According to automation provider ABB, paintshop robotics have moved on to a bold new era
The use of robots to automate the processes of automotive paintshops is now entering a ‘third generation’. That is the verdict of Didier Rouaud, manager paint and sealer process engineering in the US for automation provider ABB. Rouaud says the successive generations can be differentiated by developments in several key areas, including the width of the paint booths, the fixturing of the robots and the sophistication of their programming.
For the first generation, key parameters were: 20ft-wide paint booths; lateral robot movement along floor-mounted rails; and laborious programming routines. For the second, booth widths were reduced to 18ft, the robots ran along elevated rails and the beginnings of off-line programming were becoming apparent. For the third generation which he says is now a reality, the hallmarks are: booths as small as 14ft; robots fixed to a single anchor point, but with greatly extended reach; and programming carried out in an easy interactive fashion “much like a video game”.
ABB has a comprehensive product portfolio, but Rouaud highlights the following innovations:
- The No-Patch programming method which eliminates the ‘patchwork’ required when panels are painted with multiple robots
- Stay-On programming which keeps the atomiser on the area to be painted with no trigger off periods, thus reducing both overspray and cycle time
- The Cartridge Bell System (CBS) which is a simple directcharge waterborne atomiser that uses paint cartridges
- The IRB5500 robot with unique kinematics allowing maximum reach in narrow spray booths
- The RB1000 atomiser which can work with high paint flow rates and also has the ability to vary pattern size for enhanced control.
Rouaud names three particularly important characteristics of the IRB5500 robot: its large work envelope; the fact that it has no need for a rail or ‘7th axis’; and its high acceleration. The latter, Rouaud stresses, has implications for its programmable capabilities, such as the Stay-On module, and hence for final product quality. He gives the example that, if a robot slows down too much when reversing, paint will accumulate in excess amounts in those regions of the vehicle over which the slow movement takes place.
But with the ability of the IRB5500 to accelerate at a rate as high as 25m/s2, this will not occur. Cycle times will also be compressed. For instance, a time of 12.7 seconds with a robot that is limited to an acceleration of 5m/s2 would be reduced to 10.6 seconds with the ABB unit.
Similarly, the extended reach of the robot – as much as 20ft – enables full exploitation of the No-Patch capability. Rouaud says that the limitations of previous robots would have required two at either side of the booth for paint application across a horizontal surface such as a bonnet lid, creating a quality control issue: a ‘stitching’ effect in the centre. A single robot obviates this issue entirely. It is also faster, able to reduce a cycle time of 26.4 seconds to 22.8 seconds.
The other crucial item of hardware is the RB1000 atomiser. This device has a very high flow rate, as much as 1,000cc/min, or twice as high as what was previously regarded as the practicable maximum. This makes working with flow rates of 700-800cc/min “very comfortable”, says Rouaud.
There is a vital compatibility between the products involved. Conventional atomisers simply could not “survive” the high acceleration rates of the new robot, Rouaud states. Crucially for overall efficiency, however, the combination of the two allows for ‘variable patterns’ in actual paint application – most obviously the application of narrow patterns when paint is being applied close to the edge of the target area but much more broadly when the atomiser is centrally located.
Rouaud says that, consequently, cycle times can be significantly compressed. A painting operation on the complete side of a vehicle which might previously have taken a single robot 440 seconds can be reduced by as much as 40% to just 264 seconds.
Rouaud provides figures for the overall ‘footprint optimisation’ which can be achieved. A basecoat booth which is 39.5m in length would require a width of 5.5m with older equipment but only 4.5m with third-generation ABB equipment. This also means that fresh air consumption is reduced from 322,400m3/h to 275,400m3h. However, there is no need for the length to remain fixed; with no need to accommodate a rail system, the booth length could be reduced to 35m without compromising performance.
The possibilities don't stop there. Interior painting can be carried out in just one zone rather than two. Flash-off can also be carried out in the same zone. The result could be a facility with a footprint which is just 41% of the current standard.
In short, the technologies involved – both hardware and software – combine synergistically with each other to generate multiple benefits for both product and process. Rouaud is confident that the ultimate effects fully deserve to be regarded as those of a new generation of automotive painting system.