Vibration assisted cutting (VAC) is a new metal machining technique in recent years, where high-frequency and low-amplitude vibrations are imposed to the cutting tool or the workpiece. It has many advantages than conventional cutting (CC), especially improvements in surface finish and tool life. Nowadays, the use of VAC is a good strategy for micro-machining due to long tool life and high product dimension accuracy. This study presents an experimental investigation of the VAC in micro milling. The tool wear, surface roughness, and burr formation are investigated for different cutting parameters under conventional and vibration assisted cutting. When the vibration speed is higher than 3 times of the cutting speed, the tool life can be prolonged in this study. The experimental results show that VAC process has better surface finish (43.51% reduction in value) compared to that in CC, when the cutting conditions are feed of 4 £gm/rev and cutting speed of 3.39 m/min. It is also found that VAC can diminish the formation of burr formation. By introducing MQL to VAC, the tool life is extended because the MQL could reduce the friction between the tool and workpiece.

There is limited information on the utilization of sorghum for human consumption in El Salvador. Increased wheat prices have driven the baking industry to seek alternative cereals for manufacturing of their products. The white color and bland taste characteristics of Salvadorian sorghum is ideal for use as a partial substitute of wheat (up to 50 percent) or alone in baked goods and a wide variety of foods. Further information on the grain quality, milling characteristics and impact on end-product was assessed to make better use of the available grain. Three different varieties of improved and local cultivars (RCV, Native and ZAM 912) were evaluated for their grain, flour and end-product quality. Grain hardness, color and composition of the grains varied from hard to intermediate to soft. Burr, hammer and roller milling were used for sorghum flour production. Impact of grain characteristics and milling quality was evaluated through the flours produced and their end-product quality. Grain hardness significantly affects flour and final product characteristics. Harder grain, RCV, produced flours more difficult to cook and with a grittier texture than those produced from Native cultivars (floury endosperm). Cupcakes produced from harder grain flours had lower volume and harder texture than cupcakes made from the Native varieties. ZAM 912 was an intermediate hard sorghum variety and produced the darkest flour and darkest cupcakes due to its pericarp hue. Appropriate use of this grain’s flour can be used in baked products with a darker hue (e.g. chocolate pastries). Harder grain flours can be utilized in coarse crumb products (e.g. cookies, horchata, and atole). Hammer mills produced the coarsest particles for all the varieties evaluated. Burr mills produced flour with similar cooking and end-product texture qualities as the roller mill. However, burr mills are not suitable for production of large quantities of whole sorghum flour. Nevertheless, they are more affordable for small entrepreneurs. Cultivars analyzed produce quality flour that can be used in an array of baked foods, i.e. ethnic beverages, porridges, cookies, flour mixes, tortillas, sweet breads. Whole sorghum flour substitution as low as 25 percent in wheat-based foods can represent significant cost savings for its users.

published_or_final_version / Industrial and Manufacturing Systems Engineering / Master / Master of Philosophy

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Machinists often simulate a part program to verify its correctness, since mistakes can cause damage to the part, machine, oneself, or others. A popular approach for part program simulation involves representing the stock (the material the part is being carved from) as a heightmap. Although this approach is computationally fast and memory efficient, only objects that are representable as functional surfaces (e.g., z = f(x, y)) can be machined. This thesis presents a new heightmap-based data structure, called a multidirectional heightmap, that does not have this limitation. A multidirectional heightmap, in response to an overhang, recursively subdivides itself until each piece can be represented by an axis-aligned heightmap. More precisely, a multidirectional heightmap is a kD-tree with the property that all cells are functional: each cell contains a heightmap that represents a functional portion of the stock. To improve accuracy, each regular heightmap can be replaced by a 3-Way Heightmap, a new type of heightmap that samples the tool along all three stock axis directions (three ways) rather than just one. The experimental results herein suggest that the multidirectional heightmap data structure achieves a good level of performance with respect to memory usage, CPU usage, and approximation error.

The use of cutting fluids in machining process is very essential for achieving desired machining performance. Due to the strict environmental protection laws now in effect, there is a wide-scale evaluation of the use of cutting fluids in machining. Consequently, minimal quantity lubrication (MQL), which uses very small quantity of cutting fluids and still offers the same functionality as flood cooling, can be considered as an alternative solution. This thesis presents an experimental study of face milling of automotive aluminum alloy A380 under four different lubrication/cooling conditions: dry cutting, flood cooling, MQL (Oil), and MQL (Water). Experiments were design using Taguchi method for design of experiments. Empirical models for predicting surface roughness and cutting forces were developed for these four conditions in terms of cutting speed, feed and depth of cut. Optimization technique using Genetic Algorithms (GA) was used to optimize performance measures under different lubrication/cooling conditions, based on a comprehensive optimization criterion integrating the effects of all major machining performance measures. Case studies are also presented for two pass face milling operation comparing flood cooling condition with MQL. The comparison of the results predicted by the models developed in this work shows that the cutting force for MQL (Oil) is either lower or equal to flood cooling. The surface roughness for MQL (Oil) is comparable to flood cooling for higher range of feed and depth of cut. A comparison of the optimized results from the case studies, based on value of utility function, shows that the optimum point for two pass face milling operation having MQL (Oil) as finish pass has highest utility function value.

