Electrical discharge machining (EDM) is perhaps the most prevalent non-traditional machining process in industry. Therefore, a great amount of effort has been invested towards improving the process. One result of these efforts was the introduction of CNC capabilities to EDM machine tools. Though CNC capabilities are predominantly used for performing orbital EDM, they may also be used for electrical discharge (ED) milling. Cylindrical tools are typically used in ED milling. While other tooling concepts have been developed for use with CNC EDM, this area of EDM is lacking in research. In this work an oblong set of tools for ED milling is presented. The set contains tools capable of machining cavities with both round and sharp features. Motivation for development of the tool set is discussed along with the benefits accompanied by the use of these tools. The cavity profiles considered in this work are divided into three groups based on concavity, continuity and geometric composition. Based on these groups, algorithms are presented for tool type selection and tool size calculation. Tool path planning strategies for each of the tool types are also presented. Two examples are presented in which the algorithms are applied to 2D profiles. The first of these profiles is star shaped, while the second is gear shaped. Both examples were machined on a 4-axis CNC EDM using the oblong tools presented in this work. When compared to equivalent cylindrical/square tools, the oblong tools used for the machining of the cavities provided a substantial increase in frontal area corresponding to improved material removal rates. Furthermore, for both examples, the complete machining of a single layer is accomplished with only one pass of the tool. / Thesis / Master of Applied Science (MASc)

Previous work has shown that when inorganic compounds are milled with quartz in a high energy ball mill the elements are sequestered into the quartz matrix and cannot be easily recovered by simple extraction methods. In this study lead (II) oxide, copper (II) oxide, magnesium oxide, zinc oxide and sodium hydroxide were milled with quartz sand and the recoveries of the metals investigated in detail. The standard EPA3050B method (acid digestion of sediments, sludge and soils) for extractable metals was compared to exhaustive HF digestion method based on ASTM C146-94a (test methods for chemical analysis of glass sand) and UDC 666.123:543.06 (chemical analysis of soda-lime and borosilicate glass). From these two analyses the total recovery of metals was determined. It was found that the elements extracted by the EPA3050B method decreased in an approximately logarithmic way with milling time. The metals are apparently strongly sequestered into the fractured quartz. Total HF digestion of the insoluble matrix gave good recovery of the “lost” elements. A reliable analytical procedure has been developed and the mechanisms leading to this sequestering are discussed. Particle size analysis and electron microscopy of milled samples support a process of brittle alloy formation as the proposed mechanism whereby the elements are sequestered into the milled quartz.

Face milling machinability investigation of two difficult-to-machine nickel-based superalloys, namely Inconel 718 and Waspaloy, has been carried out with four different types of tungsten carbide tools under various cutting conditions. The tools comprised of one double-layer CVD-TiCN+Al2O3 coated (KC994M), two PVD-TiN coated (KC720 and KC730) and one uncoated (KMF) tungsten carbide tools. The objectives of the study include investigation of tool performance, failure modes and wear mechanisms under the cutting conditions employed. In addition, surface integrity of the machined surfaces, with regard to surface finish, subsurface microhardness and metallographic examination of the subsurface microstructure, was investigated. CVD-coated KC994M gave the best overall performance in terms of tool life at low and high cutting conditions on both workpieces. The second best-performing tool was the uncoated KMF grade which gave as high tool lives as KC994M at lower cutting speeds. However at higher cutting speeds, KMF was generally outperformed by PVD-TiN coated tools. Short tool lives were obtained at higher cutting speeds of 75 and 100 m/min due to premature failure by chipping. Tool wear at low cutting speed range was due to a combination of progressive microchipping and plucking through a fracture/attrition related wear mechanism associated with cyclic workpiece adhesion and detachment and abrasion/diffusion-related flank wear. Plucking and microchipping were the dominant wear mechanisms. Coating layers on the rake face of both CVD and PVD coated tools were almost completely removed within the first few seconds of cutting at all cutting speeds tested, thus becoming ineffective. On the flank face, however, they remained intact for a longer period and hence increasing tools performance at the medium cutting speed range. Analysis of the subsurface microstructures and microhardness measurements showed that plastic deformation was the predominant effect induced onto the machined surface, the degree of which influenced by the cutting speed, tool wear and prolonged machining. In addition surface irregularities in the form of tearing and embedded hard particles were found to occur which was mainly associated with the chipping dominated wear mode.

Previous work has shown that when inorganic compounds are milled with quartz in a high energy ball mill the elements are sequestered into the quartz matrix and cannot be easily recovered by simple extraction methods. In this study lead (II) oxide, copper (II) oxide, magnesium oxide, zinc oxide and sodium hydroxide were milled with quartz sand and the recoveries of the metals investigated in detail. The standard EPA3050B method (acid digestion of sediments, sludge and soils) for extractable metals was compared to exhaustive HF digestion method based on ASTM C146-94a (test methods for chemical analysis of glass sand) and UDC 666.123:543.06 (chemical analysis of soda-lime and borosilicate glass). From these two analyses the total recovery of metals was determined. It was found that the elements extracted by the EPA3050B method decreased in an approximately logarithmic way with milling time. The metals are apparently strongly sequestered into the fractured quartz. Total HF digestion of the insoluble matrix gave good recovery of the “lost” elements. A reliable analytical procedure has been developed and the mechanisms leading to this sequestering are discussed. Particle size analysis and electron microscopy of milled samples support a process of brittle alloy formation as the proposed mechanism whereby the elements are sequestered into the milled quartz.

LD2668 .T4 1940 M33 / Master of Science

Call number: LD2668 .T4 1948 F75 / Master of Science

Call number: LD2668 .T4 1948 S7 / Master of Science

Call number: LD2668 .T4 1961 M56

Call number: LD2668 .T4 1963 V81 / Master of Science

Call number: LD2668 .T4 1965 P231 / Master of Science