MMU2S PETG Torture test
I just finished a 1000 tool change test with the new MK3S/MMU2S uprade https://www.thingiverse.com/thing:3192133 , what a great improvement, goodbye skipped layers, goodbye filament grinding.
Of course I encountered some load/unload issues due to strings with PETG, but nothing else, I can reach near-zero string when lowering temperature but it starts to under-extrude.
Since I print mainly with PETG I'm used to deal with strings and I made some modifications to the filament path.
These days I did not use anymore the MMU2, because it was not reliable and I was tired wasting filament for nothing, but this test changed my mind.
MK4/MMU3 - VORON 2.4 350 Stealthburner
RE: MMU2S PETG Torture test
Care to comment on the filament path mods you've done? Any settings tweaks requrired? What do you think about Nicolai's ramming settings for PETG?
I'm about to receive a MMU2S in two weeks. (Keeping fingers crossed.) So I'm looking for any experience with printing non-PLA materials with it.
RE: MMU2S PETG Torture test
Hi vojtech-p6,
I have similar setting as Nicolai, but actually the default settings in the last Slic3rPE works for the PETG brand I use, just increased ramming to 4, 9 time on 10 I get a perfect tip, and the 10th is stringing for unknow reasons. You must try by yourself, there are no magic settings.
For the filament path I use PTFE tubes with 2.5mm inner diameter between spools and MMU, the same between MMU and extruder, I use a selector like this https://www.thingiverse.com/thing:3310038 and redesinged the extruder https://www.thingiverse.com/thing:3467644 .
Regards.
MK4/MMU3 - VORON 2.4 350 Stealthburner
RE: MMU2S PETG Torture test
Increasing the inner diameter of the PTFE tubes makes a huge difference, I have read. I just received my MMU2 (and am waiting for the sensor cable to be shipped, it was missed in the kit) and I had purchased larger inner diamater tubing ahead of time. Pushing filament though it is smooth as silk, but I feel some drag when using the default tubes from Prusa.
RE: MMU2S PETG Torture test
I have been trying to reliably print 2 colours PETG with the MMU2S for about 18 months and today finally worked out what I think is a pretty good system. My settings:
1. 260 degrees Celsius (low temperature PETG is unacceptable for the product I print and sell as it has a dull surface)
2. Ramming off (set the ramming time to 0 seconds)
3. Printer settings > Cooling tube position 15mm, Extra loading distance -14mm
4. All cooling off (if you must, just 10% fan on bridges and for very short print time layers you might need auto cooling)
5. Filament settings > Advanced > Unloading speed at the start 200mm/s, Unloading speed 2mm/s, Number of cooling moves 0
Leave other MMU2S settings as they have been set by Prusa.
I should say too I have a Mk3S with mosquito v 2 hotend (sooooo much better than e3d v3 for nozzle changes and also a more sudden heat change between the block and cooling tube) and prusament PC blend hot end parts. MMU2S razor is not installed.
My theory is that all ramming is bad for PETG. PETG is very goopy and any ramming at all increases the changes of fat tips failing to load. Instead, you want to rip the filament out at 200mm/s for 15mm then slow to 2mm/s and draw it up slowly so the tip cools before it could be squished by the extruder cog. Cooling moves are bad because they make the tip squished. There will be a little string but it will be short (about 15mm) and straight and almost never cause need for manual trimming. After the 200mm/s movement, the string cools fast enough to break off and stay short while moving at only 2mm/s.
These settings have been working so good I am considering buying another MMU2S for my other Mk3S. I am now printing MMU2S 2 colour PETG commercially and it is saving time where I used to have to glue 2 colours together.
RE: MMU2S PETG Torture test
I have been trying to reliably print 2 colours PETG with the MMU2S for about 18 months and today finally worked out what I think is a pretty good system. My settings:
1. 260 degrees Celsius (low temperature PETG is unacceptable for the product I print and sell as it has a dull surface)
2. Ramming off (set the ramming time to 0 seconds)
3. Printer settings > Cooling tube position 15mm, Extra loading distance -14mm
4. All cooling off (if you must, just 10% fan on bridges and for very short print time layers you might need auto cooling)
5. Filament settings > Advanced > Unloading speed at the start 200mm/s, Unloading speed 2mm/s, Number of cooling moves 0
Leave other MMU2S settings as they have been set by Prusa.
I should say too I have a Mk3S with mosquito v 2 hotend (sooooo much better than e3d v3 for nozzle changes and also a more sudden heat change between the block and cooling tube) and prusament PC blend hot end parts. MMU2S razor is not installed.
My theory is that all ramming is bad for PETG. PETG is very goopy and any ramming at all increases the changes of fat tips failing to load. Instead, you want to rip the filament out at 200mm/s for 15mm then slow to 2mm/s and draw it up slowly so the tip cools before it could be squished by the extruder cog. Cooling moves are bad because they make the tip squished. There will be a little string but it will be short (about 15mm) and straight and almost never cause need for manual trimming. After the 200mm/s movement, the string cools fast enough to break off and stay short while moving at only 2mm/s.
These settings have been working so good I am considering buying another MMU2S for my other Mk3S. I am now printing MMU2S 2 colour PETG commercially and it is saving time where I used to have to glue 2 colours together.
Still tweaking these settings, I've found Cooling tube position of 4mm, extra loading distance of -15mm and unload speed of 1mm/s are working even better. Tips don't 'creak' as they get forced back into the hot end (sometimes they did with the above settings). I've been printing esun white petg and prusament gold petg.
My theory is that the best Cooling tube position will be determined by the distance the filament needs to move to get from the molten plastic pool up to a spot where the tube is below the tg of the plastic, this 'necks' the filament without doing anything to fatten the tip. Then moving just 1mm/s means the plastic won't stick to the cooling tube, stops stringing, but also has time to cool down enough so that when it passes through the extruder cogs it won't get squished which could then cause a load failure later.
I would be really interested to know if the same methods work with an e3d v6 hot end, with petg and pla. I've always managed to unjam e3d hotends by blocking the fan technique (lots of videos about this on youtube) but if you ever jam a mosquito (only once thankfully they are very hard to jam) you will need an oven or blow torch. I used the kitchen oven at max temp and pushed some PC blend through it over and over again to get the petg out.
RE: MMU2S PETG Torture test
I just finished a 1000 tool change test with the new MK3S/MMU2S uprade https://www.thingiverse.com/thing:3192133 , what a great improvement, goodbye skipped layers, goodbye filament grinding.
Of course I encountered some load/unload issues due to strings with PETG, but nothing else, I can reach near-zero string when lowering temperature but it starts to under-extrude.
Since I print mainly with PETG I'm used to deal with strings and I made some modifications to the filament path.These days I did not use anymore the MMU2, because it was not reliable and I was tired wasting filament for nothing, but this test changed my mind.
Attachment removed
I just finished rebuilding my mmu2s with the new mk3+ parts and had similar results with this print with generic PLA. I had 0 failures, no filament grinding, layer skips, or any other bad behavior. In my opinion the MMU2S has become much more reliable with the latest parts and firmware.