Changing nozzle size during print
I want to print a large object with fine detail on the top couple of layers. I have the Revo nozzles on a MK3S. I would like to print most of the object with a larger nozzle (0.6) and then pause the print like with a color change and then change to a .25 nozzle to print the text/detail on the last couple of layers. I would also want to change the layer height and color at the same time. While I could print the entire object with the smaller nozzle, it would take days and printing that much with a tiny nozzle has a higher likelihood of clogging. Is there a set of G codes that I could manually insert? Or, is it possible to print the base part then start a new print at the level of the top surface with out the bed leveling after changing the nozzle and settings? Maybe one could slice the project twice for each nozzle size, and then manually paste/replace the code for the top layers with the second nozzle size at the pause for the color change?
RE: Changing nozzle size during print
I didn't try it, but it looks possible.
1.Enable expert settings in Prusa Slicer.
2.Go to "Printer settings" adn in "General" tab look for "Extruders" and change it from 1 to 2.
3.The "Extruder 2" should appear. Adjust nozzle diameter there.
4.In "Custom G-code" tab find "Tool Change G-code"
This is a place I couldn't try out, so You must figure it out Yourself. Most probably the:
"M600" (color change command)
will do. Check https://forum.prusa3d.com/forum/how-do-i-print-this-printing-help/mm-print-how-to-show-display-message-for-next-color/ for some suggestions how to display a message.
This command will be executed each time tool is changed. If necessary the [next_extruder] can be used to provide an extruder number.
5.In "Print Settings" "Advanced" change all extrusion widths to zero. This will make it to take the width from extruder nozzle size. Notice, it means that the "nozzle diameter" must be slightly different than the real hole in a nozzle. For 0.4 it should be 0.45 and 0.25 it should be 0.3. The extruded path width is most stable if slightly larger than the hole size.
6. Add height range modifier to Your part. Click the "gear"->"Add settings" and add "extruder" option. Select all choices (pertimeter and etc.) and select extruder 2 for each of them. Of course this is a place when You may also change the layer height.
7.Now You are almost done. Now it all depends how Your printer will react on T0 and T1 commands which will be injected after Your custom tool change code. The MMU enabled prusa will try to use MMU, I don't know if non-MMU unit will ignore it or barf.
If T1/T0 commands are problem You may try "Print settings" "Output options" (+) G-code substitutions and add two "Whole word" substitutions of T1 and T0 which will change them to nothing. Again, I didn't try it on the printer.
8. Slice, check if extrusion width have changed in the zone You defined.
9.Export and print. The printer should, if You used proper commands, eject filament and ask for color change or alike. Change the nozzle then and continue.
Again, I didn't try it but will be glad to hear how it came out.
RE: Changing nozzle size during print
While you could theoretically slice such a setup and get gcode to do so, in practice you would be unlikely to succeed with an actual print. Changing nozzles so that they are at perfectly the same distance after the swap is unlikely and without them being the same you would have issues at the layer after the swap.
You would also have to perform the swap at temperature on the bed to make sure the part doesn't detach and even a very slight knocking of the steppers would result in a position change in x/y leading to a layer shift. Basically I wish you all the luck in the world as you will need it.