Tooling-Up the Perfect Finish

Article From: Products Finishing,

Posted on: 2/1/1998

Making the switch to waterborne coatings...

Since the Clean Air Act Amendments (CAAA) of 1990, the list of new environmental mandates imposed by the EPA on coating applicators has steadily grown. The latest wave of environmental laws focuses on hazardous airborne pollutants (HAPs). HAPs are the 189 chemicals, including the solvents toluene, methanol and xylene, identified in CAAA as smogproducing, ozone-depleting or health-endangering. Like the restrictions established on VOC emissions, the HAPs legislation will curtail the use of traditional solvent-borne systems.

How are machine tool producers achieving compliance with the government's clean air requirements? For some the answer has been to switch to powder or electrocoating systems. Both methods provide excellent transfer efficiency and drastically, if not completely, eliminate VOC and HAP emissions. Also, venting, filtering and solvent recovery equipment are unnecessary. However, the methods require a significant investment in new application and curing equipment, and typically color options are limited.

The vast majority of machine tool finishers have found no reason to abandon their airless or conventional spray systems. To comply with EPA emission standards, they have simply moved to more environmentally friendly coatings with lower VOC and HAP contents. Such coatings include high-solids epoxies, urethanes, alkyds and single- and two-component waterbornes. High-solids epoxies have captured the lion's share of the market and are considered to be more abrasion, chemical and corrosion resistant than waterbornes. However, great strides have been made in waterborne technology in recent years.

Chemists in the laboratories of both coating manufacturers and their suppliers have been developing waterborne coatings that are more durable. As a result, waterbornes have penetrated industrial finishing markets traditionally exclusive to solvent-borne systems. Within the past year, breakthroughs have occurred in the development of two-component waterborne coatings. Several waterborne products now on the market exhibit performance and handling properties that meet or exceed those of conventional solvent-borne epoxies and urethanes. The newest generation of waterbornes may be the perfect choice for meeting future EPA regulations.

Geared for growth. Headquartered in Fond du Lac, Wisconsin, Giddings & Lewis, Inc. is one of North America's leading producers of machine tools and industrial automation products. The company's equipment operates in manufacturing plants in more than 69 countries around the world, creating products used in the aerospace, automotive and electronics industries. Sales in 1996 surpassed $700 million, and the Giddings & Lewis work force now exceeds 4,000 people worldwide.

Giddings & Lewis attributes a great deal of its success to being able to meet the customers' changing needs. Starting as a one-man operation in 1859, the company first produced sawmill machinery and steam engines for the burgeoning lumber trade. At the turn of the century, it made the switch to manufacturing lathes, drills and horizontal boring machines.

Today, machine tool users are looking for equipment that can enhance productivity and quality. In response, Giddings & Lewis has devoted a great deal of its capital and engineering resources to speed and precision technology. The company invests more than $60 million annually in research, product development and custom engineering.

To bring new products to market faster, Giddings & Lewis created IMPACT, a team-oriented design approach. Representatives from engineering, marketing, manufacturing and other departments meet to discuss everything from linear motor speed and machine geometry to material selection and warranties. Even graphics and coatings applied to exterior housings are examined. With new restrictions on VOC and HAP emissions, this component of the machine design has received a great deal of attention.

Coatings specified for Giddings & Lewis machinery must be able to withstand extreme service conditions. Contact with caustic cutting oils, lubricants and cleaning solutions as well as abrasion and impact from heavy objects can make short work of an inferior finish. While the coatings serve primarily an aesthetic role, their long-term performance is still a key concern.

For years, design engineers at the company found high-performance, solvent-borne coatings to be the answer. The finish for a typical machine consisted of an epoxy primer followed by a two-component polyurethane topcoat. When new clean air regulations were enacted, the company switched to high-solids versions of the coatings, dramatically reducing VOC emissions while maintaining the same level of finish quality. The move allowed the company to operate well within the EPA's guidelines.

For Giddings & Lewis' CEO, Joseph Coppola, however, this was not good enough. "As the industry leader, I felt we needed to go beyond what was acceptable," said Mr. Coppola. "Moving to waterbornes appeared to be the right thing to do, not only from the standpoint of being a good corporate citizen, but for the benefit of our employees. The only question was, did a waterborne coating exist with performance characteristics comparable to our solvent-based system?"

Testing the waters. To answer Mr. Coppola's question, Bill Spreeman, the company's director of safety and environmental services, conducted a study of industrial waterborne coatings. He invited coating manufacturers to participate by submitting their most durable waterborne finishes for testing. According to Mr. Spreeman, most were eager to help. "They were glad that we were taking the initiative to explore the use of waterborne coatings, something they felt others in the machine tool business would do sooner or later."

The timing of the Giddings & Lewis study turned out to be ideal for researchers at Sherwin-Williams Chemical Coatings, Cleveland, Ohio. After nearly six months of laboratory testing, the researchers were ready to field test Kem Aqua® Hydralon™, a two-component polyamide waterborne epoxy. In laboratory tests, the coating formed a tight, dense coating film that provided enhanced abrasion, chemical and corrosion resistance. The researchers now had a chance to see if it would display these same characteristics in a real-life setting.

