Study on the Ultrasonic-Assisted Vibration Tapping Using Automatic Tracing Frequency System

Study on the Ultrasonic-Assisted Vibration Tapping Using Automatic Tracing Frequency System

K. L. Kuo (Department of Vehicle Engineering, National Taipei University of Technology, Taipei, Taiwan) and C. C. Tsao (Department of Mechatronic Engineering, Tahwa University of Science and Technology, Hsinchu, Taiwan)
DOI: 10.4018/ijmfmp.2014010105
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Abstract

In the past, researchers thought that the introduction of ultrasonic-assisted vibration in tapping processes could generate smaller tapping torque than nonultrasonic-assisted vibration process. However, since the ultrasonic vibrator's temperature increases with processing time, the temperature of the workpiece may get too high. As a result, the ultrasonic vibrator may generate an unstable resonant frequency and amplitude, which can cause poor quality in the workpiece. This research used ultrasonic-assisted vibration and LabVIEW software to develop an ultrasonic-assisted vibration automatic tracing frequency system (UAVATFS). With this orthogonal array experiment, UAVATFS and the appropriate processing parameters (vibration amplitude, vibration frequency) were used to perform tapping on a titanium alloy workpiece. The effect of using this system on internal thread processing was investigated.
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Theories On Ultrasonic-Assisted Tapping Process

Ultrasonic Processing System

The ultrasonic-assisted vibration processing system mainly comprises of an oscillating circuit generator, a signal amplifying circuit, a vibrator, an amplitude amplifier (horn) and tool. According to the principle of ultrasonic vibration, the oscillating circuit generates oscillating power, and then the oscillating power, through piezoelectric material, converts alternating voltage into vibration across the thickness and amplifies the amplitude using a set of horns. This vibration is then transmitted to the tool or the target workpiece to produce vibrations to augment the traditional processing, as shown in Figure 1. A general oscillating circuit is an RLC circuit, where the capacitive reactance (XC) lags the zero reference angle for resistance by 90° and the inductive reactance (XL) is ahead of the zero reference angle for resistance by 90°. So there is 180° phase difference between XL and XC. At a frequency when the two opposite electrical impedances cancel out, the circuit is a pure electrical impedance circuit. Therefore, the output current is the maximum and the power is the maximum. This is called resonance, as shown in Figure 2.

Figure 1.

Vibrator vibration mode

Figure 2.

Relationship between output current and frequency for oscillating circuit under the resonance condition

The purpose of the vibrator is to ultrasonically convert high-frequency complex electric energy into kinetic energy. Since Massachusetts Institute of Technology developed barium titanate (BaTiO3) in 1947, which has 39 times higher piezoelectric coefficient than quartz, it is suitable to be made into actuator. currently, it is a common choice for piezoelectric vibrators. Ultrasonic processing usually uses low-frequency vibration. To lower the working frequency range for a vibrator, a sandwich type piezoelectric vibrator is commonly used by clamping metal onto the two ends of a piece of piezoelectric ceramic. This is called composite piezoelectric vibration, for which the structure is shown in Figure 3.

Figure 3.

Basic structure for piezoelectric vibrator

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