Tuning settings to remove blobs on corners

rhys161

Hello, im hoping someone can point me in the right direction, im having an issue with blobs on the corners of my prints. I have tried all sorts of different settings to try and remove them like making the jerk settings much higher and pressure advance but still seem to be having issues. It looks like its slightly over extruding on starting a new layer which starts on the corner of the test cube. I will supply some images on this post.

Settings
; Drives
M569 P0 S0 ; Drive 0 goes backwards
M569 P1 S0 ; Drive 1 goes backwards
M569 P2 S1 ; Drive 2 goes forwards
M569 P3 S0 ; Drive 3 goes backwards
M350 X128 Y128 Z128 E32 I0 ; Configure microstepping without interpolation
M92 X800 Y800 Z3157 E190 ; Set steps per mm
M566 X1200 Y1200 Z18 E120 ; Set maximum instantaneous speed changes (mm/min)
M203 X12000 Y12000 Z1200 E3000 ; Set maximum speeds (mm/min)
M201 X1000 Y1000 Z100 E5000 ; Set accelerations (mm/s^2)
M906 X855 Y855 Z855 E855 I30 ; Set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout

I also have 0.1 of pressure advance on too.

Any help would be greatly appreciated!

thanks

dc42

How long is your Bowden tube?

If it's just on starting a new layer that you have this problem, do you have "Retract on layer change" enabled in your slicer, and what are your retraction settings?

rhys161

Thanks for your reply!

bowden tube is around 500mm long.

Retraction distance 2.5mm
extra restart distance -0.1mm
retraction speed 1800mm/min

Using S3D

Ive tried using my old config settings from ramps such as the jerk settings etc but it doesnt seem to change. im running 128 microstepping could that be ruled out or would it not be that?

dc42

My own experience suggests that with a 500mm Bowden tube, you will likely need 5 to 6mm retraction at speed 3600mm/min. Perhaps less if you use Capricorn tubing.

Adjust the pressure advance to get the best looking corners where the layer change does not take place.

deckingman

As above but also try printing at a lower temperature (hot end that is, not bed).

DR8

From my experience if I go beyond 5 mm the filament will clogg the hotend because it's entering in the sweet spot and it can cool down too fast or it can be in a pre-melted transition. If you have the option coasting you should enable it. Cura have it. I have 3.2 mm retraction with a bowden tube of 700mm lenght. I'm using e3dv6 original. Also I have retract extra prime -0.08mm.