I'm thinking of picking up a cheap welder to use for a little
home-brewed electrochemical machining (aka electro-etching). Has
anyone tried this? Which would be more appropriate for this
application, a CC or a CV machine?
I believe that a transformer-based CV machine is basically a transformer with a
big capacitor bank. At any rate, my wirefeed has a bunch of honkers in it. CC
stick machines I believe have transformers that are wound to maximize
inductance. But either would work fine if you aren't suddenly varying the load.
The reason stick machines are CC is that if the weldor varies the arc the
current will try to stay as much as possible the same so the weld doesn't vary
as much. For a fairly constant load, I'd imagine either would work OK. What kind
of current and voltage are you looking for?
Unless you mean "Electrical Discharge Machining", or EDM, you've
been seriously disinformed. Electro-etching takes milliamperes at
less than ten volts. You could do it with a couple of flashlight
batteries. If you're really talking about electro-etching, then I
might suggest that you might do a little studying on the subject.
Electrical Discharge Machining, on the other hand, is one of the things
that drops my jaw in awe, and could, conceivably, take the kind of power
that's necessary for real welding.
" The ECM process requires low voltage DC. Voltages from 5v to 15 v
are usually used but may go as high as 30 v in certain cases.
Currents from 100 to 20,000 amp are being used with even higher
currents being considered for the future.
A welder would have a higher voltage than you need, but might work for
doing some experimenting. You might also consider Microwave Oven
transformers with a rewound secondary.
I ran an EDM machine many years ago, voltage was under 30V, don't know
the amps but it wasn't on the order of 100A or more. The power supply
charged a capacitor which then discharged as a spark between electrode
and work piece with a flow of electrolyte to wash away the tiny bit of
material removed by each spark. We used pieces of copper tubing as the
electrode to burn out 'high speed" alloy tools like taps that had seized
in a work piece. EDM removed the hard tool steel as easily as mild
steel and allowed us to salvage a piece with lots of materials and labor
invested in it. Slow but the only option was to cut out the damaged
area, weld in a repair, and then turn, drill and tap, bore and ream, etc
to replace what was lost. Grove Valve & Regulator, gone now but we made
the valves for the Alaska pipeline.
See Radio Shack if you're looking for electrochemical etching or
chemical etching similar to the process used for circuit boards. They
used to sell kits of tape and "resist" pens to protect the copper
plating on a circuit board that you want to keep, then use acid to
remove the rest of the material.
Rich Grise wrote:
At this point, I would guess somewhere between 10 and 50 V, and
probably 5-10A as a minimum, possibly much more depending on how much
area needs to be etched (and how patient I am). I expect some
experimentation will be involved. I may end up needing a step down
transformer to get the voltage in the right range.
Those numbers seem in line with the info I've run across so far. The
industrial machines run with very small (sub-mm) gaps between
electrode and work. My setup will be a bit cruder with a substantially
larger gap, so I imagine I'll need to bump up the voltage quite a bit.
And I'll be working at lower currents, at least initially -- until I
get a handle on the process -- but I should still end up with much
higher material removal rates than during my earlier experiments with
a 12V/6A battery charger. I'll keep the microwave transformer in mind
in case the welder doesn't work out. Thanks.