List of my Fixes for the MMU2S
After a lot of work I got my MMU2S to run reliably. I've run a number of prints recently up to 14 hours long with worst case 1 user intervention. To achieve that I had to do a lot work to sort it out. As a result I wrote down my list of fixes and I thought I would put them up in case any of these help any body else who are having issues similar to mine.
- Check that the hot end PTFE tube is correct ID. Should be 1.85 – I found mine was larger ~2.0mm and was causing the tip to be too large.
- I suggest adding a “C” Clip to the hot end PTFE Tube. I found mine was moving in operation and causing a clicking noise in the extruder. It was also the probable cause of extrusion issues I had once when I tried to run a single filament print which I had to stop because it wasn't extruding properly.
- It is essential to check that the filament can pass easily through all PTFE Tubes and the MMU2S Unit as per the instructions. I found the following problems:
- PTFE tubes between the Buffer and the MMU2S unit were rubbish. They appeared to have manufacturing marks. One was so badly damaged filament could not even manually pass through before installation. I ended up replacing all with larger diameter (3.0mm ID) in order to get the filament to pass without restriction.
- I found that the ID of the 5 PTFE Tubes in the MMU2S PTFE Holder were too small for the tips of filaments to pass through when being unloaded from the hot end for filament changes – the tip actually sits in these tubes when not in use. 2 options:
- Replace with larger ID PTFE
- Ease out with 2.0mm hex key until tip passes through without any restriction.
I used option 2 which helped greatly resolved loading/unloading failures.
- The IR sensor needs to be correctly set up. I actually found the instructions a bit misleading as I had to move mine right instead of left (as noted in the instructions) to get it to work correctly. I also found it had to be rechecked when in actually in operation as although it was working as per the manual (Section 7.1), it was still giving errors in operation. I’ve added another note below.
- I would recommend replacing Selector. I used this one ( http://www.thingiverse.com/thing:3688458 ) – many thanks to the designer. This uses a magnet to reduce false FINDA readings and opens up the FINDA Channel improving filament feeding operation.
Once you are ready to use the MMU2S I would suggest doing the following checks in addition to calibrations noted in the manual. Avoid the temptation to start printing straight away unless you want a lot of frustration.
- Load all filaments. Then load all filaments to the nozzle. Ensure that the filaments all load first go and extrude correctly. If they don’t you will need to trouble shoot until they do. I would recommend cycling between feeding all 5 filaments to the nozzle and not to consider attempting a print until they all load correctly first attempt.
I now run all filaments I’m going to use to the nozzle and then cycle through running them to the nozzle at least once before commencing a print to ensure that they are all loading correctly. - Whilst loading the filaments I recommend rechecking the operation of the IR sensor. Do this by going to the LCD menu – Support- Sensor info.
Check that the PINDA sensor correctly changes from “0” to “1” upon loading to the nozzle and back when unloading.
I found that despite being set as per the manual mine was initially flickering between “1” and “0”. It must change positively between the 2 and if flickering needs further adjustment until it operates correctly. - During operation check that all filaments are feeding from the spool etc without catching anywhere.
- In operation remember to clean out the MMU2S unit after every print as it builds up scraps of filament from stringing etc. Suggest using a can of spray duster or similar plus brush. Also check to make sure that there are no strings caught in the PDFE tube between the extruder and the MMU2S Unit. I also recommend opening the extruder idler to ensure that there are no strings etc.
Hope this is of assistance to somebody.
RE: List of my Fixes for the MMU2S
"I found that despite being set as per the manual mine was initially flickering between “1” and “0”. It must change positively between the 2 and if flickering needs further adjustment until it operates correctly."
I've seen when the extruder motor runs it's possible that the idler that blocks the IR sensor can sometimes go in and our and trigger false positives or negatives. Very temperamental.
RE: List of my Fixes for the MMU2S
Yes, that's what I found. When I was trying to get the MMU2S to work initially I kept getting "User Intervention Required" a lot.
When I then kept testing by "Loading to Nozzle" and watching the PINDA settings as the filament loaded/unloaded, I found it was giving false values (positive/negative) as you noted. I then kept adjusting it until the false values stopped. This reduced the number of user interventions significantly.
I suspect that this could be a major issues a lot of people are having which is why I thought I would post it.
RE: List of my Fixes for the MMU2S
The LED mod for the IR sensor is exceedingly helpful for knowing your IR status without having to have access to the menu (like when a tool change fails in the middle of a print).
My recommendation for sorting the IR sensor out is to disconnect the MMU and get through an entire test print (I use a 20x20x20 cube) with the IR sensor enabled and no false run out events. This better isolates issues so you aren't trying to guess where problems might be.
RE: List of my Fixes for the MMU2S
I considered the LED mod for the IR sensor but managed to get it to run properly before I needed to do it. The LEDs on the FINDA and PINDAs make them easier to troubleshoot. I was a bit nervous about soldering the LED because it I damaged the IR sensor getting replacements here takes a while.
Ultimately I think getting the MMU2S to work successfully comes down to working through the issues one at a time as you suggested. That reduces the guess work.
I was also wondering if it was worth getting a Rasberry PI and setting up Octoprint. Is the status of the IR sensor etc displayed by Octoprint on the web interface? If so that would have made troubleshooting a lot easier.
RE: List of my Fixes for the MMU2S
as far as the IR sensor goes, I bought a replacement before I started trying to modify the original, and the replacement worked without modification...
guess the tolerances are a bit fine!
Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: List of my Fixes for the MMU2S
Yes, it makes sense to have a spare ordered - it would take me a lot longer to get a replacement delivered here in Australia than to the UK.
I agree that the tolerances are a bit fine. I seems reading the various posts that everybody seems to have a slightly different adjustment to get it to work.
I read the link that Gnat provided in a previous post and that provided some useful information. It would be nice to see more information like that included in one place such as the Handbook to assist people to set theirs up. I feel that whilst the assembly manual and handbook are pretty good, they don't have enough information on how to actually set up once assembled and then work through any issues such as these. A step by step procedure would be nice.
RE: List of my Fixes for the MMU2S
I'd like to see a quick release on the MMU2 for easier cleaning and troubleshooting of the Bondtech gears.
I also think the area below the selector and Bondtech gears could be open to allow chaff and stringie's etc to fall out.
The short tubes in the selector mech where crap. ID too small and ovoid instead of round.
The screws loosening on the idler body needs to be fixed as well.
The holes into the pulley body on the outgoing side of the Bondtech gears need a larger bevel as the filament can hang up there (as mine has) to be ground away by the gears.
larger ID tubes needed between the buffer and MMU2 to decrease resistance.
I recommend this mod as my tubes started pushing out of the MMU2: https://www.prusaprinters.org/prints/6605-prusa-mmu2-ptfe-holder-m10-passthrough-adapter
I think the bend is too sharp on the tube between selector and extruder.
I am not an engineer or an artist. I am a bit of a designer that does a little of both.