Removeable stage top with nut traps, V7

In another thread A new alpha! v7.0.0-alpha2 - Announcements @rsxy commented:

There are plenty of good reasons for the one-piece stage top in V7, as discussed on that thread, but I thought I would see whether it is possible to have a removeable stage top, without the threaded holes in plastic that were in V6.

Here is a first go at implementing a removeable stage top on V7, using nut traps. This version uses a M3 screw upwards into a captive nut in a slide riser. The slide riser then has offset captive nuts to attach clips from above. The first issue is making a hole through to the bottom of the stage top, because this is a bridge between the legs. There is space by the leg in each corner to design the bridging to allow a hole up to 4mm diameter.

It prints and can be assembled:

However it is not easy to assemble. Putting the screws up from underneath is tricky, even with nothing else on the stage body. Trying to do it on an assembled microscope is not really practical.

I shall need to think a little more.

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Older designs had some nut traps that were just hexagonal holes in the bottom. Those might work here. They were quite annoying when we used them before because the nut needed to sit flat at the bottom of a deep hole, but here it might work OK, particularly if we were able to design a suitable insertion tool (I’m thinking maybe something that could be inserted from the side that holds the nut at just the right position).

I realise that then means there’s a hole in the top of the stage which may not be desirable - but it might be a compromise worth making for most people. If it’s really a problem, the nut trap would also work as a counterbored hole so you could still assemble it as you have it here if the additional trickiness/inconvenienece is a worthwhile tradeoff for the particular stage topper you want to use.

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I was also worried about extra holes all the way to the top of the stage, but then the V6 had lots of holes in the slide riser.

I don’t think it is possible to have nut holes or counterbore at the base, there is only space for a 4mm wide hole between necessary bridges at the base of the stage. However some kind of holder or insertion tool could be made to fit in under the stage. This does open up new failure modes.

Have you considered a nut to be trapped in place during printing? Print the cavity to hold the nut, add a layer pause, insert the nuts, then continue printing.

I would love to print all the flexures themselves in the favorable orientation (flat against the bed). I have often wondered whether that would be possible. It would require coupling the individual flexure pieces at solid portions (two x risers, two y risers, z upper platform, z lower platform, etc), likely fixing them with screws as you have done here… Possibly with small threaded heat set inserts instead of nuts.

Dovetails could also possibly be used to attach the segments, with friction welding with filament in a rototool or a short section of filament as a locking pin through holes.

This highlights a current question about where the ‘core’ of the Openflexure project should be going, and how we can collate but delineate customisations. For the core of the project we have an idea of the complexity of build process that we think are appropriate, a priority on making things as widely available as possible, and a level of completeness in instructions and testing before a release. Layer pauses, and other slicer actions, are beyond the actual shape of an object in an STL. This potentially ties a build to a subset of slicing software or a sub-set of printers which are able to deal with those actions, and adds a technical user step in setting up the slicing. This has so-far been avoided in the core of the project, even though there are a few places where locally modified infill density would help a lot.

However something like a removable stage top is less likely to be a core feature of the Microscope. Like adaptors for USB webcams it is useful, but is not going to get the level of attention and testing of the core components. Customisations are also by definition not considered ‘necessary’, so it is not so much a requirement that they are widely compatible with printers. At that point a layer pause (or even a separate piece glued on) is not killing the wide applicability of the core design.

What is not so clear to me just now is how we make customisations easily available while still keeping a clear line between the parts that are core (tested, clear simple instructions, widely applicable) and which parts may be unfinished, difficult to build or use, or just do not work any more. Currently the instructions have a ‘customisations and alternatives’ page. This has become very long, and contains some things that are alternatives that are still part of the core (different height stands, optics modules for infinity-corrected lenses, electronics trays for Raspberry Pi 3 or 4) and some which are definitely outside the core with little or no testing or instructions (Logitech and M12 camera optics modules).

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