Using Heat to Improve Your Cycle Time - BodyShop Business

Using Heat to Improve Your Cycle Time

By implementing heat in your shop, solvents evaporate faster, isocyanate catalysts crosslink quicker, and body fillers, sealers, basecoats and clearcoats all accelerate.

Marilyn Monroe, Tony Curtis and Jack Lemon starred in the movie, “Some Like it Hot.” But it’s not just old movie stars who should be attracted to high temperatures; every paint shop runs fastest when they “like it hot,” too. Solvents evaporate faster, isocyanate catalysts crosslink quicker, and body fillers, sealers, basecoats and clearcoats all speed up under heat.

Alligator Heaters
Kerosene and split firewood both create some heat when burning, but spraying flammable vapors around an open flame of any kind seems like a bad plan. Sadly, I was in paint shops heated by both long ago in Iowa.

I had a customer way out on some county roads, then way out on some more gravel roads. He farmed soybeans full time and bought total losses and rebuilt them in his spare time. He heated his shop all winter with firewood in a cast iron stove in the center. He would shovel the stove chock full of logs and get the room temperature up in the high 80s. Then he would slam the stove door shut, fire up the exhaust fan and start painting while it was hot – and many times, finish the last coat when it wasn’t. All things considered, his paint work was really pretty good, which shows that a good painter can overcome many obstacles.

I had a customer who won the bid to refinish a slew of 40-foot semi trailers. The trucking company jumped on his bid because the shop seriously underestimated the time and cost to do the work profitably. They rented a huge building that had rail lines running through it; can you say tall ceilings? They built lots of scaffolding to get the sanders and painters close to the trailers. Winter came, and he rented kerosene-fired, open- flame alligator heaters from a construction supply company. Nothing like a fog of iso-catalyzed urethane enamel overspray drifting toward the roaring flame heater! Tall ceilings, good luck and lots more oxygen than fumes kept us all from disappearing in a mighty flash!

Air Replacement
A basic crossdraft spraybooth has a fan that exhausts about 10,000 cubic feet per minute (CFM) of fume-laden air. If the shop didn’t install an air replacement furnace designed to deliver 10,001 CFM, then the fan quickly pulled all the air from the cabin, the paint room, the metal shop and the office if the door wasn’t shut. Speaking of open doors, when the spraybooths with no replacement air got rolling, they slammed every door in the shop like a volley of gunshots.

Here’s a happy and a sad story about early air replacement. We had a Cadillac dealer build a snazzy new building in 1986 with plenty of space for their entire fixed operations (parts, service and body). Never asking the employees or even the managers what they thought would be good for the design, they followed their fancy architect’s advice to the letter.

Being a smart fellow, he knew the air exhausted from the booth would have to be made up or many airflow problems would quickly accrue. He specified the correct size air replacement furnace and had it installed – in the middle of the body shop, so that all the replacement air had a chance to collect all the sanding dust and shop clutter before it was sucked onto the car through the filtered doors. Learn from their folly and be sure to hook the A/R unit directly to the booth so the incoming air stays clean, and the cabin is even slightly pressurized against dust sucked in from the seams and cracks.

The happy story was the first closed circuit booth I ever sold. It went to the local Volkswagen dealer in 1971. That heated spraybooth made for much cleaner and faster paint work, and they quickly had the reputation for the nicest paint work in town. Hooking a $5,000 furnace on top of a $10,000 fireproof box made for faster dry, better gloss and much less dirt in the finishes. They even rented out the booth when a competing shop needed a first-class repaint. I would like to report that all my other dealership customers in 1971 immediately bought their own heated spraybooths, but sadly they didn’t. They continued to suck all the shop air into their paint work through poorly maintained crossflow booths for many more years.

Visible Light
Our eyes can discern electromagnetic radiation between 400 and 700 nanometers long, otherwise known as visible light. Increasing the wavelengths past the color red at 700 nm moves into radiation known as infrared (IR). (Decreasing wavelengths below purple at 400 nm reveals equally invisible ultraviolet light.)

IR comes in three flavors: short wave, medium wave and long wave. Your shop will benefit most from two of the three choices. Long wave infrared bulbs are similar to the ones in the motel bathroom ceiling or the bulbs that shine on the hot dogs turning on the spit under glass at the gas station. They’re heating from the top down. It’s good for you coming out of the shower and the Polish sausage on the rotisserie, but not so much for your paint work. You want your paint, body filler and primer to cure from the bottom up. Not to say I didn’t sell a whole bunch of those original body shop IR units – round metal fixtures that held five or six of those very same long wave heat light bulbs – on a rolling stand. It was Iowa, it was winter, and any heat – top to bottom or side to side – was welcome in the body shops.

Both medium wave and short wave IR lights will speed production and improve quality in your shop starting today. Remember also that they do the same great job accelerating evaporation or cross-linking hardeners in the summer, too. It’s harder to fire them up when the air is already 95 or 100 degrees, however!

There is one useful tip that I always got during the many interviews I conducted with the various IR manufacturers over my years at BodyShop Business. As much as 50 percent of the effectiveness of any medium or short wave IR light fixture is provided by the reflector backing. Does it feel like your shop’s light has lost effectiveness and maybe it’s time for a new emitter (bulb)? It may be, but you’ll be pleased by how much faster it works if you would just clean the dust and overspray off all the shiny parts.

Blowing in the Wind
One of the best descriptions of how waterborne finishes work goes like this: Do your wet blue jeans dry faster on the clothesline on a hot day or a windy day? The answer is a windy day. Petroleum solvents want to leap back into the air from the sprayed paint; water is often content to stay within the paint film on humid days. Moving air past the finish dries both types of coatings faster than heat alone. Circulating the air in the spray cabin, whether through eyeball-style adjustable nozzles, turbine fans or bladed fans, works wonders. The benefits of hustling some air around the car must be weighed against the additional dirt and dust that hurtles through the moving air. It’s worth it, folks – fire up those fans!

Heat Rocks!
Don’t paint in front of open flames, and don’t suck out lots of air without a method to replace it. Employ IR lights at every chance, and kick in A/R furnaces and speedy air movers to turn your booth into a big oven. Make sure your paint shop has written operating procedures that include using heat to increase your cycle time and your finish quality.


Mark R. Clark is the owner of Professional PBE Systems in Waterloo, Iowa; he is a well-known
industry speaker and consultant. He is celebrating his 26th year as a contributing editor to BodyShop Business.

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