So, my issue started when I switched from a direct extruder (no gearing) to the E3D titan (3:1 gearing). At the end of each move, most notably on corners, a small blob would be made. Today I tried to eradicate this once and for all! (not an entire failure….). In the past, I've used various amounts of coast/wipe/retract settings to tweak this, as the blobs usually precede a retraction. This doesn't work as not all are made at a retraction though, some are actually made when the nozzle does a travel move (eg, from perimeter to infill). Coasting/wiping/extra distance on retract also has the downsides of messing with the layer alignment, as some parts of the layer would be partly underextruded (coast) or partly overextruded where I have upped extra distance after retraction to compensate. You can mess with these settings for YEARS and never get the perfect balance, there is always a compromise.... In the end, I'd rather find an area to hide retraction blobs, and keep good layer alignment. Add to this that the blobs only really show on 300 micron layers, I assume due to the pressure increases associated, then coasting / retract settings become tedious as you have to have different settings for each layer height as 1mm of coast will leave a lot of gaps on 100 micron layers.
So, with the idea that it was mostly due to slow travel moves, which may also be the reason for blobs on retract, I messed around with the settings....
Some background! My settings are usually....
I mostly print at 40 mm/s, 100mm/s travel moves. Cartesian machine, Bed moves in Y (weighs around 1.2kg).
M566 X600 Y400 Z8 E300 ; Jerk (mm/min)
M203 X10000 Y6000 Z300 E300 ; maximum speeds (mm/min)
M201 X3000 Y3000 Z100 E250 ; accelerations (mm/s^2)
First off, I upped XY jerk, then E jerk, then Z jerk one at a time, to high amounts with no retractions on the outer perimeter. No difference at all!
Next up was a similar experiment with accel, again nothing. Next I set it back to originals and went for the pressure advance config, This worked well actually and brought down blobbing alot, but had its own drawbacks. In fact, it gave similar results to coast/wipe/retract tweaking where the section just after pressure advance took place would be slightly underextruded. However, it is nowhere near as bad and can be set similarly for all layer heights (I assume, I've not tried it yet...). So perhaps this is the compromise I can live with to remove blobbing??
My next tests will be to have a lot more retractions, so that moving from perimeter to infill is not just a travel move but also a retract and then see if various jerk/acceleration settings affect the presence of blobs. So far, more E jerk has not.... What does everyone else do? Pressure advance seems like the best road to go down, But I can't help thinking its a work around to an underlying issue.