.
I think I have fixed the Z-axis problems on the Neptune 2S.
It was bugging me that I was getting better Z accuracy from the little child's toy MINIBO (Easythreed X1) printer than from the Neptune:
View attachment 4639
In fact the actual results from it are excellent after some tweaking of the gcode files. At around £80 it is a bargain if you want an FDM printer for small components in PLA:
https://www.amazon.co.uk/dp/B08K3GC818
(The link is for the Easythreed X2, with a screen on the control box -- not needed if you run the X1 over USB from your computer.)
The problem, as with resin printing, is the small size of the build plate. And being unheated, it needs a brim around the component to prevent warping:
View attachment 4645
But the result is spot-on for dimensions.
Notice that it has a one-sided Z lift, just like the Neptune, but no right-hand column. It means the cantilevered X-bars sag a bit, but that's of no practical consequence if you adjust the bed levelling to match.
If you can't beat 'em, join 'em. I slackened off the Neptune V-rollers on the right-hand slider so that they are running free and serving no purpose. The X-bar is now effectively cantilevered from the left-hand column only. I checked that the (somewhat inadequate) fixing screws attaching it to the left-hand slider were extra tight, and re-levelled the bed.
And it worked! Z-accuracy from the Neptune is now matching the design sizes, and the same all over the build area. I'm now very pleased with the results from it -- easily matching the BIBO printer which was a lot more expensive. Which I didn't really expect, given that is has a bowden-tube extruder against the direct-drive extruder on the BIBO.
Here it is, drawing out the first layer outline for a timbering brick (on the replacement glass bed):
View attachment 4640
It seems to me that the original printer design is flawed with a one-sided Z-lift. For it to work well without crabbing, those columns need to be jig-bored and dowelled, rather than relying on screws alone to set them exactly parallel. Some of the more expensive printers have synchronised dual Z-lifts to overcome these problems.
But I'm now very happy with the Neptune 2S, so back to the chairs...
cheers,
Martin.