MMU2S filament tips on unload
Just wondering if there is a place to find out how best to dial in filament tips. The handbook shows three examples and sais to adjust temp and possibly the unload stats in slicer but doesn't really say what to change in regard to temps for the two bad examples.
RE: MMU2S filament tips on unload
Same here, I just keep poking at those settings but I am not sure what I am doing? I need to control 20-25mm strings
RE: MMU2S filament tips on unload
I would love to hear the solution to this. I am in the same situation. Stringy tips that lead to loading and unloading errors. I've messed with temps, cooling moves, unloading speeds, etc. What is the secret. I use Hatchbox PLA. Is that the problem? I also use the Verbatim BVOH which seems impossible.
RE: MMU2S filament tips on unload
I think that I am getting closer. Here is what I have found to work so far.
Test print:
5 color "cuddling owls" at 50%. 501 tool changes.
https://www.thingiverse.com/thing:3033775
Environment:
All five filaments are eSun PLA+.
MMU2S, MK3S, Octoprint
Before the last firmware upgrade, a successful print was next to impossible due to poor recovery from load/unload failures and incompatibility with Octoprint. Lots of headless owls...
After the last firmware upgrade and latest Octoprint, the first print had 13 unload errors and 4 load errors, but recovery worked and the print completed without losing a layer! 3.4% failure rate (17 errors / 501 tool changes). The filament profile is printing at 225 degrees. The filament ends were rather thick and a little bit stringy. When fixing the unload errors, it was difficult to pull the filament out of the print head through the tube. The MMU2s couldn't pull the filament from the print head and ended up grinding the filament. When fixing the error, you need to make sure to pull the filament out of the MMU2s past the grind point, cut, and reload.
We have been using the auto-rewind spool holders and printed five of them (one for each filament).
https://www.thingiverse.com/thing:3338467
However, after about 3 months of using them, the springs are no longer reliable. Sometimes the clutch doesn't release correctly at low clutch setting and sometimes they don't have enough pull to fully retract the filament. It is likely that some of the load errors were due to the filament being pulled out of the MMU2s because of too much back pull from the auto-rewind spool holders.
For the next print, the temperature was dropped to 215 degrees. Also, the auto-rewind spool holders were replaced with the Prusa filament buffer. Result was 4 unload errors and 2 load errors (1.2% failure rate). Recovery worked and not a layer was lost. Ends of filament look less stringy.
The goal is to be able to "fire and forget" a five color print and have it just work. Tweaking will continue. If others have learned tips and tricks to help decrease load/unload errors, it would be great to hear about them.
- Brad
RE: MMU2S filament tips on unload
For the next print, the temperature was dropped to 215 degrees. Also, the auto-rewind spool holders were replaced with the Prusa filament buffer. Result was 4 unload errors and 2 load errors (1.2% failure rate). Recovery worked and not a layer was lost. Ends of filament look less stringy.
Ramming at a different temperature (than printing) can be crucial. You can see that Prusa is aware of this by comparing the Prusament PLA stock Slicer settings (215 without MMU and 205 with MMU).
However, PrusaSlicer is missing the functionality to ram at a different temperature than the one you set for printing. There are two solutions to this. 1: Print at temperature that is best for ramming (good filament tips) but print quality might suffer. 2: Use a script for the gcode like one of those two -> https://forum.prusa3d.com/forum/original-prusa-i3-mmu2s-mmu2-general-discussion-announcements-and-releases/script-to-drop-temperature-during-ramming/ and https://forum.prusa3d.com/forum/original-prusa-i3-mmu2s-mmu2-general-discussion-announcements-and-releases/mmu2-real-multi-material/#p127678
Setting a specific ramming temperature helped me to go from 95% success rate to > 99%.
