Powder coating. You probably send this operation out to the specialty shop across town. Who wants to mess with spray booths and ventilation systems: ovens big enough for a commercial bakery; paints, primers and cleaning compounds; regulatory hassles; and finding someone qualified to run it all? It’s easier to just make parts and let someone else deal with it, right?
Probably so, but that might not be what your customer wants. All they care about is getting good parts, on time and at a fair price. Even if all goes according to plan, how much longer is the lead time and how much markup are you paying by subcontracting your powder coating needs? And if said specialty shop messes things up, whose name will be remembered for the late delivery and defective product? Certainly not theirs.
Gema’s MagicCompact booth features automated color change and intelligent air flow, and is designed to minimize powder accumulation.
Learn the process
Potential hassle aside, an increasing number of shops are starting to realize “going vertical” can be a smart business move and that bringing powder coating under their own roof is among the lowest hanging pieces of fruit on the continuous improvement tree. There is some investment (maybe a good deal of it), but as those who sell powder coating equipment and supplies will tell you, it’s not rocket science.
So, if you’re interest is piqued, one thing’s for sure: You’d better learn something about the process before ordering a new paint booth and a rainbow of powder colors.
Powder coating works by spraying what is essentially dried and finely ground-up paint from a special powder spray gun toward a part. As the powder exits the nozzle, it becomes electrostatically charged, which is why it “sticks” to the grounded part (it’s that whole “opposites attract” thing). The part is then placed into an oven, where it is held at cookie baking temperatures long enough for the powder to melt and flow into a durable, uniform coating.
The parts must be clean, however, for the powder to stick. That’s why some sort of pretreatment is usually necessary, anything from a wash station to remove oils and grime accumulated during the manufacturing process to an abrasive media blast for rust and heavy oxidation. In some cases, a zinc or iron phosphate primer might also be required to assist adhesion. Which one is best depends on the environment where the parts will be used, their pre-painting condition (how dirty they are to begin with), and ultimately, what the customer requires.
Adding it up
Powder coating requires a lot of equipment. Aside from finding several hundred feet or more of additional floor space, you’re looking at some sizeable investments.
• Assuming you’re going to coat more than a handful of widgets, you’ll need a properly exhausted and sealed powder spray booth large enough to handle your workload and product variety. (You can’t just spray powder willy-nilly out in the parking lot).
• Getting parts clean might be as simple as wiping them down with a solvent-soaked rag, but more likely will probably mean a carwash-like spray unit or even a big bead blasting chamber (or maybe both).
• Because many fabricated parts are quite large, and since cure times can take an hour or more on very thick parts, you’ll need an oven big enough for a Keebler Elf factory and one that’s sufficiently energy efficient to where the high electricity bills won’t drain the company’s retirement fund (there is a retirement fund, right?).
• Finally, you’ll need an assortment of powder spray guns, funny-looking suits and aspirators for your operators, boxes of powder, cleaning supplies and various racks from which to hang parts during pretreatment, powder coating and curing.
Of course, just like buying a new press brake or laser cutter, it’s easy enough (and often quite necessary) to go far beyond the basics. For most companies, this probably means automating one or more parts of the powder coating line. Jeff Hale, marketing director at Gema USA Inc., notes there are numerous ways to define the term “automation.”
“For some shops, a continuously moving conveyor and manual spray guns are just fine, while others require a fully robotic system capable of running lights out,” he says. “This leads to questions such as how many axes of motion, how many and what type of guns will be used, part identification and tagging during the powder coating process, and so on. There are a lot of factors to consider.”
One of the factors to consider is coverage. On large flat parts such as garage door panels or bathroom partitions, for example, application is quite easy – just run the spray gun back and forth a few times and uniform coverage is (almost) guaranteed. But try that with an aluminum wheel or similarly complex part and you’re likely to spend the rest of the day on rework. This is where automated systems shine, Hale says, in that you can program them once and they’ll keep doing the same thing, hour after hour, year after year.
The accuracy of robotics also helps make powder use more efficient, which on a “typical” part might account for 15 percent of the total powder coating cost. Add to this a best guesstimate of 20 percent for labor costs, and a robot offers a significant positive impact to the bottom line.
Of course, those considerations must be balanced against part quantity. There’s no fiscal sense in installing a multi-million-dollar powder coating system (that’s not an exaggeration) unless it’s going to be spraying parts around the clock and working double time on Sundays.
Joe Glassco, director of powder system sales for Wagner Industrial Solutions Inc. in North America, says there are many ways to skin the powder coating cat and that choosing the right system requires careful planning.
“You need to consider the layout, available floor space, how many colors you want to spray, what kind of process speed and film thickness you need to achieve, available budget and long-term objectives,” he says. “If you install a fully automated system with salt spray and multiple colors, for example, you’re looking at a couple million dollars easy.
“That’s why the first thing we do when visiting a potential customer is to go through a fairly lengthy assessment to understand their needs,” he adds. “It’s true that powder coating is not a terribly complicated process, but there are a lot of variables to consider in order to size a system properly.”
If you’re biting your nails right now over the potential powder coating avalanche headed your way, stop worrying. Glassco says it’s much easier to achieve high-quality finishes with powder coating than with liquid processes (that is, painting). It also contains none of the volatile organic compounds (VOC) that paint has, making it safer and cleaner.
With a suitable reclamation system in place, powder utilization is far better (up to 95 percent can be reclaimed) compared to paint (50 to 60 percent). And if there is a boo-boo during powder coating, it’s usually an easy fix, whereas a painted part will probably have to be stripped and re-sprayed.
“With one- or two-part work, assuming you’re not worried about capturing overspray, you can get into a basic powder sprayer for around $5,000,” he says. “You still need an oven, of course, but these manual systems are an easy way to get started without a ton of cash. Just be sure to get the parts clean beforehand, buy a professional grade powder coating gun and nozzle, and develop a repeatable process.”
Interested in learning more? Glassco strongly recommends the Powder Coating Handbook available from the Powder Coating Institute’s website. It’s going to cost you a Ben Franklin, but it’s well worth it. Happy spraying.