LEARN MORE

Zones



Iscar Metals
USCAR Pushing Painting Technology to the Next Level

The Big Three automakers are getting together through the USCAR organization to develop the ways and means to apply clear coat paint in an environmentally better manner than is the current state of the art. This work is being done proactively, which is in itself a great leap forward.

The Low-Emission Paint Consortium (LEPC) is an operation under the aegis of the United States Council for Automotive Research (USCAR). LEPC was established in 1993 with the goals of testing, developing and evaluating materials, application equipment, and facilities; establishing a database; setting standards for improved painting processes. Who are these folks with such an ambitious program? The Big Three automakers, supported by an array of suppliers.

"We didn't go into this thinking short term," Richard F. Pearson, manager, Manufacturing Technology Planning, Advanced Manufacturing Engineering and Process Leadership, Ford Motor Co., comments, adding, "LEPC is established to last 12 years."

The rationale for the existence of LEPC is simple. According to Ernest O. McLaughlin, manager, Advanced Paint Process & Environmental, Paint & Energy Management, Chrysler Corp., "The U.S. Auto companies have reduced emissions in their painting operations about 80% since the 1960s. We did this by working separately. Now we need to work together." The proverbial low-hanging fruit has been picked. It is tougher to make the gains that are desired. The word desired is used deliberately. The efforts being made by LEPC are not being driven by some existing or planned legislation, and when it comes to making changes in paint systems, the legislative environment typically has a whole lot to do with what gets done. But not in this case.

As Thomas A. Meschievitz, director, Manufacturing Center, Paint Engineering, General Motors North American Operations, observes, "The three of us are faced with the same issues. We are trying to be proactive. We are working on the next generation of coating systems that we may have to implement some day." In other words, the car makers don't know that they'll have to get extremely close to a zero-emissions paint facility. But if or when this does happen, they want to be ready to deal with the challenges. Consequently, they have decided to pool their resources in a meaningful way as they work to better understand how to implement powder coating technologies. They are pooling top people from within their organization to work on the development. They are, in effect, rolling the dice on this work, but they are all in it together. "All of our resource dollars are becoming scarce," Pearson says. "A possible outcome of this project is that we may learn things about powder paint that will never go into production. That's not our driver, but it is a possibility.

"Our driver is to produce a production-viable process. So we are committing resource dollars for the long termit is a risk we share."

The most obvious evidence of the seriousness with which LEPC is approaching its charge is a 36,000-sq. ft., $20-million paint facility constructed at the Ford Motor Co. assembly plant in Wixom, Michigan. This facility, which has been set up so that it can handle vehicles produced by Chrysler, Ford and GM up to the size of a full-sized van, is the centerpiece of a program that has as its goal the development of the entire system—all aspects, from the materials to the material handling system, from the paint guns to the bake ovens, from the size of the powder particles to the process parameters—necessary to use powder clear coat.

The state-of-the-art today is to use a water-base cathodic electrocoat (E-coat). Then a powder primer surfacer (and it should be stressed that this is not widely used at this point: yes it is in production, but paint engineers are still learning). The next step, applying the color, is done with a water-borne paint (but there are still solvents in this). Then there is the clear coat, which is applied with a solvent-based medium. Solvents are the source of the emissions. And emissions are what are to be avoided because of environmental concerns.

The U.S. government has been comparatively strict regarding emissions from painting systems. This has caused the U.S. auto companies to change the way they paint. For example, high-solids paints applied with high-efficiency electrostatic equipment and water-borne base coat came along, in large part, because of regulations that were established in the U.S. This, for a period of time up until about five years ago, led to a competitive disadvantage vis-à-vis offshore competitors regarding ease of plant operations to produce the richness and luster of paint finishes. They could use high-solvent, low-solids paints. The Big Three couldn't. "As you go from high-solvent to low solvent your operating window closes down. Low solids, high solvent is easier to do," Pearson says. But regulations mean that companies painting in the U.S. can't do it. Emissions are the concern.

In the parlance of automotive paint, emissions aren't just considered to be the fumes that want to make their way into the atmosphere. Those fumes are the volatile organic compounds (VOCs) that can have a deleterious effect on health. On a modern U.S. assembly plant there is an array of abatement equipment on top of the paint shop, which represents as much as 10% of the investment in the paint facility. Not only does this equipment represent a hefty charge (one measured in millions of dollars), but it really isn't adding any value in terms of the vehicle being produced, as the purpose of the abatement equipment is to deal with a problem that should, ideally, be solved before it needs to be applied. What's more, the abatement equipment consumes energy and produces, as a byproduct, NOx, which isn't prohibited, but which isn't ideal, either.

