<p> High-speed machining (HSM) concepts were developed in response to productivity, quality and cost concerns. Significant advancements in controls and machining technologies have recently come together to enable the wide spread use of HSM on the plant floor. However, with the advancement of HSM technology, dynamic problems associated with modern machine-tool structures have not been fully addressed and are currently limiting performance in some applications. <p> A key aspect in the modelling of HSM processes is capturing the dynamics of the system during cutting. Machining over a wide range of rotational speeds necessitates the inclusion of many more higher modes in the system than traditionally considered. In addition many of the instruments used to assess performance such as force dynamometers are not designed to measure the cutting forces at high rotational speeds and hence the specific cutting force values being used are often times not being estimated properly. </p> <p> Thus the focus of this research is to develop a new procedure for predicting the specific cutting forces in the end-milling process for high-speed machining. An improved mechanistic model to predict the specific cutting force using acceleration data captured from the workpiece fixture was developed. The development of the new procedure has also lead to an improvement in the extraction technique used to establish the modal parameters of a machining system. This new extraction technique was found to be more flexible and easier to use than other available techniques. </p> <p> The new procedure was investigated to test the effect of choosing the number of modes of the improved modal parameters extraction technique on the estimation of the specific cutting force. The effect of filtrating the acceleration signal and the importance of including the run-out of the cutting tool in the model were also investigated. </p> <p> The new procedure was tested on different setups and with different cutting force models. Experimental validation of the proposed estimation procedure was carried out, analyzed and compared to the open literature. The new procedure was found to be more accurate while being easier to implement. </p> / Thesis / Doctor of Philosophy (PhD)

Materials which are both lighter and stronger have faced an increased demand over the past decades to fulfil the requirements across a range of industrial applications. More specifically, demands for titanium alloys have increased significantly due to its high strength to weight ratio which is particularly attractive for increasing fuel efficiency in aircrafts and cars and is also used in biomedical implants. Despite the increasing demand for titanium made products, machining titanium alloys remains a significant challenge. High material strength and hardness lead to excessive heat generation at the cutting zone which accumulates and results in high cutting temperatures due to the poor thermal conductivity. The high cutting temperatures together with inherent material properties of titanium are responsible for short tool life and poor surface finish. Despite the environmental and health drawbacks, a generous amount of cutting fluids is commonly used to control the cutting temperature in machining titanium alloys. However, conventional cutting fluids evaporate at high cutting temperatures which isolate the cutting zone by forming a vapour cushion resulting in further increases in cutting temperatures. This research investigates the effects of cryogenic cooling on machinability of Ti-6Al-4V alloy in CNC milling as compared to conventional dry and wet machining environments. Two literature reviews were conducted and a methodology has been developed and implemented consisting of three experimental stages of i) design and manufacture of a cryogenic cooling system, ii) comparative study of cryogenic cooling with dry and wet machining and iii) optimisation of cutting parameters for cryogenic machining. The major contribution of this research can be summarised as design, realisation and assessment of a novel cryogenic cooling system for CNC milling, termed cryogenic shower, which is retrofitable to an existing CNC machining centre. In addition, the research provides a thorough study on the effects of cryogenic cooling on machinability of Ti-6Al-4V alloy in comparison with dry and wet machining. The studies range from power consumption and tool wear through to surface topography and surface integrity. Furthermore, the optimum cutting parameters for cryogenic machining are identified. The research demonstrates that using the cryogenic shower has significantly improved machinability of Ti-6Al-4V through realisation of higher material removal rates, reduced tool wear and improved surface finish, surface topography and surface integrity.

No description available.

No description available.

Micro-milling represents a versatile and fast manufacturing process suitable for production of fully 3D micro-components. Such components are demanded for a vast number of industrial applications including safety systems, environmental sensors, personalized medical devices or micro-lenses and mirrors. The ability of micro-milling to process a wide range of materials makes it one of the best candidates to take a leading position in micromanufacturing. However, so far it does not seem to happen. By discussion with various industrialists, low predictability of micro-milling process was identified as the major limiting factor. This is mainly because of strong effects of the tool tolerances and process uncertainties on machining performance. Although, these issues are well known, they are not reflected by the current modelling methods used in micro-milling. Therefore, the research presented in this thesis mainly concentrates on development of a method allowing a prediction of the tool life in manner of tool breakage probability. Another important criterion which must be fulfilled is the method applicability to industrial applications. This means that the method must give sufficiently accurate prediction in reasonable time with minimum effort and interactions with day-to-day manufacturing process. The criteria listed above led to development of a new method based on analytically/numerical modelling techniques combined with an analysis of real tool variations and process uncertainty. Although, the method is presented in a relatively basic form, without considering some of the important factors, it shows high potential for industrial applications. Possibility of further implementation of additional factors is also discussed in this thesis. Additionally, some of the modelling techniques presented in this thesis are assumed to be suitable for application during designing of micro end-mills. Therefore, in the last part of this thesis is presented a systematic methodology for designing of micro end-mills. This method is based on knowledge and experience gained during this research.

