Avhandling--Tekniska högskolan, Stockholm. / Thesis statement on cover. Extra t.p. with thesis statement, inserted. Includes bibliographical references (p. 103-104).

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 146-148.

Rotary mills are used extensively to reduce the coarse rocks of mined ores down to a product fine enough to facilitate the extraction of the valuable minerals. On the South African gold mines alone about 110 million tons of ore is mined annually, at a power cost of about R90 million, and a liner material cost of about R30 million. The charge motion in mills has been studied both theoretically and experimentally since the beginning of the century. However, a lot of the work has been purely empirical, and some of it illconceived, resulting in there still being a poor understanding of the topic. The influence of lifter-bars upon charge motion has only been considered in the past few decades, and mostly to a very limited extent. This state of affairs has left the field wide open to further research. The charge motion of an isolated rod or ball, and how it is influenced by a flat-faced lifter-bar of any face-angle and of any height, was modelled theoretically. The charge motion of rods in a glass-ended mill was filmed with a high-speed camera. The mill was fitted with a variety of lifter-bars with different face-angles and heights, and was run at a wide range of speeds. The filmed trajectories of the rods were then tracked. The coefficients of friction between the rods and lifter-bar material were measured under vibrating conditions as are found in the mill. The power draw of the mill was also measured at a wide range of mill speeds, and with lifter-bars of different heights in the mill. A good correlation between the theoretical predictions and experimental results was found over a wide range of conditions. The impact point, at which the grinding element strikes the mill shell, was considered to be of primary importance in the analysis. It was found that the height of the lifter-bar has a strong influence on charge trajectories, as the height increases from zero up to just greater than one charge radius. Thereafter the lift increases until a critical lifter-bar height is reached, beyond which the grinding element is projected off the lifter prior to reaching the tip, the height of the impact point increasing slightly and then decreasing to a constant height. However, the change in the height of the impact point is very small, so in practical terms an increase in lifter-bar height, once it is higher than the radius of the grinding element, has a very small effect upon the charge trajectories. An increase in the angle of the lifter-bars was found to have a strong influence upon the height of the charge trajectories. A linear relationship between the mill speed and the impact angle was dicovered, and changes in the mill speed strongly influence the charge trajectories. It was also found that the power draw of a mill depends on the liner configuration, with power draw decreasing as the lifter-bar height is increased. Some new and surprising effects of lifter-bar geometry upon the charge trajectories, which are of great practical importance, have been discovered. The theoretical model is an advance upon all previous models, and agrees well with experimental results over a wide range of conditions.

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Sculptured parts, characterized by interconnected and bounded parametric surface patches, are widely used in aerospace, automobile, shipbuilding and plastic mold industries due to their functional and aesthetic properties. However, adoption of these sculptured surfaces on mechanical products increases the complexity of manufacturing and puts forward a challenge to achieve high machining quality and productivity, as well as low machining cost. Machining of sculptured parts is mostly carried out on a milling machine. The milling process can be divided into: rough cut (roughing) and fine cut (finishing) operations. Rough machining is used to remove excess stock material, while finish machining is aimed at generating adequate tool paths for producing the final shape of the part. When a sculptured part is machined from prismatic stock, a large amount of rough cut, up to 90 percent of the total machining, is required. Cutting time reduction in rough machining can considerably improve the efficiency of sculptured part machining, lower production cost. This research focuses on the productivity improvement of sculptured part rough milling machining that is affected essentially by CNC tool path and machining parameters. Two major strategies, machining path strategy and machining parameter strategy are investigated. A number of new methods are introduced to generate highly productive CNC tool path and machining parameters. Study on machining path strategy involves approaches of generating 2½D CNC tool path trajectory, creating new tool path patterns, and automatically identifying optimal tool path pattern. While research on machining parameter strategy focuses on the minimization of cutting time, based upon the changing part geometry during machining and manufacturing constraints. A method that incorporates an existing milling process model into the cutting parameter optimization to predict instantaneous cutting force and identify the most effective cutting parameters is introduced. An improved model cofficient determination scheme using numerical optimization and artificial neural network techniques is developed, and extensive cutting tests are carried to allow the milling process model to fit into the cutting parameter optimization. A method for the automated formulation and solution of the cutting time minimization problem is also introduced to allow important machining parameters, including the number of cutting layers, depth of cut, feed rate and cross-cutting depth, to be determined without human intervention. The research directly contributes to automated sculptured part machining, and has a great potential to produce significant economical benefits to manufacturing industry. The study also establishes a platform for further research and development on intelligent sculptured part machining. / Graduate

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Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on January 8, 2008) Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.