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Technology Interchange - Innovation Delivered at FABTECH 2017

Posted on Wednesday, January 31, 2018

FABTECH 2017 is now in the books. This immense exposition was held for four days at McCormick Place in Chicago. This show is North America’s largest metal forming, fabricating, welding and finishing event, and hosted more than 1,700 exhibiting companies and a total of 44,935 attendees from 120 countries. This year’s theme was a celebration of manufacturing’s industrial evolution. With more than 750,000 sq.-ft. of exhibit space, FABTECH provided attendees with access to the fabrication industry’s leading companies, latest innovations and insight into current and future trends.

Concurrent to the massive exhibition were conferences on welding, 3D/additive manufacturing, metal forming and fabricating, cutting, job shops, lasers, management, workforce development and, of course, finishing. A total of 65 presentations spanned the 28 finishing sessions. Many of these were devoted to liquid paint and other non-powder technologies, however several insightful talks focused on innovations regarding powder coatings.

Of considerable import was an update on UV-curable powder coatings provided by Michael Knoblauch of Keyland Polymers and DVUV. Knoblauch provided a detailed update on how LED UV curing was emerging as a curing technique of choice vs. traditional mercury vapor curing technology. While LED curing has found a foothold as a process in the printing industry, it has taken many years to find its place in the finishing world.

Knoblauch explained how LED curing has a higher output and energy efficiency, which translates into lower costs and cooler operating temperatures compared to mercury vapor lamps. In addition, he reported that LED curing is safer and less toxic because no heavy metals (e.g., mercury) are used to emit the light energy. Next he presented data showing excellent cure of clear, white and black powder coatings that had been cured with a 395 nm wavelength LED light source. Knoblauch wrapped up his presentation acknowledging that more R&D is needed to overcome UV absorption conflicts between pigments and photoinitiators.

Another valuable presentation was made by David Schimpff, the R&T director of DuBois Chemicals. Schimpff gave an update on a novel chemical pretreatment system, trade named PACRE. This technology is based on conductive polymers and organic acids and is purported to work well over hot and cold rolled steel, galvanized steel, Galvanneal™ and aluminum. This proprietary system is comprised of five stages, including: cleaning, rinse, PACRE, rinse and a final seal. The heart of this system, a conductive polymer, acts as an anode to fight corrosion. Additions of mineral and organic acids to the conductive polymer creates a synergistic effect that outperforms many conventional pretreatment schemes. Detailed information on coatings evaluated and respective performance can be obtained by contacting DuBois Chemicals.

John Glassco from Wagner Industrial

Joe Langemeier of AZZ Metal Coatings provided a comprehensive analysis of successfully coating hot dipped galvanized (HDG) steel with powder. He began with an enlightening overview of the HDG process, which consists of seven distinct processes: 1. degreasing, 2. rinsing, 3. pickling, 4. rinsing, 5. flux solution, 6. drying, 7. zinc bath, then cooling and inspection. This gave the audience an appreciation for the complexity of galvanizing and the precise processing control used to deliver a high quality zinc finish. Langemeier’s electron micrographs of cross sections of HDG steel showed the various layers of alloys attached to the steel substrate. Interestingly, he demonstrated the even layer zinc deposited on the steel including a 90° outer corner radius. The reason for such consistent thickness is due to the manner in which the zinc radiates perpendicular to the surface of the steel. Joe further described how even damaged areas of zinc can still provide cathodic protection to thwart ferrous oxidation that leads to corrosion. Most informative to me was his explanation regarding the transitions the zinc makes with time and exposure to the environment. During the first 48 hours, pure zinc becomes a thin layer of zinc oxide. Over the ensuing six months, the ZnO transforms into Zn(OH)2 (zinc hydroxide). Beyond six months, free flowing oxygen and CO2 cause the surface to evolve into zinc carbonate. The key takeaway from these reactions is that Zn(OH)2 is a poor surface for the adhesion of powder coatings. Hence the need to adequately pretreat the surface prior to powder application. Langemeier offered four options to accomplish this: sweep blasting with the appropriate media, zinc phosphate solution, wash primer or acrylic pretreatment. In addition, he reminded the audience that outgassing is real, so preheating the metal before applying powder is essential to a smooth, defect free finish.