RE: MMU2S filament tips on unload
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
RE: MMU2S filament tips on unload
In addition to using auto-rewind holders (more for space economy than anything else) and reducing drag as much as possible, I also saw the following suggestion:
Filament Settings > Advanced > Toolchange parameters with single extruder MM printers > Unloading speed at the start = 120mm/s
Between that and the drag reduction I've had 2 unload failures in the last roughly 1000 tool changes (and it was always when I had the tension on the rewinders set wrong for the weight of the spool). That is with using Amazon PLA, Inland PLA and PLA+, and SuperFila PLA. Sometimes there will still be minor stringing, but other than those 2 failures they have always been short enough that they got pulled back out of the way during the unload.
RE: MMU2S filament tips on unload
So far with me, when I set the unload speed to 120 mm/s and the number of cooling moves to 3 has reduced my print errors to zero using eSun PLA+.
Though after comparing filament tips between the first layer and the rest, I can see that the print temperature has a great effect on filament tips.
What would be cool would be a filament tip calibration procedure that tests different settings to get a perfect filament tip. It would try the unload, eject it and ask for user input on the result. It would repeat until it is dialed in.
Jonathan Kayne
Virginia Tech Class of 2021 - Electrical Engineering
Thingiverse Profile: https://www.thingiverse.com/jzkmath/about "I am always thinking about making. My future begins when I wake up and see the light." - Miles Davis
RE: MMU2S filament tips on unload
So far with me, when I set the unload speed to 120 mm/s and the number of cooling moves to 3 has reduced my print errors to zero using eSun PLA+.
Though after comparing filament tips between the first layer and the rest, I can see that the print temperature has a great effect on filament tips.
What would be cool would be a filament tip calibration procedure that tests different settings to get a perfect filament tip. It would try the unload, eject it and ask for user input on the result. It would repeat until it is dialed in.
Actually that wouldn't be too difficult (well, for a programmer that can script it).
- Slice a very small object (say 20x20x0.2mm) that has a single tool change in it and generate the gcode.
- Adjust settings as desired (probably doing one option at a time is best), reslice, and export the gcode.
- Compare the two files to see what is changing.
- Repeat 2 & 3 for each setting you want to play with.
That will give you the info on the GCODE commands needed and from there you could create a file that generated a print with as many tool changes as you felt needed to test setting groups. You could cycle through the tools in order so that when it moves to the next one you can pull the last one, clip the tip and label it, and then reinsert the filament before it has time to come back to that tool.
By cycling through the tools that would probably save a lot of time compared to "print, eject, remove, inspect, re-insert, rinse&repeat". Of course different filaments will respond differently so that may not be that effective...
RE: MMU2S filament tips on unload
I don't understand how I can have great tips on 20 filament changes then one with a tip 20 mm long. On different filament.
RE: MMU2S filament tips on unload
Doable... someone want to write the g-code? I'm just at the stage of assembling my printer and MMU, so I won't be able to even look at this for a while.
RE: MMU2S filament tips on unload
So far with me, when I set the unload speed to 120 mm/s and the number of cooling moves to 3 has reduced my print errors to zero using eSun PLA+.
Though after comparing filament tips between the first layer and the rest, I can see that the print temperature has a great effect on filament tips.
What would be cool would be a filament tip calibration procedure that tests different settings to get a perfect filament tip. It would try the unload, eject it and ask for user input on the result. It would repeat until it is dialed in.
Actually that wouldn't be too difficult (well, for a programmer that can script it).
- Slice a very small object (say 20x20x0.2mm) that has a single tool change in it and generate the gcode.
- Adjust settings as desired (probably doing one option at a time is best), reslice, and export the gcode.
- Compare the two files to see what is changing.
- Repeat 2 & 3 for each setting you want to play with.
That will give you the info on the GCODE commands needed and from there you could create a file that generated a print with as many tool changes as you felt needed to test setting groups. You could cycle through the tools in order so that when it moves to the next one you can pull the last one, clip the tip and label it, and then reinsert the filament before it has time to come back to that tool.
By cycling through the tools that would probably save a lot of time compared to "print, eject, remove, inspect, re-insert, rinse&repeat". Of course different filaments will respond differently so that may not be that effective...
