The following article appeared in Automotive Finishing Magazine, Spring 2000. It can also be viewed in their online archive here.

In Pursuit of the Perfect Paint Job

By Steven R. Lipple, Engineering Manager

Autotac Inc, Troy, MI

With today’s vehicles, high quality paint finishing is the first thing the consumer notices. The automotive industry is constantly improving its paint shop facilities by either upgrading the facilities it has or building new ones to take advantage of the latest technology available. The manufacturers go to extraordinary measures to prepare the vehicle’s surface before it is painted.

The vehicle’s surface will first go through a phosphate application, the ELPO (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.

Automatic tackoff machines have become a major component in the paint process for automotive assembly plants.

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 the conveyor on its way to the paint booth. As the vehicle travels through the clean room environment, it has many opportunities to attract dust and dirt. Therefore, it travels through clean tunnels and environmentally controlled booths that have their own air make-up systems.

The last step of the process that the vehicle travels through prior to being painted is the tackoff process. This process, especially during the early 1980s, was accomplished manually with two to four people using tack cloths to wipe down the entire vehicle. They attempted to make sure the vehicle was free of dust, dirt and lint before it 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. This machine would be the last step in preparing the vehicle before it was painted. A machine that could be programmed to identify the vehicle body style would automatically tackoff the entire vehicle. The development of an automatic machine eliminated the need for a manual tackoff zone. It offered a cleaner vehicle, reduced paint defects and thus eliminated the need for costly repainting.

The automatic tackoff machine has become a major component in the paint process for the automotive assembly plant. 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. This brush would match the contour of the vehicle, be able to remove the dust and dirt form the vehicle and not damage the vehicle’s finish. The best material for this job is the ostrich feather.

The machine uses ostrich feathers because of their durability and unique construction. Upon close inspection, you notice that 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 that are used in the automatic tackoff machine are made up of individual wheels ranging in diameter from 13-30 inches. Different sizes of ostrich feather wheels are arranged on a shaft to match the contour of the vehicles(s) 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.

In this tackoff system, only the feather brushes will be inside the booths.

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, you need to break them free of the static charge that is holding them to the surface. If you do not break that bond, the feathers will 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. All the hoods are ducted to a common machine plenum. This plenum is then ducted to a fan and filter box. Once the contaminants are released from the feathers and vacuumed out of the exhaust hood through the exhaust slots, they are conveyed through the ductwork and passed through a two-stage filtration system.

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 first introduction. The machines today are available with a multiple of 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 will be the feather brushes. All the mechanics of the machine will remain outside the booth, allowing for a cleaner, sleeker looking system. 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 realize that paint shop managers have no sense of humor when dealing with dirt, dust and lint.