Afternoon guys, since launching the HDZ I noted allot of people opted to upgrade the limit switch kit at the same time.
With that in mind I had an ‘interesting’ production issue on the previous orders where production time was increased by the need to extend the wires on the limit switches to accommodate. the 2.5m required for the XL/XXL models.
That got me thinking I wish I didn’t have to do this. Long story cut short if you throw some money at a problem it can be sorted…
Drum roll… It’s with great pleasure I took my first delivery of my own production line of limit switches!
Believe it or not there are 300 proximity based limit switches made to my spec in that box. This got me thinking there are likely many users who might want to upgrade their switches to prox based switches but don’t want a HDZ at this stage.
So I bring a poll, would anyone be interested in a set designed for the XL, XXL and standard 3? No complex wiring, good instructions and reliable, accurate, homing?
You would basically need to purchase enough for both ends, but it would work if you wire them in parallel. That is how I did mine. I purchased 5 hall effect switches and wired my X switches in parallel, and my Y switches in parallel and used only 1 switch for Z.
The mechanical switches are ok, but I haven’t managed to damage one yet, so my opinion may change. I would be interested in limit switches that are very accurate, and don’t allow the axis to slam against the rails.
Another thing I’d love to have is a hardware failsafe so that the machine can’t be driven past its physical limits (as indicated by limit switches). I know about soft limits, and I’ve set them, but I’ve also had Carbide Motion and UGCS freak out on me (occasionally bugs, but most times user error) and drive the Z into the wasteboard, drive the X as fast as possible into the Y rail, drive the Z too high, etc.
@ccm I’ve been using proximity based limit switches for around a year. They are much more repeatable and accurate than standard micro switches due to not touching anything.
Personally I only run 3 switches, one in each corner of home. I did run 6 at one point but this caused a bunch of issue, if a hard limit on the opposite end of X is triggered you had to do a full reset of the machine to go again. If you tried to home when the incorrect switch is triggered it jams up which means you have to jog it back before homing. I run this in conjunction with soft limits from home point. No crashes as yet.
Wonder if adding some kind of rubber stopper at the extremities of travel would help prevent potential machine damage?
That aside, thinking about a hardware failsafe it sounds like some kind of mechanical switch that when tripped could cut the power to the appropriate X/Y/Z axis motor. And probably the spindle too, just in case?
If the controller itself is in the loop (to trigger the power cut) maybe that would slow things down too much?
If the limit switches are all NC, they could be chained together and put inline with the power (assuming they were AC rated…) - hit one and the whole business would shut down. Which really wouldn’t be all that great…but would work.
I realize we’re discussing something that neither one of us would do, but, for discussion’s sake, wouldn’t that still leave you open to crashes on the other (homing) side?
To fix the homing vs hard limit switch potential conflict, would it be feasible to have homing switches a few millimetres away from the edges, so they get contacted first? That way the hard limit switches wouldn’t be tripped by standard homing operations.
If you really wanted to do this (I think it’s overkill on these machines), you could use proximity switches like the ones @Luke has for your homing switches and wire your power-cutting mechanical limit switches separately.
