I feel the tiny limit switches could be a high point of failure (I have worked on many machines where limit switches are the weak link) and I am thinking of replacing mine with reed switches. Because of how they work there would be no other modifications to electronics unlike hall effect switches that require power.
So anybody try it already?
Part of the reason the mechanical switches fail is that they aren’t placed right for the amount of overtravel in the switch. If there is a failure in the wiring (easy to do) and the carriage slams into the switch, it can exceed the overtravel of the switch and break it. It’s easy to avoid in the design, but now that we’ve got it, it’s pretty much just going to be that way. It’s a really easy mistake to make.
Proximity sensors are the way to go. With the reed switches, you need to mount a magnet. with proximity sensors, no magnet to mount, and well known solution at this point.
Thanks for the info. I am aware of the design issues that’s one reason I am looking for a good alternative right away. I am not opposed to proximity sensors but you do have to provide power to them (an extra cable and making sure it’s the right voltage…) while a reed switch only needs a magnet. And proximity sensors are a lot more expensive and larger than reed switches.
I ordered some reed switches to try out. If it does not work well I will switch over to proximity switches. Do you happen to have a link to any that works with the power from the Shapeoko by chance? The smaller the better of course.
I use the proximity switches from BeaverCNC, he sells a kit, happy with them so far. Maybe they’ll show up soon in the Carbide3D store, who knows.
various discussions here on the forum…
Pack of sub $3 reed switches and $2 worth of magnets and 3D printed mounts and I have got my limit switches working perfectly.
The Z axis was the trickiest but still pretty easy, the X and Y were a cake walk (just zip tied the reed where the original switch was).
When I got done I tested for accuracy (using fast move to the far front / left, placed a bolt just touching the edge of one of the flute ends (sharp pointy bit). Then homed and quick moved a dozen times and it always ended up in exactly the same spot.
Here are a few photos. I had to redesign the Z axis mounts just now (turns out if it went down far enough it just touched the V wheel) new ones printing now.
Part of the issue I think it with how reed switches actually work and the vibration environment. There’s a flexible piece of metal (steel) inside that is pulled toward the magnet. With vibration, they can start shaking in the housing and close the circuit.
That should probably not be a problem unless you also turn on hard limits in GRBL, a fast change in direction could close the switch, and with hard limits on, the switch goes from being a homing switch to a limit switch, and it’ll ruin your job.
I’ll keep that in mind and see if they ever fail. I did research them a bit and mine are silicone potted and one mechanical bulletin I looked up said they are ideal for vibration and shock applications but that the orientation can matter.
I already have some proximity sensors (12v-24v) and if I see any failures I will switch over.
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