The Z-Axis control holds a stepper motor in place to turn the fine focus knob on the microscope.
This requires a framework to hold the stepper in place, a stepper motor and electronics to drive it, and the big issue: a way to connect to the focusing knob.
This is a gratuitous shot of basically surplus microscopes. This is to emphasize the number of instruments which are not being used, and which darn it, should be automated and used around the clock! The Knob Question
We have come up with mutliple real and pie in the sky methods for attaching the stepper motor to the knob. Our current rig involved removing the fine focus knob from one side of the microscope. We then had to fabricate a snaper and a fitting held in place with a set screw which holds pressure against a spring clip which pushes against the gross focus knob.
Not that the stepper motor is coupled to the microscope fine focus axel with a bit of tubing. This turns out to be a wonderful material! It acts a little like a clutch, and it takes up and gives back some of the stress of starting and stopping to turn the knob. It also makes up for slight misalignments. So rather than put stress on the bearings in the motor or in the stepper assembly it protects both. This is how we coupled the stepper motors for the nano gigapan project last summer.
Fabricated and glued knob
This is an example of assembling a device out of laser cut materials, which in this case are glued together, to create a three dimensional part. I use a bit of 1/8" acryllic rod as the
axle surface here. But I think that a 8-32 or so bolt would be stronger.
The plastic knobs could also be made of rings of different diameters, which I think would be able to couple to knobs like this Zeiss Scope, where there is a substantial taper in the knob!
We have also experimented with Shape Lock plastic. This is a 'low temperature thermoplastic.' In real terms, you put a bit into a class bowl with a bit of water in it in the microwave. Heat it a bit - to about 150 f. And then fish the material out start shaping it. We made some 'spaghetti strip' bits of shapelock which we wrapped around the knob, and then squisshed tinto place but putting the knob ove the shape lock plastic. This is a highly effective technique for matching different size materials!
The the crack in the knob. It is likely that this instrument has been around a while, and perhaps whoever controls it would be a bit easier about letting it be modified :-)
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