Non-contact optical three dimensional liner metrology
We optically captured the "as-built" liner geometry of NTLX (near term liner experiments) for Shiva Star using ultra-precision ranging lasers. We subsequently verified the resulting digitized geometry against the 3D CAD model of the part. The results confirmed that the Liner contours are within designed tolerances but revealed subtle fabrication artifacts that would typically go undetected. These features included centimeters long waviness and saddle and bulge regions of 1 micron or less in magnitude. The laser technology typically provided 10 micron spatial resolution with /spl plusmn/12 nanometer ranging precision. Atlas liners in the future may have to be diamond turned and will have the centimeter wavelength and 100 angstrom amplitude requirements. The advantages of using laser technology are (1) it avoids surface damage that may occur with conventional contact probes and (2) dramatically improves spatial resolution over CMM, capacitance and inductance type probes. Our work is the result of a perceived future need to develop precision, non-contact, liner inspection techniques to verify geometry, characterize machining artifacts and map wall thickness on delicate diamond turned surfaces. Capturing "as-built" geometry in a non-contact way coupled with part-to-CAD verification software tools creates a new metrology competency for MST-7.
Fabrication of an ultra smooth liner for Ranchero
Calculations indicate that Atlas liners must have waviness amplitudes less than 10 nm over spatial wavelengths near 1 cm. A liner for Ranchero has been produced, on equipment at LANL, with waviness amplitudes as close to 10 nm as was possible. A lathe, with air bearing slideways and spindle, was used in concert with a single crystal diamond tool to produce this part. Since the dimensional characterization of this liner can be as challenging as the production, on-machine gauging techniques were used for much of the dimensional inspection. This paper discusses the fabrication and metrology of this ultra smooth liner.
Surface self-compensated hydrostatic bearings
It has long been known in the machine tool industry that hydrostatic bearing technology has several unique advantages over rolling element bearings. The thin fluid film between the bearing pads and the rail provides virtually infinite motion resolution due to lack of static friction, very low straightness ripple, high squeeze film damping, potentially infinite bearing life, immunity to fretting, tolerance to ceramic swarf, and superior shock load capacity. However, a major impediment to the use of hydrostatic bearings is that there are no standard, pre-engineered designs that are commercially available, and custom designing a bearing is often prohibitively expensive and time consuming. In light of the opportunity just mentioned, the goal of this thesis is to present and demonstrate the feasibility of a family of novel modular hydrostatic bearings which are well suited for mass production and are designed to be bolt-for-bolt compatible with modular rolling element bearings. A size 35 prototype of one of the novel designs is presented along with measured and predicted performance (load verses deflection, flow rate, pumping power). The novel design that is tested uses a set of auxiliary restricting surfaces on a profile rail and form fitting truck that make an acute angle relative to each load bearing pocket they supply, thus allowing the truck to be machined and ground as one piece, and eliminating the need for capillaries, diaphragms, or other unmachinable features. In addition to the first prototype work, a second engineered embodiment of the novel design is presented which, via a sophisticated mathematical model, is designed to have an acceptable stiffness and load capacity variation given realistic production manufacturing tolerances. Thesis Supervisor: Prof. Alexander H. Slocum Title: Professor of Mechanical Engineering