Limit Switch Selection

I know that this is a topic that is talked about all over the place but it always seems to turn into a hall vs optical vs mechanical discussion with specific switches and never really reveals why any particular switch is better, or more importantly what to look for in a switch that would indicate that it is of good quality and well suited for CNC applications.

I use a G540 and I am looking for good mechanical switches, but I want to know why they are good and what to look for in a switch so that I can do some reasonable comparative research. I have a CNC router type machine, and my accuracy requirements are not that precise, but I just want them to be reliable and last a while with best bang for the buck accuracy. Also I plan on using the same limit switches as homing switches unless someone can convince me otherwise. It is amazing that the prices of the switches vary from $2 - $150+ per switch without any real metric for gauging quality other than their component description, which all sound the same to me.

Thanks in advance for any help.

I got a set from automationdirect.com ...they are rather large, but built solid and coolant safe. At $26, they are pricey for a hobbyist, but most of their stuff is reliable.

MPJA.com has a similar looking one for $10, but I don't know if they are waterproof.

Hi

My actual switches are all high quality industrial ones, bought second hand on ebay for the same price as rubbish ones.

The biggest difference between quality and cheap switches (aside from general build) is normally the make / break contact.
You want a switch with very little travel and a perfectly clean break contact, to get accurate repeatable homing.

You should be able to touch off on a work piece, switch the machine off, then the next day, home the machine and then go to exactly the same place on the workpiece again just inputting the co-ordinates.

On my big mill I made proximity switches by boring out a piece of M10 studding and fitting a hall effect switch inside, all potted in epoxy resin.
The triggers are embedded small rare earth magnets, but you can use voids in otherwise magnetic metal by a slightly different setup if you wish

Burying them inside an earthed metal case seems to focus the hall effect into a tight area in front of the switch, they work perfectly and cost about £2 each plus the time to make them.
I use the same switches as index pickups on the spindle too.

I personally dislike combined switches, unless you have a very small machine I don't see the advantage versus the extra complexity and potential for errors.

just my two penneth worth

regards