Re: plasma accuracy

Most of the cutting heads seem to be a body with the various
consumables screwed onto the end. The torches as a whole (with long
cables, hoses, switch etc) seem to quite expensive where as the
business end parts seem to be quite cheap.

If these parts were mounted in a homebrew head and low power
settings used on some power supply or other, could such a devive be
used for thin material. When I say shim it could well be thicker
than foil.

Is the cutting voltage of 70-100 actually due to the requiremet of a
decent working distance? Could a short working distance be used
with decreased voltage?

Graham

> The secret to plasma cutting (and I would like to see a standard
> machine that can hold .025 kerf width) is NOT the power supply.

It

> is just a rather crude constant current source that has a an open

arc

> voltage of around 200 Volts and cuts at about 70 to 100 VDC.
>
> The challenge is to first ionize and "ignite" the air to make the
> 30,000 deg plasma flame and then *control* it so it doesn't cook

all

> of the surrounding components. Most torchs have specially designed
> swirl chambers to spin the air as it exits the tip. The torch

handle

> and it's design are what largely controls the quality of the cut.
>
> Hypertherm makes a "Fine cut" series of consumables for some of

their

> torch models that will hold .025 under perfect conditions,

but .010

> is doubtful.
>
> Precision plasma (different technology and $$$$$) uses shielding
> gases other than shop air and uses oxygen (I think) for the plasma
> and will do some fine cutting.
>
> Using a standard plasma to cut foil is like driving a tack with a
> sledge hammer.
>
> I'm real happy when my torch holds a .062 kerf and depending on

the

> wear on the consumables it can climb to .080 or higher. Pierce

points

> can be double the cut kerf in diameter. I try to plan my cuts so
> things that need detail are cut first on a new set of consumables.