Limit and homing switches - what did you use?

[amasters]

I completely forgot about limit switches and homing switches.

I know not everyone uses them, but I think at least limit switches on all axes.

I have seen leaf spring, photo, capacitive, inductive, hall etc.

Having been through a build, What did/would you use?

(and any useful info or tidbits to contribute)

[Bubba]

Well,
You probably won't like this one, but on two machines, I have a combination of:
1. Plain simple micro switches.
2. "Factory" enclosed micro switches.
3. Slotted Optical switches.
4. Hall effect.
I find all of them to be accurate and repeatable within the limits of my machines.

IF your going to machine ferrous materials, forget Hall effect.
IF your going to do a lot of "dusty" materials, I would forget optical (unless totally enclosed such as those made by Hoss or IHC)
IF your going to use coolant, unless they can be shielded I would not use open micro switches again unless they are in a sealed enclosure.

My two cents.

[amasters]

Bubba,

Thank you. Those are very good points.

I think that leaves proximity switches such as capacitive or inductive left standing.

Any benefit of one over the other? Machine is basically all aluminum

[Bubba]

I have no experience with those so cannot comment with any authority.

[theremin]

After an earlier discussion on this board regarding homing and limit switches, I have changed my way of doing things. I'm using no homing or limit switches at all now. I set my machine zero to the front left hand corner of the machine with both X and Y as far as they will go in the negative direction (I have handwheels on my stepper motors, so this is easy to do as long as the charge pump isn't active). Then, I have soft limits set on X and Y in Mach 3 (I set the Z soft limits to plus and minus 100, so it's essentially turned off on that axis). My G54 location is at the center of the table--I have an index hole drilled in the table there, and I have found that zeroing like this and then moving to G54 hits right on the money every time.

I might add a Z limit switch at the negative extreme of Z motion one of these days, but I really like the simplicity of what I'm doing now. If I ever have to re-zero, I just jog the carriage to the negative extremes of X and Y, turn off the charge pump for a second, make sure the handwheels have the machine to the extremes, hit zero all and I'm ready to go again. Just as fast as if I had switches in place, but no adjustments to fiddle with.

Dave

[gio666]

All the machines now have the channel for cable chain and 2 prox switch on the Y , also Z axis now have hole to mount prox switch through the backing plate. The X long axis is very easy to mount prox switch to the 8080 profile. To run 5 prox switches in total

[gio666]

Mounting to 8080 profile ,you can run wire in channel , also is a hole in end frame beside profile to run cable out the back

[BanduraMaker]

I used the pre-made hall effect switches from digi-key or something like that.

Instead of using 5 or 6 switches and one magnet per axis, I used 5 magnets and 3 switches that move with the axis. $30 cheaper that way.

Works well.

[pencil_&_paper]

From Automation Direct:

[AM1-A0-2A] Inductive Proximity 12mm dia. NPN/PNP 4mm RNG 2-Wire 10-30VDC Normally Open 2m cable, sensor unshielded. Made in Italy $21.75 each

[ST12C] Mounting Bracket 12mm dia. 90-deg $2 each