What I am getting at is that the eject sequence, where the selector is moved over and the filament is pushed out could be implemented for the user to inspect. They would only need to clip the end and push it back into the MMU to continue the process.
The only issue with manually slicing a model is that I typically get different results on the first layer, due to the different temperature on the first layer. It is usually more stringy on the first layer, which really makes me wonder why the filament temperature change feature that is in skinnydip isn't implemented in PrusaSlicer yet. I do find that cooler temperatures result in better filament tips, but the print quality suffers slightly. (210 = good print quality, bad tips; 200 = okay print quality, almost perfect tips).
If they are concerned with space on the Rambo, why not just have a computer program that you use to calibrate it while tethered? It could do far more sophisticated things that could be sent as simple gcode commands.
Jonathan Kayne
Virginia Tech Class of 2021 - Electrical Engineering
Thingiverse Profile: https://www.thingiverse.com/jzkmath/about "I am always thinking about making. My future begins when I wake up and see the light." - Miles Davis
RE: MMU2S filament tips on unload
So far with me, when I set the unload speed to 120 mm/s and the number of cooling moves to 3 has reduced my print errors to zero using eSun PLA+.
Though after comparing filament tips between the first layer and the rest, I can see that the print temperature has a great effect on filament tips.
What would be cool would be a filament tip calibration procedure that tests different settings to get a perfect filament tip. It would try the unload, eject it and ask for user input on the result. It would repeat until it is dialed in.
Actually that wouldn't be too difficult (well, for a programmer that can script it).
- Slice a very small object (say 20x20x0.2mm) that has a single tool change in it and generate the gcode.
- Adjust settings as desired (probably doing one option at a time is best), reslice, and export the gcode.
- Compare the two files to see what is changing.
- Repeat 2 & 3 for each setting you want to play with.
That will give you the info on the GCODE commands needed and from there you could create a file that generated a print with as many tool changes as you felt needed to test setting groups. You could cycle through the tools in order so that when it moves to the next one you can pull the last one, clip the tip and label it, and then reinsert the filament before it has time to come back to that tool.
By cycling through the tools that would probably save a lot of time compared to "print, eject, remove, inspect, re-insert, rinse&repeat". Of course different filaments will respond differently so that may not be that effective...
What I am getting at is that the eject sequence, where the selector is moved over and the filament is pushed out could be implemented for the user to inspect. They would only need to clip the end and push it back into the MMU to continue the process.
Yes. There is another thread (and a few others I've linked to it) where I delved into the MMU firmware and found a raft of undocumented gcode commands (U = unload, L = load, K = cut, etc..) that would do exactly what is desired.
I wouldn't try to advance filament after moving the selector as that could lead to trouble. The user simply pulling the filament out (admittedly this is more difficult in some situations (long PTFEs into the buffer) than others (filament going into short tubes directly into the MMU)) would be the easier route.
If they are concerned with space on the Rambo, why not just have a computer program that you use to calibrate it while tethered? It could do far more sophisticated things that could be sent as simple gcode commands.
All the boards are doing is translating gcode commands into action. Everything that happens (e.g. command from the LCD menu) is the result of gcode being sent and processed. PrusaSlicer offers multiple areas where you can inject your own gcode and for more advanced customization it will automatically run a custom post processor where you write a tool to read and change the gcode as needed.
My only point in my original post was to outline how someone could track down the gcode definition for "Unload speed at start" at 100mm/s vs 120mm/s (or other settings they want to test) so that they could then write a script that would generate tests with different values. Think of it similar to a temp tower, just with different settings.
RE: MMU2S filament tips on unload
I wouldn't try to advance filament after moving the selector as that could lead to trouble. The user simply pulling the filament out (admittedly this is more difficult in some situations (long PTFEs into the buffer) than others (filament going into short tubes directly into the MMU)) would be the easier route.
