limit switches on mill

[Black Forest]

If your home switches are perfectly accurate or using the encoder pulse in conjunction with home switches, AND the Acorn saved the part setup("don't know if it does, I never tried it) you wouldn't have to re-zero the part.

Mine are off by .0003 sometimes. I am not using the Z reference pulse. So I have to probe the part on start up. OK. Danke!

[RB211]

Mine are off by .0003 sometimes. I am not using the Z reference pulse. So I have to probe the part on start up. OK. Danke!

.0003 is well within the backlash of a ballscrew even, I'd call that close enough to good enough! I suggest experimentation to see what the real world results provide you with and without.

[macona]

My mill has those same type of limits. They are pretty darned accurate and the life expectancy of a microswitch inside it is probably several magnitudes greater than the machine will ever see in actuations. Id stick with what's there.

[macona]

Forgive my ignorance. If I was making more than one of the same part and I had to shut the machine down in between parts so there fore re-home the machine upon start up again I would then have to set part zero again also, correct?

My machine has the work coordinates set for the left corner of the fixed jaw on my tooling plate. Home the machine, put the part in and go. With the mechanical limit switches the machine homes within the repeatability of an edge finder so I never worry about it. I dont know how acorn does it but with mach3 you just pick off and then it will remember them till you change them. I can go years without changing my x and y offsets.

[MaxHeadRoom]

The two principle types of homing methods are the original/preferred method that can be used where encoders are used on the M/C, the L.S. was only for initial reference, the machine would rapid to the limit, stop, back off slowly until the Z pulse on the encoder was seen, this was the most accurate way.
The systems such as Mach3 etc, use the L.S. alone and again the M/C will rapid to the limit then slowly come back to see the same limit again.
The one issue with using Proximity switches is where swarf may trip them during machining, unless some kind of protection fitted.
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