Emissions are also what get sprayed in the paint booth but don't make it onto the object being painted. What happens is that the overspray falls to the floor of the paint booth, which is a grating over water. The overspray is skimmed from the water, then coagulated into sludge that is shipped off to a landfill for disposal (applying high heat to the material to reduce the amount of waste is being used at some locations).

"End of pipe control," is the phrase used to describe the preemptive approach to handling emissions with added abatement equipment.

Powder paint provides the promise to eliminate the source of the emissions—long before the end of the pipe. But there is an issue that has to be addressed in a comprehensive way in order to bring this promise to fulfillment. Consider the fact that the auto industry has had a century of experience of painting with liquid and that you can count the number of facilities using powder primer on your fingers. There is a huge infrastructure—physical and intellectual—that exists for liquid painting, not only among the car makers, but the suppliers of materials and equipment, as well. Manpower, materials, methods, and means must be created in order to move powder paint along. Which is where LEPC comes in.

A key difference between liquid-based paint and the powder variety is found at the level of overspray. The powder paint is sprayed in a manner analogous to that used for liquid paint. Although the robotic and otherwise-automated paint systems used in most paint shops increase the odds of materials going to where it needs to go, there are still misses. So the powder falls to the floor of the booth, which is a grating like in the liquid setup. But instead of being used to fill a hole in the ground, the powder paint is collected and reused. That takes care of one part of the emissions problem.

The other part of the emissions problem, the fumes, isn't there, either, as the powder isn't being transferred in a solvent medium.

Sounds great. But getting the whole thing to work is what needs to be developed—and "getting it to work" means being able to use powder at production rates and economically with high power.

To get a sense of the efforts being made by the Big Three through LEPC, consider these two not-insignificant instances:

1. Sport utility vehicles are currently hot. So GM wanted to make sure that the Moraine, Ohio, assembly plant was in top shape for producing the 1995 Blazer, which was a new version of that model. Powder primer was launched at the plant. In addition to the people from GM and its suppliers working on the system at Moraine, there was help from Chrysler and Ford personnel, as well.

2. The Chrysler minivan is considered by some observers to be the single most important vehicle produced by that corporation. When Chrysler was bringing up the St. Louis plant for the production of the current-generation minivan, its paint shop people had some additional help, from Ford and GM, to get the powder primer system going.

This sort of collaboration—which continues, as the powder primer sites are real-life test beds for gaining knowledge of how powder performs, and which resulted in the writing of the "Powder Prime Launch Manual," which is an implementation guide available to other Big Three plants—is, to put it mildly, not characteristic of the way the Big Three work. Normally, the level of secrecy border on something out of Mission Impossible. But in this case, the possibilities have too much positive potential and require too much work in order for the companies to go it alone.

(As for the trust-busters out there: Breathe easy. This collaborative work—the primer and the clear-coat initiatives—is considered "pre-competitive." There is no market advantage for the companies. You can be certain that each of the three competitors involved would like nothing more than to gain market share at the expense of the other two. This work is being done for the good of people everywhere: VOCs don't recognize corporate brands or national boundaries.)

There are several issues that need to be resolved with regard to powder. One of them is handling. The powder material moves from the container it is packaged in to a fluidized bed (fluid as in air). This causes it to be separated and suspended. Then it goes through a pipe to the gun from which it is sprayed. "Right now," says Meschievitz, "there is no device available that controls the flow of the powder so that the output is consistent." This consistency is key because it is necessary to achieve a repeatable film thickness on the vehicle. This film thickness is key both in terms of aesthetics and economics.

As for the aesthetics: right now, the powder primer paint being used in the auto industry is essentially there to help prevent stone chips from going down to the base metal. That primer is covered by two additional layers (i.e., the base coat and clear coat). Yes, powder is used for visible surfaces in other industries, such as appliance, but when is the last time you heard of anyone waxing their washing machine? The surface specs in automotive are a whole lot different. Given that the clear coat has nothing on top of it, it has to be done right. Blemishes are unacceptable.

As for economics, one of the problems that currently exists is that even though about 95% of the powder material is used (including reclaiming) compared to from 50 to 60% for liquid primer, the cost of using the powder is higher because of the film thickness applied with powder is 3 mils compared to 2 mils for the liquid primer. The inability of powder to flow-out and the inability to accurately control the thickness of the material is the reason for the additional material. (Also, the cost of the powder material is higher due to the fact that far less of it is made than liquid paint).

Another issue that has to be worked out relates to the interactions of the materials. The powder clear coat will be applied over a non-cured base coat; they will both be baked in the same oven. The base coat is applied wet (Meschievitz: "The base coat will be the last to go powder—if ever."); the powder clear coat is like talcum powder.

So a question that has to be resolved is how to keep the water in the base coat (it should be noted that some of the water has been evaporated prior to the powder coating, but the material is still wet) from migrating through the powder. This is a huge challenge with regard to achieving the required surface quality for the vehicle.

