DO I need LIMIT SWITCHES or E-stop??

[max90272]

HI guys,
I am currently building a homemade CNC mill from scratch and am learning quiet a bit on all aspects. I have retrofitted 3 axis from unused equipment with step motors controlled by a micro driver. I am using KCAM, and just last night downloaded MACH3.

I was curious as to if I need limit switches or not. I noticed that in KCAM you can tell the computer how long each axis is, which I figured would be the equivalent of having limit switches. Do I still need limit switches or E-stops, and why?

THANK YOU

MAX

[Crevice Reamer]

Hi Max. Welcome to the Zone!

With Steppers, You can probably live without limit switches, because a stepper will just stall, and not burn up like a servo will. And "soft limits" like you describe are also available in Mach3. However, you MIGHT want some Home switches.

E stop is a completely different thing. You NEED Estop, because the one switch disables all mill movement in an emergency. You also could benefit from a Charge Pump--which disables the steppers if windows goes a little crazy.

CR.

[jphagen]

drive bumper cars ?
Drive a real one without breaks?
Even with steppers stalling depends on the momentum, will wreck the
machine.
Just a thought.

[ImanCarrot]

E-Stop is essential. There's different opinions where to put it- on one of my lathes it's high up which I think is wrong. On my other lathe it's near the floor... which is where you will be if things go "bang"- you automaticaly duck.

[Konstantin]

Consider this. If you have an error in your NC and you run it for real you could potentially damage an expensive tool and loose the workpiece. So investing in a 3 switches really pays for it but it wont make your NC flawless
Besides how hard is to hookup 3 normaly closed switches to XYZ limit pin.

Konstantin.

[eightball]

Most controller boards have limit and e-stop connections so might as well use them. Ive seen e-stops for around $10 for the traditional type of red button swich, and limit switches for $2 from enco (get the light duty ones, no need for the 10A limits unless you have some really weird cnc controllers)