New Mazda2 at U2 plant paint shop. Click image to enlarge
Story and photos by Norm Mort
Hiroshima, Japan – Mazda World headquarters and its U1 and U2 car production plants are located on the southeast outskirts of Hiroshima on 2,236 acres. It is one of the largest production plants in the world; building 480,000 vehicles per year. In total, over 14 million Mazdas have come off the assembly line here since first opening in 1972. The U2 plant turns-out a completely new Mazda on an average day every 1.2 minutes.
We toured the U2 plant where Mazda currently builds the CX7, Mazda5 and the small Toyota Yaris-sized Mazda2; which all the Canadian journalists felt would sell well in Canada.
Mazda were particularly excited about the plants new Eco-friendly Three Layer Wet Paint System. With this new system Mazda was able to reduce both energy use and the amount of pollutants. The new Three Layer Wet paint System equals the highest pollutant standards in the world that were set by the Germans and brings the plant up to the 1997 Kyoto protocol.
Typical eco-friendly systems cannot reduce both VOCs (Volatile Organic Compounds which include solvents such as Xylene and toluene.) and CO2. The development target was to reduce both – a 45% reduction in VOC emissions and a 6% or more reduction in CO2 emissions. To reduce CO2, Mazda sought to eliminate its primer paint booth and baking oven through the use of a three layer wet paint system with low-solvent paint. A reduction in VOC was to be achieved by reducing the amount of solvent in the paint and reducing the paint consumption.
When the baking process between the primer coat and the basecoat and clearcoat was eliminated, mixing between the primer coat and basecoat occurred which resulted in colour turbidity. To stop the two paints from mixing Mazda developed an interface polymer. Because the interface control polymer had a different solubility parameter to the low molecular weight resin, it would move to the surface of the primer. The interface control polymer formed a highly viscous barrier that separated the primer coat and basecoat. During baking the interface polymer melts due to the heat and the surface becomes smooth while having stopped any mixing.
Takakazu Yamane. Click image to enlarge
At the same time the removal of the reciprocating coating machine and installation of a robotic coating machine resulted in an improved transfer rate for the basecoat of 68% to 80%. The transfer rate at the primer and clearcoat stage improved from 79% to 85%. The robotic coating machine path was plotted using CAD. Control software established the optimum rotation speed and discharge rate.
Presenter Takakazu Yamane from the Technical Research Centre also pointed out that the elimination of the primer paint booth and baking oven further reduced CO2 emissions by 15% and approximately 20% of the coating process was eliminated. An added benefit was a 15% reduction in paint costs, while maintaining the same coating quality as a conventional paint system.