Computer Modeling for Continuous Miners
The approach used for computer modeling of the cutting drum of a continuous miner is to program each bit individually and analyzes the cutting forces acting on the bits. The cutting forces (cutting and normal force depend on the rock type to be cut, the cutting geometry (spacing and penetration of the bits), the geometry of the bit (tip angle) and the attack angle.
The machine specifications, such as thrust and power are for providing sufficient amount of forces and torque to support the excavation operation. Machine thrust is the force required to penetrate the tools into the rock surface. Also, the cutterhead torque and power requirements are the force to rotate the head at the required penetration rate and overcome the drag force resistance of the cutters.
In the computer program, a cylindrical coordinate system is used to define the drum geometry and bit-lacing pattern. Position of each cutter on the drum is defined by its radius from the axis rotation, and the position angle from positive x-axis. The following figure shows the schematic drawing of a cutterhead and parameters used to define the bit position on the drum.
Cutterhead profile data is essential for simulating different cutting modes (sumping and shearing) of the drum and checking the availability of the thrust and power of the machine at a given sumping and shearing depth.
The information generated from the computer model includes individual cutter positions, penetration, and forces, overall thrust, torque, and power requirements of the cutterhead in the given position, variation of the forces as the head rotates, and finally boom speed and production rate. The program allows the user to monitor the variation and graphically represents these variations as the head rotates. Figure 3 illustrates a typical summary of information for a full rotation and variation of thrust, and power for a certain cutterhead design and lacing pattern for sumping and shear-down mode.