Automatic Cold Pull
- There should be an automatic cold pull feature on the i3’s and the Mini that would heat up the nozzle and then cool down while slowly extruding until it reaches 170-160 and then heat up again when it cools down completely and start retracting at 70°C to do a cold pull.
RE: Automatic Cold Pull
- You can try doing this with gcode. I wouldn't expect it to work well given the variety of filaments used, but it is worth a shot. Keep in mind, the current firmware wants you at a minimal temp before unloading. I don't recall how low you can set the extrusion temp.
RE: Automatic Cold Pull
A bit more on why I think it might be difficult: When you start pulling at the cold temp, the extruder gears won't be able to pull the unmelted plastic out. There's a good chance the Bondtech gears will slip, stripping the filament and jamming the extruder. You could wait for a higher temperature, but then it's not as much of a "cold" pull and there will still be difference between cleaning filaments. Once the filament has stripped, you wind up opening the extruder anyhow, so doing it manually really isn't that much more work considering how often it's done.
Don't want to discourage you, but wanted to point out some possible difficulties.
RE: Automatic Cold Pull
It would be nice to have the thermal part automated, maybe with on-screen prompts of when to do the manual steps: opening the idler door & pulling the filament manually at the proper times.
Whatever you find to do with your hands, do with all your might!
RE: Automatic Cold Pull
A long time ago I found a gcode file that does a cold pull. I used it from time to time on my i3 and had to adapt it to work properly.
I would be happy if some of you would try it out on there machines and give me some feedback.
(I am not allowed to ad a gcode or txt file, so i have to post the code directly, sorry)
;COLD PULL CYCLE
;3dviking.wordpress.com
;use at your own risk.
;modified by C. Rajek
;ESUN Cleaning filament Heat to 255, cools to 95
;ABS Heat to 255, cool to 170.
;PLA Heat to 255, cool to 90.
;NYLON Heat to 240, cool to 140.
G90 ; use absolute coordinates
M83 ; extruder relative mode
M302 S0 ; Allow cold extrusion
M109 S255 ; Wait until working temperature reached
G4 P10000 ; Pause for 10 seconds
G1 E20 F300 ; Extrude a bit of filament to fill the nozzle with fresh filament
M109 S190 ; Cool to 190
G1 E5 F100 ; Extrude a bit of filament to fill the nozzle in case it dripped
M106 S255 ; Turn the fan on to cool the hotend faster
M109 S90 ; Cool to 90
M106 S0 ; Turn the fan off
M300 S523 P100 ; Play a tune to signal that it is time to pull.
M300 S587 P100 ; tune continued
M300 S659 P100 ; tune continued
M117 Pull filament now ; Display this message
G1 E-200 F4000 ; Run the extruder backwards
M104 S0 ; Turn hotend off
;required to prevent printer believing file is incomplete
M84 ; disable motors
RE: Automatic Cold Pull
Just do a 'print' that has the thermal temps with delays you require. Then print it as normal. Its not hard to do some gcode to do that, but its just easier to do it via the lcd.
RE: Automatic Cold Pull
Thanks Christian.
I'll try that .gcode the next time I need to do a cold pull.
I have some of that cleaning filament but have not needed it yet.
RE: Automatic Cold Pull
Don't you get the low temperature warnings running this? I thought they triggered when you try to extrude with a cold nozzle. Or is a negative "extrusion" allowed?
RE: Automatic Cold Pull
@bobstro
Early in the script the M302 command is sent. It sets the cold extrusion value to 0°C.
RE: Automatic Cold Pull
[...] Early in the script the M302 command is sent. It sets the cold extrusion value to 0°C.
Ah. I thought there was a firmware minimum of 170C or so. Interesting.
RE: Automatic Cold Pull
Don't want to be discouraging but I agree with bobstro.
Bondech gears will most likely slip, each filament will need slightly different temperatures etc... this is near impossible to reliably automate I think. Almost certainly it will bring up more cons than pros.
At the end, you will most likely find out that performing manual cold pull is by far the fastest and hassle free method.
How often do you need to make a cold pull? I needed it only once in 18 months... If you need it more frequently (let's say once a month? then your problem most likely lays elsewhere). As for me, doesn't worth putting in the gcode tweak time. Better go old fashioned manual way.