I too have a laser welder, and have been offering eyeglass repair as
part of my shop service. I know where you are coming from with your
statement. There seems to be many different types of alloys used to
make eyeglass frames, and there are a couple that just won't bond no
matter what technique you use. I find with the base metal frames, I
have very good luck using just sterling silver wire. On a few
occations I have used 18K yellow wire and it bonded well. With some
of the titanium alloy frames, I have the most problem with brittle
weld. Like you said, even under argon, the weld is still very
brittle. When you get good, high purity titanium frames, they weld
beautifully. My rule of thumb is, when I watch the puddle during the
weld, if it cools to a flat grey color, I don't waste my time
repairing the frame...it will break later. The puddle needs to shiny
and smooth, and then the welds seem to have much more integrity.
Overall though I find eyeglass repair to be a real crap shoot. What
I ended up doing was offer my customers a 15 day money back
guarantee. If the frames broke, I would not repair them again, just
refund the money. I would estimate that I get about a 10 % refund
rate, and lots that I simply return to the customer after the first
shot with the laser. There is not a million dollars in the service,
but it has produced several new and valuable customers to my main
business operation...making jewellery.
Hope that helps a bit. If you have any more questions, don't
hesitate to contact me off list.