PREPARATION LINE
As with any painting task, preparation work is crucial and this is especially true when it comes to painting cars. According to Dale Barr, the manager of paint shop, steering, maintenance and process, the preparation line is called the “Devil’s Kitchen” because the team has to control numerous variables in order to achieve the desired result. The elevated temperatures I experienced walking past all the dip tanks may also have influenced the choice of name.
Arriving from the body shop, the body appears clean, but it’s important to keep in mind oily residue, dust or other contaminates that might not be visible to the naked eye could spell disaster for paint quality. The first step in the process is to affix the body to a shuttle crossbar that is used to link up with the preparation line’s vario-shuttle transportation system. This runs on tracks and allows the individual body to follow the path through the cleaning, degreasing, phosphate dip and electro-coating (E-coat) procedures. The crossbars can be fitted to different models of body allowing, in this case, the 3 Series and new X3 to run on the same line during the changeover phase of the plant.
The body passes through the bodywash section with its water-spraying systems and dip baths filled with degreasing agent. It makes a “dolphin jump” through the cleaning dip tanks as the vario-shuttle turns the vehicle body upside down in a circular movement to ensure that all areas are reached and no air-bubble barriers form.
The next step is an acid-zinc-phosphate bath that forms crystal structures on the surface of the body. This is the basic adhesion primer to make sure that the E-coat corrosion-barrier paint sticks to both the inside and outside of the body.
After a quick rinse, it is time for the body to dip through a bath filled with 150 000 litres of E-coat paint; here, once again, the dolphin jump is used. The flow of current between electrodes at the edge of the bath and earthed vehicle body causes the paint to stick to the body of the vehicle, hence the term E-coat.