Actually that idea I had was from a behavior that the MMU2S already does. If I am not mistaken it does this "moving the selector" option when it detects a filament runout, because otherwise the user wouldn't be able to remove the filament that is between the now empty spool and the MMU2S. It allows the user to remove the 10 cm or so of remaining filament. They might have removed this, but to me this was how the MMU2 does a filament eject.
Simply eject the filament, inspect, trim the end and push it back into the unit.
At the end of the day, it just seems that there is far more of an issue in calibration than in assembly of the MMU2S, if the forums are any indication of this.
Jonathan Kayne
Virginia Tech Class of 2021 - Electrical Engineering
Thingiverse Profile: https://www.thingiverse.com/jzkmath/about "I am always thinking about making. My future begins when I wake up and see the light." - Miles Davis
RE: MMU2S filament tips on unload
Recently I came across this feature request on github for the mmu2 -> https://github.com/prusa3d/PrusaSlicer/issues/2385?fbclid=IwAR2k_ybOARu8ktooSCckn82S8U67Dg1XQA7yE5gs2N44d93snG90tDn_IPI
Some one working at Prusa did some testing and concluded that lowering the temperature during ramming (or setting specific temperature for ramming) does not improve the tips.
He made even some photos of his tips and posted them.
Long story short: Prusa is not implementing this because apparently, they think it doesn’t help to improve tips.
RE: MMU2S filament tips on unload
I am not sure where to post this but i'm getting increasin frustrated with not being able to tune my MMU2S efficiently so I have started working a gcode script that doesnt print anything but simply changes between filaments over and over. The idea being that we can experiment with various settings including skinnydipping, dribbling, temperature changes (Slic3r++ & PrusaSlicer-Dribbling) etc relatively easily. I am no g-code wiz but have manged to get the script basically working and easily adjsutable BUT the g-code is not doing what it should/what I expect it should do. Its is pasted below, not sure how to attach files... The tuning of the MMU2S system is filament and time intensive and the typical problems are not around what exits the nozzle, the problems are between the MMU2S and the Extruder with funny tips & strings. The code below is essentially all the commands found in a MMU print but without the X,Y,Z movements, only extruder movements and hence the idea is to save time and filament without printing anything, just performing tool changes. The code can be copied, pasted & changed as many times with as many settings as desired to easily 'tune'.
If anyone can help diagnose, I am sure there are many of us that might benefit from something like this...
I have some problems in this code & I assume im missing something fundamental...
- Before the initial load (G1 E120 F250) is complete the printer is already trying to set the M109 S200 under first tool change - first skinny dip. I dont know how the gcode can skip ahead like this before a movement is complete...
- The same thing happens after T4 is selected (still first tool change), when G1 E120 F250 is activated, the tool change #2 temperature reduction is already being actioned.
- Tool change #1 extraction from nozzle is done however Tool change #2 is not done at all, in fact the printer goes straight to G1 E-35.0000 F2000 and of course I end up with long strings as its essentially riping the PVA out the nozzle without any extraction, cooling moves etc
M201 X1000 Y1000 Z1000 E8000 ; sets maximum accelerations, mm/sec^2
M203 X200 Y200 Z12 E150 ; sets maximum feedrates, mm/sec
M204 P1250 R1250 T1250 ; sets acceleration (P, T) and retract acceleration (R), mm/sec^2
M205 X8.00 Y8.00 Z0.40 E1.50 ; sets the jerk limits, mm/sec
M205 S0 T0 ; sets the minimum extruding and travel feed rate, mm/sec
M107
M862.3 P "MK3SMMU2S" ; printer model check
M862.1 P0.4 ; nozzle diameter check
M115 U3.8.1 ; tell printer latest fw version
G90 ; use absolute coordinates
M83 ; extruder relative mode
M109 S245 ; set extruder temp
G28 W ; home all without mesh bed level
G21 ; set units to millimeters
M900 K45 ; Filament gcode
; Send the filament type to the MMU2.0 unit.
