The API laser tracker ensures 2,000 features are machined within .02 inches at the University of Arizona

galaxyd_2_900x900webThe robotic telescope at the University of Arizona will be used to measure gamma ray bursts from across the universe. API trackers measure the support rings and cells that hold the telescope’s 12-ton, 21-foot wide mirror. For one component, the API tracker measured and verified over 500 features.

The API Laser Tracker is used to inspect the structure of the Large Optical Test and Integration System (LOTIS) that is to be used for the aligning of the optics of a new generation telescope available in 10 to 15 years. Lockheed Martin Corporation contracted The University of Arizona Steward Observatory and Kaman Aerospace to design and manufacture the complete LOTIS package. Kaman Aerospace selected Vroom Engineering & Manufacturing Inc. and T.A.Caid Industries to fabricate, machine, and assemble the structure. The structure consists of two main components, a Primary Cell and Head Ring. The Primary Cell is used as a support platform for a 6.5m primary mirror that weighs in at 25,000 lbs. The Head Ring supports a smaller secondary mirror that is suspended on the collimator’s main axis using a hub and tensioning vanes.

API was contacted prior to machining actuator mounting patterns in the Primary Cell. The requirements called for approximately 2,200 features to be machined within 0.020 inches of the X, Y, and Z true position over a Ø24’ part. The approach was to divide the Primary Cell into smaller machining zones and place a local datum point within each zone. API performed an initial survey to locate all of the local datums and to verify flatness of the Primary Cell’s outer flange.

After all of the machining had been completed, API was once again contracted to survey the complete assembly prior to welding the truss tube adaptors in position. The collimator assembly required that the Primary Cell and Head Ring be positioned at a specific distance ±0.125 inches apart, parallel within 0.060 inches, and concentricity of center axis within 0.060 inches. Following the completion of the welding, a second survey was done to verity final alignment.

The collimator was then disassembled and a final acceptance inspection performed on the Primary Cell. Approximately 500 features were measured while the Cell was in a vertical orientation, after which six more internal features had to be surveyed while the Cell was laying horizontal.

API has been the exclusive metrology company on this project investing over three weeks calendar time and 180 man-hours. Keath Beifus, of Vroom Engineering & Manufacturing, Inc. stated the API Laser Tracker Tracker II Plus …”provided the confidence necessary for such a large scale, close tolerance project of this magnitude. In addition, the personnel at API were highly qualified … and…would not hesitate to use or recommend API hardware or personnel in the future”.