Featured Toyota develops an electrostatic paint gun

I worked for a lot of years designing and building automotive paint systems. There were developments over the years that made significant improvements.

Due to ever increasing emission requirements the primer and color coat were switched to water based paint. The clear coat remained solvent based because they couldn't get enough sheen from water borne paint for that.

E-coat (electro coat) paint lines are used to put the primer on the white bodies (bare metal). In what looks like a glorified car wash the bodies move through a tunnel and they are rinsed of dust. Next a detergent is applied then they are rinsed with de-ionized water. The conveyor dips them in a phosphate tank. The phosphate etches the surface of the metal. The surface changes from a smooth texture to something like a piece of paper so that the paint has something to bond to. There is a final D.I. rinse and then they go through a drying oven.

The bodies are then picked up by an overhead conveyor and then go to the e-coat primer tank. That tank is charged by a 1600 amp 400 volts D.C. power supply. One electrode of that power supply is attached to the tank and the other electrode is attached to the overhead conveyor rail. As the bodies are submerged in the primer, the current increases and paint migrates to the unpainted body. The paint doesn't just coat it forms a bond to the body, once most of the body is coated, the electrical current seeks out uncoated areas. Those uncoated areas are like the inside of the folds of edges of a door where the door skin is folded over the door frame. The result of e-coat is that these cars don't have the rust problems in those seams that earlier vehicles did.

Painting the hood, roof and trunk was done by a overhead rail with a number of nozzles that oscillated back and forth as well as tracked the profile of the hood, roof and trunk up and down. These used an electrostatic charge of thousands of volts to reduce overspray and get more of the paint to adhere to the body.

These booths are maintained at 75% humidity and 75 degrees. The sequence is e-coat primer then a drying oven. Next a color coat booth then an quartz tube infared drying oven. The trick with the infared heaters is to get the heat profile of the painted body close to 200 degrees everywhere without any surface getting any hotter where the paint might boil. Clear coat booth is next then final oven.

A fume incinerator is attached to the final drying oven which is a 300' long heated tunnel. The waste heat from the fume incinerator burns off the solvent vapors from the drying clear coat and provides much of the oven heat for the 40 minute trip through the 350 degree drying oven.

Technology marches on and Toyota just announced that they have developed a charged paint gun.

https://www.yahoo.com/autos/toyota-implements-airless-paint-atomizer-215600116.html

 

Designing and building automotive paint finishing systems was my career and I loved my job but I have been retired for over 10 years. When I look at this Porsche Taycan video and see all the advancements in automation and painting in just that time, I feel like a dinosaur. For those that would like to take a peek at some of the current manufacturing this is a six minute video. Enjoy.