GregValiant 1,351
"I'd had enough of the printer for one day."
I know that one.
"2) Re "the hot end goes to 170 for bed leveling": Why? What does that do that my "M104 S{material_print_temperature_layer_0}" doesn't?"
I don't have ABL but even manually leveling, if the hot end is at printing temperature it oozes. Leaving it at 170 for leveling allows the printer to move the head around without oozing onto the build area (but it's heated enough for most of the thermal expansion to have occurred). Then it heats up to printing temperature when it's sitting over in the corner.
Each line of Gcode stands alone so an extrusion does not carry on to the next line. The printer-processor knows where the head is, a line of Gcode tells it where it's going, and it calculates getting all 4 motors there at the same time. When an axis isn't mentioned in a line then that motor just doesn't move.
You've got that fancy DD on there so TPU should be no problem. Could it be a spring-tension thing on your extruder arm? Maybe it just isn't putting enough pressure on the filament (although that's hard to believe). Have you had any problems with the extruder skipping steps with harder material like PLA?
If you have a 0.6 nozzle handy maybe you should give that a try.
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GregValiant 1,351
Because TPU is quite a bit different than printing PLA I think you should consider adding another Ender 3 in Cura with the StartUp Gcode I'm including below (name it "Ender 3 TPU" or something). When you want to print TPU just pick the other printer in Cura as well as your TPU material profile.
The main changes that I've made in this StartUp Gcode is that the hot end goes to 170 for bed leveling, then after leveling, it moves to the left front corner of the bed, and then heats to printing temperature before starting the purge lines (your second purge line didn't have any extrusion in it). That keeps it from drooling all over the place during leveling.
The second main change is to slow down the purge lines from 25mm/sec to 10mm/sec and also to lower the flow. The purge lines were designed for PLA and are way too fast and heavy for TPU.
;Start GCode
M140 S{material_bed_temperature_layer_0} ; set bed temperature to initial layer bed temperature
M104 S170 ; pre-heat the hot end to leveling temperature
M190 S{material_bed_temperature_layer_0} ; wait for bed to reach temperature
M109 S170 ; wait for hot end to reach temperature
M220 S100 ; Reset Feedrate
M221 S100 ; Reset Flowrate
G92 E0 ; Reset Extruder
G28 ; Home all axes
M420 S1 Z5 ; Enable bed levelling and set Z fade height to 5mm
G1 X0 Y0 Z10.0 F3000 ;Move to 0,0,10
M109 S{material_print_temperature_layer_0} ;set hot end to initial layer printing temperature and wait
G1 Z2.0 F3000 ; Move Z Axis down
G1 X5 Y20 Z0.3 F5000.0 ; Move to start position
G1 X5 Y200.0 Z0.3 F600 E12 ; Draw the first line
G1 X5.3 Y200.0 Z0.3 F5000.0 ; Move to side a little
G1 X5.3 Y20 Z0.3 F600 E24 ; Draw the second line
G92 E0 ; Reset Extruder
G1 Z12.0 F3000 ; Move Z Axis up to prevent scratching of Heat Bed
G1 X5 Y20 Z0.3 F5000.0 ; Move over to prevent blob squish
;End Start Gcode
TPU is fussy. Speed is a big thing and 10mm/sec is about right but with a layer height of .12 and a Flow setting at 50% you are hardly moving any material. 0.25mm³/sec is only 0.1mm/sec of filament.
When I print TPU on my Ender 3 Pro (stock bowden setup) I turn retraction off but your direct drive should be able to handle some retraction. I don't have real experience with DD but 1.5mm retraction seems like a lot.
I do change my Flow for TPU. For PLA and PETG my E-steps are at 97 but calibrating the extruder for TPU they went to 110. Rather than fooling with the E-steps every time - my TPU profile in Cura has all the flows at 113%. I end up pushing more material and so I question your 50% flow number. I'm guessing a single wall calibration cube? I suggest that you go back to 100% in Cura and watch the print and adjust the flow with the Tune menu on the LCD until it looks good on the print. Then you will have a good solid Flow number to enter into Cura.
Then we come to layer height. Mostly, I print custom gaskets with TPU. It's pretty resistant to gasoline and if the area where it's mounted sees less than about 140°C it holds up quite well. Consequently I don't care how they look as long as they seal so 0.2 layer height works well for me. My numbers give me a flow of 0.8mm³/sec which is 3.2 times the flow that you are using. I haven't had any trouble pushing the filament at that rate, but with my bowden setup retraction was a definite problem as the TPU just doesn't want to react to the extruder movement.
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gone_bush 0
Thank you for your VERY detailed reply and the amount of time you've obviously spent on it. It is very much appreciated.
1) The second second purge line didn't have an extrusion specified because I had assumed it would be inherited from the previous line. Fixed.
2) Re "the hot end goes to 170 for bed leveling": Why? What does that do that my "M104 S{material_print_temperature_layer_0}" doesn't?
3) Intriguing idea re second printer, I'd never thought of that. Done.
I've implemented your suggestions but I'm still getting clicking. The fight goes on.
The settings in my post were after a _lot_ of trial and, mostly, error to see what would work so I'm not surprised at the lack of quality.
Sorry about the delay in responding but by the time I'd posted my query I'd had enough of the printer for one day.
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