Set the current for the plasma generator from the Plasmac

hermann1976 wrote:

I found out why I couldn't edit any entries (neither nor feed rate, ampere, ect.)
In the settings it is possible to activate or deactivate the keyboard operation in the hardware tab (gmoccapy).
If I activate it then I should be able to use the keyboard, right?
But when activated I cannot set any keyboard entries. If I deactivate it then I can edit the entries. Is that twisted?

Now linuxcnc no longer starts. If I comment out the entry "net run_current plasmac_run.cut-amps-f => hm2_7i76e.0.7i76.0.0.spinout" then linuxcnc works again, but the current value is no longer output (before it was working).

PCW wrote:

taloot wrote:

rodw wrote:

PCW, thats a cool idea. I wonder how easy it would be to replace the current knob on a thermal dynamics with a digital pot controlled with the spindle?

good idea but u will gain nothing

also i dont think 0-10v will be stable and amp stability important to control the arc density

Actually with the Telwin you gain something quite significant, the ability to change the current in real time

Why do you think the current control would be unstable? The 7I76E analog output stability depends
chiefly on the 10V supply stability (Whether or not you could replace the Hypertherms POT with a voltage
source remains unknown)

taloot wrote:

u cant control it dynamically. because the arc voltage will be changed. so THC will have problems
anyway i make qtpyvcb with function for dynamic control..based on speed..with virtual gas console.. it might help.. for plasma

taloot wrote: Edit: This seems to work in Axis but not Gmoccapy. As an experiment I changed the name of postgui.hal to postgui.tcl and also changed it in the ini file and it now works for both Axis and Gmoccapy.

PCW wrote:

Lots of high end systems vary the current dynamically. A first order model of voltage vs height versus current would allow THC scale compensation at different currents with nothing more than MX+B done by LinuxCNCs scale component (the coefficients could be determined with a few trial cuts at different currents and checking the THC set Z height)

Volts  = 7.53 * Height(mm) + 89.2

hermann1976 wrote:

taloot wrote: Edit: This seems to work in Axis but not Gmoccapy. As an experiment I changed the name of postgui.hal to postgui.tcl and also changed it in the ini file and it now works for both Axis and Gmoccapy.

Thank you, this is working.
Is this a temorary solution or could it be for fix?

set start [clock seconds]
set timeout 3
while {1} {
    if {[hal list pin plasmac.state-out] != {} &&
        [hal list pin plasmac_run.cut-amps-f] != {} &&
        [hal list pin plasmac_config.arc-fail-delay-s] != {}} {
        break
    } elseif {[clock seconds] >= ($start + $timeout)} {
        puts "\n*** TIMEOUT WAITING FOR PLASMAC HAL COMPONENTS TO LOAD ****\n"
        break
    }
}

rodw wrote:

taloot wrote:

u cant control it dynamically. because the arc voltage will be changed. so THC will have problems
anyway i make qtpyvcb with function for dynamic control..based on speed..with virtual gas console.. it might help.. for plasma

But when the the cutting speed falls as you approach a corner, the THC is disabled by the velocity anti-dive (or Cornerlock). But you do raise an interesting point. Plasma is a constant current device so voltage is varied to keep the current at the desired level. It might be possible to manage the current to keep voltage the same during velocity slow downs. This should result in maintaining the intensity of the arc (is that called power factor?) This should prevent the widening of the kerf during velocity slow downs...