Multi-Material Support w/ Single Extruder MK4 - What if...?
Hi All,
This is a bit of a "what if" kind of post, but I don't think it's that far fetched and it struck me as an interesting technical problem.
I'm working on a part that is mostly flat and printed directly on the build plate, but one end needs to go up about 5mm and thus, requires generated supports. Although this works fine, I hate the surface finish. As a potential product at my work, aesthetics are important and a bit of effort would pay off in the long run.
[Although I realize I could spend €400 on an MMU3 which would solve this entire problem, I thought it would at least be a fun discussion... so let's ignore that alternate reality for a bit...]
So, it got me thinking about printing a support object in an incompatible/non-bonding plastic to my primary material (e.g. PETG vs PLA, etc.), leaving that on the build plate, switching filament to the primary material, and then printing the main part. In other words, making your build plate a 3D surface that acts as a mold/jig for printing a specific part. With a solid support object, I'm guessing the surface finish would be significantly better, if not perfect.
Now, it occurs to me that this would probably only work with very specific geometries, but I think what I have here might qualify (picture of the current support slice attached). I'd need to measure my MK4 closely, but I suspect there is 5mm of clearance between the nozzle tip and next lowest part (fan or X bearing?).
Any thoughts on how one might achieve this in the g-code, how you'd avoid issues during bed leveling, and how you'd generally avoid crashes? I'd love to hear from anyone with some knowledge on how this might be done. Again, I'm happy with a quick and dirty solution, and this doesn't have to be a universal method, just something that could work in very specific circumstances like this.
If you were confident that there was enough clearance, this would actually be a fairly easy "hack" to take advantage of multi-material support structures without needing any special equipment, or the aforementioned €400...
I hope someone else finds this idea appealing, or at least intriguing. 🙂
Thanks in advance and all the best,
holmburgers
RE: Multi-Material Support w/ Single Extruder MK4 - What if...?
Quick follow-up as my work day is winding down:
Imagine the following printing regime...
1) Slice the support object(s) in the support material and save the g-code,
2) Slice the primary object (without auto-generated supports) in the primary material and save the g-code,
3) Combine the g-code texts into a single file, delete the end routine of slice #1, add a "filament swap" command between the two slices, and delete the start-up/homing/bed-leveling routine from slice #2,
4) Print.
Now, of course all of this demands that you somehow determine that, either you have enough clearance between the nozzle tip and next lowest object on your extruder to completely clear your support object, or through some wizardry of g-code understanding and processing you determine or prevent the possibility of a crash. I will be relying on the former.
For my application, I think if I determine my clearances are indeed OK, then I might just give this a try. Of course I would start with a simple, brief test, and I'd be standing at the printer ready to hit STOP at a moments notice.
Anyways, this seems like a relatively straightforward way to think about doing this, and I welcome any constructive insights!
Easier to use manual multimaterial printing:
https://forum.prusa3d.com/forum/prusaslicer/manual-multicolor/
Cheerio,
RE: Multi-Material Support w/ Single Extruder MK4 - What if...?
I think, it is questionable, if MMM is better.
1) you might be looking at quite a number of filament swaps
1a) in principle you could combine this trick with MMM to reduce the number of filament swaps.
2) I could see problems with actually mixing pla with PETG during the swaps. While I was being initiated to PETG printing, all the problems made me having separate nozzles for the two materials. So I could see smaller number of more controlled swaps as beneficial.
I certainly like the idea. Though, in some YouTube video, mixed material supports were tested using XL, and those results (Pla+PETG) were not convincing. I suppose it could work as support of long bridge like here....
Another thing, PrusaSlicer has now a print head model included to support serial printing. It might be helpful here.
RE:
This post is written to @holmburgers using @strjan's post as a reference.
I think, it is questionable, if MMM is better.
1) you might be looking at quite a number of filament swaps
1a) in principle you could combine this trick with MMM to reduce the number of filament swaps.
For 5mm this should be manageable. One just needs to budget the time to sit at the printer for the first 5mm. With only 2 materials this will result in 1 color change per layer. First layer will print material 1 then material 2. Second layer will continue printing material 2 and then material 1. Third layer will continue printing material 1 and then material 2. Etc, ad infinitum (or until the end of the layers needing filament swaps).
I did this for the inlay for this birdseed scoop on my (at the time) MK3S. I parked myself at my printer with a book to read to be on-hand for filament swaps until the base was done. I then let the printer finish the rest of the model unattended.
2) I could see problems with actually mixing pla with PETG during the swaps. While I was being initiated to PETG printing, all the problems made me having separate nozzles for the two materials. So I could see smaller number of more controlled swaps as beneficial.
Ah, yes. This is the rub. I honestly don't know how PrusaSlicer writes the gcode for swapping between filaments with different melt temperatures. Will it change the nozzle temperature? If so, when; before swap, after swap, depending on which is hotter? I just checked the Marlin G-code page for M600 and found there is an argument for "resume temperature", but neither the Prusa Buddy G-code nor the rep-rap G-code pages reference this argument so I doubt the temperature change can be done during the filament swap on our Prusa printers. You may need to also manage nozzle temperature during swaps if PrusaSlicer doesn't. I would expect the need to start heating up to PETG temperature before the swap to PETG, and start cooling to PLA temperature after the swap to PLA. Otherwise you would be trying to push (or pull) PETG at PLA temperatures. Brief exposure of PLA to PETG temperatures shouldn't be a big deal.
I would certainly make sure to use contrasting colors for the different materials to help determine how well purged the nozzle is at each swap to avoid printing with a mixture. (Lost In Tech has an interesting video of macro-lens high(ish) speed videos. At timestamp 4:25 he shows a change in filament colors where you can see that the new filament starts coming out in the center of the extrusion.)
I certainly like the idea. Though, in some YouTube video, mixed material supports were tested using XL, and those results (Pla+PETG) were not convincing. I suppose it could work as support of long bridge like here....
Another thing, PrusaSlicer has now a print head model included to support serial printing. It might be helpful here.
I would only use the print head model as a guide to visually inspect clearances while the 2nd model is being printed. I would expect PrusaSlicer to constantly complain about collisions (you can ignore these if you don't see collisions in the g-code review). Pay attention not only to when laying down filament for collisions, but also to travel moves. The avoid crossing perimeters setting might help. An extreme z-hop (5mm+default or more) might be needed to avoid crashing into the first model during travel moves if you can't prevent all travel moves from going through the 1st model. I forget if z-hop height is a property that you can apply using modifiers (either mesh modifiers or layer-height modifiers), but if it is, you can apply the extreme z-hop only to the first 5 mm and reduce the z-hop by 1mm each mm of print height. Because z-axis movement is so significantly slower than x/y-axis, you don't want to be z-hopping very high for long or your print time will significantly suffer. Being able to enter the z-hop height as a formula (like constraint values in FreeCAD) would be nice for this application, I don't think you can.
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs
RE: Multi-Material Support w/ Single Extruder MK4 - What if...?
I just saw another thread that might be of interest. In this thread @daryljohnson writes:
It's important to make sure you have Multi-material printing enabled and disable the "Share filament settings for all tools" option if it's present. When everything is configured correctly, the software will automatically add the corresponding temperature and parameter changes to the G-code whenever the tool is changed during the print process. This way, your printer will no longer print PETG at PLA temperatures, and you won't have to edit the G-code manually.
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs