Design and Analysis of Ultrasonic Horn for Micro Drilling

Abstract

Micro drilling is mainly used in the field of precision manufacturing industries such as drilling of holes in Printed circuit board materials. But the main problem we often encounter while performing micro drilling is the hole location accuracy and hole positioning accuracy of the drilled hole. In order to effectively tackle these issues, a novel technique called ultrasonic assisted drilling has been implemented, which can impart both ultrasonic vibration and rotary motion to the drill bit. Horn or amplitude transformer is a key element in transferring the ultrasonic vibrations received at its input end from the transducer to the drill bit. So the design of horn has a huge impact on the amplitude of ultrasonic vibrations being imparted to the drill bit. The most important aspect of Sonotrode design is the determination of resonant frequency and resonant length of the horn. Hence, mathematical modeling of horns has been done for different horn shapes and their theoretical lengths have been calculated. The drill bit designed for our study is a 1mm diameter single step drill, with a flute length of 6mm which is generic for PCB materials. The calculated resonant lengths and amplification factors have been validated by using Ansys 15.0 workbench interface. Modal analysis was performed to calculate the mode shapes as well as natural frequencies of different shaped horns and the dimensions of the horn producing the resonant frequency within the range of 19500- 20500 is selected. Also, the amplification factors achieved by using a specific horn, which has already been calculated theoretically has been validated by using harmonic response analysis.