The Shop > CNC
The basics
awemawson:
I think the consideration is different depending on the power of the drive systems. With a a few kW or so of servo power behind the axis drives of my big CNC lathe or the Beaver Partsmaster CNC Mill it would (in my opinion) be irresponsible not to have limit switches as over travel can cause considerable expensive damage if things go awry.
However if the system is using relatively lower power systems where over travel just stalls the drives without mechanical damage it's another kettle of fish.
When I cocked up and drove the CNC Mill Z axis into the work once it sheared off bolts holding the soft jaws to the vice the sheer strength of the bolts I calculated as 9 tons :bugeye: No limit switch would have saved that situation, but my point is that the forces can be very considerable.
http://madmodder.net/index.php/topic,9305.msg102982.html#msg102982
PK:
I'll add my voice to the limit switch thing. I wouldn't fit them to anything with NEMA 23 or smaller steppers. Our full sheet router has them now, and you can still see the sheared off mechanical stop bolts from when it didn't!
Homing is only useful if you use fixtures to produce parts.
John Stevenson:
And the title of the thread is ? The basics.
PK:
To rephrase:
Basically, you don't need limit/home switches on a basic machine.
John Stevenson:
Sorry PK, wasn't replying to you, only the post in general.
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