; E stands for extruder number, F stands for filament type (0: default; 1:flex; 2: PVA)
M403 E0 F0
M403 E1 F0
M403 E2 F0
M403 E3 F0
M403 E4 F2
; go to approx centre of volume
G0 X125 Y5 Z150
; select extruder
T0
; initial load
G1 E120 F250
G1 E1 F250
M221 S95
G92 E0.0
G21 ; set units to millimeters
G90 ; use absolute coordinates
M83 ; use relative distances for extrusion
;--------------------
; CP TOOLCHANGE START
; toolchange #1
; material : PET -> PVA
;--------------------
; CP TOOLCHANGE UNLOAD
M106 S255 ; Part fan on to cool hotend
M109 S200 ; SKINNYDIP TOOLCHANGE WAIT FOR TEMP NORMAL MODE
M106 S0 ; Fan off
M300 S2000 P1000 ; BEEP WHEN EXTRACTING
G1 E-15.0000 F9000
G1 E-24.5000 F1200
G1 E-7.0000 F600
G1 E-3.5000 F360
; This is the cooling moves
G1 E20.0000 F600
G1 E-20.0000
G1 E20.0000
G1 E-20.0000
; This is the filament extraction from extruder
G1 E-35.0000 F2000
M109 S245 ; RESTORE PRE-TOOLCHANGE TEMP NORMAL MODE
T4 ; Selects extruder 5
G92 E0
M109 S205 ; RESET THE FILAMENT PRINT TEMEPERATURE FOR NEXT FILAMENT
; EXTRUDE SOME MATERIAL TO PURGE NOZZLE - THIS WOULD NORMALLY BE DONE IN WIPE TOWER
G1 E120 F250
G1 E1 F250
; CP TOOLCHANGE END
;-------------------------------------------------------------------------------------------------------------------------------
; CP TOOLCHANGE START
; toolchange #2
; material : PVA -> PET
;--------------------
; CP TOOLCHANGE UNLOAD
M106 S255 ; Part fan on to cool hotend
M109 S170 ; SKINNYDIP TOOLCHANGE WAIT FOR TEMP NORMAL MODE
M106 S0 ; Fan off
M300 S2000 P100 ; BEEP WHEN EXTRACTING
G1 E-15.0000 F9000
G1 E-24.5000 F1200
G1 E-7.0000 F600
G1 E-3.5000 F360
; This is the cooling moves
G1 E20.0000 F600
G1 E-20.0000
G1 E20.0000
G1 E-20.0000
; This is the filament extraction from extruder
G1 E-35.0000 F2000
M109 S205 ; RESTORE PRE-TOOLCHANGE TEMP NORMAL MODE
T0 ; Selects extruder 1
G92 E0
M109 S245 ; RESET THE FILAMENT PRINT TEMEPERATURE
; EXTRUDE SOME MATERIAL TO PURGE NOZZLE - THIS WOULD NORMALLY BE DONE IN WIPE TOWER
G1 E120 F250
G1 E1 F250
; CP TOOLCHANGE END
M104 S0 ; turn off temperature
M702 C ; FINAL Unload FILAMENT
M84 ; disable motors
RE: MMU2S filament tips on unload
Oh, a few more things:
- The forums are helping a heap more than Prusa's manual/tips
- Temperature reduction on filament change works, it makes logical sense and I believe its possible to get rid of ramming completely
- I have the selector magnet MOD - a must have
- One or two other minor mods to smooth the filament flow paths
- Latest firmwares etc as of 25/11/2019
- I am not going to give up on PET and PVA
- I am also not going to give up on reducing my print temperatures. My current temperatures are there for a reason, to get good layer adhesion.
- The IR sensor is super finniky, some filaments work, some cause the sensor to flicker 1/0 and I cant move the chimney thing over any more - anotehr mod is required.
- The current firmware has an error in reporting the Finda probe status. The moment a print is started & fails it doesnt update the LCD screen which leads everyone on a wild goose chase and I'm sure its costing Prusa money because they are surely sending out free Finda proxy sensors left/right & centre.
