DEVELOPMENT OF A TESTING FACILITY FOR EXPERIMENTAL INVESTIGATION OF MEMS DYNAMICS

Abstract Dynamic characteristics of overhung and/or moving components play a pivotal role in determining the overall performance and reliability of microsystems (MEMS). In addition to the structural dynamics of the components, the response is very sensitive to multi-physics phenomena such as electrostatics, gas damping, and friction. Therefore, the ability to experimentally analyze linear and nonlinear dynamics of microsystems under varying environmental conditions is very important. This paper describes a facility for experimental investigation and validation of linear and nonlinear dynamic response of microsystems under varying environmental conditions. A detailed account of the facility components and software developed for excitation and data collection is given. Experimental results and discussion for various MEMS structures are included to illustrate the effectiveness of the experimental facility

A Rotating-Tip-Based Mechanical Nano-Manufacturing Process: Nanomilling

We present a rotating-tip-based mechanical nanomanufacturing technique, referred to here as nanomilling. An atomic force microscopy (AFM) probe tip that is rotated at high speeds by out-of-phase motions of the axes of a three-axis piezoelectric actuator is used as the nanotool. By circumventing the high-compliance AFM beam and directly attaching the tip onto the piezoelectric actuator, a high-stiffness arrangement is realized. The feeding motions and depth prescription are provided by a nano-positioning stage. It is shown that nanomilling is capable of removing the material in the form of long curled chips, indicating shearing as the dominant material removal mechanism. Feature-size and shape control capabilities of the method are demonstrated

Rotational dynamics of micro-scale cutting tools

The dynamics of micro-scale cutting tools used during micromachining is critical to attainable process precision. Forced and self-excited vibration behavior of a micromachining process depend critically on the dynamic response of the microtools. As these micro tools are rotated at very high speeds (40,000 to 250,000 rpm) the rotational effects can play a critical role in their dynamic response. However, their the complex, multi-dimensional, and pre-twisted geometry causes a coupled dynamic response, thereby rendering the prevailing simplified one-dimensional (1D) modeling approaches inaccurate. Towards addressing this modeling challenge, in this work, we present an application of spectral-Tchebychev (ST) method to predict the three-dimensional (3D) coupled dynamics of microtools including the rotational (gyroscopic) effects. To capture the dynamics of the sectioned geometry of microtools efficiently, a unified modeling approach is followed in the modeling, merging 1D-ST models for the sections having circular cross sections, and 3D-ST models for the fluted section, which exhibits coupled three-dimensional motions due to the complex geometry. The presented solution technique is applied to predict and understand the dynamics of rotating micro-endmills and micro-drills. Natural frequencies, mode shapes, and the frequency response functions (FRFs) obtained from the unified 1D/3D-ST model are shown to have an excellent agreement with those from a commercial finite element (FE) software. The unified 1D/3D-ST model is then used to analyze the accuracy and limitations of reduced-order modeling approaches that could be used to model the rotational dynamics of microtools. Finally, the effect of rotational speed on radial throw arising from the rotational dynamics is investigated