On 24 Jul 2004 03:12:54 -0700,
(E-Mail Removed) (Mark Harriss)
wrote:
>Hi John,
> I did try multiple 630VDC capacitors up to 40 KV in
>series/parallel arrangements but they all died in under 5
>seconds no matter what. The aluminium solder was bought ages
>ago from Dick Smith and is made by Multicore. It needs a hot
>tip which will suffer corrosion from the flux (it stripped
>2mm of scale from a 150W Birko iron in minutes.
>
> The gas timer will be next cab off the rank for my unit.
>I still need to get my own handle yet though buying one from
>the states looks to be about 30% of the local price.
>
> Does TIG welding aluminium require actual high current HF
>power or is 50Hz good enough?.
>
>
>Thanks
>Mark Harriss
Hello Mark,
thanks for the info on the solder. Pity about the multiple capacitor
bank. I think the Tesla coil boys use a particular polycarbonate
type that are more rugged than normal polycarbonates for pulsed
use and have some slight self healing ability. I remember checking
them out price wise and they were about four or five dollars each from
a mob called Crusader or a name something like that down at Padstow.
The Tesla group have all the details on this capacitor. Anyway, they
were too expensive for me. Did you use resistors (in the megohm
range) across each cap in your original multiple mini capacitor bank.
Yes, 50 Hz is fine for welding aluminium using an ordinary common
transformer machine. Some welders have a "balance control"
that can bias the AC current waveform to be slightly more positive
or negative as required.
Electrode negative heats the job more than the tungsten electrode.
Electrode positive heats the tungsten electrode more than the job
but has a nice cleaning action on the aluminium. So playing with
the balance control allows the operator to have more, or less
cleaning action, according to what the job requires.
People have being using plain ordinary transformer welders
with no balance control for decades. You'll be fine.
With the expensive inverter machines full of bells and whistles
the AC welding current can be varied from 20 Hz to a few
hundred Hz. The higher the welding current frequency the
narrower the heat cone becomes. One of the students
at the Meadowbank Tafe welding night class brought
in his new $6000 suitcase size inverter tig machine and
let us all have a play with it. At 20 Hz the heat cone was
fluttery and wide. At the higher frequencies, I noticed a definite
narrowing of the heat zone. Good for penetration on thick material.
I only had a five minute play but it was great.
We all wanted to play with it. Variable pulse settings, variable
background current settings, adjustable sequences, for heating
up and gradual cool down to avoid craters and memories for
recalling the settings for particular jobs. What a machine!
I bought a cheap auto darkening helmet which helped me
enormously but later I found out that the view through it was not
as clear as other students autodarkening helmets. I paid $200
for mine, I have seen the same model go for $100 new on
ebay. Try a few on the job before you buy one. The one I
liked owned by a fellow student was a $300 Preditor brand.
To me, the clarity of this student's Preditor helmit was
as good as our teachers expensive Speedglas helmet.
Avoid this one. AG3 (AG111)
That is the model I have It is not good.
http://cgi.ebay.com.au/ws/eBayISAPI....829460081&rd=1
Give that brand/model a miss.
Hey Mark, you still haven't told me how you joined the
heavy black cable to the front panel studs. :-)
You mentioned buying a tig torch from the USA.
Silverwater welding down here in Sydney have a
small tig torch, 100 amps max for short periods for $110.
Have you bought stuff from the USA? Any problems with duty
or customs? I have been looking at used electronic test equipment
from the USA on ebay and it looks so good, price wise.
Regards,
John Crighton
Hornsby
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