Pulleys lost grip  

Re: Pulleys lost grip

if you open up the hinged cover then you could clean it with a brass brush. brass is a softer metal so it should not damage the pulleys.

Re: Pulleys lost grip

And to help prevent this happening, set the initial load to 19 mm/s so that the speed of the two drives is matched.

I use a pen knife to clean out the gears, individually and very carefully.

Peter

Re: Pulleys lost grip

Thank you both

I will try both solutions and report back

It was pretty late last night I need to take some time to focus on this
Hope to be back operational again soon, as I like the MMU2 a lot 🙂

Re: Pulleys lost grip

Uffff

Seems I lost channel 3 😕

After cleaning the pulleys I checked if there is any friction in the system.
Everything is smooth just for channel 3 I can´t move the filament through the selector 😳
When I push filement from the extruder site into channel 3 down to the white tubes, there is no friction.
Do I push filament after the pulley into the selector, no friction either. When I push it up to the pulley, no friction
Just when I try to push it from spool holder to selector in 80% I can´t even force it into the selector manually
I disassembled the selector and checked the the path. The little white tube before the selector for channel 3 looks
like any other tube

It looks like this causes also the rubbed of parts of filament on pulley 3

I have no further idea, any help is highly welcome

Re: Pulleys lost grip

did the pulley set screw come loose and it is just spinning on the shaft
does the bearing in the selector assembly look damaged is it still centered on the pulley teeth.

Re: Pulleys lost grip

The pulley is rock solid, also the bearing is not damaged

Loooks like the calibration is not spot on for channel 3 anymore

I can pull manually any filament through the selector to the orange tube
Just for channel 3 it get stuck at the selector. Do I pull it from the extruder side it goes smooth
also from channel 3

When I feel it hits the selector, I switch off the printer and turn the rod of the selector 10-15°,
then I can pull it in without any resitance

As it is working for channel 1,2,4,5 how can I calibrate it for channel 3 ?

Re: Pulleys lost grip

the only thing i can think of is the selector is binding on something around #3
move the selector to 1 or 5 and look around 3 and see if something looks wrong.

Re: Pulleys lost grip

see if any of the 3mm bolts are loose on the threaded nut or the motor body.

Re: Pulleys lost grip

After one day to calm down, I disassembled the unit 😮

Indeed one of the screws for the lead screw nut of the slector was not screwed into the nut (Step 15 2nd picture)
Looks like the thread of the nut was damaged. I put a new one in
Not sure if this was the issue as the screw was not really loose and it worked for more than 1k changes as mentioned in my opening post

Testing now :geek:

Re: Pulleys lost grip

i toyed with the idea of using thread lock on the hex and square nuts since over time i have had a few come loose on mk2s and the mk3 before mmu2 conversion. the vibration of the machine combined with heating and cooling cycles can start to back out a bolt.

Re: Pulleys lost grip

OK, looks like I´m back in the multi color game

The print took about 6h and involved about 200 color changes
Thus I feel comfortable to start my prints (2 colors, about 140 changes; 12h) again

Thank you very much first of all for the support I received in the forum, specifically daniel.a6

What was the root cause?

I think it was not the not screwed in M3x10 (Instruction step 18, picture 2+3)
Once I re-assembled the unit after changing the nut with a new one (Instruction step 15, picture 2),
the channel not working anymore was 4 instead of channel 3 before re-assembly 😯

The observation was the same. Filament could be introduced from the hotend direction without any issue.
When I tried from the spool holder end there was no chance. It looked like the channel (3 first, 4 after reasembly)
was slightly misaligned thus the filament got stuck at the selector or went into any direction but the selector itself.
By chance I noticed I could easyly introduce the filament opening the pulley body and start from after the pulley.

I assume it was a misalignment of the pulleys itself. Even if it worked for more than 1k changes over several weeks
and the pulley screws were not loose.

After repeating step 11 pulley adjustment very carefully several times (<0.25 mm changes 😳 ), getting the right tension on the spring screws (instruction step 34) and re-calibrating the filament length very carefully.... it worked

I like tinkering around with things not working, but I´m under "pressure" to get about 20 prints done before 6th of December.
Thus this was a frustrating exercise to loose about a week. Hope the lessons learned will be usefull for somebody else

Re: Pulleys lost grip

we try, it is so hard to diagnose something through texts and a few photos. i had one pulley walk a little and i went and re-adjusted and re-tightened it.
everything on the machine is basically going through heat cycles, hot/cold, expand/contract. things that were tight get loose. usually before i start up i kind of check over the machine and check some areas with an allen key.

i had my MK3 frame get loose twice before i thread locked those 3mm Button head bolts, even when i cranked them down they would just get lose.

Re: Pulleys lost grip

And to help prevent this happening, set the initial load to 19 mm/s so that the speed of the two drives is matched.

Peter

Hello Peter!
I've got my MMU2 last Friday 😎
But where do I set this initial load speeds? Either I'm blind or they are very well hidden.

Thanks a lot!

Re: Pulleys lost grip

But where do I set this initial load speeds?

Slic3r, Filament settings tab, select "Advanced". The field label is "Loading speed at the start" and the default value is 3.

You will have to set this for all your filaments.

Peter

Re: Pulleys lost grip

Thanks a lot! 😎