Evaluation of rock cutting performance of conical cutting tool based on commonly measured rock properties

Abstract

Efficiency of rock cutting process plays a critical role in performance of mechanical excavation units. The composition of cutting forces (normal and drag force acting on cutting tools) and the total force (F_T), specific energy (SE), and percent of fine material (FM) produced in cutting process are important indicators of efficient cutting process. The other key factors in assessment of machine performance are tool wear, energy consumption, dust production, and machine maintenance, availability, and utilization. In this study, small scale linear cutting experiments were performed with a conical pick on thirteen sedimentary and metamorphic weak to medium strength rock samples at a range of 0.5 to 6 mm cutting depths in unrelieved cutting mode. F_T was measured by using a 3D dynamometer and recorded by the data acquisition system, and FM was determined by sieve analysis. Finally, SE was calculated using both the cutting force signal and the volume of the cuttings for each test. Subsequently, an analysis of the effective cutting geometry was performed based on cutting depth, using the specific energy as an indicator of cutting efficiency. Statistical and regression analysis was used to correlate F_T, SE, and FM with the rock properties and cutting geometry. The results revealed that the uniaxial compressive strength, Schmidt rebound number, and density are the main parameters that affect F_T and SE, and the brittleness index is the main parameter that affects FM. A nonlinear predictive model is introduced that offers a reasonable estimate of F_T, SE, and FM to assist engineers in determining the effective operational cutting geometry for a given rock type for unrelieved cuts.