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Any one know if it's best to use a Z Lift for the Extruder in multiples of the layer height or should I just experiment with Z Lift to see what works best to make sure the the extruder doesn't knock the part.

I sometimes set it to half the layer height. Seems the more Z-Lift there is, the more of a blob I get at layer start.

If I am printing 0.2mm layers I set it to 0.1mm. No scientific reason; I figure that using the very least lift to clear during moves is best. No point to lift more than needed.

Cool, thanks guys, I'll give it a try.

If you can reduce most of your backlash like I have, 0.3mm seems to work the best for me and that's with layer heights ranging from 0.05mm to 0.3mm.

PenskeGuy wrote:I sometimes set it to half the layer height. Seems the more Z-Lift there is, the more of a blob I get at layer start.

Delay, not all firmware calculates time taken to reach commanded position... the higher the value, the further away from the part you are before the next G code is called(extrude) so you end up with more material extruded than should be for the ACUTAL position of the hotend is reached.

And yes... backlash/slop is the major factor, in a sloppier printer, the more lift needed(because ACTUAL movement may not be as much as commanded). Then the more extruder retraction is needed to absorb the time needed to return to the required location while extruding the required amount of material.

So... If your machine has little backlash/slop and you have a high value for lift, you are FAR from your part when the extruder starts pushing filament- you get blobs where it touches down. Lots of backlash/slop and the value is too low, you 'crash' into your part.

*this can also change along the length of whatever method you're using to move the Z axis, a thread of any form can change along the length, the taller the part your actual movement may be different at bed level than at 200mm so it may change as you print taller parts.

Thank you guys, appreciate the relation between Z-lift and blobs. (hate blobs)