Help Adding Limit Switches to MiniMill with Probotix Breakout board

[HANZC]

Hello All-

I am a complete newbie to machining and have a new to me (used) CNC Mini Mill. Getting Mach3 setup and thought it would be a great idea to put some limit switches and eSTOP on before i destroy something. Any advice on below greatly appreciated.

1) I know very little about electrical systems and hoping someone could take a look at the controller schematic below and let me know if these TEMCo switches (link below) would work for this application?

2) Would it be a simple in-series wiring to the Probotix as shown on schematic without any resistors/fuses/etc or is there more that needs to be done? What gauge wire? Open to any recommendations of how to go about this and recommendations for switches.

3) What gauge wire would you recommend for E-Stop and is this straight forward as shown on the schematic?

Below is my setup with links to the limit switches and the breakout board. Again, thanks for your help.

Here is the setup:
PBX-RF breakout board running Probostep drivers
Mach3 on Windows 7
Little Machine Shop Mini Mill
CNC Fusion kit with Nema23 200step: 1@420oz and 2@280oz

Limit switches: https://www.ebay.com/itm/TEMCo-HEAVY...v/281563450355
Probotix board: https://www.probotix.com/PBX-RF-RF-I...eakout%20board

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[dazp1976]

Wiring looks good. That's how I'd do it in series.
I'd go with Cat5 or Cat6 cable for limits & 20AWG or thicker for Estop.
Can't comment on the switches themselves.
Have you used shielded cable so far or not?

TBH on mine I didn't bother with limit switches in the end. I set up the soft limits in Mach3 in relation to home position instead with it stopping 3mm from either end. Seems to work just as well as long as I G28 home at the end of everything before turning off. Drawback is if it stalls/misses steps I have to mess about putting it back in the correct position to reset home again.

[storm2313]

If your using Mach 3 you may want to review this video on soft limits to save you the headache.

[dazp1976]

[QUOTE=storm2313;2218784]If your using Mach 3 you may want to review this video on soft limits to save you the headache.

QUOTE]

Decent vid.
That's the key to soft limits, 'ref all home' at 'machine co-ordinate 0.0000'
As long as you get that right then basically seems no need for physical switches.

Looked at mine earlier,
Mine is set up a little different.
I've got travel of 230mm x, 160mm y, 280mm z.
My home is dead center of the table and 12mm from the top of z.
Soft limits max set as x -113mm & +113mm (she stops 2mm short of either end)
On the y it's -79mm & +79mm (this one stops 1mm short either end)
On the z it's -266mm & +10mm (stops 2mm short)
Seems weird now but It was early on as I was learning and just stuck with it. Would be a lot easier now if:

I picked a corner, hit the end, moved it back away +/- 1mm depending which side I'm at, ref all zero, set soft limits there.

Also got my safe z active at 25mm so if I have clamps on the edge of work to cut in the center it will lift and glide over the top of them on a rapid move to zero or home. Learned that one the hard way lol.

[dazp1976]

If your using Mach 3 you may want to review this video on soft limits to save you the headache.

There is one fatal flaw with that vid though.
He's basing everything on both your machine and work co-ordinates 0.0000 position being in the same place.
If for instance home is in the corner of the table but your work is in a vice in the center with 0.0000 being at the edge of your stock in a different position to home. Simply going to zero and referencing won't work. It will throw it out and soft limits will be wrong.
You need to run a G-code to go to G28 (home) and then 'ref all home' once it's there.

My WCS 0.0000 position is never in the same place as home position is. So at the end of every job my last program has a G28 M30 at the end. This sends the machine back to it's home 0.0000 & not WCS 0.0000, check machine co-ordinates are 0.0000 and I power down.
When it comes to powering back up I can just hit 'ref all home' without having to do anything and it's ready to go.