Sheetcam Post for Ohmic Sensing AND Floating Head?

[Nacs Fab]

I am sorry, I guess I do not understand how these post processors work because the language is jibberish to me. LOL I have been talking with acourtjester (Thank you Sir) here on the boards about adding Ohmic to my plasma but I want to retain my floating head as a backup. So if the Ohmic fails, does the machine go ahead and trip the floating head limit, raise to pierce height... pierce... then go on cutting as normal? Of course, that's what I would wish it would do? I have looked on the internet and not found a post to use with both Ohmic WITH Floating Head.

If anyone has time to educate me on how this works, It may help. I was smart enough to put together a CNC Machine based off information out there, but this is a bit over my capabilities.

[djreiswig]

SheetCam outputs gcode using the post processor you pick. If you want to automatically backup your IHS you would need to do this with your table controller. Gcode doesn't have a way to choose certain things based on inputs. It can be done in a convoluted way with mach3 macros, and I believe the LinuxCNC has the capability as well.

[acourtjester]

When using both the ohmic sensor should do the normal thing find the metal surface and setup for the pierce. If not then the floating head switch will trip and stop the operation. You would then clean the torch tip or the metal surface so the ohmic sensor works the next time. In Mach step back a few lines then click on set next line. Mach will then restart the operation from there and try to work using the ohmic sensor. If it works it will then proceed with the cutting operation as it should. If not the Floating head will trip again it is working (as it is a safety) you will need to find the reason the ohmic sensor did not work and try again. I have water get into the torch tip (very few times) you would need to remove the consumables to dry out the tip and try again. Normally it is either dirty tip or wet tip that has the ohmic sensor fail.

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[Les Newell]

This isn't really a post thing. This has to be done in your Mach configuration.
How do you intend to have this wired up?
The easiest option would be to have the touch-off switch wired up as part of your emergency stop chain. If the ohmic sensing fails the machine will stop and you can continue as suggested by acourtjester. In this scenario the standard 'Mach3 THC with scriber' post will do the trick.

Depending on how creative you want to get there are various options but they mostly involve playing around with Mach macros or brains. This definitely falls in the the more advanced category.

[robertspark]

Nacs Fab, Sorry I have not had the time to come back to you since the pm, but it would probably be beneficial to discuss on the open forum as someone else may benefit from this.

I agree with Les.

I would suggest you create a touchoff macro in mach3 (mach4, uccnc, linuxcnc..... Whatever gcode interpreter software you are using) to automatically set the correct offset based upon which sensor is triggered and give you a message to inform you that the ohmic touchoff is not working or floating head has failed.

I don't have such a macro for mach3, but do have one for uccnc (which is c# and not cypress visual basic)

In sheetcam, all you do is ask it to do a touchoff via macro number (say M1000 or whatever unique number you choose.... I used m3100 as I do my touchoff with G31)... Then get it to retract to the pierce height and continue the gcode sequence as normal. Sheetcam just calls the macro, it does not need to know or set the offset because the macro does that automatically based on whether the ohmic sensor or the floating head was triggered.

The macro itself uses G31 (in mach3 you could use g28.1 but that is not available to me in uccnc), and it performs a test to see which input is triggered so it needs 1 digital input, and 1 digital output pin.

The digital output is wired to a relay (or an optoisolator, if you have a floating one where both pins are available and one is not 0v or +V (5,12,24 etc))

The relay is wired across the ohmic sensor input Which also needs a floating output (2 pins which are basically a normally closed relay , again neither of the pins are connected to 0v or +V (5,12,24 etc))

And finally the floating head is a switch wired through its normally closed contact pins.

here is a sketch:

Basically the ohmic sensor input is wired in parallel with a normally open relay and both of those are wired in series to the floating head normally closed switch . The two ends of the circuit are then wired to your breakout board (preferably as 12/24v for noise immunity)

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The macro works as follows....
When it starts, it tests the g31 probe input pin to see if it is active (as the two inputs are wired in series, active would be the circuit being open circuit as this indicates either the ohmic sensor or the floating head have been triggered)

If not it will begin the probe sequence of say (in metric) g31 Z-100 F600 as normal and once the G31 signal is triggered and motion stops it will now test the input to see if the ohmic sensor was triggered or it was the floating head. It does this by closing the relay in parallel with the ohmic input and checking the input, if the input is not active because the circuit is now continuous it knows the ohmic input was triggered and it sets the offset as zero via G92 Z0 and returns from the macro. However if when the relay is closed the input is still active (the circuit remains broken as it is a normally closed circuit) the macro knows that the floating head was triggered and it sets the temporary offset as the switch offset (in metric) say G92 Z-2.5, it also sends a message to the status box saying (ohmic sensor not triggered, check) or something to that effect that means something to you. The macro returns and the cut sequence continues given the Z offset has been set correctly automatically to the right input triggered..... So the gcode will retract to the pierce height, fire the torch etc...