<p>U radu je izvršeno modeliranje i simulacija procesa obrade glodanjem sa predviđanjem temperature u zoni rezanja pomoću metode konačnih elemenata. Kao ulazni parametri obrade za model uzeti su brzina rezanja, korak i dubina rezanja a kao izlazna performansa temperatura u zoni rezanja. Kreirani model za simulaciju obrade glodanjem proveren je eksperimentalnim testiranjem sa istim parametrima obrade. Izvršena je analiza eksperimentalnih rezultata sa predloženim modelom. Rezultati ovog istraživanja su pokazali da se modeliranjem i simulacijom procesa obrade glodanjem može adekvatno predvideti temperatura u zoni rezanja.</p> / <p>The work explains process of modeling and simulation of milling predictive<br />temperature in the cutting zone by using the finite element method.The input<br />parameters for the processing model are cutting speed, feed and depth of a<br />cut. The temperature in the cutting zone was used as an output performance.<br />Designed model that simulates milling is checked by experimental testing<br />with the same machining parameters. The analysis of the experimental<br />results with the proposed model was carried out. Results of this study show<br />that the modeling and simulation of milling process can adequately predict<br />the temperature in the cutting zone.</p>

A cadeia da instrumentação para o monitoramento do desgaste da ferramenta por emissão acústica está constituída por sensores, condicionador de sinal, conversor A/D e transmissor. A seleção ou projeto de cada uma das etapas é de suma importância para manter o conteúdo do sinal de emissão acústica (neste caso a fonte de emissão acústica é a usinagem). O sinal de emissão acústica de interesse tem componentes que vão dos 100kHz a 1 MHz. Devido às características do projeto, são desenvolvidos o condicionador e o transmissor. São apresentados os projetos do pré-amplificador e filtro (que pertencem ao condicionador), os quais realizam suas respectivas funções de amplificação e filtragem. O pré-amplificador, cuja função é a de fortalecer o sinal fraco na saída do sensor, amplifica o sinal em 20 dB. Ele tem uma resposta plana na faixa de interesse (freqüências inferiores a 1 MHz). O filtro, que é do tipo banda passante, tem por função eliminar as componentes vinculadas às vibrações mecânicas e os ruídos elétricos e eletromagnéticos, assim como evitar o fenômeno do \"aliasing\" no processamento do sinal. Ele não deixa passar as componentes do sinal de freqüências inferiores a 100 kHz e superiores a 1 MHz. Tem uma resposta plana na banda de interesse, o que garante a manutenção do formato do sinal. São consideradas nos projetos indicados as respostas dos componentes eletrônicos para as freqüências de trabalho e a proteção dos circuitos contra ruídos na alimentação dos mesmos. / The instrumentation for tool wear monitoring by acoustic emission is composed by sensors, signal conditioner, A/D converter and transmitter. The selection or project of each step is very important to keep the container of acoustic emission signal (in this case the source of acoustic emission is the metal cutting). The interesting acoustic emission signal has its components, which comes from 100 kHz to 1 MHz. In spite of the project characteristics, the conditioner and the transmitter are developed. The projects of the pre-amplifier and the filter are presented (they belong to the conditioner), which makes their functions of amplification and filtration. The pre-amplifier, which function is to amplify the weak signal on the output of the sensor, amplifies the signal by 20 dB. It has a flat response on the frequency range (frequencies less than 1 MHz). The filter, which is the type of flat-band, has the function of eliminating the components connected to the mechanic vibrations and the electric/electromagnetic noises, therefore to avoid the aliasing phenomenon on the signal processing. It attenuates the signal components of frequencies lower than 100 kHz and higher than 1 MHz. There is a flat response on the frequency range, which warrants the maintenance of the signal format. It is considered into the projects indicated the electronic components\' responses to the work frequencies and the circuit protection against noises into their feeding.

