More colour, less waste

Whether using hand spray guns or robots, long paint supply lines and atomisers must be thoroughly cleaned with solvent between each paint change. Both paint and solvent are wasted, increasing costs and causing negative impact on the environment (particularly solvents, which contain volatile organic compounds). ABB working closely with Japanese automakers came up with a more efficient method of switching colour without losing paint or time.

ABB thought that having a traditional paint line with many different paint tanks and all the lines and hoses needed to paint just a few items was a terrible waste, not only of paint and solvent, but also of time, labour and money. Why not move the paint tank to the end of the robot arm itself?

In the Cartridge Bell System (CBS) developed by ABB, the robot is separated from the paint delivery system. There are still paint and solvent tanks, albeit much smaller for special colours. These feed to a cartridge handling unit where the paint is filled into the cartridges. Each cartridge is dedicated to one colour, so keeping cleaning to a minimum. A full cartridge contains only paint below the piston and no solvent; as solvent is pumped into the cartridge, the paint is driven out, until the piston is fully extended with only solvent above it. The robot required only a solvent-filling line; all other lines are single-usage and lead only to the cartridge station.

The exchange unit on the CBS can be flexibility adjusted with as many colours as needed, with two cartridges for each colour (one being filled while the second is in use). When a cartridge is empty, the robot arm swings over to pick up a newly filled cartridge, set in place by the cartridge handler and held in place by the robot using negative air pressure. In the meantime, the first cartridge is being filled. The cartridge can be changed in less than 10 s.

Significantly, this approach leads to safer electrostatic painting, because only the cartridge itself needs to be charged and isolated from the ground. Up to 90% of all the paint is transferred to the automobile body, hugely cutting paint losses. And small-lot paint runs are far easier to handle, and much more efficient and affordable.

Material loss at colour change went from 120 mL of solvent and 32 mL of paint to just 10 mL of solvent using the CBS as only the atomiser bell cup is cleaned with solvent.