Vending machine maker’s change to powder puts more change in pockets
Conversion from liquid to powder yields longer finish life and substantial time and material savings. Vending machines take a beating–not only from an occasional disgruntled customer, but also from the environments in which they’re placed. The finish quality on these machines is a key element in their longevity.
That’s why Rowe International, a Whippany, N.J.-based vending machine manufacturer, switched from liquid paint to powder in its coating process.
Another reason was New Jersey’s demand that Rowe comply with the state’s strict emission standards. The liquid paints it was using didn’t cut the mustard in this regard, either.
In addition to helping Rowe meet these stringent quality and environmental standards, powder proved to be effective in coating the many odd component sizes and shapes designed into a vending machine. One machine can have as many as 350 coatable components.
All these factors came together to give Rowe some substantial time and money savings.
Rowe puts its products through periodic salt-spray tests to gauge finish quality. According to Ed Brookman, manager of industrial engineering, Rowe found that components with a high-solid paint finish lasted through 160 hours of salt-spray exposure. The powder-coated components Rowe tested withstood 800 hours.
In addition to needing protection from external elements, vending machines must also be protected from themselves. The extremes in heat and cold these machines generate to meet the needs of the products they dispense threaten the finish of internal and external components.
“If you have a refrigerated machine, humidity builds up on the inside,” Brookman explains. “We found epoxy-based powders to be more durable than liquids under these conditions.”
In late 1988, as part of its new JIT-based manufacturing-system redesign, Rowe replaced liquid with powder. The new system was designed and supplied by the Nordson Corp., Coatings Division, Amherst, Ohio.
In addition to its environmental concerns, one of Rowe’s key requirements was total product coverage.
The deep dimensions of Rowe’s cabinets, their numerous weldments and the hundreds of discrete components that go into them presented many challenges, both to Nordson and to the powder suppliers, Morton Powder Coatings, Reading, Pa., and H.B. Fuller, Wilmington, Mass.
Morton formulated coatings for the cabinets and doors, while Fuller’s coatings are used for internal components.
The vendor team was charged with developing a coating system that would give Rowe’s machines a durable, textured exterior finish, and provide adequate coverage for interior components.
“Rowe’s old dipping system gave them virtually 100 percent part-encapsulation,” explains Bill Morris, Nordson’s area manager on the project. “Powder had to have the same capability.”
One thing stood in the way: The Faraday Effect.
“We had to develop a textured material to overcome this phenomenon,” explains Walter Lindner, Morton’s Eastern regional sales manager. “Rowe’s products have a number of welded shelves and recessed units on the interiors. We had to develop a coating that could coat those surfaces on a largely automatic basis. We also built in the chemical resistance they needed for the coating to withstand the humidity that builds up inside Rowe’s cabinets.”
In electrostatic powder coating, particles are given a like charge. The problem occurs in corners. Just as positively charged metal particles repel each other, these like-charged powder particles create a force field that inhibits uniform coating.
As the coating supplier with responsibility for covering Rowe’s many interior components, Fuller found the Faraday Effect was particularly challenging.
“Rowe has so many different machines that a huge variety of parts come down that production line,” explains Jim Long, Fuller’s eastern regional sales manager. “The coating material we supply has to have enough latitude that it will charge in the Tribomatic booth to coat all of them.”
Nordson, Morton and Fuller worked together in fine-tuning the powder-coating system so that the coating hardware and materials would accommodate each other’s performance requirements.
“The challenge comes because every customer’s parts are different,” says Long. “So the close working relationship between the customer, the equipment vendor and the powder suppliers is necessary not only to design a system with the right number of guns, but to position and move those guns properly within the booth.”
The coating system consists of:
- Nordson “Tribomatic” spray booth for applying smooth powder to internal components.
- Manual spray booth for applying off-colors.
- Texture booth for applying textured powders to cabinets and doors.
- Overhead, nonsynchronous power-and-free conveyor system from Unibilt Division of Jervis B. Webb., Farmington Hills, Mich.
According to Brent Brosch, national sales manager for Unibilt, power-and-free was the only type of conveyor system that could accommodate Rowe’s limited square footage.
“We packed a great deal of conveyor into their building,” says Brosch. “The finishing area in particular was very small and congested.
“If they had stayed with their original in-line liquid process,” Brosch concludes, “I don’t think they could have continued in the same facility much longer.”
After surface preparation and oven drying, parts are ready to be coated. The power-and-free conveyor system transports parts between cleaning, painting and curing stations.
Coded carriers pass through readers which automatically identify the part and direct it to the proper spray booth. Carriers can be segregated without segregating colors, saving color change time.
The three paint booths are run by a single-shift crew of five, plus a lead man. The liquid system required the same number of people, but on a shift-and-a-half (14 hour) basis.
The Tribomatic booth is used for coating the discrete components. This is where the Tribo-charging technique combats the Faraday Effect.
The texture booth coats cabinets and doors. Here, high voltage power charges the particles for adequate adhesion.
Clean and economical
The people running the booths are happier with the new system, says Rowe’s Ed Brookman, because they are no longer coated with overspray at the end of the day.
Not only are the people cleaner, adds Brookman, but the equipment is easier to clean and maintain as well.
“High-solid paints are abrasive and cause a lot of wear and tear on equipment,” Brookman says. “Although powders are also abrasive, they are easier to clean off equipment, so we save maintenance, equipment and labor costs.”
Brookman adds that powder yields substantial material savings.
“Powder gives you 95 percent utilization,” he continues. “You get a 60 percent transfer efficiency, but you can collect almost the entire 40 percent overspray. We expect to see a material savings in the neighborhood of $50,000 a year.”
Rowe also saves on waste disposal. Brookman points out that the dearth of landfills on the East Coast translated into “ferociously high” waste transportation and disposal costs.
Nordson’s Bill Morris hopes the success of powder coatings on Rowe’s complex product line convinces skeptics of powder’s competitiveness with liquid for such challenging applications.
Concludes Morris: “This system proves that intricately designed parts can be powder-coated successfully in an automated system.”