Notice that the switch offset is set as a negative number.... So many post processors have an extra unnecessary sequence in them of unneeded motion...
G31 Z-100 F600 (probe z axis)
G92 Z0 (zero z axis) <<<< change to negative switch offset
G0 Z2.5 (switch offset) <<<< not necessary
G92 Z0 (zero z axis ... Again) <<< not necessary

Whilst this is not much different... No need to move the axis to reset the temporary offset again

Back to the macro sequence....
If the initial test was true
.....When it starts, it tests the g31 probe input pin to see if it is active (as the two inputs are wired in series, active would be the circuit being open circuit as this indicates either the ohmic sensor or the floating head have been triggered)...

This indicates that either the ohmic sensor is triggered (crud in the shield) or the sensor is touching the material or the floating head has been triggered

So it closes the relay and retests the input, given both sensors are normally open, if the g31 input is no longer active it knows it is crud in the shield) so it will now throw a message to the status box (ohmic probe skipped, check ohmic), and continue the touchoff sequence with the relay closed (ohmic sensor bypassed) and apply the switch offset when g31 is triggered
G31 Z-100 F600
G92 Z-2.5

If during the initial test the input is active, relay closed and the input is still active.... The macro now knows that the floating head input has been triggered which indicates maybe the torch is already too low and touching the material (possibly), what I do {via the macro} is move the z axis up 15mm and retest the g31 input... If all is now ok, I run the normal sequence again.

If it fails the test this time, then, the machine will pause and await operator input + flag a message to the status box why the machine has stopped (Error! check floating head switch!).

I'll do a macro for Mach3 later on.

[djreiswig]

That's basically what I have. I can't remember exactly how I did the macro, but the sequence is very similar.
I also added a button that I can use to override the type of reference coded into the gcode to force it to be one or the other. Then if I'm cutting some rusty metal where the ohmic is going to have problems, I can force it to use the switch without redoing the code.

[Nacs Fab]

Very good discussion fellas! Thank you everyone and thank you Robertspark for your help. We have some great people here

[East German]

Hello

I also have both probing systems on my machine. If the ohmic doesn't work, the offset switch will cut the head a little deeper. Very interesting topic. I am currently testing MyPlasm System that has it as standard.

[robertspark]

East German, I would be interested to see an detailed honest review of the myplasma system once you've put it through its paces (not after another controller but it would be nice to be able to give other options based upon a linkable review by an existing plasma user (not a star eyed new user happy to see motion)

[East German]

East German, I would be interested to see an detailed honest review of the myplasma system once you've put it through its paces (not after another controller but it would be nice to be able to give other options based upon a linkable review by an existing plasma user (not a star eyed new user happy to see motion)

I will do that. So far I have to say that many functions that you have to fight hard for in Mach3 work immediately in the system. I'm still thinking about where to report the test.
I'm actually a Mach3 fan but the new system is much easier to install and use.
At the moment I am absolutely thrilled.

Test cuts 3mm steel and 3mm brass

Peter

Look this:
https://www.youtube.com/watch?v=iCuzYlEKaH0

[robertspark]

East German, I would be interested to see an detailed honest review of the myplasma system once you've put it through its paces (not after another controller but it would be nice to be able to give other options based upon a linkable review by an existing plasma user (not a star eyed new user happy to see motion)

I will do that. So far I have to say that many functions that you have to fight hard for in Mach3 work immediately in the system. I'm still thinking about where to report the test.
I'm actually a Mach3 fan but the new system is much easier to install and use.
At the moment I am absolutely thrilled.

Test cuts 3mm steel and 3mm brass

Peter

Look this:
https://www.youtube.com/watch?v=iCuzYlEKaH0

I would post a review on here as this is a non specific forum (although advertising is I expect frowned upon).... But an honest review is not advertising imo .... It is just is

[chicken835]

I am interested in more information/ review of the MyPLasma system. I am have been playing with a Langmuir crossfire table for about a year and want to add THC. Looking at different options I have come across MyPlasma and it looks interesting.
thanks,
Mike

[East German]

See here:
https://plasmaspider.com/viewtopic.php?f=3&t=30045

Peter