Abstract
It is important for companies to increase the efficiency of drilling as well as prolong the lifetime of the drilling tool. Since some previous investigations indicated that a superposition of well drilling with an additional vibration increases the drilling efficiency, this paper introduces a novel well drill which is assisted with additional vibrations by means of piezoelectric sandwich bending vibration transducer. The proposed drill uses bending vibrations in two different directions to from an elliptical trajectory movement, which can help the drill to break the surface of hard material more efficiently and clean away the lithic fragments more easily. The proposed well drill with bending vibration transducer is designed to have a resonance frequency of the first bending vibration mode of about 1779 Hz. The motion equation of the particle on the edge of the drill bit is developed and analyzed. The vibration trajectory of the particle on the edge of the drill bit is calculated by using finite element method. A prototype of the proposed drill using bending vibrations is fabricated and tested to verify the aim of drilling efficiency increase. The feed speed of the vibration assisted drilling is tested to be about 0.296 mm/s when the excitation voltage of the transducer is 300 V, while this speed decreases to about 0.195 mm/s when no vibration is added. This comparison shows that the feed speed of the vibration assisted drilling is about 52% higher than that of the normal drilling, which means the proposed drill has a better efficiency and it is important to consider vibration superimposition in well drilling. In addition, the surface of the drill hole gained by the vibration assisted drilling is smoother than that of the normal drilling, which makes the clearance easier.
Highlights
Geological mining usually needs to drill deep holes into the ground to detect the condition underground and find out if there are some valuable mineral resources
The average feed speed of the vibration assisted drilling is 52% higher than that of the normal rotary drilling when the excitation voltage is 300 V. These results show that the bending vibration increases the feed speed in rotary drilling obviously
Several experiments are conducted to compare the efficiency of the vibration assisted drilling with that of the normal rotary drilling
Summary
Geological mining usually needs to drill deep holes into the ground to detect the condition underground and find out if there are some valuable mineral resources. The percussive-rotary drilling can be more efficient than the normal method, especially in the conditions where the rocks are hard, such as marble, shale and so on. In this method, the drill bit collides with the rock with high intensity, which can help the drilling flush out rock fragments [6]. There are some important advantages lying in the percussive-rotary drilling It is more efficient than the normal rotary drilling in the same condition (such as the same pressure and the same material). Their volumes are large and it is difficult for them to be optimized to have the best percussion effects and amplitudes These devices can increase the efficiency of drilling, they can only produce axial percussion. The following advantages can be anticipated: better surface condition, higher drilling efficiency and smaller chips (easier for removal)
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