Help with theory: Minimum layer height on a delta?

Gone2Far

My delta has 160 steps/mm. Since the steps are finite, the resolution of the calculations to print a flat layer by moving angled arms must also be finite, and indeed, if I look very close, I can see tiny tiny circular patterns in the top surface of a flat solid layer. I would think that, if nothing else, would limit the minimum layer height to bigger than the limit of one step, 1/160mm=0.00625mm.

Further, there is clearly some amount of slop in the arms, joints, linear rails, bed, belts, and other components of the printer, limiting the usable repeatability of a particular layer height to more than the sum of all the individual slop that contributes to the head height variation.

Third, there is bound to be some variation between the mathematical model of the bed shape and the actual shape and "bumps" of the bed, such that too thin a layer will result in head crashes into the bed on the first layer.

Have I missed any causes of error forcing taller layer sizes?

Question for those with delta printers: what are you finding to be the minimum layer size to get repeatable prints? Any suggestions for good experiments to ascertain the limit for my printer? What changes can I make to improve layer heights with the best "bang for the buck"?

Thanks in advance to any insights on this!

Phaedrux

I don't know about any delta specific limits but for FDM in general I think 0.05mm layer height ends up being a fairly firm lower limit.

T3P3Tony

@gone2far probably the ultimate limit on FDM layer height is nozzle size. E3D have done some good work on this with the 0.15mm nozzle:
https://e3d-online.com/blog/2016/11/07/0-15mm-nozzles/
It is possible to improve resolution on the movement axis and use methods such as thicker first layers etc to handle bed unevenness but at a certain layer height there is just not enough coming out the nozzle.

Gone2Far

@t3p3tony So the filament cooks? Is that the issue? Thanks.

peirof

Hi,

i have finish see the post...

think is similar question...

https://forum.duet3d.com/topic/7442/what-is-the-minimum-layer-height-i-can-print

T3P3Tony

@gone2far it's worth reading that blog post, it's not just that the filament spends too long in a hot nozzle.

Gone2Far

Thanks for the pointer to the other thread. You're right, that is quite similar.

Luckily for me, my nimble extruder (love it!) has 2600 steps per mm, so the issue of no extrusion due to thin layers going below 1 step isn't affecting me, I think.

At this point, I'll just have to experiment to see what I can get.