imaging and machine vision europe june/july 2010
www.imveurope.com
14
automotive production Driving developments
Modern automotive production is highly automated, with robots and machines carrying out complicated tasks at every step of the process. Stephen Mounsey discovers how machine vision makes this automation possible, and how it can trace parts through the entire process
glue a reference point on the car, and you then know that each car coming off that production line has the cut in the same place relative to the reference point.’
Robots have a role to play at almost every stage in modern automotive production, including the ‘Body in White’ stage pictured here. Machine vision drives these processes, enabling robots to work to a high degree of accuracy
Automation in a car factory can take the form of versatile robots or more dedicated pieces of equipment. One robot may perform several tasks on a stationary vehicle before the workpiece is moved to the next robot bay in the production line. Where more dedicated machines are used (a painting tunnel for example), the car may move steadily though the production line. Vision systems are important in both cases. Jean-Luc Grannec is business unit manager of Edixia, a subsidiary of the French Group Tiama responsible for supplying vision systems to the automotive industry. Using the process of fitting the doors onto the car as an example, Grannec cites the importance of vision in such a dynamic environment. ‘One of the most significant challenges manufacturers face when assembling the car is getting the
components in the correct place,’ he says. ‘The tolerance required when fitting a door is a few tenths of a millimetre; the conveyors moving the car [through the production line] cannot achieve this accuracy. [Without machine vision], you can only achieve a window of probability that the part will be somewhere in the region of plus or minus three millimetres, and so you’ve already failed. On top of that, the robot may have a limit of repeatability of about 0.2mm, and the clamps gripping the door in the handling tool may also have a tolerance of 0.2mm.’ A vision system must be installed in parallel to a robot in order to monitor the distances between the car and the door at several stages in the joining process. ‘The same vision package could be used, say for laser cutting on the car, or any other process. You
Keeping in line According to Grannec, robot control is an overarching aspect of all of the vision products Edixia supplies to the automotive industry, most of which are aimed at a very specific process within either the production of components or the assembly of the vehicle. He explains, for example, that fitting a door to a vehicle is a task that uses the company’s ‘gap and flush’ measurement system: ‘We install the [gap and flush systems] mainly in the Body in White area of the manufacturer’s plant,’ he says, referring to the stages of automotive production in which the bodywork (including all doors) is assembled, prior to other components being added (engine, chassis, wheels, etc.). ‘“Gap” is the number of millimetres between two metal sheets, and “flush” is the difference in their level,’ explains Grannec. ‘For this application we can provide fully automatic tunnels, so that the car just passes through without stopping, and when the car emerges from the tunnel, the line operators can access real-time information about which sections are within tolerance or otherwise. They can of course correct the car, but they can also keep track in real-time of any problems, for anything about to occur in the upstream processes,’ he explains. ‘This system could be installed in a tunnel, mounted on robots or [packaged] in an operator-held gun.’ At the Body in White stage, the manufacturers may also check the geometry of the car’s bodywork in its entirety: ‘In this case you don’t measure gaps and flushes between metal sheets, but you measure some points on the Body in White shape,’ explains Grannec, saying that x, y, and z measurements must be taken accurately, which is achieved through laser triangulation. Machine vision allows these dimensions to be measured within the production environment in-line, rather than checking a selection of the cars away from the production line: ‘If you are taking some cars off to a lab to be measured, then first of all you cannot measure all of the cars, and secondly you get the result maybe a day later, and in the meantime you have manufactured 1,000
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32