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When the material is extruded to prime the nozzle before the print starts it doesn't always stick to the bed for the first 20 or 30 mm of the line, causing the material extruded just after to peel off the bed as it is pulled up by the nozzle, eventually it does stick down to print a line but the parts that are not stuck to the bed can get caught by the nozzle as it comes back down to draw the second part of the line, this then ruins the first layer of the print of the actual model. On the occasions where the material does not get caught by the nozzle, there is stringing between the nozzle and the end of the line which itself can cause the first part of the bottom layer to have problems.

should I include a retraction after the priming has finished as it travels to begin the print or would this cause under extrusion of the start of the model thereby defeating the purpose of the priming in the first place.

The gcode that makes the nozzle prime at the beginning of the print is as follows:

; Ender 3 Custom Start G-code
M104 S{material_print_temperature_layer_0} ; Set Extruder temperature
M140 S{material_bed_temperature_layer_0} ; Set Heat Bed temperature
M190 S{material_bed_temperature_layer_0} ; Wait for Heat Bed temperature
M109 S{material_print_temperature_layer_0} ; Wait for Extruder temperature
G28 ; Home all axes
G1 F1800 E-3 ; Retract filament 3 mm to prevent oozing
G29 ; BLTOUCH Mesh Generation
G92 E0 ; Reset Extruder
G1 Z5.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed
G1 X0.1 Y20 Z0.3 F5000.0 ; Move to start position
G1 X0.1 Y200.0 Z0.3 F1500.0 E15 ; Draw the first line
G1 X0.4 Y200.0 Z0.3 F5000.0 ; Move to side a little
G1 X0.4 Y20 Z0.3 F1500.0 E30 ; Draw the second line
G92 E0 ; Reset Extruder
G1 Z5.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed

I am using an Ender 3 running Marlin 1.1.9 with BlTouch Auto Leveling, With slicing done by CURA 3.5.6

Any suggestions you have for how to stop the priming problems will be greatly appreciated.

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  • $\begingroup$ Does this happen regardless of the part being printed and the location of the initial line? If so, consider just raising the hotend temperature 3 or 4 degrees. $\endgroup$
    – Carl Witthoft
    Dec 23 '18 at 20:13
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Have you tried using a raft

I had the same issue on my mini delta when I first started printing with it. After checking and double checking the bed level I ended up discovering that using a raft base in Cura solved the issue.

It does use more plastic however I have had absolutely no issues with respect to sticking in the dozen or so prints since then.

Additionally it makes removing the print from the bed really easy as I'm not worried about damaging the print with a scraper.

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  • $\begingroup$ The print for the main model does stick quite well to the bed because i use the Brim setting, its the line that extruded on the left before the main part is printed that makes sure there is enough filament in the nozzle, that I am having trouble with. One thing that might help you not have to use a raft base is to try using isopropanol alcohol to wipe down your bed, it massively improved how my prints stick to the bed. I was previously using window cleaner which I thought was good but after a while, prints wouldn't stick at all. $\endgroup$
    – Liam
    Dec 22 '18 at 8:54
  • $\begingroup$ I use this: amazon.co.uk/gp/product/B003D8QFQO/… and this: amazon.co.uk/gp/product/B016Y59W4E/… $\endgroup$
    – Liam
    Dec 22 '18 at 8:56
  • $\begingroup$ @Liam My Cura code does a pre-extrusion just after doing the Z-axis zero and before moving to the start of the print, and not intended to touch the platform bed. This priming extrusion happens 3 or 4 mm above zero, so the material just "floats" away. $\endgroup$
    – Carl Witthoft
    Dec 23 '18 at 20:16
  • $\begingroup$ What's the benefit of not touching the bed? I find that it massively increases the chance of the parts that aren't stuck down getting caught on the nozzle on the way back. $\endgroup$
    – Liam
    Dec 24 '18 at 11:40

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