My MK3S+ Extruder motor keeps skipping backward and clicking  

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

Generally a clog; but can be the filament dragging somewhere: malinstalled PTFE being crushed somewhere (too high is a common issue); filament holder placed in a position it catches and filament won't feed; printing ABS at 190c; Or it can be the wrong firmware; the motor current values in the start gcode have been modified or removed; And, it can be a bad driver or motor.

You might start by looking in the stats pages and see if the Einsy is detecting E-axis crashes. Verify the gcode is using the default Prusa motor currents (slice something with 100% stock profiles);  and then verify the E-motor connectors are properly fixed at the Einsy.

Other thing to check are that the idler door screw (the hinge screw) isn't jamming the door; that the Bondtech gears are lubricated and aligned; and that both gears align with the filament path; and that the gears aren't rubbing somewhere they shouldn't; and that the driven gear set screw is on the flat, not the shaft round. And that filament can move freely up and down the filament path and into the hot end (open the door and slide filament all the way down the extruder into the heat break and out).

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RE: My MK3S+ Extruder motor keeps skipping backward and clicking

How do I check for E-axis crashes? The stats page only lists X and Y and shows zero for both.

For Gcode, I only use prusaslicer default settings outside of temps, but I have only changed those 5 degrees or so off default. I never manually add or remove Gcode. Don't even know how to.

I have this exact problem with Prusa PLA, Hatchbox PETG, and Mika3D SilkPLA, which are the only three filament types I have tried. The hotend temps for PLA are 215-220, and PETG was 235-240.

Ambient room temp is 69F, about 21C.

Gears are perfectly aligned with each other and the filament path, and the filament can slide in and out freely with the tension removed from the gears. I haven't lubricated them since I built the printer, but that was literally a week ago.

Filament is not getting caught on anything, and the spool holder is directly above the unit.

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

@obsessed

I thought the printer tracks all axis... perhaps I'm wrong. Also - crashes are only tracked when not in stealth mode.

So show a photo of a ruined print. It might help point to a different cause. Also - by any chance does the filament hop when you hear a click? Is it one click or a series of clicks?  Twisted filament will sometimes cause noise at random times, but generally has never ruined a print.

And - zip and post a project file (.3mf from Slicer).

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

Here are some pictures of a (what I would consider) simple dumpster lid (from a "2020 Dumpster Fire" model).  Slicer file is also attached.

Something I have been able to deduce, perhaps it's coincidence, but it always happens on thin layers...anything 0.10mm and under. Again, maybe coincidence, but maybe a cause. I'm too new at this to know.

Also, the surface is VERY rough, which I typically don't have this problem, but when the print starts skipping, it looks like this.

Dumpster Lid and Pics

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

When I had a similar problem, I swapped my heat break from the Prusa modified version to the stock E3D-V6 version (no step). And it fixed it. The problems started after I swapped out a nozzle following the Prusa guide.  Cold pulls were pretty clear the filament was being stuck in the cold side of the heat break just above the nozzle. 

But, you're the third person complaining of unexplained underextrusion on new Mk3S+ printers this week. They aren't hearing any clicks though. You might want to open up chat and ask the techs at Prusa for ideas.

I don't see anything obvious in your setup ...  except you're printing kind of hot for PLA and using 0.95 for the extrusion modifier: unless you've done a cal cube for that I'd stick with 1 and drop your print temp 10c. But I doubt 5% under and 10c over will cause the bridging to fail like it is.

As a test, unload the filament after one of these bad prints, and take a photo of the melted end you pulled out. If it looks anything like this, a large bulge at the end, the heat break is suspect.

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

Posted by: @tim-2

When I had a similar problem, I swapped my heat break from the Prusa modified version to the stock E3D-V6 version (no step). And it fixed it. The problems started after I swapped out a nozzle following the Prusa guide.  Cold pulls were pretty clear the filament was being stuck in the cold side of the heat break just above the nozzle. 

I have had to do the same thing several times.  This should be in the Prusa guide.  Unfortunately, it probably does not read well to recommend trying something other than your own product.  

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

@tim-2

@cwbullet

Okay so I had a print fail last night (overnight). This particular one was sliced at 0.15mm, I lowered the temp 5C, and increased flow rate to 1.00. So that didn't help.

This morning I pulled the filament out. It looks identical to the ones Tim posted.  The end was a little blob, exactly 2.2mm in diameter. I pulled mine out hot.  Is there a better way to pull it (perhaps cold)? Do I just loosen the idler gear screw all the way and tug?

