Plasma power control?!?!

[*Plasma Junkie*]

Hi All,

Got me an air plasma system with A3000 control & F4MB torch. Argon / H2
I have major problems with the power control settings on the A3000.

Basically I have 3 options on this system:
* No control
* Current control
* hydrogen control

No control = new nozzle/electrode set gives me typical voltage & power output on known param recipes & after approx 20 - 30 hrs the voltage & power start dropping away.

Current control = I set a plasma power value of say 40KW & the current will increase/decrease to keep the power constant.

Hydrogen control = again I set a plasma power value of say 40KW & the hydrogen flow will increase/decrease to keep the power constant.

My problem is: When using either Current or Hydrogen control my anode/cathode life is disastrous!! I have gotten 3 hrs on hydrogen control before the gun spits all over my parts!! sad face ==>

I still use no control but dont like the idea of 'no control'!!
Has anyone else had problems like this or does everybody here use one of the controls & how does it work out for you guys?
Obviously i thought of changing to helium as it is less harsh on the nozzle electrode but that would mean a requal for everything we currently produce, so thats a no-no.

[derek]

We have F4 gun and control system in our company. I have the same problem before. I use 42 KW.
1, No control, this first I used for spray TBC, but you will lose the deposition rate after running 20 -15 hours, you have to do same thing.
2, Current control, this works to keep the deposition rate, but the gun hardware life is only about 25 hours, we have to change the nozzle and electrode.
3, Hydrogen control, I am not recommend to use this, your hardware will be burnt fast.
4, We have double 90 degree powder injector, when we see the deposition rate drop, we reduce the Ar flow rate, it can change the condition of plasma and let more powder inject in plasma and increase the powder heating time in plasma.

We use 2 and 4 to keep the deposition rate, the new hardware can run 30 hours. The SM manual said the hardware can run 40 hours in perfect condition, but in production condition, you want to make production faster at same time you lost the hardware running time.

[*Plasma Junkie*]

Thanks for the reply Derek,
That has really helped me. I was recommended to use the Hydrogen control but that caused too many problems with gun life & spitting.
I use approx 40 to 42kw for majority of the work in our company & rarely see passed 20hrs due to all the stop/starts of 15min avg cycle times. Plus same as you we use 2 x 90 degree injectors for MCrAlY & ceramic during same cycle. Even while changing btween the recipes you can notice a few sparks, spits while ramping up or down. The SM manual 40hrs is possible i'd imagine if the F4 could run longer on a 'milder' recipe without stopping.
Anyway thanks for reply derek & have a good weekend man.