Custom slicer

[mariep 0]

During a CS lesson, I'ld like the students to generate a gcode so that they can print their results on a UM3.

I'm making some tries, but their seems to have some issues.

I've look at this post that gives what should appear in the header. But it seems that there must also a ender mandatory, as after the first print, the printer had trouble to print anything. So using Cura, I've generate a gcode to try to mimic it. Are the last 18 lines mandatory (see in the test.gcode file)?

Also, I'll like to know how the quantity of filament to extrude is computed (the E value)? I guess it depends on the distance traveled and the speed, but the ratio I've computed doesn't give a nice result, as you can see on the picture :(.

test.gcode

Edited February 2, 2018 by mariep

[tinkergnome 927]

5 hours ago, mariep said:

Are the last 18 lines mandatory (see in the test.gcode file)?

 

Well, the M104 commands are disabling the heaters of the print cores, and M107 disables the fan.

But i think, the firmware does this anyway after the end of a print (but i'm not sure).

 

5 hours ago, mariep said:

I'll like to know how the quantity of filament to extrude is computed (the E value)?

 

AFAIK the extruded volume is calculated as follows:

 

layer_height * line_width * length_of_the_line_segment

 

You need the filament diameter in addition to calculate the needed difference in length, that's all.

 

[mariep 0]

Thanks for the quick answer

 

13 hours ago, tinkergnome said:

Well, the M104 commands are disabling the heaters of the print cores, and M107 disables the fan.

But i think, the firmware does this anyway after the end of a print (but i'm not sure).

 

I was asking more for those lines :

Quote

G0 F15000 X8.0 Z0.5 E-4.5 ;Wiping+material retraction

G0 F10000 Z1.5 E4.5 ;Compensation for the retraction

and those comments :

Quote

;SETTING_3 {"extruder_quality": ["[general]\\nversion = 2\\nname = empty\\ndefin

;SETTING_3 ition = ultimaker3\\n\\n[metadata]\\ntype = quality_changes\\nquality

;SETTING_3 _type = draft\\nextruder = ultimaker3_extruder_left\\n\\n[values]\\ni

;SETTING_3 nfill_sparse_density = 0\\nwall_thickness = 2\\n\\n", "[general]\\nve

;SETTING_3 rsion = 2\\nname = empty\\ndefinition = ultimaker3\\n\\n[metadata]\\n

;SETTING_3 type = quality_changes\\nquality_type = draft\\nextruder = ultimaker3

;SETTING_3 _extruder_right\\n\\n[values]\\n\\n"], "global_quality": "[general]\\

;SETTING_3 nversion = 2\\nname = empty\\ndefinition = ultimaker3\\n\\n[metadata]

;SETTING_3 \\ntype = quality_changes\\nquality_type = draft\\n\\n[values]\\nadhe

;SETTING_3 sion_type = none\\n\\n"}

 

13 hours ago, tinkergnome said:

AFAIK the extruded volume is calculated as follows:

 

layer_height * line_width * length_of_the_line_segment

So for a layer_height of 0.2mm, a line width of 2mm, a segment of 20mm, I have a volume of 8mm^3.

I guess I have to compare it to the volume of the filament. So for a filament of 2.85mm diameter, I have a volume of 3.14*(1.425)^2*h mm^3. And I have to solve 3.14*(1.425)^2*h = 8, which gives me something around 1.25, but this seems a bit much. According to Cura, the results is around 0.2

 

Edited February 3, 2018 by mariep

[tinkergnome 927]

11 hours ago, mariep said:

I was asking more for those lines :

G0 F15000 X8.0 Z0.5 E-4.5 ;Wiping+material retraction

G0 F10000 Z1.5 E4.5 ;Compensation for the retraction

 

 

This is just a short relative movement to reduce the "stringing" line at the end of the print.

Not strictly necessary, but consider it as an interrelated block with the surrounding "relative mode" switches(G91 / G90).

Those switches are "sticky" and you probably don't want to keep the relative mode enabled all the time...

 

G91 ;Relative movement
G0 F15000 X8.0 Z0.5 E-4.5 ;Wiping+material retraction
G0 F10000 Z1.5 E4.5 ;Compensation for the retraction
G90 ;Disable relative movement
M82 ; absolute extrusion mode

 

The comments at the end are also not needed and do not change the state of the printer.

 

 

11 hours ago, mariep said:

So for a layer_height of 0.2mm, a line width of 2mm, a segment of 20mm, I have a volume of 8mm^3.

 

Usually the line with is equal (or close) to the nozzle diameter, 2mm sounds a bit odd?

Cura uses a default (wall) line width of 0.35 (for a 0.4mm nozzle) - and 0.5mm width for the infill lines.

If i calculate your example with a line width of 0.4mm, i get an extrusion length of ~0.25mm for this segment (1,6mm³ and 2.85mm filament) - better?

 

 

[mariep 0]

Thanks a lot for these infos, it seems to work fine! After only a few iterations, we had a nice Sierpinski triangle.

However, the G280, seems to extrude a lot of filament

[cruzjohn 0]

Normally the line with is equivalent (or close) to the spout measurement, 2mm sounds somewhat odd?  
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