Analysis and optimization of traveling wave vibration of large diamond thin-wall drill bits

Abstract

Objectives: To reduce the vibration and noise generated by thin-walled drill bits during the drilling and cutting process, various designs of thin-walled drill bits were studied, including conventional thin-walled drill bits, open-hole thin-walled drill bits, open-hole and interlayer thin-walled drill bits, and thin-walled drill bits with positioning wheel. The reasons for vibration and noise reduction of thin-walled drill bits in different schemes were analyzed at a theoretical level. A new scheme for thin-walled drill bits was proposed, which exhibited good vibration reduction effects, protected the hearing of thin-walled drill bit operators, and complied with China's environmental indicators for workers. Methods: Modal analysis and traveling wave vibration analysis of thin-walled drill bits were performed using Workbench software to study the effects of different thin-walled drill bit designs on traveling wave vibration. First, a solid work model of the thin-walled drill bit was imported into Workbench software and meshed. The inner hole of the thin-walled drill bit was constrained (cantilever type), and the first 30-order modes of the thin-walled drill bit were calculated under standard earth gravity. Using traveling wave vibration theory, the δ value of the resonance margin of the thin-walled drill bit in different schemes was calculated to determine the effectiveness of avoiding traveling wave resonance. Results: At a drilling speed of 187.32 r/min, the conventional thin-walled drill bit had a δ value of 0, leading to rear traveling wave resonance. The opening of 8 groups of round holes and 8 S-hole thin-walled drill bits had a δ value of 5.18%, which was the best opening design scheme. Further interlayering the thin-walled drill bit resulted in a δ value of 6.11%, showing the best effect in avoiding traveling wave resonance. In the δ where 2 to 12 positioning wheels thin-walled drill bits were installed, the δ of 2, 3 and 11 positioning wheels thin-walled drill bits was less than 1.00%, effectively avoiding traveling wave resonance. Conclusions: Thin-walled drill bits with traveling wave resonance will produce strong vibration and noise. Reducing the deformation of the thin-walled drill bit increases the δ value, leading to better vibration and noise reduction. To ensure the precision of the drilled hole, the positioning theory was applied to the thin-walled drill bit. When comparing δ values for drill bits with 2 to 12 positioning wheels, the designs with 6 and 12 positioning wheels had larger δ values and better vibration damping effects. Considering installation convenience, 6 positioning wheels were determined to be the optimal number, providing a theoretical basis for reasonable determination of the number of positioning wheels.

Keywords

• diamond thin-wall drill bits
• opening and interlayer
• positioning wheel
• traveling wave vibration