Advanced Nozzle Priming

AETEK

Hello,
Cleaning the nozzle is important. The filament remaining in the hot end tends to denature when it is not moved. This leads to problems in printing quality. Especially important is the filament adhesion at the first layer. So that good filament quality is available for the first layer, it makes sense to get rid of the remaining filament remnants of the last print in the hot end.
For this I have always used the "Skirt" function of the Slicer program.
It sometimes happens that scraps of the skirt filament are pulled into the working area.
In addition, the amount of filament used to clean the nozzle varies considerably. For very small objects, the cleaning is then incomplete. For large print objects, filament in the skirt is wasted.

In order to avoid the mentioned disadvantages, I thought and came to this conclusion.

1. In START-GCODE, a precisely defined amount of filament is output at the edge of the print bed, which is independent of the print object.
2. Through coordinated travel paths, filament residues adhering to the nozzle are scraped off as far as possible. The target work area should not be contaminated with filament residues.

This is an example for Simplify3D:

;STARTING GCODE START ------------------------<br>; Avoid special characters + umlauts<br>;------------------------------------------------------------------------------------------------<br>M140 S[bed1_temperature]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ;Set Bed Temperature + Continue&nbsp;&nbsp;&nbsp; <br>M109 S190&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp; ;Prepare Hotend for Homing Z. Set Hotend Temp 190C + WAIT<br>G28 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; ;Home X Y Z Axis<br>M109 S[extruder0_temperature] &nbsp; ;Set Hotend Temperature + Wait&nbsp;&nbsp;&nbsp; <br>G92 E0 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; ;Reset Extruder<br>;------------------------------------------------------------------------------------------------<br>;&nbsp;&nbsp;&nbsp; START CLEANING WITHOUT SKIRT<br>M107&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; ;Fan off<br>G21&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; ;Metric<br>G90&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; ;Absolute Coordinates<br>G0 X1 Y1 Z0.20 F5000&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; ;Goto Clean start position&nbsp;&nbsp;&nbsp; <br>G92 E0&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp; ;Reset Extruder<br>G1 X1 Y160 E50 F500&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; ;Extrude 50mm Filament<br>G90&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; ;Absolute Coordinates<br>G0 X1 Y1 Z0.40 F500&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; ;Move from Back to front<br>G0 X20 Y20 Z0.15 F200&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp; ;Sheer waste <br>G0 X20 Y20 Z5 F200&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp; ;LIFT Z to 5mm while waiting for Start Print Temperature<br>G92 E0&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp; ;Reset Extruder<br>;&nbsp;&nbsp;&nbsp; END CLEANING WITHOUT SKIRT<br>;----------------------------------------------------------------------------------------------------<br>M109 S185 B250 F1 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp; ;Autotemp on 185...250C (For PLA only)<br>;STARTING GCODE END --------------------------<br><div><br></div><div><br></div><div><br></div><div><span>At the end of printing, it is pleasant to see the print head move out of the way and the print bed come forward to release the print result. I have installed this function in the <b>END-GCODE</b>.<br></span></div><div><img alt="" src="https://jgmakerforum.com/uploads/editor/jq/xxd3kcslwein.jpg" title="Image: https://jgmakerforum.com/uploads/editor/jq/xxd3kcslwein.jpg"><br></div><div><br></div><div><br></div><div><span>;<code>ENDING GCODE START -------------------------<br>M107&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; ;Fan off<br>G92 E0 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; ;Reset Extruder<br>G1 X0 Y300 Z320 E-3 F4000&nbsp;&nbsp; ;Quick move Nozzle away while retracting 3mm Filament<br>M104 S0&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; ;Turn hotend off<br>M140 S0 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; ;Turn heatbed off<br>M109 R45 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp; ;Cooldown and wait to reach 45C<br>M84 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; ;Disable steppers <br>M81 &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; ;Power off<br>;ENDING GCODE END -------------------------

Better ideas and suggestions for improvement are welcome.

Greetings
AETEK

Samuel Pinches

I like your suggestions, not many people are aware of the thermal degradation that occurs to PLA in the nozzle.

At the moment, the start/end gcodes on the wiki are similar. When the nozzle is homed, the nozzle is actually not over the bed at all, I wonder if there is a way to take advantage of this in the purge/clean cycle?

lsh60

   Hola a todos.
Gracias por tus sugerencias.
Saludos.
Luis

netzmark

Hi Samuel,

Can you tell me why start/end gcodes on the wiki there is no G21 and G90 declared in starting? Is this not default for JGaurora and no need to declare it?

