Introduction to printing with MMU
Hello all,
I purchased my MMU several months ago but only got around to putting it together last week. It has been a great experience, but I wish somebody had told me a few of the things that I've read piecemeal elsewhere or discovered for myself. I decided to put everything together that I wish somebody had told me. Feel free to take any of this content and distribute it as CC-By-SA. As background, I use GNU/Linux exclusively.
You are learning two skills: Bowden and multi-material
I have never printed with Bowden before, so while I was aware of the various problems (retraction, stringing, speeds), I had no personal experience with them. I suspect this is true for most MK2/S owners. This meant that in addition to learning about multi-material, I spent some time learning and experimenting with Bowden-related stuff.
This leads to the next point:
Your old MK2 is dead. Mourn it and move on.
Because of the Bowden component, I regressed significantly in my printing ability. Having mastered beautiful prints using the MK2, I was back to square one in terms of learning the printer, almost from scratch. This meant having to seriously re-examine the following:
I think a mental switch flicked for me when I realized "This isn't the MK2. This is the MK2 MMU". Once I thought of it as a new printer, I was able to start putting together how best to print with it.
Your Slic3r is dead. You have to use Prusa Slic3r.
This part irritated me the most. I use Slic3r from Git and expected that I should be able to load Prusa's config bundle without making Slic3r unusable. This is doubly irritating because Prusa's Slic3r is missing several features (for example send to print -> start print, renaming prints on octoprint, etc). I hope it doesn't become a habit of Prusa Research to fork and modify beyond reconciliation as they have done for both Marlin and now Slic3r. For now, Slic3r and Prusa Slic3r are functionally non-compatible if you want to import the config bundles for the MMU. Definitely you cannot go back and forth between the two as previously.
There is no fire and forget any more. You have to be there for every print.
You can't print an MMU print after another without some work
This wasn't obvious to me and I don't think I saw it in the manual. Here's the rule: After each print: Unload all filament, cut the end and reload all filament. This isn't as bad as it sounds, but it is definitely effort each time. Otherwise, filaments loaded into the chamber will collide with others that are meant to go in. There appears to be no way for the printer to figure out what filament is in there and 'reset' so it's ready to go. At the end of the print, the printer similarly doesn't unload the last filament and prepare for the next print.
Single mode still requires intervention.
The "T?" line of the G code in the "single mode" is asking which tool (aka extruder) you want to use and presents with a menu on the MK2MM. But even if you switch this, beware of switching between MM and single mode is a recipe for (a very minor) disaster without unloading/reloading the filament.
Calibration lines are your god now
If the calibration lines don't come out properly, don't print.
The Prusa team is trying to hint so heavily at this that they inserted a stop after calibration lines to ensure everything is well and encourage us to stick around and watch. It's my experience that on occasion, bad calibration lines don't equal a ruined print. However, the prints and the filament interactions are exponentially more complex than the MK2/S. Having printed extensively before, I thought the filament would purge and everything would be better later. Sometimes this is true. More often, when there's no calibration line, something else has gone wrong. Respect this.
Use good filament
As stated above, problems here aren't additive but synergistic. The small problem in that cheaper filament will probably ruin the print when multiplied by the small problems in other filament and the complexity of MK2MM. I use filaments.ca filament which works well. Some of my cheaper, older reprapper filament that was barely usable anyway is completely unusable now.
Multi-material objects are hard to find
I've found very few good resources:
I think that's it for my collation of things I wish I knew. Please let me know if there were other "I wish I knew" items for you and I'll include them for future beginners in MMU
tarek : )
Re: Introduction to printing with MMU
just found this post, excellent tips. Ive been struggling at times since the update as well
Re: Introduction to printing with MMU
I find this post kinda depressing. I'm trying to get a decent print with the MMU and only get clogs and other issues. If this post is true it seems there's no hope of getting back the reliability I had.
