Research into robotic machining of car frames

Citation

(1999), "Research into robotic machining of car frames", Industrial Robot, Vol. 26 No. 1. https://doi.org/10.1108/ir.1999.04926aaf.002

Research into robotic machining of car frames

Research into robotic machining of car frames

Keywords Comau, Robotics

Many vehicle manufacturers are investigating the potential of constructing their cars around a one-piece, aluminium space frame, keen to exploit the combination of light weight and strength. So a research project, part funded by the Government, has been set up to evaluate the use of a robot in overcoming the problem of machining the unwieldy frames after they have been fabricated.

Supplied by Comau UK in April 1998 to Warwick Manufacturing Group's International Manufacturing Centre on the central campus of Warwick University, the so-called "TRICEPT" robot is thought to offer advantages over conventional prismatic machining in that the large workpiece remains static whilst the tool moves around it to complete the machining cycle (see Plate 1).

Plate 1 Dr Ken Young, principal research fellow at Warwick Manufacturing Group with the Comau TRICEPT robot

Said Warwick Manufacturing Group's principal research fellow, Dr Ken Young, "I saw a TRICEPT operating successfully at Volvo's engine plant in Skovda, Sweden, where it was integrated into a cylinder head line. It opened out oil ways at compound angles in 4-, 5- and 6-cylinder variants of the head, achieving a good finish. A conventional machine tool to do the same job would have been much more expensive."

Three linear actuators and a three-axis wrist provide TRICEPT with six degrees of freedom within a nominal volume of X: 2,000mm, Y: 1,500mm, Z: 600mm. Speed of the linear axes is 0.5 metres per second over their 600mm stroke and the rotational axes in the wrist are also rapid at 270šs per second.

The wrist, which can handle a payload of 100kg, at Warwick Manufacturing Group carries a 30,000 rpm spindle from the Swiss company, IBAG. During an open day at the beginning of July, attended by 80 people from industry and academia, the machine executed a demonstration cycle using just three of its computer-controlled axes. A bell holder from a wrecked ship had previously been reverse-engineered and the 3D computer model used to program the TRICEPT to mill the shape out of resin. The demonstration ran for two and a half hours, during which time half the complex bell holder form was completed, showing that the robot is just as fast as a machining centre.

Other applications for TRICEPT include laser and water-jet cutting, deburring and woodworking. Press-fit assembly using up to 1.5 tonnes force is made possible by the high structural stiffness of the three linear actuators arranged around a rigid, centre tube. Maximum static bending deflection in X and Y is 0.0003mm/N and one third of this value in the vertical axis.

Many successful installations are to be found in Europe, Scandinavia and America. In addition to the application at Volvo, examples include: Boeing, USA ­ milling 4.5 metre aluminium aircraft parts using a seven-axis robot on a linear track; General Motors, Brazil ­ gearbox assembly; Opel, Spain ­ assembly of steering columns; Sandvik, Sweden ­ high-precision loading of components into machine tools; and Ikea, Sweden ­ milling of decorative wooden doors for kitchen units.

There is a further interesting application in Sweden where an articulated-arm robot offers domestic door lock and hinge components to a TRICEPT which machines and assembles them. Dr Young and his team will also be researching the use of a robot as a flexible workholding device at the request of one of its industrial partners.

For further details contact: John D'Angelillo, UK Manager, Comau UK Limited, Unit 3, Hortonwood 32, Telford, Shropshire, TF14EU. Tel: +44 (0)1952 670396; Fax: +44 (0)1952 670398.