I run bar pullers in my shop.
The only problem with a prox switch is if you ever use a collet setup, you will over stress the collet by closing it with no material to grip.
I personaly set my machine up to count the material and stop it One short of pulling material out. After the machine stops alls they have to do is put a new piece in and hit go.
Even if they are no load puss nuts button pushers they can usually keep up with this.
Of course checking the part dimension is a whole nother story!
thanks
Michael T.
"If you don't stand for something, chances are, you'll fall for anything!"