Toyota Material Handling Manufacturing Sweden's factory in Mjölby applies lean thinking by painting its warehouse trucks with a highly automated paint shop. The only remaining manual work is hanging the parts on an elevated conveyor belt. Then they start an automated journey, going through pretreatment, drying, robot painting, hardening and cooling, before they are finally taken down from the conveyor and sent to the assembly line.
The paint shop uses powder paint that is sprayed onto the parts. While the powder has a negative electric charge, the metal parts are given a positive electric charge, so that the powder paint particles stick to the parts. The paint is then 'baked' onto the parts in the oven. This process avoids the use of solvents, which can cause water and air pollution. Especially emissions to air of volatile organic compounds (VOC) are potentially harmful to employees and the environment. The use of powder paint also avoids the use of water-based paint, which causes water and air pollution to a lesser degree.
The paint shop in Mjölby works in a highly sustainable and lean way. Agneta Ring, Sustainability Manager at Toyota Material Handling Manufacturing Sweden, explains its ecological benefits: "In 2009, we invested massively in this paint shop, knowing that it would reduce our environmental impact. It was high on our list along with improving the work atmosphere for our employees." With this commitment in mind, the project team set new targets: zero drainage, reduced powder paint waste and energy consumption, as well as a massive reduction in CO2 emissions, by switching from LPG (Liquefied Petroleum Gas) to district heating in the pretreatment process.
The environmental performance has been optimised at every step of the painting process. One of the largest gains has been recorded in the washing station, where dirt and oily residues are cleaned off from the steel plates. In the old paint shop, the washing water was heated using LPG, where now it is sourced by the district heating from the municipality network.
This has led to a CO2 decrease of a full 340 tonnes annually. Moreover, the washing water is filtered and distilled; it passes through carbon filters and ion switches before it is finally treated with UV-light to remove any possible bacteria. Then, the water is ready to be used again. This has led to a reduction of waste water by 90%. "It was a truly remarkable day when we, as a symbolic gesture, cut off the drain pipe leading to the public sewer," says Agneta Ring.
When the parts have dried, they are transported to a paint box, where industrial robots do all the work. Not only is the paint powder-based and solvent-free, all superfluous powder paint also falls through a mesh floor decking and is vacuumed back for reuse.
"Today we have a totally solvent-free working place and we have managed to increase the powder paint reuse ratio from 67% to 86%. This contributes to financial savings worth 75,000 euro annually," confirms Marcus Johansson, Production Development Project Manager at Toyota Material Handling Manufacturing Sweden.
The paint shop's camera system also helps to 'see' if the components hang correctly before entering the paint boxes, according to the Toyota Production System value Poka Yoke. This method keeps the robots from colliding with misplaced components, minimising equipment damage and saving up to 50,000 euro annually.
Agneta Ring concludes: "One of our cornerstone pillars in our sustainability efforts is the 3R-principle: Reduce, Reuse, Recycle. This paint shop is a great example of our lean thinking that support healthy finances and a safe working place while also reducing environmental impact."