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K-Bar Saves Over $44,000 by Reducing Paint
Waste and Burnoff
Improved part inspection and process changes
decrease cost
Company
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K-Bar Industries,
Inc.
Faribault, Minnesota |
| Results |
Decreased powder
paint use by 8,800 pounds per year, saving over
$27,000 annually. Burnoff of racks and reject parts
decreased by 20 percent, saving over $17,000 annually. |
| Cost |
Paint system improvements
cost $36,000. |
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K-Bar Industries,
Inc. manufactures metal outdoor-maintenance power equipment,
shop equipment and parts for its parent company Northern Tool
and Equipment Company, as well as metal parts and assemblies
for other retailers. The company coats over 3,000 different
parts of various sizes and shapes in its automated powder
coating line.
In 1992, K-Bar installed its powder paint
booth. Parts were hung on hooks or racks and traveled on a
conveyor past four oscillating, automatic powder guns. Parts
passed between two manual touchup stations before heading
to the curing oven. Many of the powder paints were reclaimed
for reuse. Hooks, racks, and parts needing rework were sent
out for burnoff stripping.
Powder coating systems apply opposite electrostatic
charges to the paint and the parts to draw the coating onto
the parts. Powder paint particles break down each time they
pass through a reclaim system. Smaller particles do not hold
the electrostatic charge as well as first-pass powder. This
decreased attraction reduces the system’s transfer efficiency—with
more overspray and less paint on the parts.
Incentives for Change
K-Bar wanted to improve the first-pass transfer efficiency
of its coating operation. Nearly 35 percent of the paint purchased
in 2001 became waste. Reject parts and fixture stripping cost
over $87,000.
The company established Kaizen teams to
begin looking at various improvement options. Then, K-Bar
requested a MnTAP intern to help reduce the volume of waste
paint and reduce the number of parts and fixtures sent out
for paint stripping. The goal was to reduce paint waste by
25 percent.
Reject Parts
Coated and cured parts that did not pass visual inspection
were placed in a scrap bin and sent out for paint stripping
then returned for recoating. In 2001, burnoff of these parts
cost $42,600.
After the intern analyzed reject parts in
the scrap bin, K-Bar determined that some parts should not
be stripped. Dented and defective parts could be pulled out
and scrapped for recycling. Inadequately covered parts could
be sent through the powder paint line again and repainted
without stripping.
Inspecting parts with greater scrutiny and
raising operator awareness about sorting scrap helped reduce
the volume of parts sent for burnoff, saving $25,000.
Paint Booth Operation
The intern analyzed paint booth operations. Operators manually
adjusted the movement of the four automatic paint guns to
get the best possible coating coverage. Guns were not switched
on-and-off between parts or runs. When coating longer parts,
operators often used the guns’ maximum settings to ensure
proper paint coverage. Coating thickness/mil build was visually
assessed but not measured.
The intern reviewed the system’s settings
and found that tuning the existing four-gun system was inadequate.
Vendors were asked to propose changes to the paint system.
With their input, K-Bar chose a new six-gun system with digital
controllers and a light curtain, costing approximately $36,000.
Using a lower pressure, the three new guns
on each side of the booth produced a more-uniform coating.
Because more paint is attracted to the part on the first pass
less becomes overspray that needs to be reclaimed. Depending
on the part, not all guns trigger.
The system’s lower operating pressure
minimizes the amount of powder that bounces back, which decreases
the need for booth cleaning. With better first-pass coverage,
manual touch up is needed only for difficult-to-reach part
recesses or unusual shapes.
The light curtain is linked to a controller
on the guns which turns them on-and-off between large parts
and between part runs. This results in powder and energy savings.
To better monitor mil build, K-Bar started
more closely tracking and evaluating coating use so it can
further fine tune and optimize its system. Documenting painting
parameters in greater detail for similar part families helped
K-Bar set digital paint programs and helped operators become
more consistent.
Fixtures
In K-Bar’s conveyorized paint lines, multiple part fixtures
were used to suspend parts—parts were hung on hooks that
hung on bars suspended by conveyor hooks. These fixtures carried
parts along conveyors that passed through the metal pretreatment
washers, entered a drying oven then the powder coating paint
booth.
Rack design. The fixture racks were
made of one or two hollow, square steel-tubes with rings for
hanging hooks. On occasion, rinse water stayed in the fixture
then would drip as the parts were powder coated, streaking
the finish and causing rejects.
The MnTAP intern worked with K-Bar engineering
staff to redesign the rack fixture. A thinner, shorter, single
solid bar with racking holes was designed. By eliminating
the hollow bar, and the ridges and gaps of the weld seams
that could hold water, finish defects attributed to drips
were eliminated.
Rack burnoff. Coatings build up on
part fixtures over time and need to be stripped off periodically
to maintain a proper electrical ground for attracting paint
to the parts.
One big advantage of K-Bar’s new paint
system was computerized digital controls, which allowed the
company to save computer programs with all the operating parameters
for coating specific part configurations. Computer programs
facilitate setup and continuous improvement. In order to get
repeatable coating results from a program, a consistent ground
is needed. K-Bar had to significantly increase the frequency
of burnoff for fixtures and hooks, increasing costs by $8,000
a year.
K-Bar planned to continue optimizing fixture
rack design and loading, and to look at air jets to reduce
the coating build-up on fixtures.
Overall Results
Using the research of the MnTAP intern, K-Bar decreased paint
use and waste significantly, while improving quality, first-pass
transfer efficiency and throughput.
Burnoff costs decreased a total of $17,000.
Paint use was reduced from 3.75 to 3.20 pounds per hour, saving
$17,400 through July 2003. Paint system improvements cost
$36,000, with a projected payback of one and a half years.
K-Bar estimates it will save $27,000 annually in powder paint
costs.
New Equipment Hints
Keep vendors informed of how your system is operating so they
can make improvement suggestions. Maintaining a relationship
with your paint system vendor gives you access to troubleshooting
advice or information on equipment improvements.
For More Information
MnTAP has a variety of technical assistance services available to help Minnesota businesses implement industry-tailored solutions that maximize resource efficiency, prevent pollution, increase energy efficiency, and reduce costs.Our information resources are available online. Or,
call MnTAP at 612.624.1300 or 800.247.0015 from greater Minnesota
for personal assistance.
This project was conducted in 2002 by MnTAP
intern Justin Saeger, a mechanical engineering junior at Minnesota
State University, Mankato.
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