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Author Topic: Oscillating bit in Z axis to equalize tool wear  (Read 10462 times)

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Offline BR549

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Re: Oscillating bit in Z axis to equalize tool wear
« Reply #30 on: October 24, 2012, 09:31:58 AM »
Still working on it,

I have seen some of the strangest things doing so.



 (;-) TP
Re: Oscillating bit in Z axis to equalize tool wear
« Reply #31 on: October 24, 2012, 09:45:06 AM »
Do tell!  ;-)

Thanks for working on this.

Offline BR549

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Re: Oscillating bit in Z axis to equalize tool wear
« Reply #32 on: October 24, 2012, 01:35:10 PM »

OK is this possible from Mach3 CB ? yes

Will I release the test CODE? NO it is still dangerous. THe running of such a function COULD end life as we know it on this planet (;-) .


What you have to do is Hard wire through relays 2 outputs from MACH3 back into the LPTport pins and setup THCup and THCdown as inputs

Next create code to trigger the thc to go down unitll you are a certain level. THEN trigger the THC up to go back up to a certain level.

IT takes  DO while loops running concurrently to make it function. The big problem is keeping the CB macro from buffer overflow. IF it does then ODD things can happen and uncontrolled movement HAS been know to happen. ALSO you have to make SURE you do not overload the CPU as then either the Gcode or MACRO or both will lock up.

You also have to provide safeties to be able to break out of the loops AND safely shut the function down or you can end up in an infinate loop with no easy way out other than [CTRL ALT DELETE} and reboot.

IF you error out you MUST restart MACH3 to clear the CB threads that can create a problem by showing up later in your code.

IF " I " can figure it out YOU can also(;-) , (;-) TP
Re: Oscillating bit in Z axis to equalize tool wear
« Reply #33 on: October 24, 2012, 03:31:44 PM »
Well, I can see why you think I should stick to doing this via a pre-processor!

I am curious though - I am using Mach3 to generate step and direction signals that go to a Gecko stepper motor controller.  How are you getting from the THCup/down to actually driving the Z stepper?

Offline BR549

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Re: Oscillating bit in Z axis to equalize tool wear
« Reply #34 on: October 24, 2012, 03:54:15 PM »
The THC up/down is an internal function of MACH3 used for plasma systems that HAVE a THC device.

IF you input a signal on the LPT pin that is setup as THCdown() MAch3 will drive the Z down reguardless of the Gcode values. It overrides the Z position internally and drives the Z down.

Same with THCup() only it drives the Z up.

YOu can build a simple 2 button systems and manually control(overide) the Z DURING a GCODE program run. THe problem here is you do NOT have precise control over the Z. It just does a TURN ON THE DRIVE to go down or TURN ON THE Drive to go up. (SLAP AND GO) The THC device itself regulates the Z based on the arc voltage it sees from the plasma cutter.

NOW you could build a simple SMALL variable speed (DC) gear reduction motor that has a disc with slots and and 2 optical switches 180 degrees apart.  When the signal #1 turns ON then activate the THCdown() and when the signal turns off stop.

When Switch#2 turns on then active THCup().

You would have to adjust the speed based on the time you need each function to work. NOT precise but could work. You can also adjust the %speed of the Z motor

(;-) TP
« Last Edit: October 24, 2012, 03:57:21 PM by BR549 »
Re: Oscillating bit in Z axis to equalize tool wear
« Reply #35 on: October 24, 2012, 06:40:44 PM »
Thanks for the explanation.  So if I could generate signals to THCup and THCdown with great precision, would you say that this would give me precise control over the Z movement?  Because I can generate signals that are good to better than a microsecond very easily (meaning THCup for X microseconds, pause for Y microseconds, THCdown for X microseconds, pause for Y microseconds, repeat).  If X and Y are stable values, do you think I can get exact repeatability, same as if I did G code to move up and then back down over and over?

Offline BR549

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Re: Oscillating bit in Z axis to equalize tool wear
« Reply #36 on: October 24, 2012, 07:10:03 PM »
Pretty close (;-) You will just have to try it.

(;-) TP