My Newb Plasma Table Attempted Build

dvn4life1972 wrote:

tommylight wrote: it seems your Z axis is loosing position while working, can you try setting a lower probe speed, please ?

It only does this when THC is enabled. When THC is disabled it never does. I can try it, willing to try anything to make it work right.

Should have said lower all Z axis speeds, by half, just to be on the safe side.

dvn4life1972 wrote: It only does this when THC is enabled. When THC is disabled it never does. I can try it, willing to try anything to make it work right.

Could you do a short cut with THC disabled and the material ramping down slightly as the torch moves. So the material should be closer to the torch at the start then further away at the end. Can you observe what the arc voltage does as the cut progresses. Maybe then do another with the ramp opposite, so finish closer than the start.

I did the cut from the higher side (closest) first, 4in long. Once the arc voltage stabilised it started to increase as the work piece got farther from the torch tip, and the opposite going the other way (eventually touching the workpiece at the end due to no THC).

Pat

dvn4life1972 wrote: I did the cut from the higher side (closest) first, 4in long. Once the arc voltage stabilised it started to increase as the work piece got farther from the torch tip, and the opposite going the other way (eventually touching the workpiece at the end due to no THC).

Pat

Did the torch move at all down for the first case and up for the second ?

I had the THC disabled, Phil requested the test with it off. I can do it again with it on. It usually doesn't dive until after a long run though (somewhere beyond 12 or more inches of linear cutting travel).

Again, did the torch move up or down during that test?
What were the readings on voltage display during that ?

The torch did not move up or down. Pierce was about 185v, then moving from high/closest end to low/farthest end it started at 140v and ended at 155v.

Going the opposite direction it started at about 144v (after pierce) and dropped to about 138v by the end when it was physically touching the steel

Pat

That all seems very reasonable, so that is good.
Can you do a dry run of some gcode with at least 20 to 50 probes/piercings and note when it happens and what exactly happens ?

dvn4life1972 wrote: I did the cut from the higher side (closest) first, 4in long. Once the arc voltage stabilised it started to increase as the work piece got farther from the torch tip, and the opposite going the other way (eventually touching the workpiece at the end due to no THC).

Pat

So this just confirms arc behaviour where arc voltage increases about 10 volts per mm change in cut height.
Or in my test on one plasma cutter it was 7.53 volts/mm over 16000 readings.

dvn4life1972 wrote: I did the cut from the higher side (closest) first, 4in long. Once the arc voltage stabilised it started to increase as the work piece got farther from the torch tip, and the opposite going the other way (eventually touching the workpiece at the end due to no THC).

Well that seems to behave correctly, I have no idea why it would decide to drive the torch down, maybe noise or moon phase.
You will probably need to set up halscope and hopefully we can see what is happening.