Precision Engineering, Volume 37, Issue 2, April 2013, Pages 364-371.
Ping Guo, Kornel F. Ehmann.
Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Road, Room B110, Evanston, IL 60208, USA
The elliptical vibration texturing process is an innovative machining method for the fast generation of textured surfaces. It adds a tertiary motion component to the tool tip, which introduces deliberate elliptical vibrations between the cutting tool and the workpiece. The elliptical locus lies in the plane that is defined by the cutting direction and the radial direction in the turning operation. This paper proposes a new design for a resonant mode 2D tertiary motion generator (TMG) that can deliver the required elliptical trajectory at an ultrasonic frequency. The device works in the resonant mode, with tangential and normal vibrations at a nearly identical resonant frequency. Simulation and experiments were carried out to perform a modal analysis of the system. Different design parameters were adjusted to achieve large vibration amplitudes in both tangential and normal directions. The elliptical vibration texturing process was implemented by integrating the newly developed TMG into a turning operation. Preliminary test results of dimple array patterns are presented that validate the performance and principle of the proposed design.
Elliptical vibration texturing uses ultrasonic vibrations with frequencies exceeding 20 kHz of the cutting tool for the fast generation of micro surface textures, i.e. micro-dimples. The dimples are generated at the rate of the tool’s vibration through cutting depth modulations. The elliptical tool motions are realized through a specially designed tertiary motion generator (TMG) consisting of two piezoelectric vibration transducers. The transducers work in the resonant mode, with their two linear vibration modes coupled at an identical frequency. The high operating frequency of the TMG leads to high texturing efficiency and makes the technology very appealing for mass production of textured surfaces, which have many applications in the energy, biomedical, automotive and other areas.
Schematic of the process
Example of generated surfaces