So I need to replace the heat break? On a brand new printer?

Can someone send me a link to the replacement I need? Is it as easy as just disassembling it and swapping it out? I'm getting tired of losing 90% of my prints, and this is super frustrating for someone that is new trying to learn things having issues. I bought Prusa because I had read those are the best/most reliable, and I come to find that it appears to be mis-engineered a bit.

I'd assume there is a reason they modify the heat break vs. the "non-Prusa" versions?

Thanks for the help folks. I appreciate it!

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

Try that same gcode that failed, but this time - as soon as the first layer is down - manually set the print SPEED to 125% in the TUNE menus ... let me know the result.

This test may help verify the heat break is the issue before you take time to replace it.

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

If you want to get one on order:

https://www.amazon.com/Genuine-E3D-Break-1-75mm-V6-175-BREAK/dp/B077Y2MHW8

Changing it means a complete disassembly of the hot end. And you'll need to download and follow - to the letter - the E3D-V6 disassemble/assembly guide. Placement of the nozzle and heat break into the heater block is crucial.

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

@tim-2

Thanks!

Any reason not to opt for the titanium version for $8 more? Says it isolates the heat better. Gimmick?

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

As for unloading - to have a look for this problem a simple unload works.

To perform a cold pull - to clean the actual nozzle innards - there is a specific procedure. Look for the guide to do that on the Prusa site. The procude is pretty basic though: let things cool down. Open the idler door so filament is free to move, set the extruder to 80c, immediately start pulling up on the filament. At some point around 60 to 80c the filament will pop loose from the nozzle.  Don't yank, and when pulling there is a chance the filament will begin stretching. Let it stretch as you continue pulling. Again don't yank on it - a constant pull is best.

But - read the guide first so you know when to do what - timing is everything here.

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

@obsessed

I have titanium on one printer.  I have found no difference in print quality, jamming, or reliability.  

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

@obsessed

I own the titanium version, not yet installed. It is for when I upgrade to the tungsten carbide nozzle with solid copper heater block (work to be done :). So if it were me, and I was replacing the Prusa part - yes - I would buy the titanium version over the stainless.

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

Bought the titanium version. I'll wait to get it installed and report back.

Thanks so much for the help! I greatly appreciate it!

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

Just remember that following the E3D-V6 assembly guide is not optional. Read it a couple of times before starting, too, so that each step is ingrained. It will make the work go faster and lesson the chance of missing something important. 

And a minor correction to an earlier post of mine - the thermal grease goes on the heatsink-heat break threads - they do NOT get to 250c (typical thermal grease will work). But I have heard of people putting thermal grease on the heater block end even though E3D doesn't say it is needed there - it does get to nearly 300c and would require special thermal grease. As an aside, adding a good high temp grease when installing the heat break, nozzle, heater cartridge and thermistor - as an anti-seize - can likely help down the road when taking things apart. 

https://www.amazon.com/Slice-Engineering-Boron-Nitride-Paste/dp/B088CHBZQ4

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

@tim-2

When you say follow the instructions perfectly, you are referring to the same instructions used for assembling the V6 hotend, correct? I can't find specific instructions for the heat break itself, but rather as part of the overall assembly instructions.

Sorry, just want to be crystal clear in case there is something else I should be referencing.

Thanks for the link to the paste; I picked some up.

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

@obsessed

https://e3d-online.dozuki.com/Guide/V6+Assembly/6

The guide has a little bit of ambiguity as to how far into the heater block the heat break should go ... I opted for deeper -- getting the gap edge nearly flush with the heater block. One of the photos show it a thread higher than the block - I think that is not 100% correct. 

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

@obsessed

Here is another good set of instructions:

https://www.matterhackers.com/articles/how-to-assemble-an-e3d-v6-all-metal-hotend?rcode=PPCADS&gclid=CjwKCAjwkN6EBhBNEiwADVfya8JJF7Ioiorepym-IzAQNl-01ye7EAqSyxwOCUJEywpGd88kHynoOxoCv3kQAvD_BwE

RE: My MK3S+ Extruder motor keeps skipping backward and clicking

Except that procedure is fully 100% wrong or at least misleading right out of the box. They start with the nozzle too far into the heater block just like Prusa's 1/3rd turn backwards does to users, and if you follow it the nozzle will be tightened right up against the heater block when you get to the point of doing the hot torque -- and their photos even show it built with nozzle against the block.  No - do not follow the Matter Hackers procedure.