 16 hour ASA print; I have done many, many of these without issue but on this occasion it simply stopped extruding entirely mid-print.  The problem occurs when loading filament, both PLA and ASA.  The extruder cog thingy in the door rotates easily and the other cog seems to turn without any particular issue, as far as I can tell, when running freely.  I've fiddled with the extension bolts: had the heads about 1 mm out from the printed surface up to flush with the printed surface; out 1 mm from the printed surface is better but the clicks remain.

And you're quite right that the filament doesn't drop cleanly away from the nozzle, it bunches at the nozzle.  Unfortunately I can no longer find the cleaning wire that came with the printer. Maybe I should simply order a new nozzle and cleaning wire at the same time?

RE: Ye Olde extruder clicking

To Tim's points (which landed while I was typing): thankfully the idler gear doesn't flex when I shove it, just rotates.  The idler door has never been taken off and, if I look carefully, I'm fairly sure I can see the washers in there.

RE: Ye Olde extruder clicking

There are two places where the Prusa version of the E3D v6 hot-end tends to clog. One is the nozzle itself, it can happen with dust or carbon deposits. Keeping the filament clean, possibly by passing it through a lint-free wipe before going into the extruder helps. Upgrading to E3D Nozzle X helps, it has a non-stick coating. The other is the cold-end of the heat break when not cooled enough. It's the red bits on my cold pull picture - the filament tends to ooze back up the cold-end and accumulate, possibly obstructing movement. Prusa's specific version of the heat break has added space there (to help the original MMU to work better), increasing the accumulation of plastic. This can quickly lead to extrusion problems. People report that ensuring good cooling (no enclosure, or replacing Noctua with Sunon) of the heatbreak or reducing retraction length or replacing the heatbreak with an standard (non-Prusa) E3D v6 heatbreak solves this problem.

Whether it is also your problem stays an open question. Replacing the nozzle and purchasing a cleaning needle or drillbit is probably a reasonable next step.

RE: Ye Olde extruder clicking

Before I go deeper into disassembly I have ordered myself an E3D  Nozzle X, plus cleaning filament to give me some sort of maintenance routine.  Finger's crossed that's the answer.  I'll report back on progress.

RE: Ye Olde extruder clicking

Posted by: rob.m7

Before I go deeper into disassembly I have ordered myself an E3D  Nozzle X, plus cleaning filament to give me some sort of maintenance routine.  Finger's crossed that's the answer.  I'll report back on progress.

I've put together my notes on changing nozzles here and notes on cold-pulls here. I picked up a couple of Nozzle-X nozzles, but they're really only needed if you are printing abrasives at high temperatures. They have the same thermal characteristics as other hardened nozzles. Since realizing this, I've started using P3-D's "Apollo" series that are coated, also somewhat harder than brass or copper (though not as hard as hardened steel) and provide superior thermal characteristics compared to brass. There's certainly nothing wrong with the Nozzle-X nozzles, but they are expensive if you're just printing PLA. 

One other tip: The support pages for Nozzle-X specifically notes that the coating is not covered by warranty, and recommends against using wire a brush for cleaning. A strip of nozzle works very well as a rudimentary "toothbrush" for cleaning off coated nozzles when hot.

RE: Ye Olde extruder clicking

I've put together my notes on changing nozzles here and notes on cold-pulls here.

A very nice writeup indeed!

A few thoughts based on my experience:

• When loading the E3D (eSun) cleaning filament into the nozzle the first time after printing, I set the nozzle temperature to the max allowed temperature of the material last printed, to avoid decomposition while ensuring good flow. On subsequent attempts, I go higher, the max allowed temperature for the eSun cleaning filament is 280°C
• After loading, I keep extruding more (either by saying 'no' to the 'correct color' question or by going to the Settings/Move-Axis menu) until I see a clear cleaning filament coming out. Then I go to Preheat/Cooldown, to turn off heating and keep extruding until the cleaning filament is coming out barely liquid. The closer the filament is to the melting point, the closer to the nozzle it turns white while extruding.
• When doing a cold pull, I've had more success of pulling an unstretched imprint of the extruder by letting the eSun cleaning filament cool down way more than to 90°C,  so I usually let it cool down all the way to room temperature. Similarly, to avoid it melting, I set the target temperature to 100°C (Settings/Temperature). This way the printer only ever softens it, but doesn't melt it. This temperature is enough to get the eSun cleaning filament loose. Higher may be needed for other materials.
• The temperature specified by E3D for nozzle changing is 285°C ( https://e3d-online.dozuki.com/Guide/Changing+Nozzles/45). Hardened copper nozzles when used with the upgrade hardened copper block can be removed and installed cold. The reason for installing the nozzle while at the highest allowed temperature is to make sure it is sealing to the heat break across the whole temperature range as the aluminum block expands more than the nozzles. The torque required to achieve that tight fit at room temperature would damage the aluminum block.
• The target torque for tightening is 3 Nm for E3D nozzles and 1 Nm for Olsson Ruby nozzles. I use a cheap digital torque adapter from Aliexpress to measure the moment while installing.

RE: Ye Olde extruder clicking

I am dealing with clicking sound (not just sounds, it really negativly influent the print quality) from time I vent from MK2S to MK2.5. It is still the same in MK2.5S. There is definitelly no blockage. The starter for this are the retractions. If I have a print with many very fast retract-extract commands, the bondtech gear damages the filament and it will start to click and not feed the filament. Sometimes it is ok because some longer extraction follows and it continues, sometimes it really damages the print. I played with the idler tension for weeks, still not 100% solved. I did the full disassembly during MK2.5 to MK2.5S upgrade, also changed the nozzle. The only thing I found, that the new extruder design has a small mistake in the filament path on the top. In the idler part, the filament entry hole and the filament exit hold (to PTFE tube) are not aligned. There is some 0.5mm mistake which causes filament to be bended. It was also documented on the forum and even github, sofar no offical correction from Prusa. Maybe this is causing the problems. Otherwise I am also out of options.

Milos

RE: Ye Olde extruder clicking

Posted by: milo.v

Otherwise I am also out of options.

Milos

Hi Miloš,

another reported reason for retract-related blockages is the internal shape of the Prusa variant of the E3D v6 heatbreak. Compared to the standard v6 it has been drilled to a bigger diameter at the bottom (2.2mm vs 2.0mm) to help with MMU (v1) filament forming. This space can fill with plastic on prints with many retracts (or when using a filament exposed to moisture) and result in clicking and underextrusion.

Vojtěch

RE: Ye Olde extruder clicking

It can be, I have still the original E3D v6 from MK2, not sure where this version for MMU came out.

Strange is that if I notice this issue, call for filament change in menu, remove filament, insert again  and print continues correctly. Until another section with to much retract/extract. With normal models this is only ocationally, not such an issue. But I tried to print lithophane and there it is mission impossible.

Milos

RE: Ye Olde extruder clicking

Lots of great information, thanks guys, I have bookmarked those references for later and also ordered an Apollo nozzle to give me options.

If the heatbreak turns out to be the problem, is there any guidance anywhere on how to replace the Pruza heatbreak with the standard E3D one?  I guess it's [just] a matter of disassembling the hot-end but if there's specific guidance that might be beneficial.