Extruder Tip Rubbing When Printing Cross-Hatched Infill

RTCE

New Member
#1
I am using Colorfab PLA and the Slic3r configuration files downloaded from Gordon's gMax site. Specifically, I'm using the "high quality" print setting configuration. When I print models with the default cross hatch infill (see photo), I notice the tip of the extruder rubs significantly on the previously printed lines. This does not seem to be the case when the perimeters are printed, just the infill.

Has anyone else seen this? Is there a Slic3r parameter that I could adjust.

Again, the perimeters print without rubbing, and the resulting outer surface of the printed part is very good. I would hate to just lower the "extrusion width ratio", since it may fix the infill rubbing, but lower the quality of the perimeters and exterior.
 

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#2
The rubbing on the infill may be caused by the extruded filament stretching and breaking as it bridges across the perpendicular infill that was laid down on the previous layer. As the hot filament breaks, the ends will sometimes curl up as it cools. When the extruder passes over the curled ends on next time by, it will chatter or rub. On small prints, the rubbing may be so hard that the print will detach from the bed. On larger prints, it typically causes top surface finish defects, as the small bumps cannot be covered and smoothed adequately with just 3 or 4 layers.

Slowing down the speed that the infill prints in thr Slic3r settings may help, or just turn down the speed of the print head during printing by turning the knob next to the LCD. The percentage value shows the print speed as compared to the gcode file settings.

I have also had luck using a desk fan to blow air across the print bed and cool the filament faster, preventing the breakage.

I also suggest that you do not combine infill layers. I've had several misprints when trying to combine 2 or 3 infill layers. I typically keep that setting at 1.

Your print in the photo looks very good.
 
#3
What RPZ says is plausible. Try to switch the infill over to honeycomb on a medium print (smaller than that one but larger than a t nut) and see if it still happens.