"You could take the best powder primer-applying plant in the world and if you tried to use it for applying powder clear coat, you wouldn't be producing cars in that plant," says McLaughlin. There are similarities. But the surface requirements for the clear coat are so demanding that it is taking a $20-million paint facility to master them.

About the investment: "Before you put a new technology into a billion-dollar assembly plant, technology that can shut the plant down, you'd better make sure you can make it run," warns Meschievitz. So the facility was built. It was opened in late 1996. The reason it is located at Wixom is because Ford has a pilot paint line in the plant. Vehicles can either be prepped prior to arrival at Wixom, or they can be prepared with just an E-coat and the rest can be performed at the facility.

The plant's production (Lincolns are assembled there) isn't interrupted. "We have to learn how to handle tons of powder per day," Pearson says. "We can't do this in a lab." The LEPC shop can simulate up to 75 vehicles per hour. It is as close to the real world as they can get.

So when will this become all the way into the real world? The shortest term is five years out, if process and material validation happens within the next three years. This time will be necessary in order to create the equipment and materials necessary to do the job, which will be accomplished by suppliers. But at least the suppliers will be getting one set of requirements from the Big Three.

Which is in itself a huge accomplishment.

 

Standards for Other Things, Too

One of the discoveries made when the LEPC facility was being developed at the Ford Wixom plant was that there was an insufficient supply of compressed air to handle the additional paint line. As the consortium members looked into increasing the supply, they discovered that each of the Big Three had its own standards for compressed air systems. Which means that a supplier that wants to be of service to each needs to have three different system types to meet the requirements.

So what may happen is agreement among the Big Three not only on compressed air specs, but for other things, like ovens and conveyors, too. All of them would share the same requirements. Which would reduce the number of variants. Which would have beneficial economic effects right across the board.

"We knew that we would be developing industry standards for powder," says Ford's Richard Pearson. "But standards for these ancillary parts of the process are a spin-off that we hadn't anticipated."

 

Painting Axles

American Axle & Manufacturing (Detroit) operates an axle plant in Buffalo, NY. It has another facility 35 miles away, in St. Catherines, Ontario. Light truck axles produced at both plants are being painted in a 67,000-sq. ft. paint shop that was added to the Buffalo plant, an addition that is capable of reliably painting 6,000 axles per day (two shifts).

The painting had been done by a vendor. But it was being done manually and there were quality concerns. So American Axle management determined that doing the job in house was more beneficial. They made the decision to build the new plant, and from the time the contract was awarded to full production in the paint shop, only nine months elapsed.

The paint shop was built on the other side of railroad tracks from the existing American Axle manufacturing facility. A power-and-free conveyor from Jervis B. Webb (Farmington Hills, MI) that had been installed in the main plant in 1968 was extended so that the axles could be conveyed through a 350-ft long gallery to the new paint facility. Actually, there is a whole lot more Webb conveyor involved than the 350 ft. In all, the new paint shop has some 1.4 miles of conveyor.

The 200-lb axles (there are seven models produced) are transported from the end of the assembly line and into the paint shop at a rate of 410 per hour. Upon arrival, the axles are handled by a Webb-designed robotic transfer system. Axles not only arrive from the manufacturing building, but also from the St. Catherines plant. There are four robots, model S-420iw from Fanuc (Auburn Hills, MI) robots that handle the axles for load/unload operations. Axles are loaded onto double-axle carriers that transport the axles through the paint system. Actually, the paint system consists of two duplicate lines to meet throughput requirements.

Axles are manually prepped at a rate of up to 250 axles per hour per line. After prep, the axles start through a finishing system developed and installed by Thermal Engineering Corp. (TEC; Columbia, SC). First, they pass through an 81-ft three-stage spray washer for pretreating, then through a 75-ft. gas-fired oven and blow-off unit to dry the parts. There is then another manual prepping (openings are plugged; areas are masked). Next, the axles are conveyed through infrared temperature bring-up ovens, then into the two 43 ft. × 20 ft. down-draft, dry-filter paint spray booths. In each booth four ITW Ransburg (Toledo, OH) reciprocating paint bells apply about 90% of the coverage; the balance is applied by twin Fanuc robots. The coating applied is a zero-VOC material, XN-174 from United Paint and Chemical (Southfield, MI). When applied it is green in color. When it dries—within 15 minutes—it turns black.

After the axles exit the paint booths, the conveyors converge and the two parallel lines run the axles through a 85 ft. × 22 ft. TEC Turbulator gas oven for drying. Because space is a concern, the axles are oriented in a diagonal space-saving banking system. Out of the oven and on to demasking. Then it is back to twin Fanuc unload robots. The St. Catherines axles are placed back into shipping racks, and are transported via truck or rail to their destinations. The Buffalo axles go to the plant's shipping facility.