Help please  

Re: Help please

well you didn't give much information.

i would guess you have the machine configured as is from prusa.

if that is the case then you have the standard Spool holders where the spool is riding on the metal axle shaft with the 2 bearings on either side.

these stock spool holders cause major problems.

you will want to convert them to these:
https://www.thingiverse.com/thing:3113520

these spool holders take a lot of friction out of the system allowing the calibration for the PTFE length to be more consistent and also help keep the filaments from stripping out on the pulleys.

next you will need to examine the system for any areas where the filament can get hung up. 2 most common areas are the selector body when the filament comes out of the spool TPFE tubes and enters into the body where the knife is. the entrance needs to be smooth and there should be a little taper to help guide the filament in smoothly.

next is down in the extruder you want to take the orange tube off and get some scrap filament pieces and stick them into the extruder manually with different shaped tips.( hand cut different angles from blunt to 45 degrees) carefully insert the filament multiple times and rotate the filament so that it enters the small white TPFE tube by the sensor at different angles. if you feel the filament hit something, gets hung up, hits something and then goes into the extruder pulleys then you need to clean up the entrance to the pulley carefully( i recommend a mini jewelers round file with a tapered tip) you carefully need to manual smooth and shape the entrance without opening up the bottom of the hole so that the filament glides nicely into the pulley.

the reason is any hangups of the filament cause the pulleys in the selector assembly and the extruder to strip out the filament and make a half moon in it where it completely loses traction. there is no overload clutch in the system. so if the filament skips the pulley chews into it and that makes it also lose step location. then the entire system gets out of time and it gets worse with each error until the filament totally jams.

additionally once the entire trip from the spools to the extruder is smooth and repeatable many times you have to tune the tension on the springs.
the upper assembly body is pretty unclean from the 3d printing and the springs can bind so you have to carefully clean out the slots on the 2 upper screws so that the assembly lid can properly float on the hinge otherwise it just binds and puts too much tension and the filament strips out.
you have to look at the traction marks on the filament and i find you have to go lighter on the initial settings so that the pulleys do not over grip the filament.

do one thing at the time. start with checking for problems with the filament having a nice free clear path to the extruder then retest and keep making adjustments one at a time.

Re: Help please

Thank You for your help.

I will start on the spool holders as these are indeed not very good and full of friction.

Then I will try the other suggestions.

Again thx I will continue to persevere and report back.

Re: Help please

my approach is the machine needs to have good mechanical timing and reduction of friction as much as possible.
so that the software can kind of catch the little things.

There are additional factors. some filaments could just not work well with the machine and many people have the unit in small cabinets with elaborate systems that replace the spools with a different system.

i use Hatchbox PLA. i have not even attempted PETG, nor have i tried soluble material on Spool 5 yet.

Re: Help please

Don't forget to calibrate and recalibrate the tube length for each tube.
Pay also attention how well the feeding is working. As already mentioned by Daniel, the are many places where the filament path might be an issue. You should see/hear where the issues occur.

Re: Help please

don't give up, after a week of adjustments I am finally up to 2000+ color changes no errors.

Re: Help please

All,

I have been struggling for a few weeks with my MMU2 on my Mk2.5.

Basically I can load all 5 filaments - which are Prusa filaments and kick off a print and it will run loading and unloading until it will fail at some point.

For instance I tried the 2 colour benchy with Filament 1 & 4.

It printed and changed colours maybe 10-15 times before it did not feed filament 4 in correctly. I fixed that by pushing the filament a little further manually to the extruder gears. So it continued but it did have some missing layers. Then filament 1 did the same thing - again I fixed it. It happily continued printing for maybe 30 minutes and then I had a flashing RED LED on Filament 1. I dont know if it was loading or unloading but I could not push the filament in at all.

I have printed (I have another MK2.5) another selector that has a better slot for the blade and fitted that. Tried the benchy again and the 3 colour gecko.
Again everything starts fine but fails after maybe 1 hour - usually with a flashing RED LED.

I dont know what to do now and I really need some help and advise from people who have their MMU's actually working. Maybe I just need to buy a Palette 2 for multi colour printing as I am not convinced MMU is good enough.

I would start out by watching the video MMU2 Troubleshooting 101: The Easy fixes by Chris Warkocki
It is full of good troubleshooting tips plus it helps you learn how the mmu works.

The video goes over the ways to check friction of the filament paths and ideas on how to reduce friction.
I was able to get the stock spool holders to work by removing the stock end caps and degreasing the bearings like you do for fidget spinners.

If you stick with it, you can get the MMU 2.0 to be able to print models with 500+ tool changes.
I have been able to print the "Prusa MMU2 Color Torture Test" serveral times without any skipped layers.
https://www.thingiverse.com/thing:3192133

As for the Palette2, it is just trading one kind of problem for another. Bottom line is multi-material printing is still hard to do.
If you do go down that path, get the Palette2 Pro with the all metal Splice Core Pro. Along with the Splice Core Pro, you get spare parts and 12 month service.

Re: Help please

Thanks Bruce.

I will try and get back to the MMU.. Kinda lost the will with it at the moment, but i know it will bug me till i sort it.

Going to start with upgrading the spool holders and then debug the filament path to the extruder.

Thanks again for your help & I dont want to throw more money down on the Palette 2 yet. I want to see how the users get on with them - they are just shipping.

Re: Help please

hey for testing you could just cut some filament so it's off the roll and see how well it works.

I bet at this point I can use my MMU with all 5 spools just on a shaft.(stainless steel) I will test this soon 😀

Re: Help please

And have a look at this mod:

https://shop.prusa3d.com/forum/general-discussion-announcements-and-releases-f53/mmu2-another-solution-for-layer-skipping-due-to-fi-t25334.html#p115345

It is a massive improvement for consistent loading of the filament

Re: Help please

Will have to try that mod also. I have adjusted my spool holders and tested the feed is smooth.

Tried 2 colour printing today and it failed again.

The main blue colour was feeding great for a good while but i noticed it missed a layer.

The problem is there is a gouge in the filament where its been trying too hard...Do I need to back off the selector screws a bit?

Anyway picture attached for review

Re: Help please

selector screws would be a good spot to start.

mine screws with filament loaded is about 2 or 3 mm recessed in.

Re: Help please

The problem is there is a gouge in the filament where its been trying too hard...Do I need to back off the selector screws a bit?

1. Watch your prints carefully and try to see why the layer is missing. Is it due to not loading far enough or get the filament stuck somewhere?
2. Gouge in the filament is no problem for me. Sometimes it's better to push harder instead of risk load/unload issues.

It's very important that you try to catch the moment where the issue occur. Just changing some settings hardware/software might help you in the first place but without the understanding what happened, you might will have issue with different color (same filament brand) or different brands.

Re: Help please

if the filament is passing the finda prob test, it's gotta be slowing down on something.