Re: [CAD_CAM_EDM_DRO] TIG Welders

Excellent explanation on how the 'cleaning' phase of AC welding
works.

I'm still wondering why, with only a couple-o-kilowatts out, you need
almost 15 kilowatts in.

Doug Harrison mentioned something about reactive 'idle' current that
doesn't show up on the _meter_. New concept for me. Suppose its
something similar to circulating current in a stepper winding.

Still, 12KW dissipation in the box?

-G

----- Original Message -----
From: Hans Vogel <hvogel@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
Sent: Saturday, January 13, 2001 5:08 AM
Subject: Re: [CAD_CAM_EDM_DRO] TIG Welders


> OK, Although this can be a complicated explanation here is a condensed
version.
>
> DCEN (Direct Current Electrode Negative) Meaning the electron flow goes
from the tungsten to the workpiece. This mode is normally
> used for steel materials.
>
> AC This mode obviously alternated between DCEN and DCEP (Direct Current
Electrode Positive).
> The EP portion of the cycle actually "bounces" positively charged
relatively large ions (compared to electrons) onto the workpiece.
> These ions impinging plus the transitional current flow (AC) causes the
surface oxides on the workpiece to dislodge then providing
> the following DCEN cycle to actually heat and penetrate the un-oxidized
material. Sound kinda crazy at first but when you consider
> the application of AC TIG or GTAW (Gas Tungsten Arc Welding) which is
Aluminum or Stainless Steel One would realize that Al oxide
> which coates all unprotected aluminum is a high melting point ceramic.
this ceramic actually shields the base material al from
> bneing penetrated or welded efficiently.
>
> The pulsed mode may be a few different things. First it may just be a DC
base signal with a pulsing amperage wave above the base
> signal. this is used more with wire feed welding.
>
> The second possible description is where the AC wave form as described
above is changed to somethin other than the frequency of the
> power source. The shape and period of the wave form is changed to
"Balance" time spent in either DCEN or DCEP. This would balance
> penetration and Oxide cleaning respectively.
>
> Bottom Line:
>
> With MIG use DCEP. for All materials. The DCEP heats the wire sufficiently
for burn off.
> If your machine has a pulser, use it when welding Steel out of position
(overhead, vertical) because it will have lower heat input
> than straight DC. The pulser should be used with Aluminum in all
positions. Do not use the pulser if your welding steel in the flat
> position due to better penetration with DCEN with no Pulsing.
>
>
> With TIG Use DCEN for Steel
>
> And AC for Aluminum
>
>
> I hope I was of some help. It took me the better of 6 years to find some
of this stuff out.



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