Extruder Idler Adjustment  

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Eikonic
(@eikonic)
Eminent Member

So im on week 2 of owning a mk3 after doing the kit build. So far i think all is going well. I ran almost without error for a week. Then a few days ago the video showing how to adjust the extruder idler came out. I decided to check mine out and realized that, compared to the video, mine was way too tight...? So i followed the instructions as shown, started a longer print (10 hrs i think) and a few hours in i started hearing a clicking coming from the extruder. Similar to the other thread about the clicking extruder, i ended up with a jam. Heres a bit of how that sounded...

https://www.dropbox.com/s/onfmt9oco87ib59/VID_20180719_074111.mp4?dl=0

Fortunately i was able to free it with a bit of work, and cleaned everything up. I noticed alot of (what im assuming was) filament dust between the bondtech gears, along with the jam blob. So thats what lead me to believe i was probably too tight. I dont think filament should be turning to dust.

So, i put everything back together, followed the same procedure to get the idler set correctly, and I had another failure. Though, this time, i noticed the idler was not moving. I retightened, loaded more filament, and tried printing again. This eventually happened 3 or 4 times over the course of a few days. It seemed like the tension suggested in the video was not tight enough, and the bolts were shaking themselves loose after a few hours of printing. I flip flopped on how tight to make them several times, but it always seemed that after erring on the side of looser, they would ultimately get so loose the idler would disengage.

So after so many failures or instances of finding the idler not moving, I decided the method suggested in the video was not working for me for whatever reason. So i went back to tightening the screws until they were flush with the holes. This then lead to another noise... still clicky... but more like a creaky old rocking chair! Heres a video...

https://www.dropbox.com/s/bajdeoux919s2fu/VID_20180720_154735.mp4?dl=0

I figured i had another jam blob, but no, everything was fine when i opened to look. So, figuring maybe i was now TOO tight, i backed off both screws a bit at a time while running until the noise stopped. So, currently, this seems to be the bolt tension i can trust. My prints look fine ( i think), there is no clicking or creaky old chair noise, and i have run several prints without the bolts coming loose.

So can anyone give me any tips or insight here on what is going on, and how i can get this dialed in properly? Again, the video instructions were not working for me (seemingly), unless im missing something. Its just a bit of an annoying situation as i now kinda have a fear that the idler is going to quit again and cost me several hours of printing. Im constantly checking on it. Id like to get back to trusting that its set properly.

Posted : 24/07/2018 5:24 am
Zinga
(@zinga)
Trusted Member

Does your idler spin (very) freely if you flick it? Even with barely any tension, if filament is moving through the gears your idler should spin. Also, make sure you put both bearings inside the idler.

For my printer, the ends of the tension screws are flush with the holes on the outside of the idler mount (and even that's probably more than I need).

Posted : 24/07/2018 8:10 am
Eikonic
(@eikonic)
Eminent Member

yup, spins ncely and both bearings are in there. i even just took the whole door apart right now to fully inspect things. i did a light sanding on the surfaces the shaft pin passes thru, as there seemed there MIGHT have been a few plastic burs, but probably nothing remotely big enough to cause an issue.

side note, Zinga, when you say....


For my printer, the ends of the tension screws are flush with the holes on the outside of the idler mount

...do you mean flush with the door side, or flush with the side you tighten them on? again, i just tightened mine down to ALMOST flush with the tightening side. and that was the whole point of the thread... that would seem to be much to tight compared to how the video was instructing.

Posted : 27/07/2018 3:23 pm
Zinga
(@zinga)
Trusted Member

Flush with the door side, but I'll have to try the method they showed in the video. The way I was doing it was a holdover from the Mk2, where you tighten until you can see slight teeth marks in the filament (without deforming it into an oval) after backing it out.

Posted : 27/07/2018 3:51 pm
Eikonic
(@eikonic)
Eminent Member

If you do try the new method id be interested to hear how you found it. I will stick with my almost-flush method for now.... no reason to change until i see a problem i guess.

Posted : 27/07/2018 8:29 pm
james.k30
(@james-k30)
New Member

I'm a novice with 200 hours on my first ever 3D Printer the MK3 and I ran into the issue of clicking - finding the printer clicking and working 8mm off the surface of where it quit extruding. This led to a lot of issues.
Somehow the PTFE got melted/chewed by the gears and I have a much shorter PTFE out of my Hot endnow after putting a bevel on the existing peiced which is about 20mm too short. I had no PTFE on hand.

I had had a number of errors before and likely had tightened my idller too tight after rebuilding the extruder to correct a fan failure.

I reassembed and got a few smaller objects printed. But I'm running into a situation now where the extruder isn't extruding consistently and i am seeing that my idler has enough play axially to fall out of mesh. I'm also finding issues with the clicking coming in intermittently - with lots of dust.

I have lost my teflon washers for the idler lid for one - but from the gap I am seeing on shaft axially it looks like I am going to have to shim towards fixed gear.

Suggestions? I just want to ge back and running and do some nice long prints again.

