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Laser welding steel


#1

I am just beginning to learn to use a laser, and I am learning
largely by trial and error. Since there are several variables to set
on the machine, there are plenty of things to try, and errors to
make!

At the moment, I an looking for guidance with a tool-making idea I
have.

I would like to create a punch that would make three or four
indentations at a time. Broken bur shafts seem like a good choice for
such a punch. Since I have access to a laser, I would like to try
using it to weld them together.

Will this work? What settings should I use? I should probably
mention that the cover gas feature does not work.

Would a PUK welder be a better choice for this job?

By the way, I use the laser at work, but my boss cannot afford to
send me to a class to learn to use it. The goldsmiths I work with
don’t seem to be willing or able to explain how they use it (and
there are language barriers as well). What can I read that will
help? The lit I have from the manufacturer is not very helpful.

Thanks!
Noel


#2

Sure, a laser will weld steel. I don’t know how well it will work
for a punch though, sometimes the welds can be a little brittle. I’d
go over them several times to make sure you’ve got a nice, deep bead.

Can’t tell you what settings to use, I’ve welded with around 8
different units and every darned one takes different numbers to do
the same job. On my favorite laser, I’d probably use 193 volts, 4 mS,
4 Hz, and a.3mm beam width. On a different machine those settings
might not even mark the metal, or they might blow a hole in it.

I didn’t have much training on how to use them. Just a little talk
on how to turn the machine on and what a couple of the knobs meant.
The most useful training is just using the thing a lot to see what
works.

I’d leave the beam duration at whatever the other guys had it on.
They’ve probably already found the setting that works best with your
machine. This is the adjustment I understand the least, so I rarely
fiddle with it.

Do most of your adjusting on voltage. Start low and work up. You’ll
need a higher voltage for a wide beam and a lower voltage for a
narrow beam.

A narrower beam width will make a deeper impact, a wider beam will
make a shallow, smoothing impact.

Set the frequency to whatever you’re comfortable with. If I’ve got a
big area to cover I set it high so it shoots quickly and I can make
an overlapping bead. If I’m doing something delicate and there’s a
realistic chance I could screw something up, I set it low, so it
doesn’t fire an additional shot that might go somewhere I don’t want
it to.

To join two bur shafts lengthwise, I’d hold them together and tack
each end with a couple shots, then hold them at the sharp end with a
pair of pliers. Adjust the voltage so that you’re getting a nice
round splat. Use a fairly narrow beam with a fairly high hertz to
make an overlapping bead down one side, then flip it and go down the
other. If you’ve got some thin steel wire, I’d use that as filler and
go back down either side of the bead between the burs, then one more
time down the middle. Do that on both sides. Finally I’d open the
beam up a little wider, then go back over the beads one more time to
smooth them down a little. Don’t let the burs get too hot at the tip
or you’ll ruin the steel. Careful not to burn yourself on the hot
metal too, that’s the worst.

Mostly just play around with your machine though. Get to know its
peculiarities and learn by doing.

~Willis


#3

Right now I am traveling, so don’t have access to my cheat sheet that
I made up for my boss to use on the laser, but my settings for
welding steel are pretty close to what I use for gold. Differing
lasers seem to have quite different “sweet spots” that work best for
specific jobs. There is no reason at all you can not use dthe laser
to get very very good welds on steel, stainless steel, etc.

As always, practice on scrap first. Experiment to find which
combination of settings gives you a deep penetrating weld in a
metal, and then backing off on the settings and widening the laser as
you back fill the weld. Open V or X butt joints work best for
assuring full pentration, with is key to any weld.


#4

Willis pretty much hit it on the head. Every laser is slightly
different and each metal will respond differently, so for me there
is always a bit of trial and error the first time I begin a new
project. I would rather the first pulse does little or nothing to a
piece, than blast portions of the metal away. Then the next step is
to increase the power and find the setting that gives me full
penetration of a weld. No matter how pretty a surface you achieve
with your multiple welds, you must get the metal welded completely
through if you want a strong weld. Many different combinations may
work, but if you notice cracking along your weld, you need to
readjust until you pulse leaves melted metal without any cracking.

(as the saying goes, while the cat may not approve of any of them,
there are more than one way to skin a cat, and that goes for laser
welding too) Do not be afraid to destroy a few pieces of scrap,
finding a combination that works, before working on the final
project.

