FARO Inspection Device Aids in Robot Calibration
- Sunday, 01 June 2008
Parallel Robotic Systems Company (Hampton, NH) designs and produces high-precision positioning systems to provide effective solutions for difficult motion problems, correct errors in automated welding lines, develop newer and better product designs, and further testing in bio-mechanical research.
Their six-degree of freedom robots are based on the hexapod (six-legged) system that offers high load capacity and range of movement, while maintaining high precision and repeatability. That makes them useful in a wide variety of applications, ranging from industrial to biomedical.
When building every Hexapod robot, there are six spheres attached to the Hexapod’s table and another six attached to its base. It is critical that Parallel Robotic accurately locates each sphere’s center and ensure the distance is the same relative to the robot’s base ring. The struts that connect the spheres must also be exact.
Using a stationary coordinate measuring machine (CMM) provided accurate measurements, but acquiring one large enough for their needs wasn’t economical. Some robots are so big, in fact, that even outside metrology services weren’t an option because of limited availability locally and the high cost of transporting them long distances. The bottom line: Parallel Robotic Systems couldn’t qualify their robots’ performance conveniently, efficiently, or economically using stationary CMMs.
Enter Gage-PLUS from FARO Technologies. Gage-PLUS – a high-tech, yet user-friendly portable manufacturing inspection device – provided Parallel Robotic with a feasible solution that had benefits not found in the fixed CMMs, which are far more expensive and complex. Instead of taking the part to a CMM in a climate-controlled room, quality control personnel can mount the Gage directly to the machine producing the part in order to verify that it has been made correctly. If the part is not within tolerance, the user is able to quickly make corrections, reducing production downtime.
It also offered Parallel Robotic Systems the desired accuracy of up to .0002in. (.005mm) – without the need for regular calibration – and allows them to perform ISO traceable part and assembly inspections directly on the shop floor.
With minimal training, they are able to check basic geometry, distances, angles, and reduce operator error with simple on-screen prompts that illustrate what to do. As the Parallel Robotic Systems user guides the Gage’s tip over the surface of a part, the system’s laptop computer simply and easily records all of their measurements. High precision caliper, height gage and micrometer measurements can be performed, and operators can quickly create basic 3-2-1 alignments and add nominal data for instant results verification.
Made specifically for use by shop floor personnel, the Gage is accurate and powerful enough for advanced measurement, including SPC statistical analysis and GD&T. It can perform first article inspections or rapidly create custom routines for repeat part measurements. All user measurements are automatically recorded and comprehensive reports can be generated.
Parallel Robotic can now see an actual representation of the behavior of their Hexapods’ moving tables and can compare geometric characteristics between features. They use the Gage in the calibration phase and in the qualifying procedure, both of which are required for every robot.
“Typically, it took about six hours to calibrate each robot using outside resources, including travel time,” said Parallel Robotic’ engineering manager Andy Chui. “With the FARO Gage, this has been reduced to one hour and we can re-measure the parts anytime we want. In my opinion, the convenience is priceless when we must have something measured immediately.”
On occasion, customers request instant robot re-calibration changes. Without the Gage, the entire robot would have to be removed from its mounting structure and sent to a CMM large enough to perform the measurement.