Just wanted to share this, because a lot of people think that mechanical switches are inferior or not repeatable when compared to optos or hall effect sensors. Mechanical switches are cheap, easy to source, and just as good as any other solution. Even the rapid homing operations on this, the needle never varies any more than 0.005mm.
Edit: As some users have pointed out, the problem is with mounting them rigidly, or their adjustment components rigidly enough that they don’t drift over time. https://www.youtube.com/watch?v=5l7UMoEBP6g
I have some cheap microswitches from fleabay; the repeatability in the press direction is fine (even at different speeds), but they vary a little when releasing.
@Qitian_Dasheng_Sun_W That’s common, and fine for a limit-switch purpose. @ThantiK@Michael_Andresen Thanks for the video. I knew they were “good-enough”, but never knew the repeatability was THAT accurate.
The ones I used for that Z probe were quite expensive low force ones.
I use cheap ones for limit switches and they seem reliable enough on release. I used to use the press but somebody posted the release was more accurate. They are both the same over centre spring effect so probably no difference.
Mechanical switches are fine when they are mounted securely, the problem with most printers is that they are not mounted securely enough, and over time they start to move. For X and Y it does not matter much, but it can easily cause problems on Z. I didn’t include it in the video, but after +100 home cycles, the gauge was no longer stopping at the same position. And that was with a much stronger mount than the original prusa version, still in plastic though.
Many designs also touch the Z switch with the end of a screw so that the length can be adjusted, but the screw needs to be tight enough that it won’t screw/unscrew itself to cause drift in you Z point over time.
Of course, some of these use a screw sticking out so far that the end can miss the switch entirely if it’s not perfectly straight, but that’s a different problem.
Does loctite work on wood? Because that’s what the screw in some of these designs (not naming names) are screwed into. Not wood screws, just some inch thread roughly equivalent to M3/M4 screwed into wood instead of into the matching nut.
I totally forgot… Please also notice the hall sensor I use, is not the same as on a hall-o, the one I use is a hall switch, the difference is that it got a digital output instead of analog, so no extra logic is needed to convert it to something the arduino can use. At the same time there are build-in debounce and hysteresis.
I could do a test of a hall-o too, if i had one… so if anyone got a spare laying around, I could do some testing
I’d like to see how hall effect sensors compare, I always thought they wouldn’t be as accurate as a physical switch, but I don’t really know anything about this stuff
