Is it possible to probe BEFORE heating in CURA?

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Is it possible to probe BEFORE heating in CURA?

Postby jweaver » 2016-Nov-Sun-10-Nov

I have been talking to the developer of some custom firmware I am using, as the "oozing" I get during probing sometimes affects my print.

And their suggestion was to probe FIRST.. Then move to the corner and heat, and this seems more than reasonable.

But does anyone know how to do it in CURA? I assume I would do this in the start.gcode, but am not sure if its possible. Mine is currently set to:

;Sliced at: {day} {date} {time}
;Basic settings: Layer height: {layer_height} Walls: {wall_thickness} Fill: {fill_density}
;Print time: {print_time}
;Filament used: {filament_amount}m {filament_weight}g
;Filament cost: {filament_cost}
;M190 S{print_bed_temperature} ;Uncomment to add your own bed temperature line
;M109 S{print_temperature} ;Uncomment to add your own temperature line
G21 ;metric values
G90 ;absolute positioning
M82 ;set extruder to absolute mode
M107 ;start with the fan off
;G28 X0 Y0 ;move X/Y to min endstops
;G28 Z0 ;move Z to min endstops
G28
G29
G1 Z15.0 F{travel_speed} ;move the platform down 15mm
G92 E0 ;zero the extruded length
G1 F200 E3 ;extrude 3mm of feed stock
G92 E0 ;zero the extruded length again
G1 F{travel_speed}
;Put printing message on LCD screen
;M117 Printing...

Can I move any of this around to get it to probe before heating?

Jon
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Is it possible to probe BEFORE heating in CURA?

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Re: Is it possible to probe BEFORE heating in CURA?

Postby RetireeJay » 2016-Nov-Sun-11-Nov

All the lines that start with a semicolon are "commented out" so you can ignore them.

Nothing in the startup code shown here turns on the heater before the probing starts. BUT... the presence of the Extrude command (G1 F200 E3 ;extrude 3mm of feed stock) demonstrates that the code assumes that the heater has already been turned on. You can't do a cold extrude. So that means that Cura is issuing a temperature command prior to, and independently of this startup code.

It would be instructive for you to post the first several lines of the actual G-code that Cura generates, up to the point where it starts the actual printing motions (G1 X.. Y.. E..).
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Re: Is it possible to probe BEFORE heating in CURA?

Postby Mooselake » 2016-Nov-Sun-11-Nov

Move the commented out lines at the top that turn the heaters on to below the probing, and uncomment them. That way you'll have control over where the heating starts. Otherwise, like RJ says, Cura (or the much more configurable slic3r) will turn the heaters on for you by adding lines before your startup code.

However, the extruder and bed will expand slightly (remember we're dealing in tenths of a mm, or smaller) and give you less accurate results A better method is to retract your filament after it heats up and before you probe, such as when you finish your previous print. For example, add this to your end gcode:

G28 X0 ; move to the far left
G91 ; relative positioning
G1 Z10 ; move extruder position up a little
G1 E-0.5 ; retract a half mm, increase if necessary

Untested, so you might need to tweak it a bit. This will move your extruder off to the side (remove G28 X0 if you've set a park position, I don't use Cura). Next tell it to move relative to where it is, instead of relative to zero. This gets the hot stuff out of the way. Then suck the filament back a bit, the actual length will be hot end and extruder dependent. Add this before any code that turns off the extruder heater, if you can, although it won't cool off fast enough to go to cold extrusion prevented,

I'd test it, but we're about to leave for the airport to pick up the youngest moosette, who's giving a talk on entrepreneurism tomorrow at the local engineering U.

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