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Author Topic: Advanced probing with laser  (Read 866 times)

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Advanced probing with laser
« on: December 11, 2017, 08:13:45 PM »
Hello again,

I've been working to use a Blum measurement laser for some time now & the probing routine itself is running.
Due to thermal expansion I can't use a "static" reference value from the Y-coordinates but rather need to probe "through" the laser.

My question is: Can Mach3 read out (and save to userDRO) the coordinate when a switch goes back to "normal" state after being triggered??

The routine has to be like this:

- Laser signal without contact is LOW
- Spindle with milling cutter moves in Y-axis towards the laser
- Laser has contact and the signal goes HIGH
- The milling cutter continues the move in Y through the laser and as long as the laser is blocked by the milling cutter the signal output is constantly HIGH
- The milling cutter has moved out of the laser and the laser switches the signal to LOW --> This coordinate needs to be read out (HOW?)

- I calculate the diameter from the first value at the switch to HIGH and the second signal switch to LOW.

Really appreciate the help because this is keeping me already busy for weeks...

Cheers,
Hancock
« Last Edit: December 11, 2017, 08:15:26 PM by hancock »
Re: Advanced probing with laser
« Reply #1 on: December 11, 2017, 09:01:58 PM »
Hi,
I supsect that you could quite happily have Mach read both when the switch makes and again when it unmakes.
The problem is there will be a delay between when the switch changes state and when Mach recognises that it has
done so. I think the normal macro pump rate is 25 times per second  or a potential delay of 40ms.

If there were a 40ms delay would your measurement be accurate enough for your purposes?

Craig
My wife left with my best friend...
     and I miss him!
Re: Advanced probing with laser
« Reply #2 on: December 11, 2017, 09:06:26 PM »
Hey Craig,

I would probe with 3mm per min (very very slow), so 40ms would be fine for my accuracy.

How would you suggest that Mach reads the LOW/HIGH/LOW switches?
The standard Gcode command just reads the first switch. Would you recommend to run two probe commands in a row to get both switch coordinates?

Thanks & cheers,
Hancock
Re: Advanced probing with laser
« Reply #3 on: December 11, 2017, 09:20:28 PM »
Hi,
no, I was thinking that you would poll the probe/switch/input  every 40ms, ie the macro pump rate.

I am more familiar with Mach4 rather than Mach3 but reading an input in a macro is easy enough. The macro could
run every 40ms.

Another possibility is to use a brain.

Craig
My wife left with my best friend...
     and I miss him!
Re: Advanced probing with laser
« Reply #4 on: December 12, 2017, 07:29:17 AM »
Is there a convenient way/code to get the Y-coordinate when the Digitize signal switches it state (HIGH/LOW)?
Re: Advanced probing with laser
« Reply #5 on: December 12, 2017, 03:16:29 PM »
Hi,
read OEMDRO 801.

Craig
My wife left with my best friend...
     and I miss him!