Donner recommends applying the agent, run-
ning it for an hour or two, and then draining it. Next
comes the critical part: “I recommend filling and
flushing the system with water at least five or six
times,” he said. “If you don’t, traces of that [bacte-
ria-killing agent] will start corroding components
inside the machine.”
Only then do you refill the chiller with deionized
water, check it with a conductivity meter to ensure
the water conductivity is at zero (a check of the wa-
ter’s purity), and then add the needed chemicals
provided by the laser machine manufacturer.
“Once the chemicals are in [the chiller], you need
to run it for a good hour before you can shut it off,”
Donner explained. “You need to dilute the chemi-
cals. If you just dump them in the water, you have
a bunch of chemicals that will just sink to the bot-
tom of the chiller tank, because the chemicals are
heavier than the water.”
Donner checks the sacrificial anodes that col-
lect dirt from the cooling water. These anodes pro-
tect other resonator components. If those anodes
are not cleaned, dirty water could be entering the
system, which can damage RF tubes and similar
components—and which can be very expensive to
“You need to check those sacrificial anodes to
make sure they’re clean,” Donner said. “Even tita-
nium sacrificial anodes, which should last the life of
the machine, still collect debris, so you still need to
Finally, Donner checks the screens and restrictors
on the water lines that filter and control the water
flowing into optical elements, including mirrors in
the beam-delivery system and focusing elements in
the cutting head.
When inspecting certain machines, Donner
checks a Lanny valve above the cutting head, then
looks for a tiny stainless steel screen in the Lanny
valve itself, as well as a restrictor connected to the
valve. He then unscrews the screen, sees the gunk,
and shows it to the operator (see Figure 10).
“Nobody I’ve worked with has known this screen
was there,” Donner said, adding that cleaning or re-
placing screens like this can save shops thousands
of dollars in replacement parts. He added that
cleaning screens frequently doesn’t solve the larger
issue. The chiller water has to be clean to begin with.
Some elements of the machine will need replac-
ing at some point, no matter how clean the cool-
ing water is. Conventional (not titanium) sacrificial
anodes are one example. But with careful main-
tenance, many components can last much longer
than their expected life.
A Money-saving Routine
Making sure the system is clean to begin with is re-
ally the key to it all. If the beam path is pristine, lens
changeouts occur properly, and the chiller water is
kept clean and consistent, most components in a la-
ser should stay clean as well.
Half the battle is just knowing how to keep the
system clean, and what components to check during preventive maintenance. If everything is as it
should be during the next PM cycle, you’ll need only
to inspect and clean components—not spend tens
of thousands of dollars, or more, replacing them.
Senior Editor Tim Heston can be reached at
Photos courtesy of Donner Laser Consulting,
Small things matter. On certain machines, the small screen (right) can be found in the Lanny valve (left). Cleaning
those small screens can make a world of difference. got casters?®
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