Nov 10 2009
NASA's Marshall Space Flight Center has enlisted the Form Talysurf PGI 1230 Surface Measurement and Talyrond 295 Roundness/Cylindricity Measurement Systems from AMETEK Taylor Hobson to perform critical surface analysis of a damaged bearing assembly from the International Space Station.
The results are expected to help NASA experts determine the cause of the damage to the Solar Alpha Rotary Joint (SARJ), a 10-foot diameter ring that allows the station's solar panel array to rotate and track the sun. Until the cause is found and the problem fixed, the station's starboard solar array cannot be properly rotated for optimum power generation.
A damaged trundle bearing assembly (TBA) - one of twelve aboard the starboard SARJ - was removed and returned to earth aboard the space shuttle. Along with the damaged bearing assembly, a team from NASA's Marshall Space Flight Center measured 17 spare units and 12 others that had been life tested aboard a test SARJ. The team conducted an extensive examination of the bearing assembly, including extensive dimensional and surface profilometry measurements using the Talyrond 295 and Form Talysurf PGI 1230 from Taylor Hobson.
Each trundle bearing assembly includes three rollers, each of which is essentially a tapered roller bearing comprising a tapered sleeve fitted onto an internal rolling element bearing. The positions of the rollers in their housings, along with the clearance requirements of the styli on the Taylor Hobson instruments, presented some unique challenges for the Marshall team.
The team relied on the Talyrond 295, a high-precision roundness/cylindricity measurement instrument, outfitted with optional Radial Straightness Unit for axial profiles, while for circumferential profiles it used the Talysurf PGI-1230, a surface measurement device. Using some very imaginative part positioning, the team was able to take advantage of the unique versatility to, in effect, use a "roundness" machine to measure straight features and a "straightness" device to determine the round features.
Profilometry confirmed that the roller surface geometries of the bearing assemblies were manufactured to original specifications and that the wear profiles corroborate dynamic computer models and high-fidelity traction test rig results. The information will aid in the selection of preferred TBAs for flight as well as the potential of TBAs for reuse in orbit.
The Talyrond 295 roundness/cylindricity measurement system with diamond-turned, air-bearing spindle offers unsurpassed radial and axial accuracy and fully automatic operation. Straightness and positioning accuracies on the Talyrond 295 have been enhanced, propelling it toward benchmark status. All components of the automatic center and level mechanism are manufactured to a high order of accuracy using materials that optimize resolution and repeatability. The spindle rotates continuously during the centering and levelling process. This not only saves time but more importantly provides the stability necessary to achieve target eccentricities better than 0.2um.
The Form Talysurf 1230 is a fully automated, high specification 2D measurement system that serves as a benchmark for the form measurement industry, offering 12.5mm gauge range with 0.8nm resolution and providing simultaneous assessment of form, dimension and texture with a single traverse. Key features include system noise reduced to less than 1nm (RMS); 0.1um straightness over 200mm traverse; and X axis horizontal data spacing to 0.125um.
Source: http://www.taylor-hobson.com/