I have a cheat sheet I set up and leave at the laser station so
anyone else here can sit down, and have a rough idea where to start
with this particular laser. I just checked, but I did not note any
settings for steel, as I did not expect anyone else to need to weld
steel. I have found that most steels welds pretty well at the same
settings I am using for Yellow 14K: roughly 180 to 190V, 4.3ms, and 1
to 2 Hz, to start with. I adjust after the first pulse as I see the
need. Beam diameter, I keep very tight for first penetrating pulses,
and then spread the beam, and possibly lower the Voltage as the weld
progresses. It is always a learn on the fly sort of thing, as I see
the response of the setting I am using on the particular metal in my
hand.

The first laser I worked on was an older Crafford Laser Star @115
joule without pulse shaping, and even though my own laser is a
Crafford, BrightStar 150 joule, I had to develop/discover entirely
new settings when I moved to the new machine. My setting may be
totally useless on another laser.

One of the first projects I did when I first sat at a Laser Star
machine at a demo, was the simple welding of two steel ball bearings
together while holding them in my fingers. That first pulse created a
weld that I could not crack with a hammer, so I knew steel was
weldable on the machine, even though it is something I seldom need
other than for the occasional Stainless repairs on watch bands and
cases.

If you want a filler material to strengthen your steel burr welds,
you might use regular paperclips, or you may find a repair wire,
designed for repairing eyeglasses of unknown alloys quite helpful. I
keep a spool of EyeGlass Repair Wire from Rofin, that Scott Isaacs
sent me, on hand for building up the occasional mystery metal job
when nothing else seems to work on. This is a very nice alloy for
filling in such cases where you must get a strong weld, and beauty
is not the primary goal.

Good luck.


#5

Hi Noel,

Just for grins, I grabbed a couple burs and commenced to weldin’. I
have a LaserStar 100 joule unit and started with the factory setting
for “Platinum Size Thick” (250 volts, 4.0 ms, 2.0 Hz 0.30mm width)
and ended up bumping up the voltage a bit. 275 was just enough to
punch through the joint, and created a few weld spatters that filed
off with a couple strokes. My laser has a pretty tired lamp so you
might want to start with the “plat size thin” setting. I would
normally have used argon, but as you said you didn’t have that
option, I didn’t use it.

I welded the burs on both sides of the joints, with about a quarter
inch unwelded at both ends to really check the integrity of the weld.
I purposely welded them together slightly askew so I could test the
strength of the weld by trying to straighten them. I did no building
up or adding of wire, just used the metal in the burs themselves.
After cooling and a little cleaning up, they took a pounding with a
deadblow hammer and then clamping flat with a vise. Both burs are
bent slightly around each other and the weld still hasn’t broken.
It’s not jewelry level in appearance, but it’s pretty strong.

We didn’t get any training either, the purchase included some but we
just never got around to going up there to get it. We winged it with
the factory book and got through fine. Start with the factory
settings and play around with those. You will probably find that
voltage will be your most used power control, but the dwell time (ms)
has a definite effect on weld quality, so don’t be afraid to mess
around with it too. If you don’t have the operators manual, pm me and
I’ll send you copies of the pertinent pages. Even if it’s a different
make and model, the basic operation and principles should be the
same.

You will probably also find that the laser was made for welding
platinum, but it stinks with silver. Try hard silver solder wire
drawn down to 30 gauge instead of sterling laser wire. Deox silver
casting grain cast into an ingot and drawn down to 30 gauge works
even better if you can spare an afternoon to pull it (no one I can
find sells deox sterling wire). White gold works, but not at all
well, especially without argon. The lower the karat, the harder it is
to work with. Don’t count on any white gold weld to hold (or not have
porosity) without something else helping it along. Like silver, white
gold hard solder works better for filling and building up than
karated wire. Yellow golds work pretty well, but the higher the
karat, the more like silver it acts, something to do with
reflectivity versus absorption.

Voltage and dwell time can be compared to shutter speed and f-stop
in photography. They can be used to produce similar results in one
situation, but because they achieve those results in completely
different ways, they can cause completely different results when they
are used to solve a different problem. Attempting to use one to
correct a deficiency that is caused by the other will usually only
make things worse. When you change multiple things at once, you can’t
tell what works and what doesn’t, unless you have the base knowledge
of what each setting does independently. This is basic procedure for
setting, testing and troubleshooting anything that requires
adjustments of multiple variables, from photography to test-flying
aircraft. If something all of a sudden starts not working right,
check or change the last thing you did back to where it was before
trying anything else.

Have fun learning that beast! It’s worth the effort, and will take
much less effort to learn than you think. It won’t ever replace your
torch, but it does have it’s uses.

Dave Phelps