[Bluedog]

When homing my mill, as the X axis moves towards the home position it sometimes triggers the Y axis switch as a limit stop, stopping the process. Is there a way to have Mach back farther away from the switches after homing each axis?
Thanks!

[TOTALLYRC]

When homing my mill, as the X axis moves towards the home position it sometimes triggers the Y axis switch as a limit stop, stopping the process. Is there a way to have Mach back farther away from the switches after homing each axis?
Thanks!

Try going to the config tab. then homing/limits. Set the home offset to a greater value.

Mike

[ger21]

No, Mach3 only backs up until the switch opens. Home Offset just changes the value of the DRO's with respect to machine zeros.

Sounds like noise is causing your problem. Try increasing the debounce to 3000-5000 in the general config.

[Bluedog]

Thanks, I had already tried the home offset and discovered it only affected the values and not the position of the axis. I'll try the debounce setting. Maybe a dumb question, but what is debounce? Will changing it affect anything else on my machine?
Thanks everyone.

[TOTALLYRC]

Thanks, I had already tried the home offset and discovered it only affected the values and not the position of the axis. I'll try the debounce setting. Maybe a dumb question, but what is debounce? Will changing it affect anything else on my machine?
Thanks everyone.

I learned somthing new today.

The debounce is how long a signal must be active before mach accepts it as a valid signal. Setting it like ger21 said will help prevent short duration blips getting thru as real signals.

Mike

[Guldberg]

I consider it somewhat "cheating" to just increase the debounce. Most likely (if not always) the spontaneous trigger of a switch is caused by noise, so the real key issue is how to minimize this. Ferrit magnets as the one you see on moitor cabels etc. can do a lot for you and is cheap of ebay. They surpress "false" signals, but still dont eliminates them. You need, if possible, to keep the signal cabels apart from everything else, steppercabels, powercabels etc. Usually thats not possible, thats why somebody invented shielded cable. Be especialle carefull not to break the shield and if you have to, like at plugs and similar, do it inside a metalbox connected to the shield. As for the shield, ground it at each end to the grounding circuit

[Claude Boudreau]

I think shielded cable should be grounded at the source only, just cut and insulate the shield at the switches . This is to avoid a ground loop and possible induced current in your shield conductor.

[Guldberg]

It seams to be an issue of religion wether to ground on one end or both. Ive read different papers on grounding that suggest to ground in both ends, but dont just ground to the machine or similar, be sure to connect the grounding points with a wire at least 6mm2 thick, this will ensure uniform potential(?) at each point

[hlombard]

No, Mach3 only backs up until the switch opens. Home Offset just changes the value of the DRO's with respect to machine zeros.

Sounds like noise is causing your problem. Try increasing the debounce to 3000-5000 in the general config.

Thanks this recitied the same problem on my machine !

When referencing, the X axis would not back off the home switch.

Thanks

[tarmon]

Doesn't answer your original question but here is a suggestion or three.

1) Physically keep the switch cable further apart from other parallel cables (including the spindle power) even separating them by an 1" will help.

2) Try to reduce the length of overall cable that the switches are wired with. TTL signals were never meant to work with 10'-20' of cabling (and yet that's what we are doing<grin>). I would use two input pins on the I/O board to separate limit switches from homing switches to keep the overall cable length short as reasonable on both. Also go from one switch to the next directly without returning to the I/O box would be a way to keep the cable run shorter.

X,Y,Z switches should be wired in series with NC switches with one side tied to ground and the other side (input to your I/O card) tied to a pull up resistor (~1K ohm) to 5V or 3.3V if that is all you have.

So when *no* switches are activated the input signal is "low"

This gets you better noise immunity than wiring it with normally open switches as in the in-active state the wires are actually tied to ground level which is harder to induce a noise voltage glitch on than a pulled-up to 5V pin is.

FYI Some PC I/O CNC cards have pull down resistors on the input signals. If you have one of those then the resistors will need to be removed.

3) Add a 0.01 - 0.1uf cap (radio shack/digikey) between the input pin for the switches to ground right at the input IC of your I/O board (if this pin is buffered through an IC. If it isn't buffered, then at the PC connector itself).

Do not leave long leads on this cap.. Keep them short as possible.
I put them right on the back of the I/O on the actual IC pin.
For some crazy reason this doesn't seem to be done on most PC CNC interface boards as standard practice.

A decoupling cap would be helpful on any input signals that you use on the I/O so I would add them to all that you use.

4) Also (you probably know this!) but for shielding to be effective the switch wires must be shielded from other signals...As just adding a shield around a group of cables doesn't protect the a signal in the group from another in the same group. And whether you ground the shield at the I/O card side only or on both ends probably won't matter much.

Anyway good luck solving your problem.

[Bluedog]

Thanks to everyone for the help. I changed the debounce setting to 500 a while back and everything works great.

[ProtoXNH]

Hello, having similar problem where I can't clear the reset when I one of limits is met. using PNP NO proxs, xyz+ wired in parallel on a common input, xyz- all have there own input, but its a shared limit/home switch. C10 board input resistor set to pull down. Ive got autolimitoverride selected andhighlighted green, set the debounce to 15000?????? in settings screen it wont let me select manuallimit override. 1 time it did and it worked!!!!!! but I can't repeat it????? any advice ??? thanks.

[flick]

You could change the script for the RefAll button. I did this for a different purpose - to improve accuracy of the homing motion.

[shujaa]

[QUOTE=ger21;530522]No, Mach3 only backs up until the switch opens. Home Offset just changes the value of the DRO's with respect to machine zero.

Hi Ger,

I am using your screenset 2010. Y is master, A is slave. Probe input is common with X and Z.

I think i saw some script of yours for the Homing routine where the axes after coming off the home switches , move further a given amount.
This will help me in getting rid of the Home switch still active due to the probe. I hope.
Best regards.

Can i get that script ?

[ger21]

That info is in the 2010 screenset manual.

[shujaa]

Gerry,

What will be cnc'ing without your help ??
many many thanks.

[shujaa]

Hi Gerry,

will the X DRO show zero after they have moved the distance put in G53 G0 X5 ?

will this also work with RefCombination (10) ?

[ger21]

If you want to have X zero after it backs off, you'll need to use a Home Offset value in Config > Homing Limits. I think you'd want to use -5 for the offset value. Yes,
It will work with RefCombination.