THC not working

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21 Oct 2021 02:45 - 21 Oct 2021 02:57 #223754 by bevins
THC not working was created by bevins
I am running the latest QTplasmac on a new build.
I am using thcad and that seems to be sampling ok cause I am getting good volatages.
The  voltage is getting sampled I imagine when it gets arc ok active is coming on when it gets up to 99% of feedrate.
Then while cutting, the voltages are changing while cutting a 3" circle from conversational tab, up or down never comes on. The piece is propped up a bit so it is on a slight angle so it should be coming on. The voltages vary up to 10-15 volts.

I am pretty sure I am missing something in the config I guess or something I am not doing properly. 
Can someone look at my config I posted to see if something is wrong?

/edit   running 2.9 master with the latest QTPlasmac with ohmic probing. XYZ gantry working fine. Using thcad-10

Thanks,
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Last edit: 21 Oct 2021 02:57 by bevins.

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21 Oct 2021 03:21 #223758 by phillc54
Replied by phillc54 on topic THC not working
There seems to be some discrepency between the velocity and acceleration settings.
You should set all the JOINT velocitys and accelerations to what you require then set the corresponding AXIS velocity and acceleration to double the JOINT values. Then TRAJ MAX_LINEAR_VELOCITY should be at least the same as the highest JOINT velocity, for QtPlasmac it could be √ jointXmax_vel² + jointYmax_vel²
 

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21 Oct 2021 03:25 #223760 by rodw
Replied by rodw on topic THC not working

There seems to be some discrepency between the velocity and acceleration settings.
You should set all the JOINT velocitys and accelerations to what you require then set the corresponding AXIS velocity and acceleration to double the JOINT values. Then TRAJ MAX_LINEAR_VELOCITY should be at least the same as the highest JOINT velocity, for QtPlasmac it could be √ jointXmax_vel² + jointYmax_vel²

 

Just to check my understanding. This is when both the X & Y  axes are both at max velocity  so travel is at 45 degrees using pythagoras. Is that right?

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21 Oct 2021 03:26 #223762 by phillc54
Replied by phillc54 on topic THC not working
Yep, that's it. I normally don't bother as on my little table it doesn't make for a lot of gain.
The following user(s) said Thank You: rodw

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21 Oct 2021 03:39 #223766 by bevins
Replied by bevins on topic THC not working

There seems to be some discrepency between the velocity and acceleration settings.
You should set all the JOINT velocitys and accelerations to what you require then set the corresponding AXIS velocity and acceleration to double the JOINT values. Then TRAJ MAX_LINEAR_VELOCITY should be at least the same as the highest JOINT velocity, for QtPlasmac it could be √ jointXmax_vel² + jointYmax_vel²

 

OK will try working on the config. I didn't think this mattered. I just threw up some numbers to get it working and moving. I think I understand the correlation though.

Thanks,

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21 Oct 2021 03:41 #223768 by phillc54
Replied by phillc54 on topic THC not working
There is a good chance that the low setting in TRAJ didn't let it get up to enough speed to get THC to activate. There is a THC Active LED that shows when it is active.

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21 Oct 2021 10:03 #223802 by tommylight
Replied by tommylight on topic THC not working
As a general rule, circles are not good for testing THC, use squares.
Also smal circles in wizard are done at 60% feed rate so the velocity lock is active all the time disabling the THC.
And set the VAD to 65-70%, default is way to high.

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