Change filament WITHOUT purging?
So the M600 command initiates the filament change. I've had absolutely no issues with this. I have done many filament changes on multiple prints and it just... works. (Albeit a slight issue after the confirmation when it oozes a little extra which I've had to grab with the pliers).
Anyhow, what I want to know: Is there a way to do a filament change WITHOUT the purge? I want it to just carry on as before as the filament colour change would be perfect for the model. In this instance a small 22mm gaming miniature of a log fire. The yellow->orange->red gradual change would be perfect. But the purge option means that the layer is an absolute cut-off rather than a blend.
I've looked at the M603 option but I don't think that does what I need. I'm toying with the idea of M702 (unload filament), M701 (load filament) with or without an M1 (user stop) for the change, but I'm not sure about values for the insertion distance. So I'm rather loath to try it in case I seriously mess up the extruder.
Has anybody tried doing this? Is there an option somewhere in PrusaSlicer that I've not found?
RE: Change filament WITHOUT purging?
If you had a MMU2 you could just specify zero purge volume for changing from the yellow to the red. Maybe looking at the G-code PrusaSlicer generates for MMU2 mode would help design a procedure? Of course, you'd need to omit the parts that expect to actually communicate with a MMU2 unit. I don't know how much of the process is a single command to the printer and how much is controlled by the G-code.
RE: Change filament WITHOUT purging?
Ok I'm going to start by saying kids don't try this at home, and then I'm going to tell you that you can just cut the filament with scissors while the print is running and start feeding in the next color without stopping the print. just keep a gentile pressure on the filament as its feeding in, I hold it 3 or 4" back once it takes it you can let go and it will keep printing. if your pushing down to hard on the filament it will press the extruder into the print and make the layer line look like a bulge there, if you choose to you can just do the change during infill and the perimeters will be fine without trying. I personally have never had an issue with this, but I'm still going to say try at your own risk.
have fun
The Filament Whisperer
RE: Change filament WITHOUT purging?
@kevin-reid Thank you for that suggestion. I will make a new profile using the MMU2 and see what gcode the system produces and take a close look. Although I suspect the amount of retraction will be significantly different.
RE: Change filament WITHOUT purging?
I don't think this is something to worry about. It purges very little filament so no waste there. But what it accomplishes is the equalization of pressures inside the extruder so that the print carries out correctly.
RE: Change filament WITHOUT purging?
@hooch
I'm not really worried about waste. That small amount is insignificant. What I would like is to retain the blend between the the two filaments when printing, so that the model has a gradual colour change rather than an abrupt one.
I just need to figure out exactly what values are used for the retraction for the unload, but I suspect it is buried in the printer's firmware as the gcode itself just has a simple "M600" command with no parameters. Which means I need to go digging into the code.