I think that design would make a dovetail that’s way nicer than any printed dovetail I’ve ever seen. That said, I actually quite like the layers-on-layers feeling of the current solutions because the friction lock is really nice when quickly setting it up/adjusting it.
I made a beefier dovetail-with-pinch-bolt mostly as an exercise in learning freecad, and it does appear to work quite nicely: it snaps on and off in quite a satisfying way, friction locks when it’s not got the pinch bolt done up, and is absolutely unshakeable when tightened. I took your advice and beefed up the size of the dovetail a bit, it’s about double the depth of the one currently on the microscope. I also changed the clamping arm so that all the parts that get squeezed by the pinch bolt are thick enough not to bend, which I think makes a big difference.
rail.stl (17.1 KB) slider.stl (34.5 KB)
I played about some more and have made a version that, as per Julian’s suggestion, has the male dovetail on the slider. It’s a slightly more complicated model, but it prints nicely and I’m quite pleased with it. The clamping part needs some work still, as it’s not as strong as we’d like, but I think it’s converging to a relatively neat solution.
simple_dovetail.stl (78.9 KB)
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That is a lot of prints at once! Looks like they all printed well. The stringing on the cable tidy caps is a design flaw that needs fixing not a printer issue
When it is a way to go to get to the printer any print takes a day, so the bed may as well be full. Except when it all fails of course.
All the parts stuck well with no brim.
Apart from the stringing, the covers and cable tidies work out well 
The wall near the outer leg lower flexures is wedged and the flexures are unequal length - and almost bridged by the over extrusion of the first layer. You can just about make it out in the picture.
It does not actually seem to hamper the movement of the stage.
The illumination dovetail is nice. I think I would like it printed with the male dovetail part a little closer together. So it is quite loose until you do up the bolt and you can then choose how much friction there is over a wider range.
The over extruding seems pretty high. Over time the bed sensor on the prusa can drift. This can leave the head too low leading to very high “elephant footing” but good adhesion.
I think for the illuminator there is a trade-off in range and strength. I think except for initial assembly it will not make too much difference as the plastic will creep over time. I think I would be more confident of the longevity of a part that is kept for long times in a minimally deformed position. It would be worth checking wether this is an easy-to-twiddle OpenSCAD parameter, and doing some testing.
Currently there’s no parameter for tightness - it just prints everything in the obvious geometry (i.e. assuming the parts have the mating faces in the right place, and leaving no deliberate gap). That worked OK for me, but pleasingly once you’ve had it locked in place for a few minutes, plastic creep means that it self-corrects to work nicely regardless of how loose/tight it was before
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@j.stirling has released the final version of this new illumination mount as part of the v7.0.0-alpha1 release of the microscope.
It will also fit on an Openflexure Microscope v6.1 and also should fit on an Openflexure Delta stage v1.2. Reasons to upgrade an existing microscope:
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It will allow you to put the sample clips alongside the condenser, which gives much better access for putting slides in and out.
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It has a locking screw so it will not slide down if knocked.
The illumination assembly Instructions has links to the three STLs needed.
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I love this new illumination mount. I replaced it all my microscopes now. Can this lock mechanism be used for the optics too?
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That was in our minds when we designed it. The current XY stage mechanism means there’s not enough clearance for the larger dovetail underneath the stage, but in a hypothetical future revision we’d love to use the same dovetail for both. It would make the upright build way simpler, for starters!
