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Bridging Gaps with Laser


#1

I’ve stumbled upon this way to bridge gaps. Close the aperture down
and maybe also increase duration, shoot at an angle to the two
surfaces, like a bank shot in pool. Surprisingly the molten metal
jumps the gap but looks porous and weak, Go back over the join with
lower power, higher aperture to flow things smoothly. It seems once
you have even the slightest connection its easy to ‘push’ more metal
into the join. Kinda like filling but without the filler wire. So far
I’ve done gaps up to, I dunno…010" or so. It might go more but I
haven’t tried yet.

Two questions.

Is this type of join inherently weak because the first ‘tack’ is
porous despite that subsequent layers have a nice smooth cosmetic
look?

Any laser wizards have some other ways of bridging gaps?


#2
Any laser wizards have some other ways of bridging gaps? 

I normally use a filler wire to bridge the gap, then build up on or
with it depending on the size of the wire. As for a bridge being
brittle I am of the opinion that it depends on the material being
laser welded and the weld conditions.

Wayne M Schenk


#3

I have not had great luck by that bank shot approach, but I have
bridged quite a few gaps by tacking wire to the solid area beyond
the gap, bending the wire across, and then tacking it on the
opposite side beyond the gap. On big gaps I sometimes need to build
several of these bridges. (On small gaps this bridge can sometimes
be made by balling the end of the wire and tacking it on both
sides). I then fuse the bridges into one thicker bridge, and then
back fill the entire area with the wire. I then trim away the
excess, if necessary, although using the bank shot now, I can blend
and use any extra metal by pushing it into place with the pulse. As
long as you readjust the laser and remove your original porosity you
should have a solid structure, equal to the original, assuming you
are using matching metal, and not solder to fill the gap.

The laser is an amazing tool, that even after 6 years I’m still
explor= ing and learning about. I love to see questions and comments
on Orchid about the laser as I know we are all finding new and
different ways to use this tool, and I know that I am nowhere near
truly mastering it yet, or using it to it’s full potential!


#4

Not a laser technique, but an old stick arc welder’s trick was to
take a welding rod (with the flux removed) and lay it across the
hole /gap and weld each side to the rod…

Wasn’t necessarily the strongest weld, but on thick material it gave
you a base to reflow weld rod and native material above it. This sort
of sounds like what you are doing here, on a much thinner scale…

Kay


#5

I’m no wizard, but my experience is that the gap filled is pretty
strong in platinum, not quite so strong in yellow gold (the higher
the karat, the lower the strength of the joint), and not worth a hoot
in white gold or silver. A lot depends on how deep you go on the
first round. I haven’t done very much with palladium, but I would
think it would be like white gold in strength. You can move white
gold around a little better and more smoothly with argon, but it’s
still pretty brittle. I also find I can fill a gap in width in the
same order of strength, platinum, yellow (low to high karat). white
and silver. It also doesn’t seem to work hardly at all with steel and
titanium and other eyeglass metals. Moving the metal around, I mean.

By the way, you CAN damage a diamond with a laser! I punched a tiny
hole in the table / crown facet junction of a small trap cut the
other day while filling in a small hole in the corner of a platinum
bezel. The stone was an E - VVS so it didn’t have anything to do
with hitting an inclusion or anything (which I have been warned
about). I was using a very small aperture (0.2mm) and around 210
volts with a pretty good dwell time (4ms?). I was aiming slightly
above the stone, pretty much parallel to the facet junction, away
from the table and into the edge of the bezel. Didn’t think I even
hit the stone, but it might have been reflected light that did the
deed.

Be careful where you point that thing!

Dave


#6

I have not found a difference in strength on the gold (W or Y) bridge
work, or for that matter on stainless. I have to make very sure that
I have not created a poreous bridge, or no metal makes a strong
joint. In the shop I was last in we did quite a bit of repair to
Rolex cases and bands, including gap filling, with very good results.
Silver on the other hand, still often frustrates me!


#7
Not a laser technique, but an old stick arc welder's trick was to
take a welding rod (with the flux removed) and lay it across the>
hole /gap and weld each side to the rod... 

Right, some of my early training was welding, gas and arc, so some
of that carries over into laser work pretty well.