POWDER CASE STUDY:
Wagner is a remanufacturer of brake shoes that are used within a
drum style brake for cars and trucks. The epoxy powder coating is used
as a rust inhibitor. The smaller brake shoes have bonded pads, while the
larger brake shoes have riveted pads. A new facility was built in mid
1993 for the processing of brake shoes. The old brake shoes are
disassembled, cleaned, powder coated, cured, fitted with new brake pads,
and repackaged for distribution to customers. The facility operates 90
hours per week.
The operation was initially
designed with 7 separate remanufacturing cells. Each line contains one
(1) 4' long short wave oven. The heating elements are T3 lamps with a
reflective housing. Gas convection ovens were considered for the
application, but too much floor space was required. The short wave ovens
have the advantage of small footprint and reasonable energy consumption.
The disadvantage has been the maintenance requirements for the systems.
Within several months of the facility opening, the heaters began to
fail. Every week there are two short wave ovens that undergo repairs
averaging 7 hours per week of labor plus the parts cost. The cost of
parts and labor equals 26,000 per year. More important than the parts
and labor cost is the downtime and the associated overtime costs.
wave infrared oven achieved all of the goals for a new curing oven:
The facilities engineering
team at Wagner Brakes decided it was time for a new approach. Due to
past problems, the team decided that long term testing was required
before jumping into heating technology. After two years of testing, that
new approach has been approved. The decision was made to install seven
replacement medium wave electric infrared ovens from Blasdel
OF USING IR FOR THIS APPLICATION:
The medium wave infrared ovens are either 6' or 10" long depending
on the part size and weight. The short wave infrared ovens were 4' long.
All ovens are 3' wide. The short wave ovens were operating at full power
to cure the powder. The new medium wave Blasdel ovens were designed to
operate at less than 50% power. This would allow future increases in
line speed. It also meant that the ovens would be slightly longer in
length, which would not adversely affect floor space. A convection oven
would have required a minimum of 50' for the same project.
The short wave infrared ovens require an average of 7 hours per week of
preventative maintenance. After two years of operation there have been
zero heaters that prematurely failed in the Blasdel medium wave oven due
to heater problems. There have been several heaters damaged due to
conveyor problems, but this is not related to the heater design. With a
typical life expectancy of 25,000 hours for Solar Products panel
heaters, the customer will continue to operate for a long time with very
few maintenance problems.
Often times the input power rating is viewed as the actual power
usage for an electric infrared oven. In this case, the 10' oven running
9" brake shoes has 108kw of electric infrared installed. But, in
actual operation, the energy usage is 41kw. The energy calculation is
41kw*hrx5.5cent per kw*hr= 2.25 per hour of operation. Based on the
current production rate, that equates to 2/10 of 1 cent per part. In
other words, it costs 1 cent to cure 5 brake shoes. The energy
consumption for paint and powder applications typically accounts for
less that 1% of the product selling price. Our guess is that this amount
is well below that 1% margin. The best part is that Solar Products panel
heaters maintain a consistently high radiant efficiency (80%) over time.
NOTE : Each 18" oven half
can operate independently. This allows the heater output power to be
adjusted to the part weight. Because the brake shoes range in weight
from 1.5 - 15 lbs, they require different power output to match their
curing times. The 10' oven is used for heavier parts.
The brake shoes range in size from 7"
- 12" radius plus a heavy brake shoe for trucks (15lbs). The
information relates to a 9" brake shoe in a 10' long oven.
||Steel brake shoes
||Black epoxy powder - 2.0 mils thick
||Automatic electrostatic spray gun in booth
|Length of oven
|Zones per oven
|Actual power usage
||25 kw per hour
||41 kw per hr
||Medium wave electric infrared
||Solar Products medium wave panel heaters
||Dual chain conveyor
|Weight of part
||1.5 - 15lbs
|Gel and cure time