A cadeia da instrumentação para o monitoramento do desgaste da ferramenta por emissão acústica está constituída por sensores, condicionador de sinal, conversor A/D e transmissor. A seleção ou projeto de cada uma das etapas é de suma importância para manter o conteúdo do sinal de emissão acústica (neste caso a fonte de emissão acústica é a usinagem). O sinal de emissão acústica de interesse tem componentes que vão dos 100kHz a 1 MHz. Devido às características do projeto, são desenvolvidos o condicionador e o transmissor. São apresentados os projetos do pré-amplificador e filtro (que pertencem ao condicionador), os quais realizam suas respectivas funções de amplificação e filtragem. O pré-amplificador, cuja função é a de fortalecer o sinal fraco na saída do sensor, amplifica o sinal em 20 dB. Ele tem uma resposta plana na faixa de interesse (freqüências inferiores a 1 MHz). O filtro, que é do tipo banda passante, tem por função eliminar as componentes vinculadas às vibrações mecânicas e os ruídos elétricos e eletromagnéticos, assim como evitar o fenômeno do \"aliasing\" no processamento do sinal. Ele não deixa passar as componentes do sinal de freqüências inferiores a 100 kHz e superiores a 1 MHz. Tem uma resposta plana na banda de interesse, o que garante a manutenção do formato do sinal. São consideradas nos projetos indicados as respostas dos componentes eletrônicos para as freqüências de trabalho e a proteção dos circuitos contra ruídos na alimentação dos mesmos. / The instrumentation for tool wear monitoring by acoustic emission is composed by sensors, signal conditioner, A/D converter and transmitter. The selection or project of each step is very important to keep the container of acoustic emission signal (in this case the source of acoustic emission is the metal cutting). The interesting acoustic emission signal has its components, which comes from 100 kHz to 1 MHz. In spite of the project characteristics, the conditioner and the transmitter are developed. The projects of the pre-amplifier and the filter are presented (they belong to the conditioner), which makes their functions of amplification and filtration. The pre-amplifier, which function is to amplify the weak signal on the output of the sensor, amplifies the signal by 20 dB. It has a flat response on the frequency range (frequencies less than 1 MHz). The filter, which is the type of flat-band, has the function of eliminating the components connected to the mechanic vibrations and the electric/electromagnetic noises, therefore to avoid the aliasing phenomenon on the signal processing. It attenuates the signal components of frequencies lower than 100 kHz and higher than 1 MHz. There is a flat response on the frequency range, which warrants the maintenance of the signal format. It is considered into the projects indicated the electronic components\' responses to the work frequencies and the circuit protection against noises into their feeding.

This study investigates the tool wear of advanced PVD TiALN/TiN multilayer coated end mill inserts when dry and semi-dry machining 4340 low alloy medium carbon steel. A factorial design of experiment setup consisting of two levels of speed, three levels of feed, two levels of depth of cut, and two levels of cutting conditions (semi-dry and dry) was used for the study. The combination of cutting conditions that gave the best response for different components of cutting force, cutting power, surface roughness and tool life were determined using MANOVA & ANOVA analysis and Tukey comparison of means test using MINITAB statistical software package. From a study of the Energy Dispersive X ray (EDX) analysis and primary back scatter images obtained from the worn out crater surface of the insert, it was observed that diffusion wear prevailed under both dry and semi-dry machining conditions. A tool life model was developed using multiple regression analysis within the range of cutting conditions selected. A model for flank wear progression was also developed using mixed effects modeling technique using S Plus statistical software package. This technique takes into account between and within work piece variations during end milling and produces a very accurate model for tool wear progression. This is the first time application of the mixed effects modeling technique in metal cutting literature.

The development of miniaturized technologies has become a global phenomenon that continues to make an impact across a broad range of applications that encompasses many diverse fields and industries including telecommunications, portable consumer electronics, defense, and biomedical. Subsequently this trend has caused more and more interest in the issues involved in the design, development, operation and analysis of equipment and processes for manufacturing micro components. One technology used to create these miniaturized components is micro end milling. The cutting forces of the micro end milling process provide vital information for the design, modeling, and control of the machining process. To gain an understanding of forces in micro end milling operations, a model of average chip thickness is derived and the differences between conventional end milling and micro end milling are enumerated. From the experimental results, empirical models for specific cutting constants were derived and compared the generally accepted forms for conventional end milling operations. These models provide a tool for the estimation of cutting forces in micro end milling.