Tuesday, April 14, 2026
Triangular Levelling on PIKA V0.02
The levelling arrangement on PIKA has changed significantly. The Stage has two height adjustment screws on the left: one at the top (+y) and one at the bottom. There is a third on the right at the mid point. The right one is only adjusted of either of the left ones bottom out.
Levelling with aluminium foil is having problems. When I start out with a new foil, the error detected when doing several probes at the same point (the "span" here) is relatively small:
--- Probing corners (1000.0x1000.0)---
BL: -93.646 µm (span 1.000)
BR: -73.375 µm (span 3.218)
TR: -76.854 µm (span 2.000)
TL: -103.823 µm (span 4.469)
After 17 levelling attempts, it gets pretty bad:
--- Probing corners (1000.0x1000.0)---
BL: -74.188 µm (span 10.875)
BR: -70.032 µm (span 22.531)
TR: -81.271 µm (span 15.063)
TL: -72.313 µm (span 6.437)
The latest foil I've used is far more lumpy than the previous lot, and that may have something to do with it. However, I'm not convinced it'll be useful for anything other than rough alignment.
So I've tried lowering the probe so that it just makes a mark, and drawing 10x10 100μm grids. Looking at this one:
You can see that the left edge is fainter than the right, so I need to raise the two screws on the left slightly. But that's not too bad over 1mm. If I move the probe and re-zero the height, I'll get the same pattern when I try to make a grid somewhere else, so it's a consistent slope.
The glass surface does not seem to be micron-flat though. There are definitely places where the tip will scratch the ink before others, and I moved both the probe and the glass slide around while probing one of these patches to verify that it's not a probe positioning artefact. I'll have to look out for that, but unsure how much difference it'll make in the end.
On the whole though, the PIKA V0.02 is easier to level, and the built-in microscope pole is very much more stable - which makes it easier to track what's going on (or going wrong!) with the microscope. It is now in the "pika" directory on the RepRapMicron github.
