How to Rack Up Efficiency

By: Paul Mills

When it comes to designing a racking system for a powder coating finishing line, too little time is spent talking with the people who actually work with the products. Failure to communicate can cost both time and money.

All too often, racking is an afterthought. More time and effort is spent thinking about the washers, application equipment and ovens than about how the parts are going to move down the line to each of these stations.

As Antonio Beniquez, engineering manager for Mighty Hook, observes, “Racking is sort of the red-headed step child of powder coating. It’s not as sexy as ovens and washers and spray booths. So while customers think about their powder formula, spray equipment and sensors, many of them don’t think enough about how they are going to hold the part or move it through system. Yet, bad racking can have an enormous impact on a coating line’s technical performance and profitability.”

Dan Davitz, design and sales executive for Production Plus Corporation, the makers of Magic Rack, agrees. “Parts are not just magically levitated. Our job is to figure out the best way to hold a part so it’s easy to load and unload, and to present each part for optimum results,” he says. “We try our best to work with the whole team as early as possible when a new system is going in, but too often a systems installer will not think about anything below that conveyor itself. There are times when we had to say, ‘you are going to need a load bar because your parts are 12 feet long and if you put a hook on each end and go around that turn—don’t expect your part to still be there when you are done.’”

A common problem is that people who need to work day in and day out with racks are often left out of the conversation, says Scott Rempala, president and CEO of Mighty Hook. This can build resentment, create reluctance, and prevent the buy-in that you need. “My advice is that when you are looking at a rack development program you get everybody together who have to touch that rack and run through all the issues. Just because an engineer designs a rack for a given density doesn’t mean that workers can load, unload, or burn off that rack in time. They may end up getting only half the density that the managers thought they were going to get. I’ve even seen sabotage where workers are purposely bending or breaking tooling. If you don’t get the buy-in it doesn’t matter how great your design is, you are going to run into roadblocks and political issues. You can have a wonderful, well designed rack that is only being used at 50 percent of its capacity,” says Rempala.

Chris Merritt, general manager of North America for GEMA USA, agrees that more teamwork would be helpful. “We are constantly talking to customers about how to hang the parts, how to get them closer together, or how their operators will get parts on and off the line. But I realize we are rarely saying that to a racking company, and the information may not be getting passed along to the rack designers.”

Merritt has seen problems coming from the this kind of communications breakdown. “A rack manufacturer might use an A-frame design with a six-inch-wide support. But, we didn’t know that, and the booth was designed with a fourinch throat. That’s a problem that could have been avoided.”

Racks for Powder Coating

“Designing racks for powder coating is different from almost any other type of application,” says Davitz. “In dip applications like e-coating, racks are submerged, and with many liquid spray applications the racks get jostled around by the high pressure of the spray. We don’t have these problems with powder coating. That often makes it simpler, and even sometimes less expensive since we often have off-the-shelf products for powder coating a wide range of simple parts,” says Davitz. By simple, he means parts that already have holes to hang them, or a straightforward way to fixture them. If that’s the case, then powder coaters can get racks the same day or next day and be hanging parts in minutes.

But, of course, many parts are not so simple. “That’s where engineering experience comes in,” says Davitz. “A big part of our job is to help people with problem parts that may not have holes or an easy way to hold them. Other times, there may be a hole on the part, but the customer won’t let us use it. The hole may be part of the design part and a customer will specify that nothing can come into contact with it.”

“Powder also tends to go in all kinds of different directions,” says Beniquez. “Some basic things, like the thickness of metal we use to build a rack can affect the electrostatic spray. So we need to consider the part orientation, and phenomenon like Faraday cage effects that can make it more difficult to coat surfaces compared with liquid coating.”

“Inconsistent part presentation is a problem with poor racking,” agrees Merritt. “For example, recently I was visiting a customer who was using racks designed so that parts tilted the wrong way. That formed a kind of bucket that resulted in excessive drag-out from the washer, causing a lack of uniformity in the surface pretreatment and potential failures of the coating,” explained Merritt.

Staying Well Grounded

Because powder coating relies on electrostatic attraction, maintaining a good ground is critical, and the racks and hooks form an integral part of the electrical circuitry that must be properly maintained.

