[jimcolt]

The internal boards all have a "conformal coating" that is intended to keep dust from shorting components.

I did not get a real good answer from you on the height. There is nothing in the power supply that controls the voltage......voltage is 100% controlled by the resistance of the plasma arc. Things that change the resistance are:

- arc length. If the plate moves away from the torch (warped down) .010"....the arc voltage will change by (increase) about 5 volts. The torch height control is supposed to maintain voltage by monitoring it....and adjusting the z axis (up and down) to maintain the correct voltage. If the z axis has some mechanical slop....or if there is a setting or overshoot issue with the THC electronics....the torch will oscilate up and own a bit, causing the ac voltage to oscilate up and down.

If the Z axis is off....making no up or down corrections....and you still see voltage variation....is the plate moving?

- Slugs of moisture or oil or other contaminants in the air supply will change the chemistry of the "air" being used to develop the plasma arc....this changes the electrical resistance of the arc, causin voltage changes. Usually this will show also as rapid consumable wear and poor cut quality.

- Changes or fluctuation in inlet air pressure (restricted, plugged or "too many" filters can inhibit air flow)....this will also affect voltage of the arc. You should put a pressure gauge after all filters right at the air inlet to the plasma......if it is lower than 90 psi or it fluctuates....then there is a restriction somewhere in the air system....this pressure check neds to be made when air is flowing to the torch.

-Loose or dirty work ground connection will cause varying voltages....with a height control will normally cause the torch to dive into the plate.


Jim Colt

Jim,

The voltage varied around 5-8 volts from setpoint, I.E, set at 117, it would drop down to 112 and as high as 123 or so. When cutting cleanly, its usually with 2 volts.

I actually had trouble with it again today, I cut a full .250" x 4x8' sheet of parts fine, I went to cut a couple small parts and had them mess up. Voltage varied, cut wasn't fully pieced everywhere.


I'm not as certain now as to what the issue is. I rechecked the ground clamp, and looked into possible moisture in air problems. When this issue is happening, it does seem a bit like a moisture issue- although the consumables seem to be holding up very well. The cut starts clean most times, then degrades to a rough cut, with failure to fully piece the sheet in small sections along the part.

Air seems dry. I have had no real issues with moisture since I started using the double filter setup. I purged the machine for several minutes.


I removed the Powermax's cover and looked for issues. I did find a curious situation on the high voltage side of the main board.. what appears to be dirt/dust, light in color, in almost arc-like shapes on the traces on board.

I decided to spray board with a electrical contact cleaner, and it appears theres a film/coating on the board that was peeled/washed away by the spray. The "dust/dirt" didnt seem to wash away easily, so I left it alone.


I retried a cut, and things seemed normal again. At this point Im a bit unsure whats going on- just pleased I was able to finish a few jobs today to stay a bit on schedule.