Original Date: 07/23/1996
Revision Date: 01/18/2007
Best Practice : Paint Usage
Nascote installed a Durr Paint System during the construction of its facility in 1985 with paint booths to house automated reciprocators and manual paint spray stations. With low product mix and order quantity, the initial system satisfactorily handled both throughput and quality (Figure 2-2). However, Nascote’s customer base and quality demands increased, and new materials imposed efficiency problems for the paint booth. Consequently in 1993, the company initiated a two-year, major paint system upgrade.
The initial paint system, developed to paint the engineered thermoplastic material Xenoy, used a dual component (2- K) paint. Personnel used six manual handgun stations in the prep booth (refer back to Figure 2-2) to provide cut-ins to areas too difficult to paint using just the basecoat system. The sequence of both basecoat and clearcoat booths consisted of reciprocator, robot, reciprocator, robot, and manual touch-up. All reciprocator zones contained three hydraulic reciprocators. Two reciprocators painted the side wings of automobile fascias using two guns each, while the third reciprocator used six spray guns to paint the main beam surfaces of the fascias. Hydraulic robots were added later in what was originally manual spray zones. These machines exceeded the reach capabilities of the manual painters and could run continuously for long periods of time. The last portion of each booth used manual painters to eliminate mottling, to back up broken machines, and to paint areas requiring improvement. The non- conductive Xenoy was not painted electrostatically since electrostatic painting on non-conductive materials created a safety hazard. The freshly-painted charged surface also attracted contaminants.
Another substrate material, reaction injection molded (RIM), was added to the product line in 1992 and required application using a single component (1-K) elastomeric enamel paint. All RIM products required two passes through the paint system, one to apply a prime coat and the second for base and clear coats. The RIM products used the electrostatic application process in basecoat because the surface charges could be dissipated through the use of ground straps and the conductive primer.
After baselining the old process and accounting for new products, Nascote designed an alternative to a totally new system. The improved painting system uses the existing paint booths with one booth lengthened by four feet (Figure 2-3). All the original reciprocator, robotic, and manual zones were replaced by 40 Fanuc P-155 robots using Sames 501/502 electrostatic spray guns and Binks RCS fluid metering systems. There are now five, fully automated paint spray booths with eight robots per booth. This system is modular so each booth is dimensionally and functionally identical with the exception of the coatings sprayed to facilitate path development and transfer. This allowed Nascote to acquire takeover business without interruption to the customer. (Booth #1 is no longer needed for cut-ins and is used strictly to apply primers and adhesion promoters.) All basecoat and clearcoat booths contain a six-foot manual inspection zone with downdraft airflow to reduce the potential for paint contamination during the periodic visual inspection of the wet paint film. The first zone in both base and clearcoat is equipped with manual spray equipment that could be used to apply paint if necessary.
During this time, a third substrate was added at the customer’s request. The new material, known as thermoplastic olefin, can be painted using either a 1-K or 2-K painting process but requires the addition of a conductive adhesion promoter prior to the basecoat paint application. Using the new robotic equipment, this requires only a single pass (wet-on-wet) through the system. Xenoy can now be painted electrostatically when used in conjunction with a conductive adhesion promoter and grounding straps.
The original equipment was removed and robotic replacements brought up to operating functionality during a semi- annual, two-week shutdown. There was no interruption in shipments. Nascote’s investment in its paint system upgrades totaled approximately $13 million for complete modifications. By eliminating wasted paints associated with color, style, and material changes; developing the electrostatic painting of Xenoy; and improving quality and throughput, Nascote realized a return on investment in 16 months. This effort contributed to the award by General Motors Fascia Supplier of the Year award to Nascote in both 1994 and 1995.
Figure 2-2. Previous Nascote Colorline Basecoat, Clearcoat Paint System
Figure 2-3. Robotic) Nascote Colorline Basecoat, Clearcoat Paint System
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