The 0.4 vs 0.2 mm nozzle thing is interesting, on face value the 0.2 nozzle and a lower layer height should make anything made on an FDM printer closer to the fidelity you can get from a resin process
@Phil G @Vistisen @James Walters
Hi Phil,
The critical setting for getting fine detail from FDM is not the nozzle diameter. It's the
line width.
Normally the line width is set the same as, or very close to, the nozzle diameter. But it doesn't have to be -- you can draw a narrow line with a wider nozzle by reducing the flow rate. What you lose in the process is the dimensional placement accuracy. What you gain is much faster speed than would be possible with a tiny nozzle, and much better fusing of the layers for strength.
So it's a trade off between speed/strength and strict accuracy.
For the 4mm COT track with a
0.4mm nozzle I have set a much reduced line width of
0.25mm:
Cura is showing this in yellow because it takes a dim view of the idea. However the Cura programmers obviously are not modelling track in 4mm/ft scale. It does actually work, and allows us to print strong chairs which fit the rail nicely (after a few "corrections" to the dimensions), and at sensible speed.
Cura is the only slicer I have found which will allow such a big discrepancy between nozzle diameter and line width. Other slicers (which are mostly based on the Slic3r code, e.g. Bambu) won't permit such a big discrepancy. Which is a shame because they have the variable layer settings which are not available in Cura.
All of which means I have returned to Cura after much faffing about. I'm pleased with the results I'm now getting from this -- using the Neptune4 with standard 0.4mm nozzle, and PLA+ filament. For best results the filament needs to be dry, and some adjustment may be needed on the touch pad to the flow rate, to match an individual extruder and the measured filament diameter. Only trial and error can determine this.
This also has the advantage that there is no need to change the standard nozzle, which on the lower-cost printers such as the Neptune4 is not simple. And would need to be changed back for the filing jugs.
One effect of the reduced dimensional accuracy is on vertical surfaces, such as the sides and ends of the timbers and the socket walls. They are noticeably more rippled than using the previous profile settings for plug track timbering bricks. So that's another trade-off if you want 4mm COT track in FDM. Given all that gets hidden in the ballast I think it's acceptable.
I wasn't intending to explain all this stuff until I had got it actually released and fully tested, but Tim has somewhat forced my hand.
cheers,
Martin.