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Experience with PUK welder


#1

I bought a PUK welder several years ago. I do use it fairly often but
mostly for tacking parts on before soldering them. Don’t believe the
hype. It is not practical for retipping. The welds are brittle and
the tips break away fairly easily. If you weld near a stone, the
stone will likely be damaged by the arc. Diamonds are the exception.
It is usless for repairing most glasses frames. It works on titanium
but again the weld breaks easily if twisted. I’ve never used it
successfully on 18k yellow gold. I do a lot of jewellery assembly
and the machine is excellent for that purpose but if you think you’re
buying a cheap alternative to a laser welder you will be
disappointed.

R. Hood


#2
.... The welds are brittle and the tips break away fairly easily.
If you weld near a stone, the stone will likely be damaged by the
arc. Diamonds are the exception. It is usless for repairing most
glasses frames. It works on titanium but again the weld breaks
easily if twisted. I've never used it successfully on 18k yellow
gold. I do a lot of jewellery assembly and the machine is excellent
for that purpose but if you think you're buying a cheap alternative
to a laser welder you will be disappointed. 

If it makes you feel any better, laser welders too, have their
limits, especially those, like older machines or some of the less
costly ones available now, that don’t offer pulse shaping abilities.
Laser welds are generally inherantly work hardened, and perhaps for
the same reason you can get brittleness in a PUK weld. Here you’ve
just generated a little molten pool of metal in what amounts to a
larger, rigid, mass of cold metal. The molten metal solidifies
quickly and then equally quickly, cools. As it cools, it shrinks.
Unlike a cooling solder joint where everything got hot, in this
instance, the weld alone is cooling, thus stretching it. Some metals
just get a bit harder. Others downright crack. Pulse shaping allows
the weld to be cooled a bit slower, allowing just a tad of annealing
to happen as it cools, thus avoiding some of the cracking problems.
But lasers can blast stones, give cracky brittle welds, and otherwise
not always live up to the promises of sales people who may not always
themselves be expert laser welder operators…

With that said, lasers seem to have fewer of these problems than do
the PUK welders, perhaps just because you’ve got a few more
paramaters to adjust and alter. Retipped prongs don’t crack off, for
example, in most cases I’ve seen. But they ARE harder than a torch
retipped prong, which may be a good thing for wearing properties. On
the other hand, a laser repaired whole prong which now needs to bend
at the weld for setting a stone? In white gold that will often be a
cracky problem.

Platinum though, is a dream to weld. And if your laser has the
power, the usual 18K yellow golds work very nicely too. I have more
trouble with 14K yellow. Tends to crack. So do many of the nickel
white golds, especially when you’re working on a casting…

And I too often use my laser not for the whole assembly, but as a
way to attach and align and hold parts for subsequent soldering.
Among other things, I can construct a tight capillary seam, tack it
with the laser, flow solder in, and the seam is then virtually
invisible, as a good solder seam should be. Laser welds, and PUK
welds, just don’t do that, since the weld bead has width, and the
deeper the weld, the wider the weld zone ends up being. If you can
clean up the weld, it can be an invisible seam. But for detailed
precisely fitted parts, sometimes it’s messier than solder.

Peter