Filament Fails To Reach Extruder  

Re: Filament Fails To Reach Extruder

If you are getting only halfway down the orange tube, something is definitely wrong. The "bowden length calibration" might have that range, but I suspect that is not the problem.

If the MMU2 isn't feeding the filament all the way to the Bondtech, you either have too much friction somewhere, or the MMU2 isn't getting a good grip on the filament. The latter could be a tension thing or the alignment of the hobbed gears.

My suggestion: forget the spool holders. Remove the white PTFE from the back of the MMU2. Turn the printer on, let it settle, set the MMU2 over to filament 1 (should already be there), then click the middle button to load filament.

Feed a straight 30cm piece of relatively straight filament into the back opening. See if it will successfully load.

Then do the bowden calibration. It should feed down to the Bondtech, plus or minus a cm or so. Adjust if needed.

If this works, your MMU2 -> extruder path is in pretty good shape. If it doesn't, pull off the orange tube and both festos and see if there is a blockage in there.

Next, reattach the PTFE on the back, and load filament in the first slot. Don't use feed it through the spool holder and two brake pieces, though, just unroll a long straight piece and feed it directly into the PTFE. Make sure it feeds in pretty smoothly. Do the load and bowden calibration. If they don't work, debug that piece of PTFE to see where the problem is.

If that all works, then try again using the spool holder and the associated brake hardware. If it works, the problem magically disappeared. If it doesn't: explore the friction being added here.

Re: Filament Fails To Reach Extruder

Thank you for the reply!

I was trying to make the filament make a 90 degree turn to get to the printer due to limited space. I rearranged my entire workspace to get the filament to unload straight into the printer.

I then looked at the hobbed gears within the MMU body and noticed that the exit of the white PTFE tubes and the entrance to the sorter (where the short orange PTFE tubes are) were not aligned. Although I went through the process of aligning the hobbed gears multiple times as the instructions say but I decided to align them with the entry to the sorter since the hobbed gear kind of acts like a channel to direct the filament to where it needs to go.

I also checked the path of the filament through the MMU and each channel it travels through. There was a small amount of debris that looked like anomalies from when the parts were printed. No big deal, got them out of the way.

Finally got the first layer calibration to work.

Decided to go with the 2 Filament sheep
- It was working fine with the first color, switched to the second for a quick pass, then it went back to the first and it appeared that the gears were turning but there wasn't sufficient grab on the filament so it just kept spinning. I gave it a little help to see if it would grab the filament which it did but then it got spat back out about half a centimeter.
-I got an error message on the Prusa saying that something was wrong with the MMU and to press the button when the issue was resolved (The screen was stuck on the 1>2 filament change) but since I couldn't get it to work I abandoned the first print.

-Started another print which prompted the same error before anything got printed and because I couldn't think of anything better to try, I decided to help the filament along and gave it a slight push and the MMU decided to grab it and the issue was resolved. It went to print again but again, the gears are turning with no filament moving. The LED above sensor one is blinking red. I couldn't get the filament to move so I aborted the print. I removed the filament to check to see if it was blocking itself but the tip is fine.

-As I was typing this out, I had the printer idling (not printing anything nor preheating) and the I just got error message again, quote, "MMU needs user attention. Fix the issue and then press button on MMU unit." Keep in mind that nothing was going on, it just displayed the message while idling.
-Restarted printer and no error message after idling for a bit.

I could try swapping out the filaments but it's not the issue because it printed the feet of the sheep really well it just had an issue swapping on the fourth swap (#1>#2>#1>#2-error).

I could also keep brute forcing it (not literally) and just keep trying to print until it decides to work?

Tried a one color print:

Just a simple 1 cm cube.
- Nothing loaded in filament 1 so decided to print with filament 2.
- the idler body with the bearings isn't pushing down on the filament so there is no way for the hobbed gears to grab anything. Will try to troubleshoot...

In the meantime, does anyone have suggestions or sees something wrong that I'm not getting? Thank you.

Re: Filament Fails To Reach Extruder

is there some debris around the ball bearing for the filament sensor?

and did you redo your tube length after doing all that stuff?

you have to be getting closer to getting it to work.

Re: Filament Fails To Reach Extruder

I still have hope that this will work eventually...

I checked the area around the ball bearing and it was clear of debris. One thing I did notice is that the hole for the ball bearing goes all the way down to the bottom; this bottom is also where the bottom of the filament when it passes through the F.I.N.D.A. shaft. The bottom of this shaft has some slight imperfections where filament can get caught so maybe an addition of a 0.875mm channel at the bottom of the F.I.N.D.A. shaft could help guide the filament but not interfere with task of the ball bearing moving up? Could be a problem depending on the sensitivity of the sensor...

