Re: [CAD_CAM_EDM_DRO] TIG Welders

If its a DC out welder maybe the kW in are not calculated using the appropriate formula that accounts for the AC waveform.

GW wrote:

> 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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