Also I have the problem with wiping and not sure where it comes from. Ending the wipe line there is definitely too much filament spilled onto the bed and when the head goes to the printing area the material is towed by the nozzle. Typical settings of DaHai (also decreased E21 to E9 but it changes not too much). Should I maybe raise the nozzle up to break away from the printed wipe-line or extruded back some E-3 or so so? Can you advise me something?

Samuel Pinches

@netzmark I haven't updated the wiki yet, but I've submitted a Cura profile to Ultimater last week, and waiting for them to accept it. The start gcode I suggested was:

 
G21                     ;set units to millimetres
G90                     ;set to absolute positioning
M106 S0                 ;set fan speed to zero (turned off)
G28                     ;home all axis
M420 S1                 ;turn on mesh bed levelling if enabled in firmware
G92 E0                  ;zero the extruded length
G1 Z1 F1000             ;move up slightly
G1 X60.0 Z0 E9.0 F1000.0;intro line
G1 X100.0 E21.5 F1000.0 ;continue line
G92 E0                  ;zero the extruded length again

You could definitely try an additional line before the last line, but the aim is to have the nozzle primed and ready for the start print, so I don't think I'd recommend adding too much retraction.

G1 E20.5 F1000 ; retract 1mm

netzmark

Are you sure: G1 X60.0 Z0 E9.0 F1000.0;intro line ?   Z0?

G1 E20.5 F1000 ; retract 1mm - is this really retraction?

Samuel Pinches

because we are in absolute positioning (G90), yes it is. I put the Z0 'swipe and bounce' to hopefully "wipe" the nozzle on the bed, so that as it finished the prime line it is already moving away from the bed, hopefully leaving debris with it.

netzmark

Sorry. So the intention is to print at absolute height level 0mm (+ mesh correection) not at 0.20 as Da Hai proposed.

What do you mean "...as it finished the prime line it is already moving away from the bed...". Guess you mean "away up" but which part of code do this? There is stil Z0 set in intro line. Isn't it?

Samuel Pinches

The first move in the gcode output from the slicer will go to z=first layer height. Being close to the bed surface means there is no place for oozing to happen anyway, other than close to the bed.

netzmark

Understand. It's sample of my slicer output code.

;TYPE:SKIRT
G1 F1500 E0
G1 F1800 X146.676 Y145.928 E0.0103

So starting code like this is ok:

G21 ; set units to mm

G90 ; set to absolute positioning

M106 S0 ; set fan speed to zero (turning off)

G28 ; home all axis

M420 S1 ; enable the mesh correction

G1 Z15.0 F6000 ; move up 15mm at 6000mm/min

G92 E0 ; reset extruder length to zero

G1 X0.0 Y0.0 F1000.0 ; go to edge of print are

;G1 Z0.20 F1000.0 ; go to Start Z position

G1 X60.0 Z0 E9.0 F1000.0 ; start intro line

G1 X100.0 E21.5 F1000.0 ; finish intro line

;G1 Z5 F1000 ; nozzle raising to take it off from the printed filament (to test if necessary)

G1 E20.5 F1000 ; retract 1mm

G92 E0.0 ; reset extruder distance position

netzmark

One more question. I have inserted starting code but the one outputed by slicer is a bit different, has few more added lines that I can't find where are from. Pointed with >:

;Layer height: 0.2
;Generated with Cura_SteamEngine 3.5.1
>M140 S60
>M105
>M190 S60
>M104 S210
>M105
>M109 S210
>M82 ;absolute extrusion mode
G21 ; set units to mm
G90 ; set to absolute positioning
M106 S0 ; set fan speed to zero (turning off)
G28 ; home all axis
M420 S1 ; enable the mesh correction
G1 Z15.0 F6000 ; move up 15mm at 6000mm/min
G92 E0 ; reset extruder length to zero
G1 X0.0 Y0.0 F1000.0 ; go to edge of print area
;G1 Z0.20 F1000.0 ; go to Start Z position
G1 X60.0 Z0 E9.0 F1000.0 ; start intro line
G1 X100.0 E21.5 F1000.0 ; finish intro line
;G1 Z5 F1000 ; nozzle raising to take it off from the printed filament (to test)
G1 E20.5 F1000 ; retract 1mm
G92 E0.0 ; reset extruder distance position
>G92 E0
>G1 F1500 E-6.5

I know what they mean but don't know where in Cura are defined.

Samuel Pinches

Well, I think they might be all hard coded. The top ones obviously vary with your set temperature.

netzmark

it looks like that (I hate softwares living with their own life...).

See there is retraction -6.5 in last line, it's from Cura retract settings not from my starting section. Maybe I really should rise up the head before it to retract the filament being not on the 0 but higher?

See pictures. Maybe it is all normal and I dig without reason?