RE: MMU2S filament tips on unload
This is a filament setting suggestion for the MMU2s upgrade. I have spent nearly three months trying to "tune" the filament to consistently work well (and work consistently). I have tried everything from the Prusa website as well as many, many other forums and sites. I have finally landed on a set of settings that I have been able to use on all of my materials (mostly Prusament), including soluble BOVH, with several hundred material changes in each print. So far, with these settings, I haven't been able to get it to fail due to material load/tip issues. I wish I had this day 1 because it has been a very frustrating journey to get here. I didn't come up with these settings on my own, but found them in a post in a random forum, with a link to a youtube video starting and was instructed to watch starting at 8:00 min into the video. It is buried, random, and unconventional but I was grasping at anything to find something that worked consistently... and it works so well I can't believe it was so hard to find. If I can find it again I'll post credit here as it was definitely not mine.
Key things:
Filament Settings > Advanced > Toolchange parameters with single extruder MM printers:
Unloading speed at the start: 140mm/s (Rip that filament out of the hot end fast)
Unloading speed: 90mm/s (Rip that filament out of the hot end fast)
(Increased cooling moves/ramming)
Number of cooling moves: 3 (or 4 for BVOH)
Speed of the first cooling move: 20mm/s
Speed of the last cooling move: 10 mm/s
Ramming parameters: Total ramming time(s): 4.50
Filament Temps: In general, I use lower temps on all filaments as suggested as well (LSL of spec limits of each filament). I tried doing this without the above settings but my prints still resulted in absolute failure. For extra adhesion on the first layer, I violate the spec limits (80C bed temp for first layer) and have almost eliminated all adhesion issues.
Random Crash Prevention: This isnt necessarily related to MMU2s, but I also had an issue of random "crashes" mid print (but at the same time/location on each part), but with no external indications of an actual crash. I could sometimes get it to go away when I moved the part to a different area of the print bet and re-sliced, but not always.
I lowered my movement acceleration across the board to fix this, not necessarily the print speed. (Printer settings > maximum accelerations > 800mm/s2 or less except for extruder acceleration; Jerk limits > X/Y: 4mm/s max; Z: .4 mm/s; E: 1.5mm/s). Haven't had an issue with random crashes since I made this change.
Spool Holders: I use the auto-rewind spool holders from thingiverse for all 5 materials (no buffer box). These work flawlessly if they are attached directly to the long PTFE tubes supplied with the MMU2s unit.
My printer is now a "Set it and forget it" machine. I don't worry about coming back to failed tool changes, filament grinding, or anything else. I nearly gave up on the MMU2s... this set of settings saved it for me.
Just thought I'd post this in case others had the same issues as I have. If anyone needs to know more detailed settings let me know.. I know I was fairly general in the description.
RE: MMU2S filament tips on unload
@mike-zoll
Thank you Mike. I will give them a try. I haven't played with the MMU lately. Doing other things.
I have started using a hot end stepper fan lately, found online. It made logical sense that a stepper too hot to touch would transfer some of that heat to the filament. Perhaps effecting loading and retraction.
Thanks again to you and all the pioneer printers out there. This is a cool hobby. One big puzzle 🤔
RE: MMU2S filament tips on unload
Just to add a different picture: My tips all are crappy. PETG and PLA. They are so crappy and stringy that I need to cut them before pulling them back through the pulley body. BUT, the MMU itself and all prints are fine anyways. So tips aren't necessarily a problem. What you need is an open idler, an active extruder fan, and for convenience a LED indicator at the IR sensor. Sorry, that I put it so harsh: Proper tips might help you, but they aren't the cause of problems with the MMUs. As I stated this quite often: A week on two MMUs equal's 20000 filament changes and I usually have zero-three loading issues nowadays per week, but whenever I change filament 100% of them have tips that I can't pull backwards.
PS: I always use +5 °C on the standard Prusament settings.