I finished my MPCNC a couple of months ago and I’ve used it off and on with varying degrees of success. I’m still pretty new the CNC world. My Primo is running off of an SKR Turbo 1.4, and I compiled the firmware myself, using the builder that V1 has on GitHub, just in case any of the matters.
I have one end stop that has been giving me fits – Y2. The switch will periodically just remain in the triggered state, even though it obviously isn’t. Typically, it’s the connection on the board that has come loose for whatever reason. This time however, it seems like it is something else.
As I was contemplating pulling all of the wiring for that end stop back out, I had an idea, and I wondered if anyone else had tried it out. It seems to me that the switch could be mounted on the end stop pretty easily and work the same way. The truck would trigger the switch that is statically placed on the end stop, rather than the switch moving back and forth.
It seems that a configuration like this might be a bit of a hassle with the wiring – less convenient to organize the wires, but probably a lot easier to troubleshoot continuity problems.
Has anyone tried this? Am I missing a big downside?
Static endstops would probably be OK, but since you need a wiring harness to the trucks anyway, and it has to maintain continuity (Otherwise the motors fail) it’s less work to do than maintaining a complete other set of wiring.
You could run the wires through the rail tubes instead of the gantry tubes, and you avoid the whole drag chain thing with the stop wires, so it’s not pointless. I’ve see other people do different stop mounts, and then just bolt blocks to the trucks instead of the switches. It has been done, so it’s not a new idea. I don’t think there were any problems with it, other than that it’s a complete other wiring harness that doesn’t share any provision with any of the other necessary harnesses.
For the issue that you’re having, a broken wire will read as triggered. Disconnection at the board, any junctions in the wire, or at the switch itself will read as triggered. A poor connection might be flaky where it sometimes gives false triggers. Keep in mind though that the same problems with a motor wire will also do bad things, so it’s a good idea just to make sure that your wiring runs are as trouble-free as possible in any event.
There have been a couple of forum topics mentioning this alternate endstop wiring solution with just a bit of debate. My takeaway is that fixed switches are arguably better, but most Primo owners do not have issues with the the built-in solution.
In the previous version of the MPCNC (Burly) there was no endstop solution modeled in like there is for the Primo, so everyone had to roll their own. If you search on Thingiverse for “MPCNC endstop,” you will find 40+ solutions, and most are of the variety you describe where the switch is at a fixed position. The geometry of the Primo is a bit different, but I would expect some of them to still work for the Primo…especially if you can find models that fit your tubing size and your switch type.
The way it is designed is like a trail in the woods. Ryan tries to make it work consistently (and he concerns himself with price, part count, quality, usability, etc.). But you are under no obligation to follow that path. It is your machine and you can do what you like with it. Endstops are optional and we worked for a while without them, but they certainly can make some mistakes go away.
You can install them wherever you like. You can also skip using them. No big deal. There are some clamps that attach to the tubing that can be used for endstops. Anyone around the machine can also learn a procedure to keep it square.
Hopefully you find the issue. Wiring is a pain, but it is probably a bad crimp or switch and hopefully not solid core wire breaking or something.
OK. Thanks! I mostly wanted to make sure I wasn’t about to do something supremely stupid.
I do think for now, I’m going to run without the end stops. I’m pretty sure that the break is somewhere in the conduit. I did a continuity test as far up as I could reach with my probe. I’m exceedingly curious about how that could have come about, but I’m not going to give it too much thought right now.