70 The FABRICATOR DECEMBER 2017
quartz tubes on my machine now are as clear as
they were nine years ago,” Donner said, adding that
continual monitoring of temperature has a lot to do
with that. Certain high-powered lasers (6-k W CO2 laser and higher) have temperature monitors on the
optics. Any significant change in temperature points
to internal damage.
“If you keep your machine clean in the first place,”
The Water Cooling System
Donner said, “there are so many things you don’t
need to do.”
Put another way, good preventive maintenance
minimizes reactive maintenance. And on the road
for his consulting work, Donner performs plenty of
Like the beam path, the water in the cooling system
must be clean and have the right amount of chemi-
cals in it. If it doesn’t, dirt, debris, and corrosion can
accumulate on components that rely on that water
for cooling (see Figure 6).
For instance, consider the cooling water running
through the CO2 laser’s charged cathodes. If the water isn’t as clean as it should be, those cathodes will
become contaminated (see Figure 7).
Basic cooling system maintenance includes flushing the water every year and changing the chiller
filter every six months (see Figures 8 and 9). Also,
make sure the chiller’s air cooling is working properly and that the covers are closed. Otherwise, debris
from shop air can make it into the system.
If, say, a shop is hot and humid, and some chiller
water evaporates, never simply pour more water into the system without pouring in the correct
amount of chemical. “If you do that, you now have
diluted the chemical-water mixture in the system,”
Donner said. Microbes start growing, and the chiller
water and filter turn green. Donner recommends
operators use replenishing kits, available from laser
machine manufacturers, that can help replenish the
chiller water with the correct amount of chemical.
Problems also can come from improper water
changes, and the water color in the chiller tank can
be a telltale sign. Red water comes from improperly
applying antimicrobial agents like STA•BR •EX®.
Brown filters, like the one on the top, turn the chiller
water brown. A green filter (bottom) is a sign that the
proper chemical-to-water ratio wasn’t maintained.
Scum on the bottom was collected from the water tank
on the top.
If everything is as it
should be during the
next PM cycle, you’ll
need only to inspect and
spend tens of thousands
of dollars, or more,