What kind of end-stop switches do you use?
I did buy 2 different 5V NPN inductive proximity sensors so I can test.
Anyone using sensor like this? Better using standard switches?
I have used mechanical microswitches but would like to hear your experience with these.
I’ve never used a proximity switch but I’m curious to hear about your experience with these.
I check information, is don’t give is the Repeatability reading,
Some sensor have VERY accuracy, another have 2-3mm.
@Denis_Seguin so mechanical switch is better ?
If you don’t have Repeatability reading of sensor, mechanical is better
My friend Ed did a bunch of fooling around with putting a tool length probe on his mill. https://softsolder.com/2010/12/07/improved-tool-length-probe-switch-repeatability/ is the most relevant, but he has a number of pages about the process of assessing reliability. The point being: you may just want to set up your own length gauge and try it out and see how repeatable it is. It could be much better than the manufacturer claims, because they may have process variation from switch to switch, but if you only have one switch you don’t have to worry about the error distribution they have to account for in their literature.
http://www.cnczone.com/forums/mechanical-calculations-engineering-design/149985-forum.html is also full of interesting information.
I guess it is best to use mechanical switches.
An other question. In my design I have 4 stepper motors:
Z
X
Y1
Y2
My Pokeys57CNC supports max 8 steppers and 8 limit/home switches. Should I use separate limit/home switches for each Y motor? If I do so I can home each of them and reset the gantry if one of the Y-motors have lost steps… (I have been told).
- I guess the home switches is the important ones when it comes to quality and repeatability.
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- What kind of mechanical switch should I use ?
I don’t know how your software works. I have all three of my home switches on a single digital input: they’re all wired NC so it runs an axis until a switch goes open. (That way, if the wiring breaks, it’ll register that it’s against a limit switch and stop, and I won’t run off an axis.) If you have 8 inputs, and a lot of persistence, I’d be tempted to wire up three home switches in series to one input, and six emergency stop switches, one on each end of each axis, which again you could wire up all six in series to another input. Have the estop switches just slightly outside the home switches, so if the home switch fails the estop switch will catch it and stop the system.
I used a much cheaper variety of this: http://www.newark.com/honeywell/v7-6c18d8-048/basic-switch-extended-lever-spdt/dp/30C5402 mostly because having two holes through the body made attaching it to the mill a lot easier. (In my case I built mounts that attached to the stepper motor mounting hardware.) I’m not saying they’re great, or that I’ve tested them for repeatability, but for endstops they’ve done a fine job.
I’ve used Similar with great results, didn’t get it from China tho… but salvaged them from old machines from the scrap yard.
Yes, I’m in the process of wiring mine up. I use it as a homing sensor on the 4th axis. https://www.youmagine.com/designs/wip-homing-sensor-for-cnc-4th-axis
Using the 5V versions instead of 24V has one great advantage. If you get an unclean signal, you can use CMOS logic (the version that is not TTL-compatible) to get clean trigger points.
Thought about optical? I salvaged a bunch from an old office copier and I was hesitant about them at first, but they turned out to be simple to set up and as accurate and repeatable as my crude measuring tools allow me to determine. I just hooked up the 3.5V and ground connection to the terminals on my TinyG & control to the appropriate limit/home terminal. G28.2 works perfect and I don’t overrun my motors into the structure as I try to figure out coordinate settings!?
I don’t think optical sensors work well in an environment full of flying dust, shavings and sometimes coolant mist.
I did order some Honneywell mechanical switches - start simple 