1y ago

Still working on that damn clogging issue!

Hi all. This is an update to this post. I don't know what else the community can do to help, but I figured I'd throw some more content up there and give something bored people to look at.

Since the last update on that post, I tried working on the printer in freezing temperatures (not really but it's cold in this house) with extremely precise practices on assembling the hot end (the same hot end I had haphazardly assembled dozens of times and printed with zero issues) and yielded zero progress. Today, I tried a brand new PTFE lined heat break, along with a brand new Capricorn Bowden tube (I already had one but I needed more tubing for the heat break). Clogging in the same exact way in roughly the same amount of time as every other attempt. It's as if I've not tried anything, literally nothing is effecting the results.

I considered ordering a fancy micro-swiss or ed3 hot end, but at this point, including the stock hardware, I've gone through 6 heat breaks, 3 heat blocks, a half dozen nozzles and a foot of Bowden tubing, none of which did anything to fix my problem (or even make it worse). I would look to the extruder, but I outlined in the previous post the testing I did to rule that out (able to run >1m of filament at high and low speeds through the Bowden tube).

I'm at the end of my wits. Perfectly good printer cranking out multiple high detail prints a day, now completely useless over something so stupid as clogging. Where the hell else can I look? Could it possibly be some sort of software/firmware issue, where Klipper isn't sending or receiving the right commands or something? I know my slicer settings are at least good enough because I've tried both prints that have completed dozens of times as well as new prints with drastically reduced retraction. Do steppers need to be tuned over time? I don't think it makes sense that after a year it'd suddenly become so uncalibrated it's unusable, and when I tried calibrating it before I was just unknowingly calibrating against mild clogs, but I don't know where else to look.

29 comments

Hello, I suggested heat creep in your last post, which didn't end up being the issue. I don't remember if anyone suggested it, but have you tried checking the bowden assembly, on the motor side? Whether the stepper works, or the gears wore down (I'm pointing towards this), or there are clogs somewhere in the mechanism, even some dust that accumulated where it shouldn't had. Or did you change settings like the current limit on the steppers? If that's controlled with a potentiometer on the main board, maybe it got turned down for some reason (if so, I'd try to understand why's that). I don't know how Klipper handles motor drivers where current limits are controlled in software, I know that Marlin has a dedicated submenu in the Configuration>Advanced Configuration. If you reflashed the firmware, maybe the settings where in the eeprom and did not get transfered over or got overwritten in the flashing process.
I remembered that on a couple different printers I had the same problem as you, and it came down to damaged/untightened nozzles (which you excluded already) or wore down gears or, on the printer I'm working on right now, too low current limits which made the stepper skip steps somewhat randomly
- I think I'm going to start poking around the extruder side of things. I really don't know what to look for, as everything seems to be working over there (outside of prints anyways..). Things look clean, no clicking, gears don't appear to be damaged.. I'll take a dive when I get home.
  I don't think anything got messed up during the flash because it had been working for a month or so running Klipper. I don't know if stepper motors need to be recalibrated every once and a while, but it'd be weird for it to go from "working perfectly fine" for over a year to "completely unusable" literally in between two prints.
  Thanks for your continued suggestions.
  
  Take out the extruder stepper and rotate the shaft by hand and feel if there is binding at any point. I think I mentioned I had this same issue on my direct drive printer in your previous post. It would work fine until it didn't and randomly act like the nozzle was clogged. When printing, I think the load on the motor is going to be greater than feeding filament through into open air, which may exacerbate the problem.
  You've xhecked the hotend a bunch of times so I would focus on other areas. Something else may have broken at the same time as your nozzle swap which may just be leading you on a wild goose chase.
Any suspicion of the heat cartridge failing? Might work long enough for a pid tune but not be able to maintain temp? I'd also look I to the extruder, once you put the nozzle on its working much harder.
- I suspected a faulty cartridge, but that would reflect on the temp chart no? Unless the thermistor was somehow failing perfectly to match the change.
  I think I do have to look to the extruder. I'm nervous about it because I don't know anything about how to maintain or diagnose them, but I guess there's a time to learn everything.
One thing you haven’t mentioned replacing is the fan for the heat beak itself. May be worth giving a try.
- I considered that, but the fan is still spinning at a good speed and I can feel a lot of air being pushed by it. Additionally, one of the things I tried was pointing a desk fan at the printer (outside the enclosure, with the house ~5° cooler than it normally is), with no change in results.
  
  This would drive me bonkers but stubborn enough to want to dig into the “what” of it.
  If it were me I’d setup some kind of makeshift jig that holds the nozzle and hotend with cooling fan out from the rest where I could hand feed filament in.
  So you could bring the temp up, wait a few minutes, then push and get a feel for what’s going on. Then wait a few more minutes and do it again. Feel resistance, up the temp, and repeat.
  See if there’s some relationship between temp, extrusion, flow, etc that isn’t obvious otherwise.
I can't recall of you said it clogged while just feeding through the hotend without printing, totally possible you could have an intermittent break in a wire going to the hotend, TC would be obvious but others less so.
Did anything change to your setup before it started? Are you using a new version of a slicer? Did you update klipper? Is your extruder stepper getting warmer than usual while printing?
- No clogging while feeding without printing. If there was a wire break in the thermistor, Klipper would shut off, and if the hotend was cutting off I should see fluctuations in the temp chart.
  Everything except the nozzle was exactly the same between the last print the finished perfectly and the first print that started clogging. I've since rebuilt almost the entire hotend multiple times, including a few different nozzles. Klipper and all the plugins are the same versions, and I felt the extruder motor last night during the last clog and it was still room temp.
  
