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Tesi etd-03152011-113608


Thesis type
Tesi di dottorato di ricerca
Author
MITHU, MD.ABU HAYAT
email address
ah.mithu@ing.unipi.it
URN
etd-03152011-113608
Title
New Methodologies in the field of micromanufacturing
Settore scientifico disciplinare
ING-IND/16
Corso di studi
INGEGNERIA MECCANICA
Commissione
tutor Prof. Santochi, Marco
relatore Prof. Tantussi, Giovanni
Parole chiave
  • Microtool
  • Microproduct
  • Material removal rate
  • Microdrilling
  • Machining time
  • In-process monitoring
  • Electrochemical micromachining
Data inizio appello
25/03/2011;
Consultabilità
completa
Riassunto analitico
Manufacturing processes are continually improving and updating with a view towards enhancing productivity. With the rapid development of technology, the demand for miniature, lightweight and advanced products is increasing. To compensate these emerging global trends towards the miniaturization of products, the electrochemical micromachining (µECM) is a promising technique. The µECM utilizes high frequency pulses for micron to nano-scale dissolution process that can be driven by with or without feedback control systems. This thesis includes the activities performed during the last three years, as the development of electrochemical micromachining workcell, fabrication of microtools, parametric effects analysis, and fabrication of various microproducts on some noble materials. During microtool fabrication, tungsten micro shafts of 0.38 mm are electrochemically etched to fabricate the desired cylindrical tools with or without conical tips. In the fabrication of microtool, electrolyte concentrations are varied in the range to 0.08–2.0 M KOH for the applied potential differences of 3–15 V AC and different etching time. The microtool fabrication process has been monitored by measuring the size, shape and overall tool geometry. These prefabricated microtools are used in the fabrication of various microdrilling and micromilling processes, especially in the fabrication of single hole micronozzles, multiple hole micronozzles array and microhole fabrication on vitrectomy needles. A mathematical model has been developed for the analysis of material removal rate (MRR) based on pulsed electrical power applied in µECM. The parametric effects of the process are studied on applied potentials, electrolyte temperature, applied frequency and its duty cycle, the dimension of microtools. For the parametric effect analysis, material removal rate, machining time, the number of short circuits, the shape and size of the fabricated microproducts are considered as response factors. The proper experimental parameters, the relationship between the parameters and the distribution of metal removal are established from the experiments worked out. The experimental micromachining tests show that MRR increases with the increase in applied potential, duty cycle, the electrolyte temperature, and microtool diameter, whereas MRR decreases with baseline potential in a certain range, applied frequency, and tool length. Machining time shows the opposite trend of MRR for all the parameters except microtool diameter. It increases with increasing microtool diameter. The microtool feed rate also has a significant effect on the dimension of fabricated microproducts. The waveforms generated during machining are analyzed; an in-process monitoring and control process has also been developed based on the waveforms. The result shows that the shape of the waveform and its corresponding values are in good agreement with the MRR, machining time and on the dimension of fabricated microholes. The proposed monitoring technique could be employed as a predictive tool in electrochemical processing. Finally, the microtools fabricated have been used for fabricating micronozzles and micropockets on nickel plates, microholes on high grade stainless steel to realize the practical applications of microdrilling process.
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