Mickey Truck Bodies embraces the new millennium by automating one of the most timely and prone-to-human-error processes as it completes the testing and implementation of its fully-automated body and trailer painting facility. Production Systems Inc of High Point, North Carolina, designed a finishing package that fits inside the 12,000-square-foot building. "We really pack a lot of manufacturing into a small area, considering the number of independent processes that are housed in this space," says Brian Ball, president of Production Systems.
"The building took two years to design, build, and equip because of the complexity of the automated processes that are used. Under normal conditions, these would be designed into a larger building. In Mickey's case, we put them under one roof and used a small footprint of area."
Controlled Atmosphere Mickey's paint facility has a controlled atmosphere throughout the entire finishing process. This starts before the truck or trailer enters the front door of the painting facility.
In addition to the standard air circulation systems, the facility has extensive air make-up systems to change and refresh the interior booth air. Each system has a permanent filter that helps eliminate airborne particles.
"Dust and dirt are brought into the facility in a myriad of ways, not just from open outside doors. Just a few examples would be the dirt from tires and spotting machinery used to move a trailer into the painting facility," says Ball. "Even old paint that is kicked up into the air from dragging an air hose around inside a paint booth can cause damage to a paint finish. "To cut down on transit induced dirt from being brought into the paint facility, none of the trucks engines are ever started, and trailers are never brought into the facility with a spotter truck," says Ball. "Every piece is floated into the facility on two 10' x 6' platforms that are lifted and glided by a large cushion of air."
Each truck or trailer is loaded onto air casters at the beginning of its journey through the painting process. The air caster loading area is outside the painting facility and consists of a large piece ofhigh-density concrete, polished into a flat surface and sealed to aid in the movement of the air platforms.
Manufactured by Air Caster Corporation, the casters easily lift the approximately 20,000-lb load several inches off the ground. The loaded platforms are then moved by hand into position using follower-type rollers along an angle track. "It really doesn't require a large volume of air, as you might expect," says Ball. "And one or two men can easily move the platforms into position." Once the piece is positioned in the first station, wash-off booth an acid wash is used to clean the inside and outside of the piece. Acid etches the aluminum material and removes any grease or film residue that might be clinging to metallic surfaces. After the acid wash, a complete hot water rinse and the application of a bonding agent for paint adhesion are conducted.
The wash-off booth is constructed of 18-gauge unpainted galvanized panels prepunched for bolted assembly. The PSI booth is 60' long, 20' wide, and 18' tall. "Built across the top is a bridge-type air input plenum that also follows down the sides to disperse air," says Ball. "There are two, 20"x20"x1" permanent aluminum filter cells on each air plenum." A Vaneaxial fan with nonsparking blades moves air inside the plenum.
Entering station two, the dry-off oven, the piece passes through vertical blades of extremely high-pressure air that blow dry the entire surface of the vehicle. Manufactured by Exair Super Air Knives, these blades are targeted at the door jam locations, a problem area where water and residue tend to hide, Ball says. Technicians also have access to a manually operated air knife in the drying booth for working around the piece during entry and exit.
Although the second station is a drying booth and not a baking-oven it is still constructed with 4" thick interlocking oven panels, which are covered with 20-gauge aluminized steel. The panels are internally insulated by Delta Mineral Wool insulation board with a 4 lb per cubic foot minimum density. This type of insulation material is not affected by moisture or vibration, which is extremely important for this environment and use, says Ball. The dry-off oven is equipped with a ventilation/quick purge exhaust system. Action is provided by a Chicago 22_" centrifugal type, nonsparking high-pressure blower. The drying booth is furnished with an automated quick purge cycle built into the exhaust air system that empties the oven chamber in approximately three minutes. Inside air temperature is controlled at the master control panel.
At the third station, Mickey technicians mask the nonpainted parts of the truck or trailer. "Even at this station we introduced some new technology," says Ball. "The masking tape has a new formulation that doesn't leave any residue on rubber or metal parts."
Now Add Paint >From there, the unit is moved on air casters through a 50-foot side door >to the priming booth. The fourth station is designed to allow the paint >technicians to apply the primer from air actuated, overhead man-lifts, >which have integral paint applicators.
The PSI priming booth is 60' long and 16' tall and has one stationary and one retractable side wall. The booth's dry filtration system removes micro-fine air particles, along with a downdraft suction-exhaust system. The system is designed to work in with the roof-mounted air intake device. The top of the booth has a directly attached to a 16' wide x 60' long x 2' inside depth air input plenum with tacky-type filters.
The double section downdraft system has exhaust pits 50' long x 3' wide with an inside depth of 2'. The pit has a heavy vehicle support floor grating and a roll-type RP-media filter directly underneath the grating. "All of the filtration for this booth has an Underwriters Laboratory Class II approval and complies with NFPA-33 regulations," says Ball.