  TC break could shutdown, but depends, I had a break on my prusa that would cause the readings to jump around as it wasn't quite long enough to fall totally off, caused the firmware to hunt and ran into thermal runaway. Wondering if a fault in a heater wire could cause less obvious issues as thermistors aren't super quick to respond as far as I recall, combine that with thermal mass of your block (copper blocks have a sizeable thermal mass) and you could essentially mask the issue. Not saying it's a break just something to think about checking as they often can be some of the most annoying and hard to pinpoint failure modes.
  Have you done an extrusion calibration? If you call for 100mm of filament is it feeding 100mm? Same filament? Is it possible it's wet? I've had clogging issues with filament not being dry before. Can you get a successful print if you slow things down or increase temperatures? Possibly even trying less part cooling? Lastly, do you have a sock on your hotend?
You can try to use this hotend fix to avoid clogging https://www.thingiverse.com/thing:3203831
Also, make sure to replace Bowden coupler by new one
- My hotend has been modified to avoid the need for this mod. (The Bowden tube runs all the way from the extruder motor down to the nozzle.) My couplers are all working properly as well. I was actually worried that the new coupler I put on one end was cutting the Bowden tube and somehow getting remnants to the nozzle, but I've mostly confirmed this is not the case.
  
  "the Bowden tube runs all the way from the extruder down to nozzle", what kind of modification did you do because that's how most Bowden setup are from what I know. This video explains why the fix works https://youtu.be/7tCxO17XZtw
Also dumbest idea, have you tried a brand new spool of PLA? Just to exclude an incredibly wet filament. Because that can cause all sorts of problems
- I've tried a few different rolls, 2 of which were used for successful prints literal minutes/ hours before the issue sprung up.
  I'll admit that after a week or so of diagnosing this issue I've mainly switched to cheap crappy filament to run extrusion tests with (I'm extruding 500-1000mm into the air at a time), but the few times I've gotten far enough to try an actual test print I've put my good stuff back on and it clogs up just the same.
Any chance you post some pictures?
Looking at the filament part that was in the extruder and in the nozzle might help identify an issue or exclude some other possible issues. Also, looking at hotend and extruder and motherboard might be usefull here.
Do steppers need to be tuned over time?
No, but its worth to check at this point. Stepper drivers can die, overheat, cable can be damaged, motor can be damaged, overheat... If stepper was tuned to barely push the filament and something added extra resustance (friction) it might explain why issue started. If driver is overheating you can probably just add a small cooling fan or even a heat sink. Why I go in detail here? Because if something happens every time after about the same amount of time, it sounds like overheating issue, especially stepper driver, but I might be wrong. If filament was well grinded by extruder teeth, the issue is probably somewhere after extruder
Bonus question: did you check filament diameter and how consistent it is?
- I suspected the extruder of overheating, but it's still cool to the touch even after the nozzle gets clogged and the extruder has been clicking for a while.
  If filament was well grinded by extruder teeth, the issue is probably somewhere after extruder
  This is what I'm thinking too; if extrusion was the issue, it would make more sense that filament would not be reaching the nozzle, but the opposite is happening, filament reaches the nozzle can't get out and the extruder continues trying to push filament, either grinding it down or clicking back and forth, then as soon as the clog is cleared pushes filament like normal. (I'll set the printer to extrude 1m of filament, it'll clog, while it's still trying to extrude I'll clear the clog or disconnect the Bowden tube then filament keeps going)
  
  Ok, then I don't think it's overheating, but imagine your stepper driver is set to too low current:
  While extruding there might be extra friction involved in the heat break which can suddenly become too much for extruder. Solution is to increase stepper driver current (it can be software approach - klipper, or HW - small screw pot on the driver itself). Stepper motor is heated according to the current you've set, almost not related to the speed of the motor. In my experience extruder stepper motor is usually hot to touch, so that might be another reason to check stepper driver settings.
  Maybe adding heat break requires to adjust stepper driver current in your case. Or maybe FW update changed the values. Its just a guess, but its not hard to check that. Basically you reduce the current to have obvious skipping, then boost current untill skipping stops, then increase a bit more to be on the safe side, then check is your motor or stepper driver too hot (its usually hot enough to be able to hold a finger on the motor for few seconds only).
  I think it's best to spend enough time on extruder first and not moving to hotend before you are completely sure extruder is working fine. Stepper motors are quite powerfull, extruder can usually grind the filament or push the bowden tube from its position before stopping, even when clog occurs)

29 comments