Another plasma component...

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20 Jul 2019 00:10 #139937 by rodw
Replied by rodw on topic Another plasma component...
Corner lock is really quite a trivial feature to code. There is a stand alone example I did in the plasma forum here quite a while ago.

Basically you just monitor motion.current-vel and if it falls be low a threshold (say 90% of the original cut velocity), you set a pin to disable the THC until its back where it needs to be. This is one of the things an external THC can't do that sets PLASMAC apart.
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21 Jul 2019 19:23 #140102 by docwelch
Phill,

Because our discussion has turned back to plasmac and away from post-processors, I thought I would move us back to this thread. I've added code to adjust the kerf. Without some real kerf width vs. speed data, it's hard to know if this is really useful or complete overkill. Anyway, here it is. I stayed with your pattern of adjusting all arcs below a certain radius, not just circles.

This will only work with compensated code (no G41.1 or G42.1). I think I could get it to work with uncompensated code but it will require a little more thinking.

There are a couple of other things that Jim Colt writes about improving hole quality - start the lead in at the middle of the hole (maybe easier to set this up in the post-processor than in plasmac) and have the torch turn off exactly where the hole started while still moving (basically continue the arc a little further). I'll see if I can figure out how to do one or both of these. My thinking is that putting these things in plasmac makes a lot of sense as they are clearly plasma specific.

Steven
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22 Jul 2019 00:15 #140129 by docwelch
Phill,

I figured out how to extend an arc by 4mm when a full circle is cut. I have it programmed but ran into 2 issues:
  1. If I am trying to turn off the torch with M62, what P value is used?
  2. If we turn off the torch with this command, is it going to cause plasmac to stop thinking there is an error? I know there is an arc lost error and am concerned this action might trigger that error even though we are doing it on purpose. Can we suspend checking for arc lost for this one move since we have commanded the arc to turn off?
I've attached the new plasmac_gcode_arcs.py file for your perusal. It has all the changes that were in the file in my last post plus these new changes. You'll see on line 237 my question mark regarding the M62 P value.

Steven
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22 Jul 2019 00:24 #140131 by phillc54

Phill,

Because our discussion has turned back to plasmac and away from post-processors, I thought I would move us back to this thread. I've added code to adjust the kerf. Without some real kerf width vs. speed data, it's hard to know if this is really useful or complete overkill. Anyway, here it is. I stayed with your pattern of adjusting all arcs below a certain radius, not just circles.

This will only work with compensated code (no G41.1 or G42.1). I think I could get it to work with uncompensated code but it will require a little more thinking.

There are a couple of other things that Jim Colt writes about improving hole quality - start the lead in at the middle of the hole (maybe easier to set this up in the post-processor than in plasmac) and have the torch turn off exactly where the hole started while still moving (basically continue the arc a little further). I'll see if I can figure out how to do one or both of these. My thinking is that putting these things in plasmac makes a lot of sense as they are clearly plasma specific.

Steven

I think that with the amount of variables that affect kerf width it is a bit too much to expect for a gcode parser. This should all be handled by the post processor.

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22 Jul 2019 00:28 #140132 by phillc54

If I am trying to turn off the torch with M62, what P value is used?

PlasmaC uses M5 to turn the torch off

If we turn off the torch with this command, is it going to cause plasmac to stop thinking there is an error? I know there is an arc lost error and am concerned this action might trigger that error even though we are doing it on purpose. Can we suspend checking for arc lost for this one move since we have commanded the arc to turn off?

Not applicable as you cannot turn the torch off

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22 Jul 2019 00:34 - 22 Jul 2019 00:34 #140133 by rodw
Replied by rodw on topic Another plasma component...
its not the torch that gets turned off with the M62, Its the THC. If we get the void sensing sorted, it won't be necessary. Its this hole cutting I think where the void sensing will have the most value.
Last edit: 22 Jul 2019 00:34 by rodw.

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22 Jul 2019 00:56 #140136 by phillc54
I am contemplating moving the following spin boxes from the Run tab/panel to the Config tab.

Does this cause problems for anyone???

THC Delay
THC Threshold (V)
THC Speed
Corner Lock Threshold (%)
Kerf Crossing Override (%)

I am guessing that these parameters once set would not be changed too much.

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22 Jul 2019 01:08 #140137 by docwelch
I understand your concerns - the complexity quickly rises.

Using M5 to turn off the torch certainly will work. I had thought there was probably a digital pin we could reference from M62 to do the same thing. Cannot remember where it was but I saw someone using that command in their gcode.

I don't think changing the locations of the spin boxes would be a problem.

Steven

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22 Jul 2019 01:29 #140139 by rodw
Replied by rodw on topic Another plasma component...
You have to include M5 to turn torch off becasue if its left to M62/3/4/5 if you hit estop, the torch will continue to spew fire which is not pretty if the breakaway activates and the inverter is on the opposite side of the table to you. Ask me how I know?
It would be possible to AND2 the motion pin with a digital pin to enable the torch on relay but that breaks the sheer simplicity of plasmac. there is a motion.distance-to-go pin but I suspect it is for a specific segment, not the whole movement from M3 to M5

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22 Jul 2019 01:58 #140141 by mkardasi

I am contemplating moving the following spin boxes from the Run tab/panel to the Config tab.

Does this cause problems for anyone???

THC Delay
THC Threshold (V)
THC Speed
Corner Lock Threshold (%)
Kerf Crossing Override (%)

I am guessing that these parameters once set would not be changed too much.


Kerf crossing might be an exception for a small subset of users because your kerf crossing algorithm is better at detecting a torch dive than corner lock.

This is based on my particular machine which is only 600mm and capable of very high acceleration rates. Unfortunately, I have not been able to revisit this other than what is in the kerf crossing thread I started.

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