The ability to produce precision ring shaped parts using the turning process depends significantly on the workholding characteristics. Workholding parameters such as the number of jaws and chucking force are known to influence the roundness tolerance of ring shaped parts commonly used in bearing applications. Experimental trial and error methods are often used in practice to optimize the workholding parameters to achieve the desired part quality. This thesis develops a systematic mathematical approach for optimizing these parameters using a finished cut roundness prediction model and a model for determining the reaction force between the chuck jaws and the ring. The roundness prediction model is verified through experiments for different cutting conditions. The optimization approach takes as input the required roundness tolerance, geometry and mechanical properties of the ring, cutting forces, and the coefficient of friction between the jaws and the ring. The output consists of the minimum number of jaws and the range of acceptable chucking forces that satisfy the required tolerance while preventing slip of the ring. Simulation examples are used to illustrate the proposed workholding optimization approach for a hard turning application. In addition, based on the optimization model, the thesis proposes a novel concept of dynamic chucking force control that promises to yield part roundness that is superior to conventional chucking.

The objective of this research work is to investigate the practicality of magnetic workholding of non-magnetic synthetic quartz during high-speed grinding. This research work is sponsored by Quartzdyne and will be used as the starting point to applying single-piece rounding of its quartz. Hypotheses were created that would permit the authors to conclude that magnets are in fact worthwhile workholders for non-magnetic materials. Designs of Experiments were used to reject or fail to reject the null hypotheses. Experiments were carried out using a custom HAAS lathe, modified into a grinding center with an NSK live spindle, and neodymium-iron-boron magnets used to obtain both the holding and shear forces. Lastly, purchased polyolefin foam bumpers were used to increase the shear force, values were obtained with the Starrett force measurement machine. Input variables for the Design of Experiments (DOE) comprised of the holding force, feed-rate, part rotation, and in-feed size of cuts. Sample rotation relative to the magnets was the singular output variable. Experimental results were fitted with the correct distribution and modeled. Once a statistically significant model was attained input settings that minimized quartz sample rotation were determined and used to create an optimized program. Two sets of experiments were needed before the data could be properly fitted with a model. Thirteen out of fifteen samples remained stationary during the optimized program, which was adequate in failing to reject the second null hypothesis; a static sample at 350 RPM will remain static when undergoing high-speed rounding of its outside perimeter. Comparison of cycle times was crucial in reaching this conclusion; in fact, the cycle time of 7 minutes and 58 seconds for the optimized program was substantially less than Quartzdyne's estimated batch flow per piece cycle time of around 15 minutes. Obtaining a model was not possible or needed for the first hypothesis due to all experiments having zero rotation, therefore the authors also failed to reject the first null hypothesis; a static sample sandwiched between two permanent magnets with adequate holding force will remain stationary during rotation (min 250 RPM) Larger in-feed size cuts are possible when the quartz is square in shape –interrupted cuts. As it becomes cylindrical, cuts were reduced to experimental levels. Also, due to the amount of material being removed, the resin bonded wheel required dressing, without it rotation is expected. Variation was noticed while quantifying the shear force; it is attributed to the polyolefin foam bumper with its inconsistent coefficient of friction. A more uniform material, which can provide repeatable shear force values, would lessen the variation. All optimized program samples turned out perfectly round- even the two that had slight rotation.

This thesis presents a method for the prediction of final peak-to-valley (PTV) surface profile variation for face turning of rings of non-uniform cross section. An analytical method relates initial part form, part deflection during workholding and machining, and part elastic recovery to final PTV surface profile variation. Finite element method is used to supplement the analytical model, and experiments are conducted to validate both the analytical and finite element approaches. Analytical and finite element results correspond well with experimental observations, with average relative errors of 11.6 and 7.2 percent, respectively.

Ultraprecision single point diamond turning is required to produce parts with sub-nanometer surface roughness and sub-micrometer surface profiles tolerances. These parts have applications in the optics industry, where tight form accuracy is required while achieving high surface finish quality. Generally, parts can be polished to achieve the desired finish, but then the form accuracy can easily be lost in the process rendering the part unusable. Currently, most mid to low spatial frequency surface finish errors are inspected offline. This is done by physically removing the workpiece from the machining fixture and mounting the part in a laser interferometer. This action introduces errors in itself through minute differences in the support conditions of the over constrained part on a machine as compared to the mounting conditions used for part measurement. Once removed, the fixture induced stresses and the part’s internal residual stresses relax and change the shape of the generally thin parts machined in these applications. Thereby, the offline inspection provides an erroneous description of the performance of the machine. This research explores the use of a single, high resolution, capacitance sensor to quickly and qualitatively measure the low to mid spatial frequencies on the workpiece surface, while it is mounted in a fixture on a standard ultraprecision single point diamond turning machine after a standard facing operation. Following initial testing, a strong qualitative correlation exists between the surface profiling on a standard offline system and this online measuring system. Despite environmental effects and the effects of the machine on the measurement system, the capacitive system with some modifications and awareness of its measurement method is a viable option for measuring mid to low spatial frequencies on a workpiece surface mounted on an ultraprecision machine with a resolution of 1nm with an error band of ±5nm with a 20kHz bandwidth. / Thesis / Master of Applied Science (MASc)