Posted : 28/07/2018 4:00 pm
Eikonic
(@eikonic)
Eminent Member

I noticed the axial range being a bit wide as well when i was checking mine yesterday. I had thought about putting one of the little washers from the spare parts bag on 1 side, just to remove some of the gap, but I dont want to go fixing problems that arent there. and im assuming when you say shim towards the fixed gear, you mean push the idler back towards the X axis rails, not in closer to the fixed gear, because this is what tightening the 2 bolts does. thats what i was referring to as mine seems to have a bit of play along the shaft the idler sits on.

that said, there were several extra washers in my spare parts bag, though i assumed they were nylon, not teflon...? so maybe give those a try, unless we're talking about the same thing.

and yes, i had alot of dust too the first time i opened it, but granted, i ran for a week with no issues and only started having the problem AFTER i opened it. to me the dust was a sign of it being too tight. there realy should be a more definitive method of getting this set properly as it seems everyone is just kind of winging it.

im not sure what causes the clicking, but since iv gone back to tightening my bolts to almost flush, i have not had it happen again. so thats all i can suggest for now. if you have a problem with your ptfe tube, then that might be a whole other issue. sorry i cant be of more help, but im a noob at this too. only other suggestion i can make, if you think your idler is moving too much, is maybe print a new idler door...? maybe the one you have is slightly out of spec?

Posted : 28/07/2018 4:15 pm
james.k30
(@james-k30)
New Member

Yes toward x-axis. The drive is in the right place. Its weird but this seems intermittent. I shimmed with a washer so that it doesn't wander - although you'd think that the v groove for the feeder would hold it in place. Flushing the bolts for the door is a good starting place.

I printed an object without difficulty after I fed in good fresh "out of the bag" filament. Did a phenomenal print after I reset my first bed layer correctly.
Went to print a second object and it quit feeding again on a fine adhesion bed. Went to zero extrusion. I don't get it. cancelled 3 prints and did another first layer calibration - it was barely extruding (minimal material.

Removed filament & reinstalled filament about 3 times making sure nozzle was clean - still very poor feed.

Removed Filament and got it "pouring" again - I don not understand why feed rate is coming and going.

I like the idea about printing another door - I had printed a number of parts in Grey PLA but am now cursing the fact that I hadn't read that Extruder parts should be black and that Prusa uses PETG. I have 2 refills of filament and ordered a 3rd but none of it Black PETG. Next on the list to order.
But I'll need a reliable printer to print. Very frustrating. Makes me wonder if my Extruder motor is slowing down...

Posted : 29/07/2018 5:57 am
Eikonic
(@eikonic)
Eminent Member

as far as the extruder parts needing to be black, i THINK that only refers to the pieces that the filament sensor can see, which is probably only the top cover, and maybe the main body that houses the bondtech gears. i could be wrong, but that was my understanding. if you only have grey, you could do a print to see if it helps your idler issue, and redo it in black later. i personally dont even have the filament sensor turned on.

another thing worth checking... is your drive gear properly attached? is the setscrew fully engaged holding it to the motor drive shaft? i personally did NOT tighten my x-axis gears fully, and i had some sloppy x-axis distortion on my first few prints. slightly different issue but its a possible thing to check if its not making consistent engagement with the drive shaft. and if you're going to go in there and check/adjust that, make sure the filament is feeding straight in to the groove on the gear. and be careful with that tiny set screw... i'v only touching mine twice and it already feels like its starting to strip the hex fitting.

and since you said you would retension back to flush, i think thats too tight. my screws stick out about 1mm from the plastic, on the screw head side. so, ALMOST flush.

i know it doesnt help you but my build experience so far has been pretty problem free. aside from my clicking, which i think was my fault when i started messing with the screw tension, i was having full print success from the first time i turned it on. so, not to say that you made a mistake, but perhaps you did overlook something while building.

there are others on here much more qualified to help you trouble shoot this. sorry i cant help more, but i think those are the only additional suggestions i can make with my limited knowledge.

Posted : 29/07/2018 3:45 pm
Zinga
(@zinga)
Trusted Member


If you do try the new method id be interested to hear how you found it. I will stick with my almost-flush method for now.... no reason to change until i see a problem i guess.

This is the video you were going off of right?

Posted : 31/07/2018 12:37 am
Eikonic
(@eikonic)
Eminent Member

thats the one.

Posted : 31/07/2018 1:36 am
bobtiki
(@bobtiki)
Active Member


Does your idler spin (very) freely if you flick it? Even with barely any tension, if filament is moving through the gears your idler should spin.

Zinga, is this while the extruder is actually pushing filament, that the idler should be able to spin freely, independently of the movement of the filament? (That doesn't seem right to me, so maybe I misunderstand.)

My problem is similar, though to me it looks like the gear end of the idler doesn't mesh with the drive gear. So either it's a little loose, and it spins at an irregular rate, and occasionally clicks, disrupting the extruder flow; or if I tighten it too much, seems to spin at a regular rate part of the time, until it jams against… something, and it jumps forward and "clicks," again disrupting the extruder flow. There doesn't seem to be a happy medium.

If I follow the directions in the video to stop tightening as soon as it starts extruding, it looks like it slips more, and it isn't pushing the amount of filament it's supposed to.

Any idea how can I fix this? It seemed to have been working fine when I had the heads flush with the extruder body before, when I first assembled the printer, but now… nope. Maybe it's because I adjusted the position of the drive gear on the shaft? But I moved it more in line with the filament path… or at least I thought so.

Posted : 27/12/2018 10:41 pm
Zinga
(@zinga)
Trusted Member

The idler should spin freely when the door is open and it's not touching anything else. The second part was about Eikonic saying his idler wasn't spinning when there was filament running through it.

Maybe your extruder didn't come out quite right? The pulley on the extruder motor and the idler should be very close, but not touching, the plastic extruder body.

Posted : 28/12/2018 6:00 am
bobtiki
(@bobtiki)
Active Member

I seemed to have reached a happy medium again. It seems the best position (for me) is when the tension screw heads are flush with the body while the filament is already loaded, not when there is no filament, which perhaps led to my confusion.

Posted : 03/01/2019 2:15 am
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