Browsing by Subject "Micromechanics."

Now showing 1 - 3 of 3

Open Access
High-Q micromechanical resonators and filters for ultra high frequency applications
(2009) Taş, Vahdettin
Recent progresses in Radio Frequency Micro Electro Mechanical Sensors (RF MEMS) area have shown promising results to replace the off-chip High-Q macroscopic mechanical components that are widely used in the communication technology. Vibrating micromechanical silicon resonators have already shown quality factors (Q) over 10,000 at radio frequencies. Micromechanical filters and oscillators have been fabricated based on the high-Q micro-resonator blocks. Their fabrication processes are compatible with CMOS technology. Therefore, producing fully monolithic transceivers can be possible by fabricating the micromechanical components on the integrated circuits. In this work, we examine the general characteristics of micromechanical resonators and propose a novel low loss resonator type and a promising filter prototype. High frequency micromechanical components suffer from the anchor loss which limit the quality factor of these devices. We have developed a novel technique to reduce the anchor loss in extensional mode resonators. Fabrication processes of the suggested structures are relatively easy with respect to the current high-Q equivalents. The anchor loss reduction technique does not introduce extra complexities to be implemented in the existing structures.
Open Access
Modeling and optimization of micro scale pocket milling operations
(2014) Sert, Bengisu
Manufacturing of micro scale parts and components made from materials having complex three dimensional surfaces are used in today’s high value added products. These components are commonly used in biomedical and consumer electronics industries and for such applications, fabrication of micro parts at a low cost without sacrificing quality is a challenge. Micro mechanical milling is a viable technique which can be used to produce micro parts, however the existing knowledge base on micro milling is limited compared to macro scale machining operations. The subject of this thesis is micro scale pocket milling operations used in micro mold making which are used in micro plastic injection in mass production polymer micro parts. Modeling of pocket milling while machining of basic pocket shapes are considered first. The developed milling model is then extended to more complex mold shapes. Minimum total production time is used as the objective to solve single pass, multi pass, and multi tool problems. Case studies are presented for each problem type considering the practical issues in micro milling. A software has been developed to optimize machining parameters and it is shown that the developed pocket milling optimization model can successfully be used in process planning studies.
Open Access
Modeling of cutting forces in micro milling including run-out
(2014) Kanlı, Muammer
Micro milling is widely used in precision manufacturing industry which is suitable for producing micro scale parts having three dimensional surfaces made from engineering materials. High material removal rate is its main advantage over other micro manufacturing technologies such as lithography, micro EDM, laser ablation etc. Modeling of micro milling process is essential to maximize material removal rate and to obtain desired surface quality at the end of the process. The first step in predicting the performance of micro milling process is an accurate model for machining forces. Machining forces are directly related to machine tool characteristics where the process is performed. The spindle and the micro milling tool affects the machining forces. In this thesis, the influence of runout of the spindle system on micro milling forces is investigated. Two different spindle systems with different levels of runout are considered and necessary modifications are introduced to model the trajectory of the tool center for better prediction of process outputs in the presence of runout. A modified mechanistic force modeling technique has been used to model meso/micro scale milling forces. Detailed micro milling experiments have been performed to calculate the cutting and edge force coefficients for micro end mills having diameters of 2, 0.6, and 0.4 mm while machining titanium alloy Ti6AL4V. Good agreements have been observed between the predicted and measured forces. It is found that statically measured runout values do not translate into dynamic machining conditions due to machining forces acting on the end mill.