Jeff Hale of Gema USA Inc. gave an encouraging message on the state of the U.S. manufacturing landscape. He detailed the resurgence of a rapidly expanding producer of bicycles. After the bicycle industry all but vanished from American soil in the late 1980s and early 1990s, the Bicycle Corporation of American reestablished operations in 2016. Integral to the new plant is a high capacity powder coating line. The line was commissioned in March 2017 and uses a seven stage iron phosphate pretreatment line that includes alkaline cleaning, acid pickle, iron phosphate and a non-chrome seal. Two powder booths automatically apply a primer/basecoat and clear topcoat for a total of around 5.0 mils. To enhance intercoat adhesion the first coat is gelled before the topcoat is applied and subsequently cured completely. A third booth is available for short runs and lab tests. Most impressive is the system design that allows for complete color nchanges in as fast as 10 minutes. This has proved a boon to BCA as they require around five color changes per shift. BCA produced approximately 450,000 bikes in 2017 and are on track to assemble 1 million by year 2020.

Mike Chapman of Heraeus Nobelight provided a very instructive dissertation on gas catalytic infrared curing. He explained how gas catalytic is beneficial because, unlike other more intense forms of IR, it is essentially “colorblind,” emitting wavelengths that excite the organic binder instead of the colorant pigments. This phenomenon allows for more controlled heating across a wide array of coatings to avoid burning the coating and substrate. He further enlightened on how the gas catalytic method is flameless, emitting only harmless CO2 and water. Chapman gave examples of how this unique technology is being used commercially to rapidly cure powder coatings on heavy grade steel cylinders and also truck wheels. He underscored the need to precisely control the upper and lower heating zones as well as the entrance and exit of the infrared oven. Not only can gas catalytic IR be used to improve the curing of heavy duty goods, its soft delivery of heat can be used to cure powder on heat sensitive substrates such as medium density fiberboard. MDF lines are becoming more and more common, however Mike also described system layout for plywood and OSB (oriented strand board).

One of the most interesting presentations was given by Joe Glassco of Wagner Industrial Solutions. It was entitled “Solving Age-Old Problems with New and Emerging Technologies.” He began with a description of a closed-loop feedback system that automatically measures dry, uncured powder film thickness in a non-contact mode. The data generated is then fed back to the application system to adjust gun settings to comply with film thickness targets. The benefit of this type of design is obvious. Out-of-specification film thickness can be corrected before a massive amount of parts are coated. This minimizes rejects due to thin coating and maximizes economy by keeping film builds from exceeding prescribed limits. This technology relies on thermal optics and digital signal processing. Specifically, the film thickness monitor pulses a flash to warm the surface of the coating. The thermal response is captured by an IR sensor which measures the surface temperature progression. This progression is analyzed by an algorithm. This proprietary technique is quantitative and repeatable. Glassco provided hard data that demonstrated a finishing line had drifted out of spec for film thickness and how this feedback system got the application system back to depositing a coating evenly and in specification. A savings of about 33 percent in material costs was achieved within minutes.

Another technique Glassco presented was the use of a counter electrode to minimize unwanted electrostatic “wrap” on a part. In many cases the goal of a finishing system is to specifically coat one side of a part. Any wraparound deposited on the back is wasted material. The careful positioning of a counter electrode repels that electrostatically charged powder, keeping the surfaces that shouldn’t be coated clear. This technique ncan be similarly applied when coating MDF or minimizing the deposition of powder on hangers and hooks. Avoiding deposition and accumulation of powder on hooks enhances contact points for electrical ground and reduces the frequency of costly stripping of hanging hardware.

Glassco also offered a solution to effectively coat hard-toreach surfaces of extremely large workpieces. Wagner recommends the use of a telescoping “tribo lance.” The design of this unique product allows the operator to apply powder to hard-to-reach surfaces without the need for a precarious man lift. He gave examples of how this has streamlined application at a major agricultural, construction and earthmoving (ACE) components manufacturer.

FABTECH 2017 proved once again that innovation is alive and well in the powder coating industry.

Author: PCT Editor