Re: Introduction to printing with MMU
I have a MK2S MMU, but I don't really do all that much multi-material printing. My issue is one mainly of materials compatibility and toolchain. I'd like to use PLA as a soluble support for ABS, but that doesn't seem well-supported and I'm unsure of how to tweak the thermal behavior.
On the other side, I'm not sure of a good toolchain to generate multi-material models. I've done only very basic stuff, though it has worked just fine.
Re: Introduction to printing with MMU
I have a MK2S MMU, but I don't really do all that much multi-material printing. My issue is one mainly of materials compatibility and toolchain. I'd like to use PLA as a soluble support for ABS, but that doesn't seem well-supported and I'm unsure of how to tweak the thermal behavior.
On the other side, I'm not sure of a good toolchain to generate multi-material models. I've done only very basic stuff, though it has worked just fine.
I don't think PLA will work as soluble support for ABS. For starters, PLA isn't all that easy to dissolve. Plus, it prints at different temperatures than ABS and doesn't bond well to it. I've read about using HIPS as soluble support for ABS, but I'm not sure how well that works either. There doesn't seem to be a lot of people who have actually done it.
Re: Introduction to printing with MMU
A long time ago, I used a Dimension uPrint that printed in ABS with PLA support - seemed to work pretty well. You had to dissolve the PLA in a sodium hydroxide bath.
Regardless, my bigger wonder is how to go about doing a good job of making colored models. What tool flow do folks use for that?
Re: Introduction to printing with MMU
Regardless, my bigger wonder is how to go about doing a good job of making colored models. What tool flow do folks use for that?
I usually design everything in Fusion360. I have one component for the base part (i.e. what the model will look like if you print in a single color), and then create new components for the areas which need to be different colors. That way I can export the base model as a single STL, and quickly export each additional component to get an STL for each color.
For slicing I load the base model in Slic3r, and then add each of the STLs for the colored areas as a part modifier (if you don't know how to do this: double click the part and then click "Load Modifier" in the window).
This lets me do customized stuff very quickly, since I don't need to rebuild all the STL files to change a name or logo. I keep the same base part, and just create a different STL for the text/logo/etc.
Re: Introduction to printing with MMU
is there any way to increase the contact between the first layer of the wipe tower and the hotbed? There is only a narrow brim, and, since the first print layer is often only one color, the wipe pattern is just the very low fill zigzag. This makes for a very fragile bond to the bed that often comes loose when the tower gets to be an inch or more tall. Thanks.
Re: Introduction to printing with MMU
Here are come comments in this thread. MMU is working fine for me, but it had unacceptable set of issues while
trying to get it to work.
#tarek.l
>>You can't print an MMU print after another without some work
I am printing it one after the other w/o unloading any filament. The older prusa slicers had profiles that did not park the last used filament.
You can check for the latest out--of-the box profiles. I had my own profiles that was based on buggy stuff prusa has shipped, you might have them in you settings. I only unload filament when I stop the print before it finishes via M702 C command or system menu.
#christopher.d3
>>is there any way to increase the contact between the first layer of the wipe tower and the hotbed
I dont think there is. I thought of adding it manually or via post processing.. A quick fix would be to apply the glue that comes with the MK2S at the wipe tower location. I had the same problem as well , it was also due to the insufficient filament flow at the first layer. My solution was to set the bowden tube length 10mm shorter via system reset menu.
This allowed me to have strong filament flow at the first layer. With those 2 changes I am regularly printing with full z-height of close 200mm. I have also changed the wipe tower dimensions to be 20mm x 20mm. This makes the layer change much faster, has good bed adhesion and works fine (enough) for the filaments I regularly use.
#sasha.z
#peter.l22
>> Support material....
I am using the polysupport from polymaker (as soluable support w/ 0 z-distance). It is much easier to use and works very well.
http://www.polymaker.com/shop/polysupport/
#sasha.z
#peter.l22
>>Multi material design software....
Any software which can export mltiple .stl's for the sections of the same model should do. Both Fusion360 and Z-Brush can do that
and I have printed multi material models using them.