Tackoff: In Pursuit of the Perfect Paint Job

When it comes to today’s vehicles, a high quality paint finish is the first thing a consumer notices. The automotive industry is constantly improving its paint shop either by upgrading existing facilities or by building new ones to take advantage of the latest technology available.

But manufacturers also go to extraordinary measures to prepare the vehicle’s surface before it is painted, including making sure the surface is clean and ready to absorb a coating.

The vehicle’s surface will first go through a phosphate application, the electro deposition, primer and finally a base coat and clear coat to give the vehicle a deep, shiny appearance that the consumer has come to expect. However, as the vehicle goes through all of these steps, it is subject to contamination, such as dirt, dust and lint.

Dirt and Dust

Dirt and dust are the No. 1 enemies of a vehicle’s paint finish. Today’s modern paint shop is a clean room environment with every measure possible taken to keep dirt and dust out. The vehicle travels along miles of conveyor on its way to the paint booth and has many opportunities to attract dust and dirt.

The last step of the process prior paint is the tackoff process. During the early 1980s, this process was accomplished manually with two to four people using tack cloths to wipe down the entire vehicle before the car went into the paint booth. However, the use of manual labor has proven costly and not as efficient due to the tedious nature of the job and natural human error while trying to reach all areas of an entire vehicle.

By the mid-1980s, the first automatic tackoff machine was developed. It could be programmed to identify the vehicle body style and would automatically tackoff the entire vehicle, eliminating the need for a manual tackoff zone. It offered a cleaner vehicle, reduced paint defects and thus eliminated the need for costly repainting.

And to meet the high demands of automotive production requirements, engineers turned to Mother Nature, who provided them with a material that could withstand the constant use and demands of automotive production and be profiled into a brush that would match the contour of the vehicle and be able to remove the dust and dirt from the vehicle without damaging the vehicle’s finish.

Ostrich Feathers

The best material for this job is the ostrich feather because of its durability and unique construction. The feathers have very fine “fingers” that are ideal for picking up and holding onto the small dust, lint and dirt particles. The feather rolls or brushes are made up of individual wheels ranging in diameter from 18-30 inches. Different sizes of ostrich feather wheels are arranged on a shaft to match the contour of the vehicles to be dusted. The feather wheels are fastened onto a soft-core foam hub and secured to the feather shaft with a compression coupling. The compression coupling and soft core foam act as a clutch and allow the feathers to slip and disengage in the event of a collision to avoid damage to the vehicle and the feathers.

To aid the feather wheels in picking up the lint and dust attracted to the vehicles, the machine uses a high-voltage ionization system. The vehicles have static electricity holding the lint and dust to the vehicle’s surface, and the rotating feathers brushing against the vehicle’s surface create more static electricity. To pickup the lint and dust, they need to be broken free of the static charge that is holding them to the surface — otherwise, the feathers would just move the dust around on the vehicle.

To break it, there is a high-voltage static bar introducing positive and negative ions out to the point on the vehicle just ahead of where the feathers make contact with the vehicle’s surface. With this design, the static charge holding the lint and dust to the vehicle’s surface can be effectively neutralized, and the feathers can pick the lint and dust off the vehicle’s surface.

Another major component of the tackoff machine is the exhaust system. Each individual feather wheel on the machine is housed in an exhaust hood. The inside of the hood has an exhaust slot that runs the entire length of the feather roll. Prior to the slot is a beater bar that gently agitates the feathers to assist in the release of contaminants from the feather brush. Once these contaminants are released, the exhaust air can vacuum the contaminants through the exhaust slots in the hood.

System control has gone through many changes while keeping up with changing technology. Pneumatic actuators and proximity switches controlled the early machine. As technology has improved, electric motors, gearboxes and encoders have been incorporated for more precise and smoother operation. With these advancements, you get a machine that does a better job and ultimately results in a better paint finish.

The tackoff machine has gone through many changes since its inception. Machines today are available with multiple roller and axis configurations. A newer type machine is called a “Clean Wall Machine.” With this system, the only portion of the machine actually inside the booth is the feather brushes. All the mechanics of the machine remain outside the booth, allowing for a cleaner, sleeker looking system. Another advantage to this system is a smaller booth and reduced booth air makeup.

Every measure taken toward a cleaner environment in the paint shop is a measure toward the quality of the finish on the painted vehicle. If you have worked in any paint shop, you know that paint shop managers have no sense of humor when dealing with dirt, dust and lint. n

Steven R. Lipple is the engineering manager for Autotac Inc. He can be reached at steve@autotac.net.