“You can’t lose the ground,” cautions Davitz. “When changing parts from one cycle to the next, you risk losing ground on the very next part you hang on an old hook— even if it was brand new.” To prevent excess powder from building up on hooks, racks and hooks are often designed with only a few sharp points of mechanical contact.

“A major goal in our standard hook design is to ensure that the part always comes into contact with the exact same point. With that design, our customers can typically run from four to eight cycles without a danger of losing ground,” says Davitz.

“Minimizing the number of points of contact is a good practice,” agrees Merritt, “and if you can hang to a blind area that shields the hook from powder build up that’s also a good way to protect the ground. So if you need to hang parts from chains, for example, the fewer links, the less chance for losing the ground,” says Davitz.

Density: The Key to Successful Racking

Beniquez says he feels as though he is constantly reminding customers to consider racking parts as densely as possible within the profile of their paint booth to get the optimal amount of production out of their paint lines. Davitz agrees that customers—even the very best shops— often fail to concentrate on managing their part racking density in a way that is the most profitable in order to take advantage of their line.

“Line density directly impacts first pass transfer efficiency,” observes Merritt. “From an electrostatic standpoint, big, open holes on the line mean spraying when there’s no product present. That means doing extra work.” The best practice is to load the lines densely even if that means that there are larger gaps on the line between dense racks of parts. “On an automated line, in particular, if there’s going to be a hole on the line we would prefer big gaps on the line so we can utilize the gap and turn the spray guns off,” says Merritt. “You might say there’s a ‘sour spot’ where the gap is too small to be useful and too big to be efficient.”

“The most impressive system I have seen was powder coating at 70 feet per minute,” recalls Davitz. “I found that that kind of productivity was determined by how they loaded and unloaded the line. That plant manager explained that he did not need to slow the line to ‘people speed’ if he could load and unload racks offline. The manager looked at me and asked, ‘Is there any other way to run a system?’”

Often, designing racks means finding the balance between designing tooling for specific parts and designing tooling that offers more flexibility. “We have a customer that paints 24,000 different parts,” says Beniquez. “So we developed racking solutions designed to be adaptable and yet provide very dense racking. For example, we have crossbars that can be easily moved to different heights in a few seconds.”

“For job shops, density is their lifeblood,” says Rempala. “The ones that think seriously about it are the ones that stay in business in the long haul. At OEM or captive shops, you have plenty of knowledgeable, and skilled people, but they often have other processes to think about and racking efficiency often gets over looked. There’s definitely a continuum that runs from modularity to dedication. Job shops need modularity while OEMs want dedicated tooling,” says Rempala.

Rempala reflects on a trend that Mighty Hook sees affecting their rack design. “Manufacturers seem to be trending away from high quantities of a single part to more of a lean or kit approach to coating. It used to be more common to manufacture a bunch of parts, put them in a bin, and move them to the powder line. Manufacturers are collecting kits of parts and racking them together. I think this is driven by a transformation to lean manufacturing, but it’s also more efficient since they don’t handle the same part as many times. There seems to be a trend away from inventorying parts towards building to order.

Words to the Wise

When asked for advice about how powder coaters should approach racking, Davitz suggests that customers first consider racks that offer versatility and can be disassembled for quick changeover without having to clean them between cycles. Second, coaters should make sure the racks are designed to maximize line density. Try to load and unload of parts offline to optimize line speed. Finally, Davitz suggests that operators figure out the actual hourly cost of running the powder line considering all of the chemicals, utilities, electricity, maintenance, labor, and other costs. “When one of our customers estimated their cost, it was well over $1,500 an hour. At that price, you see how important it is to make sure every foot of your powder line is loaded optimally,” Davitz says.

“Racks may not be sexy,” says Beniquez, “but we are not building cheap equipment either. Our customers are investing in a tool, and they realize they need to take care of them or they won’t work and they might as well be throwing their money in the garbage.”

Paul Mills is a marketing and business development consultant to industry chemistry and equipment suppliers. He has been a writer for the powder coating industry since 1994. Paul can be reached at 440-570-5228 or via email at pmillsoh@aol.com.

Editor's note: The above image is courtesy of Shaffer Metal Fab Inc. in Sydney, Ohio. The patented Magic Rack® II heavy-duty racking systems uses removable support hooks and vertical crossbars to connect multiple tiers on a powder coating facility.