Milling is a commonly used machining process where a rotating cutter removes material from the workpiece. In recent years, attention has been turned towards so called dynamic milling methods which differ from the conventional way of milling. Dynamic milling normally uses, as opposed to the conventional way, more of the axial cutting edge, smaller radial depth of cut, significantly higher cutting speed and feed per tooth. The method has demonstrated potential to save both time and money under specific circumstances, for manufacturing companies.This thesis was conducted at ISCAR Sverige AB in Uppsala, Sweden. ISCAR Metalworking is a full service supplier of carbide cutting tools. The objective is to establish if there are benefits with dynamic milling methods with regard to material removal rate and lifetime of the tool by experimentally investigating and comparing tool wear that occur with conventional- and dynamic milling methods in hardened steels. Tools used were ISCAR’s MULTI-MASTER end mills, MM A and MM B, and the hardened steels were Hardox 600 and Dievar. Analysis was performed by using a USB-microscope, scanning electron microscope (SEM) and a Wyko-profilometer. The results of this study show that dynamic milling parameters can give several benefits regarding tool life and material removal rate. When machining in Hardox 600 and Dievar, both end mills were able to achieve a higher material removal rate and lifetime with dynamic parameters compared to more conventional ones. MM A outperformed MM B in Dievar, but the results were reversed in Hardox, MM B performed better. Results from the profilometry analysis showed that in Dievar, the dynamic parameters generated a smoother surface while the surface results from Hardox were more equivocal. The main conclusion was that milling with dynamic parameters is generally more advantageous and should be utilised, if possible.

Despite criticisms of its methodology, the Taguchi philosophy for quality improvement is generally applauded. Though originally intended to primarily achieve its results "off line", during the product design phase and before manufacturing, it has frequently also been deployed to solve problems "on line". Taguchi identifies the crucial design phases as "system design" and "parameter design", and his statistically-based tools are directed at the latter. The general objective of this investigation is to study two contrasting approaches to product and process optimisation, ie Genetic Algorithms, which may be appropriate to both "system design" and "parameter design" phases, with Taguchi and related statistical tools which may be appropriate to the "parameter design" phase. The literature review concentrates on the up and downsides of Taguchi Methods, focusing on the philosophy and methodologies. Its statistical content, particularly related to the use of Signal-To-Noise ratios and saturated fractional factorial designs, have widely reported deficiencies. In order to evaluate and, if necessary, overcome these deficiencies, a combination of Taguchi and non- Taguchi tools are brought into an experimentation strategy to determine robust methodologies that contribute to enhanced product performance. The approach is motivated from a design for quality standpoint and is directed principally at improving performance. The approach is illustrated using three case studies in surface finish from metal cutting and simulation systems optimisation. These case studies involve a variety of experiments different in nature, from real physical experiments to computer-based ones, and tackling a wide range of different problems such as: surface finish in milling and turning machining (metal cutting), optimum travel time and traffic junction control (transport traffic simulator) and out-of-balanceforce problem (optimisation of simple Genetic Algorithms). The study of Taguchi tools is an extension of previous work by Taher (1995). Some of his investigations are extended, principally the reliability of Taguchi saturated fractional factorial arrays, the need for factor/level analysis, criticisms of the Taguchi Signal-to-Noise ratios and the use of sequential experimentation. In addition to these, attention is focussed on the use of repetitions within the Taguchi methodology, the use of transformations or Generalised linear Models and the possibility of using robust statistics. The adoption of a sequential experimentation approach leads to a successful use of predefined Taguchi arrays influenced by user knowledge of confounding and interaction effects on main factors. From a global viewpoint, Factor/Level analysis is highly recommended. It is also determined that the reliability of results is highly affected by the use of Signal-to-Noise ratios, and alternative dispersion control tools are strongly advised. Taguchi's robust design methodologies are of value but require integration with other design and quality assurance methodologies, such as Concurrent Engineering and Quality Function Deployment. The optimisation of a simple Genetic Algorithm (for the out-of-balanceforce problem) is used as one test case for the investigation of Taguchi tools. However, this investigation is itself of interest for the general use of genetic algorithms as it addresses issues such as appropriate population size and choices for crossover and mutation modes and probabilities. Many previous investigations of these have only been of the "one factor at a time" type.

With recent genetic advances in development of gossypol-free cotton varieties, there is interest in retrieving undamaged, dehulled cottonseed kernels for development of new food and feed products. Current methods used to dehull cottonseed provide a low turnout of undamaged kernels that would be desirable for new market niches where intact kernels are desirable. The first objective of the described work was to develop a process for dehulling fuzzy cottonseed to render a high percentage of undamaged seed meats. A series of methods were tested and optimized to identify the suite of processes that provided the highest yields. The final process included steam conditioning, cracking and dehulling using roller mills, and finally separating kernels from hull material using a roller separator and air aspirator. The reintroduction of un-dehulled seed to the roller mills for a second pass significantly increased the final yield of undamaged seed meats. Lab-scale tests show that yields of 65% to 70% can be obtained using this process, representing a significant increase over conventional dehulling, which typically results in less than 5% yields of undamaged kernels. The second objective of the research was to integrate components of the lab-scale milling process into a continuous-flow, pilot-scale system. The performance of the milling system with and without steam conditioning was evaluated. Pilot-scale, continuous-flow tests resulted in undamaged kernel yields of 67.9 ± 3.0% (mean ± 95% confidence interval) during wet milling, comparable to results of initial batch processing and far exceeding yields of whole kernels from current milling techniques. During dry milling, the efficiency of the system to extract all possible kernel material was found to be 68 ± 2.9%, but most of the resulting kernel material is in broken fragments between 3.35 mm and 0.706 mm in diameter.