I am currently looking into the possibility to create a laser cut microscope. To be totally honest this kinda a solution looking for a problem. I am the author of Boxes.py a box generator for laser cutting and want to get into flexures a bit more. While there is some hype around flexures there are not that much usable examples out there in the Open Source space other than the OFM.
I am currently toying with double parallelogram flexures which look like a good building block for an xy or z stage. I at first played with decoupled x and y axis but I decided to go with putting the axis in series for now - which seems to the the case for many metal microscopes, too.
So I will start with a simple z axis and probably add something like the flat top microscope around it. Probably with an option for mounting a cheap xy slide holder from Aliexpress. I am also thinking about making this into a z axis for the PUMA microscope to get a purely optical variant.
After that a xy stage is the next step - then a combination of both. The idea is to not reinvent the wheel more than necessary and re-use optic modules and software from the Openflexure Microscope and may be PUMA.
Another thing that I want to look into in the future is backlash-free actuation. I am still missing a good idea how to attach the 28BYJ-48 without producing backlash. Directly driving the lead screws with NEMA steppers should work but is much more expensive and bulky.
For manually actuation I want to try a double lever system with a coarse and a file lever who’s movement gets added together. But I have no idea yet if this is even feasible. For now I am happy if the stages move at all.
Has anyone looked into laser cut stages already? Have double parallelogram flexures been considered for the OFM and if so what where the reasons to not use them? Or are the discussions on the OFM layout available online anywhere? This forum seems to be too young for that. The published papers do describe the final result very well but don’t give much information on alternative solutions.
Hi @ffesti. I don’t have any answer to most of your questions, but the reasons for not using double parallelogram flexures is I think because they are more complicated and have not been found to be essential. With the single parallelogram flexures there is some parasitic movement in the orthogonal direction, but this is very small in the case of Openflexure systems. That is partly because the 3D printed flexure hinges that we use have a practical limit of around 6 degrees of deflection. I have used double parallelogram 3D printed flexures in other systems requiring more motion, but not very successfully.
This is a non-engineer talking here. I think it could be possible to break all the individual components (legs, stage, optics, illumination, etc) and laser cut them. The challenge is how to you make a hinge to connect them without loosing the structural rigidity of the monolithic build.
Do I make any sense at all?
That was not quite what I had in mind but that should work pretty well actually. I am more interested in cutting the flexures from the same sheet as the rigid parts. But let’s set that aside for a moment:
Looking at figure 5 b in A one-piece 3D printed flexure translation stage for open-source microscopy it is very apparent that all four moving parts at each “corner” can be joint together by a single sheet of bendable material. The horizontal pieces could be kept together with tabs for assembly that are broken off afterwards. Alternatively or additionally holes for locating pins could be cut. This won’t work for the “legs” though as they need to be cut “from the side” so we can’t drill a hole at the top or bottom with a 2D manufacturing process. But we could just add a finger that fits in a hole of flexible sheet. Yes, this cuts into the hinge in the middle but that should not be a big deal.
For assembly one could either just glue things together or add a second layer to clamp the flexure material in place.
This would allow to make the stage quite a bit bigger. May be big enough to fit the actuator to the inside which would prevent the overall size growing, too much. Otoh I am not sure if that is really practical from an assembly and maintenance POV.
I really like your idea but I’m having trouble seeing your concept. I wondered what would it take to build the “OFM max pro plus”. In any event, wouldn’t bending metal be more likely to break than bending plastic? If I understand this correctly, it will be highly unstable.
Well, the flexures could still be made from a polymer sheet. POM aka Delerin comes to mind. It is also very easy to laser cut but is said to be close to impossible to be glued. So it needs to be clamped. I may still have some PET or PC sheets around. May be super glue sticks to those.
As the stage itself is only made of a few, very simple parts I may be able to come up with a working prototype this weekend.
I think it could be possible to break all the individual components (legs, stage, optics, illumination, etc) and laser cut them. The challenge is how to you make a hinge to connect them without loosing the structural rigidity of the monolithic build.