Ball mill is the widely used comminution device for the size reduction of iron ore particles, yet the underlying mechanisms of heat transfer and thermal breakage inside the mills heretofore are not deeply understood. Therefore, the Discrete element method was carried out to study the effect of operating parameters on charge temperature, and the batch grinding experiments of iron ores were conducted to verify the heating temperatures using a laboratory ball mill. Results show that increasing mill speed will result in the charge temperature increasing initially and then decreasing. The temperature fields of the charge and load behavior remain approximately the same for the different ball filling. The main findings of this study are that the heating temperature can contribute to enhancing the breakage behavior of iron ore particles, and correspondingly the optimal feed sizes for different heating temperatures are determined to be 2.48 mm, 2.63 mm, 2.78 mm, and 3.59 mm, respectively.

A ball mill is a type of complex grinding device. Having knowledge of its charge-load behavior is key to determining the operating conditions that provide the optimum mill throughput. An elaborate description of the charge movement inside the ball mill is essential. This study focuses on a laboratory-scale ball mill and utilizes a discrete element simulation model to investigate the impact of mill speed and ball filling on charge-load behavior. Initially, the EDEM 2.7 (Engineering Discrete Element Method) software contact parameters were calibrated through heap-angle experiments. Subsequently, four charge-motion characteristic parameters were defined and analyzed based on Powell’s theory to understand the variations in charge-load behavior. This research proposes a theoretical calculation model for predicting power in a ball mill, highlighting the significance of the CoC (Center of Circulation) and CoM (Center of Mass) in reflecting changes in charge-load behavior. The theoretical model for mill-power prediction is effective and aligns well with the EDEM simulation and experimental results, providing valuable insights for optimizing large-scale ball mill structures and controlling charge motion during production.

The liner is a wear-prone component in ball mills, subject to continuous impacts, squeezing, and abrasion from the grinding media during operation. Its service performance directly affects the working efficiency of the ball mill. The service life of mining ball mill liners is about 8 months, and frequent downtimes occur due to liner wear and loss of effectiveness, with liner replacement accounting for about 6% of the total cost, resulting in huge economic losses. This paper focuses on a Φ305 mm × 150 mm experimental ball mill, using the discrete element software Rocky Discrete Element Method (DEM) (software version number Rocky 2022 R2) for simulation modeling analysis. With Φ10 mm and Φ20 mm mono-size particle simulations serving as reference groups, this study investigates the motion states and liner abrasion patterns under different liner heights for both sizes of grinding media in Equilibrium Quality Manufacturer (EQM) and Original Equipment Manufacturer (OEM) gradations. The results indicate that the impact of liner height on the wear of the ball mill liners is related to the size and gradation of the grinding media. The degree of liner wear from highest to lowest is as follows: EQM > Φ20 mm > OEM > Φ10 mm. Due to the effect of the cylinder end cap, the wear at the axial center of the ball mill liner is more severe than at both ends, and the wear on the facing side of the liner is more severe than on the backside. A thorough study of the influence of ball mill grinding media gradation on the wear pattern of liners is of great theoretical significance for optimizing liner structures, improving grinding efficiency, and promoting energy saving and cost reduction in ball mills. This study provides theoretical guidance for understanding the mechanisms behind liner wear in ball mills and predicting the liner lifespan.

Optical mirrors have high requirements for surface precision, requiring ultra-precision processing. The revolving movement of a computer-controlled optical surfacing (CCOS) grinding system will induce vibrations in a five-degrees-of-freedom hybrid processing robot (5-DOF-HPR) and a flexible support system (FSS) in a large optical mirror processing system (LOMPS). As a result, the mirror surface will vibrate, which will ultimately affect the surface accuracy of the final optical mirror. Therefore, the differential equation representing the vibration of the 5-DOF-HPR is established based on the spatial beam unit, which transforms the generalized coordinates into modal coordinates, thereby removing the coupling terms of the vibration differential under generalized coordinates. At the same time, a dynamic analysis of the CCOS grinding system is performed, and the magnitude and direction of the centrifugal force and reaction force are calculated. Then, the natural frequencies of the 5-DOF-HPR and the FSS are measured experimentally and compared with the simulation results; thus, the accuracy and effectiveness of the model are verified. Finally, the vibration characteristics of the processed optical mirrors under different influencing factors are obtained. A theoretical and experimental basis for parameter optimization and path planning of the LOMPS is provided to improve the surface accuracy of the processed optical mirror.

This study presented a numerical model for the quantitative assessment of the heat transfer behavior of grinding media inside a ball mill. Effects of various mill speeds, grinding media filling, and the number of lifters on heat transfer were studied and verified by comparing the experimental results and the numerical simulations calculated by DEM (Discrete Element Method). The results show that the heat transfer of grinding media has a strong sensitivity to the variation of the mill speed, grinding media filling, and the number of lifters. The optimum grinding conditions for heat transfer behavior can be determined in terms of the temperature field of the grinding media. The maximum temperature rise of grinding media occurs at a range from 70% to 80% of critical speed. The maximum average temperature of grinding media up to 295.057 K appears at the grinding media filling 25% and the number of lifters 12. Subsequently, validation experiments are carried out to validate the numerical simulation results. The experimental results are closer to the simulation results, indicating the reasonability of the heat transfer model.