Printing PLA over TPU (FLEX) with a single extruder (WIP)
I tried several approaches for changing materials mid-print using my MK4 and, while I love the idea of using Single Extruder Multi Material, I had difficulty getting it to work well.
Here's my solution to print a flexible TPU choker with a couple layers of PLA to color the letters using custom Color Change G-code (printer settings). I added a tiny block as a mini wipe tower for the post-filament-change purge and plan on updating this post once that step is eliminated.
; Shape the filament tip before unload G1 E-15.0000 F6000 ; Retract filament G1 E1.7500 F5400 ; Advance filament slightly G1 E0.5000 F2700 ; Advance filament slightly G1 E0.2500 F1620 ; Advance filament slightly ; Set fan speed and linear advance factor before priming M106 S255 ; Set fan speed to 100% M900 K30 ; Set linear advance factor for PLA M600 ; Filament change command ; Purge previous filament at existing temp G1 E30 F300 ; Extrude more filament to purge thoroughly ; Set temperature for PLA M104 S215 ; Set extruder temperature to 215°C M109 S215 ; Wait for nozzle to reach 215°C
I also extended the purge line to help ensure the TPU extrudes consistently for the first layer. This may not be necessary for others but, if wanted, just replace the last section in Start G-code.
;
; Extrude purge line
;
G92 E0 ; reset extruder position
G1 E{(filament_type[0] == "FLEX" ? 4 : 2)} F2400 ; deretraction after the initial one before nozzle cleaning
G0 E10 X20 Z0.2 F500 ; purge
G0 X60 E10 F500 ; purge
G0 X100 E10 F650 ; purge
G0 X140 E10 F800 ; purge
G0 X145 Z0.05 F8000 ; wipe, move close to the bed
G0 X150 Z0.2 F8000 ; wipe, move quickly away from the bed
G92 E0 ; reset extruder position
M221 S100 ; set flow to 100%
I'd welcome suggestions for improvements or alternate approaches.
Note: I do have a MMU2s but had a lot of difficulty getting it to work on my old MK3s and have not yet tried moving it to my new MK4.