How do I keep the blue lines out of my filling part?

[YenJiWai 1]

since my machine has no retraction function,this blue line does affect my printing quality

[GregValiant 1,330]

"since my machine has no retraction function"

"Retraction" is simply an "extruder position" that is less than the current extruder position.

If the current extruder position is "12" and it is told to go to "15" then the extruder should (on most printers) rotate CCW and push the filament towards the nozzle.

If the current extruder position is "12" and the extruder is told to go to "9" then the motor should (on most printers) rotate CW and the filament will move away from the nozzle.  That is a "retraction".  There are very few stepper motors that will only spin in a single direction.

 

There are several settings in Cura that will keep the nozzle from passing over the print.  You didn't mention your printer model and a project file ("File | Save Project") would be helpful.

[YenJiWai 1]

my extrusion is powered by pressured air, so it is continueous and connot stop. the model is a cylinder and a porous scaffold in the picture is what I need. so the blue line of retraction affects the quality. I already tried combing mode. tks

EZ_圆柱.3mf

[GregValiant 1,330]

Alright.  I think I understand.  Unfortunately, there are no settings in Cura to fix this the way you want.

Fortunately the model is small and so I have a workaround.

• Click on the function button next to "Infill Line Distance" to link it back to "Infill Density".
• Set the "Infill Density" to 28.89%.  That will give you a Line Distance of 0.9 and it will also enable the setting "Infill Line Directions".
• Set "Infill Line Directions" to [0,90].
• Turn "Combing" to "Off".

That will result in this slice...

 

• Save the Gcode file and open it in a text editor.
• Search the Gcode for "G0"

At the end of each layer will be lines like:

;MESH:NOMESH
G0 X73.455 Y78.6 Z0.78
G0 X72.3 Y72.211
;TIME_ELAPSED:149.969007

Split all of those G0 lines to be:

G0 X73.455

G0 Y78.6 Z0.78
G0 X72.3

G0Y72.211

 

Near the middle of every other layer will be something like:

G1 X75.063 Y71.093
G0 X71.105 Y75
G1 X78.895 Y75 E4.12679

Split all of those mid-point G0 lines to be

G0 X71.105

G0 Y75

 

Those changes will result in orthogonal travel moves and (for the most part) the nozzle will move across existing lines.

 

If I had to do a lot of these I'd write a post-processor for it.  You could get fancy and have the nozzle move around the part before coming back in.  Your print and travel speeds are so slow that I don't think moving around the periphery is an option because the strings would wrap around the outside of the print and make a mess.

 

Here is one with Grid Infill at a density of 57.8% with the line directions at [0].

 

There would be less manual editing with that one.

 

At any rate that's what I've got.

Edited April 6, 2023 by GregValiant