Hi everyone,
I am sorry for awakening this destructive topic without bringing any real solutions/answer with me, but this issue occurred to me on my recent builds of the openflexure microscope v7.0.0-beta1.
First thing I usually do after building and calibrating a microscope is to check movability. I start out in a centered position and push the x and y movement until they stop (one at the time). I usually get ~80,000 steps in each direction (+/-). I do this to make sure the actuators and o-rings work properly. But this time, while going in negative direction (foot getting pulled into the actuator), I had the y-actuator foot snap (detached). I re-assembled with a new main_body but unfortunately the same thing happened here. I tried going to the extremes on the x-axis as well, and it snapped too. All snaps happened in the negative direction (~70,000 steps in), so slightly before it usually would stop by it self. In all cases it was a clean layer separation between the 4th and 5th layer (which is the first layer of the two actuator columns using my print settings).
I did not get the feeling that the actuator had hit the top of the travel (meaning it should stop there) but maybe it is still possible that:
… even before it has hit the top, especially if the PLA is weak. Or is it more likely that it just snapped due to the perpendicular stress of being pulled?
All parts of the build were according to instruction except that I used some left over v6.1.3 feet, but looking into the change log that should not be an issue since only the “uneeded hole on sides of feet” were removed.
I have not experimented with the printer settings since I am out of that PLA and I have main_body’s of other color that works well. One exception I thought of though, with regards to these failed prints compared to all others that have not snapped, is with the PLA. With the two main_body’s that broke I used opaque-ish PLA for the first time, pearl white (https://www.prusa3d.com/product/prusament-pla-pearl-white-blend-970g/). On their page the PLA is tagged as “silk”, which a guy on the internet said can be more brittle. I am no PLA expert and it’s difficult to get good data on the strength/layer adhesion/ductility for each PLA, but could this be a thing? @wschalle maybe you used some opaque/silk variant too? It could also just have been a poor quality PLA independent of color/silkiness/opaqueness. Anyways, I thought it was worth sharing. At least I will avoid “silk” for the main_body-part in the future.
My issue also made me curious what other OFM users think of pushing their microscopes to the limits (x and y). Is it stupid practice to push the microscope like this (at least once)?
At some point in the future I will try to repair the main_body’s with glue and pins (good idea @WilliamW thanks) so hopefully no PLA was spilled in vain.
All the best!
Per