Dakota Redesign
Drives New Paint System
By: Linda K. Schuch
Contributing Editor
April
1997- Chrysler’s redesign of its popular Dodge Dakota pickup brought
the company 1997 "Sport Truck of the Year" honors. To the automaker’s
suppliers, the redesign brought a great deal of change.
One supplier that has met these challenges well is Textron Automotive Co., Trim Operations Div., Rantoul Products. From its three plants in Rantoul, IL, the 1,160-employee company ships over 55,000 injection molded items each day to locations all over the world, using as many as 17 different kinds of plastics.
Rantoul Products has supplied the instrument panel for the Dakota since it entered the sport truck market. When the company won the contract for the redesigned panel, management determined that more space was required for the operation. "We needed to run the current product and, at the same time, set up a line for the new product," says Ed Rutkowske, Rantoul’s manufacturing engineering manager.
Rantoul continues to supply panels for earlier-model Dakotas, as service parts. Although some of those parts are painted, the older version of the product is largely made of soft foam, covered with vinyl.
In addition to the space requirements, the company also recognized the need for an overall upgrade. "We weren’t set up to the right standards. We had paint lines, but none that could handle this particular application," Rutkowske says. "Getting this job meant installing everything new—all new processing and painting equipment."
The company decided to launch the 1997 product at Plant 1 while continuing production of the 1996 model at Plant 2, allowing simultaneous production. But that was just the beginning. The fully enclosed paint line that coats the redesigned product is completely different from the line producing the older parts for service. The new system provides an operation Rutkowske calls "as close to cellular manufacturing as you can get with a painting application."
The automated paint system was designed by Dove Equipment, an integration and engineering firm in Peoria, IL. Here’s how it runs: The PC-ABS plastic components enter the paint area via an overhead conveyor, which takes them first through an ionized-air blow-off system, then into a dual-chamber paint booth where a robot applies a waterborne coating. The parts then move through a flash tunnel to drive off some water and, finally, through an infrared oven for the final cure. Once coated, the parts are conveyed directly onto the assembly line, where the finished instrument panel is built and readied for shipment.
And ship it must. Rantoul sends approximately 820 panels out the door during its two eight-hour shifts. "The products we paint in the morning will be installed sometime the same evening during Chrysler’s second shift—or at the latest, the following morning," Rutkowske says. "We have a 10-hour window in which to get the parts to Detroit, so they must be flawless when they come out of the oven."
The automated system from Dove has enabled Rantoul to achieve a reject rate of 166 parts per million, well below Chrysler’s maximum of 200. Rutkowske says the goal is 50. "We are continuously looking for better ways to produce this product. That’s what led to the new paint system."
System built on two levels.
A notable feature of the system is its use of vertical space. Although the move to a bigger plant helped, floor space was still at a premium. The solution was to build a mezzanine, where all painting operations are done.
The paint mix room is right below the spray booth. Rutkowske says having all the equipment in one area is a significant improvement over the typical setup in which the mix room is some distance from paint operations. "This arrangement minimizes both the amount of pumping required and the amount of paint in the lines," he explains.
The waterborne coating comes from United Paint (Southfield, MI) in 55-gallon drums. It is pumped in the mix room from those drums through stainless-steel pipes directly to the paint guns in the booth above. The circulation equipment—including air-operated mixers and pumps, filters and regulators—was supplied by Graco (Minneapolis, MN). The system recirculates the paint, keeping it in continuous motion for consistent flow, and automatically supplies the color needed.
On the mezzanine level, an enclosed-track, overhead conveyor built by Pacline (Missis-sauga, Ontario) brings the parts to the first operation: ionized-air blowoff. Dust, contamination and residual static are removed as the parts pass through an enclosed compressed-air knife, manufactured by Simco (Hatfield, PA). As recirculated air blows on the parts, dust is pulled into a filter, keeping the hybrid plastic components contamination-free.
The components are then conveyed into the 20-foot-wide paint booth, which is divided into two sections: one for the robotic application, the other for an emergency manual back-up. Using Dove Equipment’s design, JBI (Osseo, WI) fabricated the sheet-metal booth (and the mix room) for the new system.
The Dakota’s instrument panel includes 15 PC-ABS parts, but only seven are visible once the panel is assembled. The eight internal parts that can’t be seen are left unpainted. Cluster bezels are molded and painted black. The other six parts are batch-processed in three colors: dark gray, light gray and tan.
The plastic components enter the booth on two racks. One holds six parts to be painted gray or tan, the other three cluster bezels to be painted black. The paint robot is an ABB (Auburn Hills, MI) Model 510, which includes built-in analog control of the fan pattern and atomization pressures. Two HVLP guns from Binks Sames Corp. (Franklin Park, IL) are mounted on the head of the robot. The first gun sprays the gray and tan parts, then the robot automatically switches over to the second gun, which sprays the cluster bezels black.
Rutkowske says the company batch paints each color as much as possible. When a batch ends, the robot automatically flushes the gun before changing to the new color. "We have minimal loss of time in switch-over, and there is less flushing and disposal, which is better for the environment," he reports.
Air circulation is carefully controlled in the dry-filter spray booth. As the filters get dirty, variable-frequency drives automatically adjust the fan speed to maintain the proper airflow. The system sounds an alarm when filters must be changed.
Although seldom used, the second compartment in the booth is for manual backup if a glitch oc-curs in the robotic operation. "Since we work on a just-in-time schedule, this is critical," explains Rutkowske. "If painted parts are not delivered to the assembly area as scheduled, the whole line stops. We can’t afford that. If anything needs repair, we put a person in the booth to keep production running while someone else works on the robot."
Painted parts exit the spray booth and spend three minutes in an enclosed flash tunnel, where water begins to evaporate from the waterborne coating. Parts proceed to the last piece of equipment on the mezzanine level, an infrared curing oven from Conversion Processes Corp. (St. Charles, MO), where they remain at 165°F for three minutes and come out nearly dry. After another 15 to 18 minutes of postcure time on the racks, the parts arrive at the assembly area, which is on the floor level of the plant.
Rutkowske says the automated system is performing just as it was designed. He is especially pleased that Dove was able to design a finishing system compatible with the plant’s cellular approach to manufacturing assembly. "It’s a bigger challenge with painting than with other manufacturing operations, because it’s more difficult to get the product close enough to the point of use. The size of the equipment—booths, mix rooms, etc.—make it tough."
Rantoul’s new paint system delivers what the redesigned Dakota demands—a high quality appearance and just-in-time delivery. "Chrysler wins, and we win," concludes Rutkowske.
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