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Until a few
years ago, interest in maintaining the cleanliness of coolant
in machine tool sumps arose
chiefly from in-shop environmental concerns: odor was a problem,
there was smoke in the air, or
operators were suffering from contact dermatitis--all problems
attributable to tramp oil in the coolant.
However, while the environmental issues continue to be important,
in the current difficult economy
most shop managers recognize intuitively that maintaining clean
coolant in the machines is essential
for running an efficient and profitable shop. After all, if machine
tools ran just as well with dirty coolant
as with clean coolant no one would ever change coolant. However,
despite the general agreement
that clean coolant saves money, it is a rare shop manager who
has actually calculated the cost
savings resulting from maintaining clean coolant in the machines,
and the savings are quite significant.
The cost savings result from the following improvements in shop
operations:
  A
good coolant maintained regularly with an efficient pump/skimmer
unit can run at least one
year in the sump before it should be changed. With no skimmer
or with an inefficient belt or disc
skimmer, the coolant must be changed every two months, or six
times per year. Therefore, with
efficient coolant maintenance, annual coolant purchase and disposal
costs are reduced by five
changeouts per year, or 83%.
In
addition, reducing coolant changeouts from six per year to one
per year will similarly
reduce by 83% the labor required for changing the coolant and
the machine downtime during coolant
changeouts.
Running
with clean coolant significantly reduces tool wear compared with
running with dirty
coolant. Based on feedback from hundreds of shops, a conservative
estimate for the benefit of
clean coolant is a 10% saving in tooling cost.
The following cost savings are calculated for one machine with
an 80 gallon sump. The reduction in
coolant changeouts will save five changeouts per year, or 400
gallons of coolant in the sump per
year. The concentration of coolant makeup is assumed to be 5%.
 Coolant
Makeup: 5% of 400 gal., or 20 gal. at $20 per gal. |
$400
per year |
| Coolant
Disposal: 400 gal. per year at $2 per gal. |
$800 |
Labor
for Changeouts: 4 man-hrs per changeout, 20 man-hrs per
year
 at $20
per man-hr |
$400 |
Machine
Downtime: 20 machine-hrs per year
at $70
per machine-hr |
$1400 |
Tooling
Cost: 10% savings of $10,000 tooling cost
per machine
per year |
$1000 |
 Total
savings per machine per year |
$4000 |
| Approximate
cost of pump/skimmer per sump |
$1000 |
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Payout
time for pump/skimmer: 0.25 years, or 3 months |
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We can cite
the example of PV Engineering (Salisbury MA) to illustrate the
fact that cost savings
and improved shop efficiency are now the driving forces in the
decisions by shops to install efficient
cooling cleaning equipment. PV Engineering, founded in 1988, is
a family-owned shop serving the
defense, power generation, and medical markets. They employ 21
CNC machines, primarily
machining stainless steel. After analyzing his shop's operation,
Peter Vlismas, vice president of PV,
concluded that ineffective coolant maintenance was having a detrimental
effect on the performance of
his shop. He contacted Keller Products, Inc., a leading supplier
of coolant cleaning equipment, and
cited the following specific objectives: "Minimize waste,
run cleaner, and improve profits." Since
Keller has more than 5000 coolant cleaning units operating successfully
in shops and the cost
estimates suggest a potential saving by PV of more than $80,000
per year, the Keller salesman
quickly reached an agreement with Peter Vlismas to initiate a
test program. PV installed a TKO-14
pump/skimmer unit at the sump of one machine. In common with all
Keller pump/skimmer units, the
TKO-14 pulls oily coolant from the surface of the sump, filters
to remove suspended solids,
separates the tramp oil from the coolant with the patented Keller
maintenance-free separator
elements, and returns the cleaned coolant continuously to the
sump at high flow rate. In contrast to
the belt skimmers that PV had previously tried, a Keller pump/skimmer
with a 1/2" air-operated
diaphragm pump turns over a sump rapidly-for example, a 90 gallon
sump will be turned over
twice per hour-aerating the coolant and ensuring that there are
no stagnant areas of the sump in
which oil and solids can accumulate. The separator may be run
when the machine tool is operating or
is idle.
After running
the TKO-14 about one month, Peter Vlismas decided to equip his
entire shop with
Keller units. Keller supplies three models of TKO units to accomodate
any shop space constraints.
The TKO-14, which has a footprint of 14" x 14", could
be conveniently set on the floor adjacent to
seven of his 21 machines. For the remaining 14 machines, Peter
selected the TKO-6 with the
CLO-1 magnetic frame, which can be mounted off the floor directly
to the machine tool and requires
zero floor space. In operation, the TKO-6 performs exactly like
the TKO-14. The Keller units have
been operating for more than six months. The evaluation from Peter
Vlismas: "Coolant waste has
been greatly minimized, the machines run cleaner and more efficiently,
and the shop is more
profitable. The Keller units installed easily without interruption
of shop operations. All my objectives
for the program have been achieved at relatively low cost and
with no operating problems."
Conclusion:
Maintaining clean coolant is an important Lean Manufacturing initiative.
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