Robots On The Line—Measuring - Brief Article

Automotive Manufacturing & Production, April, 2001

BMW Manufacturing Corp. has been producing Z3 roadsters in its Spartanburg, South Carolina, plant since 1995. So far, more than 250,000 have been built. One of the tools that BMW is employing to assure high-quality build is a system from Staubli Unimation (Duncan, SC) that's called FRAMS: Flexible Robotic Absolute Measuring System. That's right. While robots are widely used in assembly operations for welding cars together, in this case, the devices are being used to measure things.

The robotic in-line measurement system for body-in-white at BMW employs four Staubli RX130 L robots equipped with S100 TriCam sensors from Perceptron [Plymouth, MI). The system is used for 100% inspection. The robots measure 137 points in 92 seconds.

One of the key reasons why the robot is useful in this measurement application is that it has a patented gearbox that provides zero backlash which is supplemented by calibration software that provides repeatability at constant temperature of /-0.035 mm. (If there is a temperature change, the software makes the appropriate compensation.)

Although BMW Manufacturing uses a variety of measurement devices including coordinate measuring machines and gages, one of the benefits of the FRAMS system is that because it is a flexible system, it can more readily accommodate changes in body configuration than, say, a setup that has fixed cameras or sensors could.

According to the folks from Staubli Unimation, FRAMS has applicability far beyond just body-in-white applications: dashboards, exhaust pipes, doors, hoods, and die cast components are among other things that it can be used to measure.