Re: Plasma voltage servo

Hey there Dale-
I am in the same boat as you, I am looking for the best voltages,
dead bands and almost everything else about "voltage servo". I have
not hooked the circuit to my table yet, I tested the operation on the
bench with a scope and found out I was stuck. When building the
circuit I installed an extra 14 pin socket with the dead band
resistors and the step oscillator capacitor wired through it, this
way I can vary the dead band and step rate easily by plugging in
components instead of soldering. ( in other words I'm sure I'll be
adjusting these ). I am using a hypertherm powermax 900 and I plan on
letting the software raise the torch after a cut and on a call for
torch I'll have a relay switch control from the computer to the servo
circuit. Hypertherm calls for 1/16", but they call for at least
twice that on pierce, so we are going to have to work that in
somehow. At present I am using a floating head with Z retraction
between cuts, this works suprisingly well except for on light metal
wich tends to get dragged by the torch. I'm sure Mariss can help us
blindfolded, but I just hate to bug the guy :)
Happy cuttin'
Todd

--- In CAD_CAM_EDM_DRO@y..., "aspaguy" <spaguy@l...> wrote:
> Hi Todd, As you can see from the note in the files section, this
> circuit was designed by Mariss, of Geckodrive fame. It was designed
> due to a thread in which I started when I asked why a stepper
> couldn't be controlled by voltage variations. Mariss asked what
the
> voltage parameters were an the best I could do with my limited
> knowledge is give him the info from my hypertherm manual. If anyone
> can correct or fine tune the circuit it would be Mariss. I'm sure
> your added information on what is required will be helpful. What
type
> and model of plasma are you using? how are you conducting the
test?,
> by hooking the unit to a complete machine, or by varying the unit
by
> hand? My hypertherm manual reccomends a 1/16" distance from the
torch
> to the material. this may be difficult to maintain with a hand
test.
> A 1/16" varience may fall inside the5%. What are the voltages you
are
> dealing with? What seems to be the optimum voltage for the "dead
> band"? how far outside the band do the voltages go? Does the
voltage
> increase when the arc distance increases or when it decreases?
> Sorry about so many questions, some of them will no doubt help
> Mariss, and some will help myself and others when implementing the
> circuit. I have built the circuit, but have not yet gotten my
drives
> far enough along to test it.
> Thanks,
>
Dale
> P.S. the original thread was about a month ago and could be found
> easily with a search of "plasma torch height controll". Also, the
> design was purely theoretical,and probably a great starting place.
> With your help, I imagine we can turn it into something really
cool!
> thanks
>
again.
>

> --- In CAD_CAM_EDM_DRO@y..., "morgtod" <todmorg@h...> wrote:
> > Hi-
> > Has anyone tried building the plasma voltage servo circuit
> listed
> > in the files section? I just built one and it only steps when
the
> > voltage is between the 5% comparator. For plasma control I need
> the
> > steps to happen outside the 5% going towards center, with a +/-
5%
> (
> > or less )dead band. Any ideas on how to get there from here?
> > Thanks
> > Todd