Testing the waterborne coatings occurred in two phases. In the first phase, coating systems were applied to three-inch by six-inch steel panels. Samples of Giddings & Lewis' existing solvent-borne coating system were also prepared for comparison. Each panel was numerically coded and sent to an independent material testing laboratory. The panels were subjected to a battery of tests, including direct and reverse impact, mandrel bend and cyclic salt fog. In addition, the coatings were checked for solvent resistance using the solvent rub test (100 double rubs), as well as for chemical resistance through 100 hr of immersion in caustic liquids such as hydraulic fluid, cutting oil, brake fluid and gasoline.

Results from the laboratory examination were encouraging for two of the waterborne coatings, which matched or exceeded the performance of Giddings & Lewis' solvent-borne polyurethane system in every category. Unlike traditional waterborne epoxies, the product held up well to salt spray testing and did not blister or crack, even when immersed in the most aggressive synthetic cutting oils.

Pleased with the findings of the laboratory tests, Mr. Spreeman initiated the second phase of the coating evaluation. Using the Fond du Lac plant as a beta site, the waterborne coatings were applied to several pieces of equipment used in the manufacturing process. Nearly 85 pct of the plant's production equipment was produced by the company. By applying the coatings to this equipment, Mr. Spreeman and the engineering design team could see first hand how the new products would size up.

The group found that even after a year of service the waterborne coatings retained their original color and gloss. Also, the coatings exhibited very little wear from routine cleaning, cutting oil overspray or hydraulic fluid spills. In areas of high moisture, such as around coolant ponds, the new waterborne coatings showed that they were corrosion resistant.

Making the switch. The results of the year-long coating investigation convinced Mr. Spreeman that a waterborne finish could be used for Giddings & Lewis machinery without sacrificing quality, reliability or the long-term appearance of the machines. However, he still had one more hurdle to overcome.

Converting from a solvent-borne to a waterborne system presented special application concerns. Dirt, chemicals and oils left on unpainted parts were known to have a greater effect on the performance of waterborne coatings. Waterborne coatings typically require better cleaning of parts than their solvent-based counterparts. Waterborne coatings also have a higher sensitivity to changes in temperature and humidity and can be more difficult to atomize.

To help ensure a smooth transition into waterbornes, Mr. Spreeman sought technical assistance from Russ Geise, a sales representative of the coating's developer. The two agreed the conversion should begin at the Fond du Lac plant. Once all necessary modifications were made to the facility's finishing operations, standards could be developed for other Giddings & Lewis plants and the company's suppliers.

Mr. Geise found the Fond du Lac finishing operation to be well suited for waterborne coatings. In addition to being isolated from the rest of the plant, the finishing area was equipped with a positive air make-up system and had numerous exhaust fans for good circulation. This would not only help accelerate the curing process, it would minimize the amount of dust and other airborne contaminants that could lead to finishing defects. The atmosphere of the entire plant was also thermostatically controlled, and temperature and humidity levels could be maintained to ensure proper coating flow and curing. For the two-coat waterborne system specified, Mr. Geise recommended a temperature range of 60F to 80F, and relative humidity levels of between 40 and 70 pct.

Along with assessing ambient conditions, Mr. Geise examined the plant's spray equipment. The two paint booths at the plant were equipped with airless sprayers and conventional spray guns. By switching to HVLP guns, atomizing air and fluid pressure could be lowered, permitting better transfer efficiency and a smoother finish. It was also suggested that all steel components in the line be replaced with stainless steel, because of the corrosive nature of residual moisture created by a waterborne system.

In the prep work area, Giddings & Lewis had already converted from a high-VOC, solvent-based degreaser to an aqueous detergent. The change created a more hospitable environment for workers and dramatically reduced the company's hazardous waste generation. Metal parts were treated with the cleaner using low-pressure spray equipment. They were then dried using compressed air and box fans to prevent flash rusting. For heavily soiled parts, stronger cleaner dilutions and elevated water temperatures were employed.

With new operating parameters established and equipment modifications implemented, Mr. Geise and Mr. Spreeman turned to training the plant's paint crew. The crew was composed of seasoned veterans, many with more than two decades of finishing experience. However, most were unfamiliar with the characteristics of waterborne systems. By conducting sprayout tests, the crew quickly discovered the proper motion, angle and spray pattern to use for obtaining the desired mil thickness and finish appearance.

Taking what had been learned from the Fond du Lac plant, Mr. Spreeman created a coating application manual for all Giddings & Lewis plants and parts suppliers. In addition, he held training courses for suppliers at the Fond du Lac facility, and along with providing surface preparation and application tips, explained procedures for coating storage and product handling necessary to prevent coating failures.

Finishing off right. It has been more than a year since Giddings & Lewis converted to a waterborne system, but the company continues to assess the benefits. In 1996, the machine manufacturer cut its VOC emissions by nearly 50 tons as a result of the switch to waterborne coatings and aqueous pretreatment cleaners. In addition, annual hazardous waste generation has been reduced from 5,000 gal to less than 400 gal, a drop of more than 90 pct. And along with having a favorable impact on the environment and improved employee morale, the waterborne products provided Giddings & Lewis with a 22 pct savings in material costs.

According to Mr. Spreeman, these outstanding results have prompted a great deal of interest from customers and competitors alike. "We're not alone in the battle to reduce VOC and HAP emissions. Many of our customers are facing the same problem. We are sharing the results of our year-long study with Chrysler engineers, and will be making presentations to other clients in the next few months. In this age of increasing environmental regulation, we believe we've tooled-up the perfect finish."


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