Wednesday, November 06, 2024
Alpha Prototype Z axis
The OpenFlexure microscope is excellent, and I highly recommend it. Its axes print in one piece, all the moving parts are encased in a sleek outer shell, it uses inexpensive steppers, and pans a microscope slide around nicely.
Unfortunately, it is a microscope, not a developmental printer. Those things do not fit well with a prototype system where the parts need to be observed, fiddled with, modified, swapped out, stuck underneath, and poked in from various angles. There is also a problem with the licence in that most common 3D model web platforms don't support it and it is incompatible with the GPL.
So, I have started development of a more modular 3-axis (possibly more...) system that should be more suitable for incremental development. This is the first crack at a Z axis for the Alpha Prototype. This has a 5:1 mechanical advantage, which with a 1/4-stepped 200 step motor directly driving a 0.5mm pitch M3 screw has a theoretical resolution of 0.5/(200*4*5) 100nm - in my dreams. It is designed to have an operational range of +/- 2mm, but will likely only be used for probing in +/-1mm of that to minimise lateral motion due to curvature. To this end it has a 14mm radius on the platform lifting arms, giving an overall sideways drift over the 1mm probing range of approx 36μm or about a 1 in 28 slope.
The probe itself will mount on the right-hand face, which I have studded with mounting holes.
Next step is to design a manually operated anti-backlash base to test it out with a thumbscrew. It should mount on the Titch probe platform, so I can compare it directly with the Z motion on the OpenFlexure Block Stage.