I redid the Bowden calibration length and noticed the filament wasn't reaching the extruder again so I removed the orange Bowden tube to see how far out it goes. There is a primary filament movement which is slow and I'm assuming is a way to trip the F.I.N.D.A. sensor before extruding the length of the Bowden tube. Then there is a secondary movement which is much faster to get the filament from the selector to the extruder.

- The filament moves during the primary "slow" move and goes about 2 cm out of the selector. When the secondary "faster" move takes place, the filament gets stuck (I guess) and doesn't travel any farther...

Re: Filament Fails To Reach Extruder

Quick follow-up:

So I think something goes wrong when it transitions from the primary move to the secondary move.

- When the filament came out of the selector and initiated the secondary move, the filament obviously didn't move so I gave it a little tug which made it come out of the selector the last couple of centimeters as the secondary move was completing.

- I then initiated the reverse: the secondary "faster" move wasn't ejecting the filament so I gave it a slight push which then allowed the gear to grab the filament and eject it out properly.

I'd say it's a jam but it moves once it gets a little help but obviously I have no intention of being a little helper every time the filament needs to move...

EDIT: I gave it a tug earlier in the process and it revealed that something had chewed the filament which is probably where it was getting stuck *facepalm*

EDIT2: Upon further inspection of aforementioned chewage, I think I smashed it with the ball bearing when I was setting the F.I.N.D.A. height, the indents were oddly spherical.

Re: Filament Fails To Reach Extruder

CAN CONFIRM, JUST COMPLETED A SINGLE FILAMENT 1 CM CUBE.

That is all.

P.S. Will try multi-colored print of sheep tomorrow when I can be near the printer in case something goes wrong.

Re: Filament Fails To Reach Extruder

start with low layer multi color stuff color stuff. will save a headache I bet

Re: Filament Fails To Reach Extruder

So I scaled the sheep to 50% to reduce print size while giving the printer a fairly decent object to print.

It was running fine, didn't have an issue switching back and forth between filament for the feet and the beginning of the sheep's wool.

Then it stopped moving the filament and it looks like the idler body gets stuck in the transition between changing from filament 1 to filament 2.

- this happened earlier so I checked nothing was blocking the idler from moving and I tested switching back and forth a few times and it looked normal before starting the print.

-When I press any of the buttons on the MMU, all three do the same thing: rotate the gears for a few seconds in the direction of the selector. But because the idler body is stuck between filament changes, it can't grab the first nor the second filament (The selector is on the second).

-I tried going through the options of load, eject and unload filament. These don't reset the position of the idler so it doesn't fix the issue.

Restarting the printer obviously restarts the auto calibration of the MMU position but it means cancelling the print.

Maybe adding a way to reset positions mid-print by holding an MMU button for an extended period of time? I don't know. I'm also not sure why it's getting misaligned.

Re: Filament Fails To Reach Extruder

The options available during jam fixing NEED updating.

That said, my procedure is:
1) Fix what I can by hand.
1a) includes turning drum by hand
2) Reset MMU only with its side button.
3) Generally, printer will continue at this point, printing air because there's no filament loaded.
4) On printer menu, select "change filament" from "tune" menu
4a) wait for motors to stop running and beeping to stat
4b) feed filament to gears, press button
5) Pray you didn't miss too much.

Re: Filament Fails To Reach Extruder

Sorry it's been a while since I've posted an update. I was replacing the nozzle and broke a wire off the heat block and had to get a new one...

Anyways, up and running and re-calibrated. I did the usual stuff and redid the Bowden calibration and everything seemed okay.

I started a print, it shoved the filament down the tube, the extruder went up a few centimeters and to the right and then ejected the filament. It then moved the selector to position 3 or 4 and then pushed out about 10 cm worth of filament and told me to replace it? Was kind of confused because that's not what I wanted to do... So I backed up the filament and reloaded with the same filament all good. It pushed quite a bit through the extruder while it was still high and I figured that was to get rid of any excess color bleed between filaments.

It then started the print but as it was prepping itself, it left about an 1 cm round blob before it did the initial wipe. Kind of weird, hope it doesn't happen next time. Also kind of weird because I thought that wouldn't happen if the Bowden calibration was corrected?

Only issue at the moment. Probably should mention that I'm only printing one color at the moment. Everything seems to be going okay so far.