Drill dimple issue

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23 Jul 2022 11:02 #248109 by rodw
Replied by rodw on topic Drill dimple issue

The plasmac component does not use Arc OK for spotting.
It was removed a long time back as many users were finding that by the time an ArcOK was received then they were getting too large a crater.
It is time based to a resolution of one thread cycle (in most cases 1mS) plus a voltage threshold for timer start may optionally be used.

 
Thanks for the update Phill. My Linuxcnc user guide must be way out of date LOL.

So could you clarify, if I set the voltage threshold at zero, would timing start from when the Torch On signal is given ?
 

I don't think its wise to start the spotting timer at the torch on signal. The reason why spotting looks for a voltage increase is that there are significant variations in relay hysteresis/delay times between different builds. Eg I might use the 7i76e spindle enable on board relay to fire the torch and you might use an external relay with 120 ms trigger time. I might get away with a 220 ms spot delay but you might need 340ms to get the same delay. When we first tested this and Phil was coding the idea, we just went with a delay from the torch turn on but we found huge differences in results so waiting for a voltage to be seen, removed some of the variations we observed.

You really need to do some work in halscope to understand the parameters but I would expect say a 10 volt threshold would be achieved within the space of a servo thread cycle from torch turn on. The threshold just needs to be high enough so the normal voltage fluctuations don't cause spurious triggers.

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23 Jul 2022 23:47 #248147 by beefy
Replied by beefy on topic Drill dimple issue
Hi Rod,

the last thing I would do is start timing at the torch on signal. I only asked the question to clarify the operation of Qtplasmac. Another huge problem if you start timing from the torch on signal is if post cut air flow is on or off. A fixed time delay only works for one of them and not the other.
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