Four Vaneaxial fans provide the air pull for the empty booth at a fan face value of 50 feet per minute. Air is exhausted through a roof exhaust stacks. The 30" diameter exhaust stacks can exhaust 60,000 cubic feet of air per minute cfm, through four 30" diameter exhaust stacks. To compensate, the air make-up will supply 60,000 cfm (nonheated air) at 70*.
The booth also utilized PSI furnished fluorescent light fixtures that are Class I, Division II hazardous location approved. The ignition proof fixtures provide a dust-tight seal using a foam gasket system with a locking-glass rim.
Technicians Get A Lift Paint technicians in three-axis manlifts apply primer. Each of the two coating booths have two lifts supplied by PSI. Four pneumatic personnel lift stations traverse a 55' roof and floor mounted rail. The 36' x 72" basket extend to a platform height of 10'. The four lifts have separate cable festooning system for air and breathing lines.
"The paint guns that are built into the manlifts use a computer-controlled mixing system that allow for an exact measurement of applicator solution and primer to be mixed at-the-gun," says Ball. "Using the at the gun mixing method greatly reduces wasted primer and many of the ecological hazards associated with unused primer."
Graco Corporation's ProMix Electronic Plural Component Proportioning System was chosen to accurately proportion and mix the applicator solution and primer.
The ProMix control unit contains an electronic controller and a mixing manifold. The controller receives signals from pulse meters housed in the system to determine the rate of material flow. It then sends signals to solenoid valves to supply the exact mechanical reaction specified and to meet the operator's material-flow demands.
Ingredients include air, resin, catalyst, and solvent. The control unit includes LED readout with an icon-driven menu. The system houses its own 'off-ratio' alarm system and automatic shutdown to insure against defective surface coating.
Once the primer coat is applied, technicians leave the booth and input a safety acknowledgment code into the computer. The interior temperature then is automatically raised to a flash-drying level.
When the heating cycle is completed, the computer automatically shuts down the heater, purges the heated air in seconds, and the unit is moved by the air casters to the fifth station.
"The fifth station, or topcoat booth, is one of the most automated stations of the entire line," says Ball. "Mickey has zero-tolerance for any quality or application problems in the topcoat. For that reason, a lot of expensive computer-commanded paint mixing and application equipment is used to insure quality control throughout the topcoat process."
Graco's Precision Mix was chosen as the applicator equipment for the topcoat booth. This system will accurately proportion and mix multiple component coatings for high-volume, low-particle (HVLP) application. The volume flow of each component is accurately measured through individual flow meters and relayed to the electronic control. The control analyzes the volume data according to preset ratio tolerances. As materials are needed to maintain the ratio, the electronic control directs the operation of the fluid control valves located on the manifold assembly for each component stream. This creates a closed loop system assuring continuous ratio compliance. Within the manifold, the individual volumes of resin and activator are first combined and blended throughout a station mixer for application use.
Mickey Can Pick Paints Color changing operations can be sequenced during the automatic purging of the mixed materials lines. The operator turns on the color change switch, selects the solvent, and pushes a dump button to clean the meter and valve, says Ball. A new color is selected and the dump control is pressed to load the system with the new color. The uses of the computer-commanded pre-mix paint guns provide an artistic pallet of over 60,000 colors and shades. This allows Mickey to consistently replicate the trademarked colors of most beverage makers, says Ball.
"Mickey also has added the capability to fill touch-up paint request with a computer stored, exact-match formulation of what the piece was originally painted with at the factory." Mickey supplies touch-up paint kits for the truck and trailer buyers at the time of delivery.
After application of the topcoat, the air-casters move the unit into the baking oven. In the sixth and final station, 140* F air is blown at 750 cfm for approximately 45 minutes.
Within the oven, a Chicago high-temperature, high-performance fan recirculates heated air. Heated air is discharged from the fan outlet directly into an aluminum supply distribution ductwork system, inside the oven. The air passes vertically upward through the manufactured product and is drawn back into the combustion chamber. This air is mixed with the proper amount of fresh air, and then is drawn past a burner for reheating and reintroduction into the circulation fan for redelivery into the baking chamber.
"It's important to bake the finish onto the surface. We don't want to get the finish "dry-to-the-touch" and then place the unit into the outside environment to complete the drying process," says Ball. "In many cases, there is a second color application to be administered to the piece." After the piece is fully baked, the air is purged using a Chicago centrifugal blower through an 18" diameter roof mounted exhaust.
"All the internal air needed for both breathing and painting applications is generated by a Kaeser DS-140 air compressor," says Ball. "This is a screw compressor that is powered by a 100-hp motor with 250mm rotors. It turns at 1,500 rpm."
The tank is a 1,040-gallon vertical ASME air tank equipped with an automatic water drain system, and a bronze relief valve. An optional provision with the tank is the Kaeser air filtration system for obtaining breathable air. This system incorporates a complete CO2 calibration and monitoring kit. Kaeser also supplied the breathing hoods for the paint application specialist.
"It's a pretty expensive and very sophisticated paint application system," says Ball. "To receive the full impact you have to go into the building and see the facility for yourself."