Whenever a new layer outer perimeter begins I it leaves a noticeable stripe/band on the print for around 20mm of travel and then graduates back to expected layer quality. This is shown on the left hand print in the first image. On this particular print its appearing in 4 places, 90degrees out from each other.
Having watched what the printer is doing closely and looking at the Gcode in some detail i've discovered: The issue is occurring once the pervious layers infill has finished, filament retracts, Z increases, and then the next layer perimeter starts printing, adjacent to where the nozzle left off from the previous layer.
Layer perimeters are starting in 4 locations, each time this is where the previous layers infill has finished. See 2nd image showing how the banding is adjacent to where infill ends.
My printer is a Kossel Mini, duet 0.85 running 1.26.1.
Sliced with Simplify3D v4.0.0, E3D Basic PLA, 210d extruder, 60d bed, 25% infill, 0.25mm layer height, 0.4mm nozzle.
I've tried:
-Updating duet firmware - in order to PID tune both heaters which i've also done.
-Increase retraction, from 5mm all the way up to 10, no noticeable difference.
--Print outer perimeter first rather than inner.
-Changing temperatures.
-Checking extruder calibration
-Decreasing extrusion multiplier
-Slowing the speed down
-Re-tightening all the belts & then recalibrate the delta motion system
I then tried turning retraction off all together and the issue pretty much went away all together - see right hand print on image 1. Theres still the obvious 'zipper' but this i'd expect, the 'over extrusion' at the start of the layer has gone all together though.
Im now somewhat baffled, i'd have thought turning off retraction might have made the issue worse.
Has anyone come across anything similar before? Its almost as though when retracting after finishing a layer, more material is coming out and being squished out the side.
Thanks
Image 1 visible banding at start point of layer perimeter on left print. Right print has retraction turned off all together.
Image 2, showing issue occurring adjacent to infill edge
