Short version:
Can you replace the magnet from the XYZ touch probe with a wire run through the drag chains and connected to the spindle casing?
Long version:
I’m horrible at remembering to connect the magnet when using the XYZ touch probe. Luckily, I do XY first, so all it does is shove the probe around.
The other day I had stuck the magnet on the X rail tube to get it out of the way while I was moving a clamp. And… guess what, I forgot to move the magnet back. Surprisingly, it worked fine!? There must be enough of a current path through the linear bearings to complete the circuit. I tried it several more times, on the X and Y rail tubes and it still worked just fine.
That got me thinking. If I replace the magnet with a wire run through the drag chains and connected to the spindle casing, then I wouldn’t need to use / remember the magnet.
When using the magnet, it’s running the circuit through the spindle anyway, so my initial thought is that it shouldn’t hurt anything.
Does anyone know of a reason why I shouldn’t do this?
I worked with a standard Z probe for a couple of years (starting with my X-Carve in 2016) before I realized the clip (or magnet) was totally unnecessary and inconvenient. You’re merely completing a simple circuit, so why not utilize a microswitch? This video shows my first version which used a scroll wheel button from an otherwise dead Microsoft mouse. Works like a champ, and I’m never bothered with secondary clips or magnets.
I currently use the Onefinity Easy Z Tool Setter and it works great. They label it as ‘Only for Elite series machines’, but if you’re willing to forego any warranty or direct support from them, it works just fine. It’s quite an impressive piece for the price! Most similar tool setters cost much more than this.
Ok, that it’s completing the circuit via the ground makes more sense than what I was thinking (that it was going through the rails and bearings), and it’ll be much simpler to just run a line to the ground rather than through the drag chains all the way to the spindle.
but the spindle PE wire actually does usually run through all the drag chains – it’s inside the spindle motor cable
Usually in industry, the stepper motor cables are shielded and contain a PE wire. The Onefinity however unfortunately has no shielded stepper cables (hence its susceptibility to EMI issues), but if you intend to bond and ground all moving parts of the machine individually as recommended (spindle (PE wire inside spindle cable), Z carriage, X carriage, Y carriages, machine’s foot), you can do this by simply replacing the not shielded stepper cables by shielded ones that also include a PE wire. The PE wire of each stepper cable can easily be attached to one of the four stepper bolts with a ring connector. All PE wires need to converge in one single point (star configuration) which is usually the mounting plate of the control cabinet, the earth pin of the VFD (⏚), or, on non-spindle setups, on the earth pin of the CNC controller. It is important that there is a continuity from each moving part of the machine to the ground of your workshop’s power wall box.
Yes, it’s extremely accurate. I tested it +/- 10mm from the ideal ‘target’ point (between 4 & 10 on the scale) and it repeated better than .001" every time (I don’t recall the exact numbers, but I did run an extensive test on it). Certainly more than accurate enough for anything I’m cutting.
The only reason I even opted to go with the Tool Setter is because the homemade Z probe is not as well sealed from dust and debris. Plus, it’s a lot lighter weight. The actual Tool Setter is heavier/beefier so it stays in place in its docked location (I use it as both movable and ‘fixed’ operation).
