Experimental Study of Operational Parameters on Product Size Distribution of Tumbling Mill

To assess the effects of the mill operating parameters such as mill speed, ball filling, slurry concentration and slurry filling on grinding process and size distribution of mill product, it was endeavored to build a pilot model with smaller size than the mill. For this aim, a pilot mill with 1 m × 0.5 m was implemented. There are 15 lifters with 50 mm height and face angle of 30˚. In the present work, the combination of the balls (40% of the balls with 60 mm diameter, 40% of the balls with 40 mm diameter and 20% of the balls with 25 mm diameter) was used as grinding media with 10%, 15%, 20% and 25% of the total volume of the mill. The experiments were carried out at 60%, 70%, 80% and 90% of the critical speed. The feed of the mill is copper ore with the size smaller than 25.4 mm, which d80 and d50 of them are 12.7 and 8 mm, respectively and slurries with 40%, 50%, 60%, 70% and 80% of solid and the slurry filling between 0.5 and 2.5. The results showed that the best grinding and grading occurs at 70–80% of the critical speed and ball filling of 20–25%. Optimized grinding was observed when the slurry volume is 1–1.5 times of the ball bed voidage volume and the slurry concentration is between 60% and 70%. The mill grinding mechanism in this work is a combination of both impact and abrasion mechanisms.

Cortical bone grinding mechanism modeling and experimental studyfor damage minimization in craniotomy

Craniotomy, as a part of neurosurgery, implies a safe opening of the skull with mechanical equipment. Grinding is a traditional machining method that can accurately and efficiently remove bone tissue. Aiming at low-damage and high-efficiency bone grinding, this study analyzed the kinematic law of a single abrasive grain during the grinding process. The theoretical model of grinding force was established based on the calculation of specific energy and friction force. The grinding test platform was set up, and the full factorial experimental design was performed to link the grinding force evolution with different processing parameters. The experimental results obtained on porcine femurs validated the model predictions where the grinding force grew with feed speed and grinding depth; it exhibited a decreasing trend with rotation speed, followed by increasing one.

Deworming the Grinder for Successful Extrication of a Mangled Hand: A Case Report and Review of Literature

Grinding machine injuries are known to cause severe mutilating injuries of the upper limb. In some cases, the machinery equipment may still be attached to the limb when the patient reaches the hospital. In treating these injuries, the patient’s hemodynamic status should be the first priority of resuscitation. Following this and whenever possible, a reversal of the grinding mechanism should be done to free the limb as this would allow assessment of the extent of zone-of-injury prior to starting the surgical procedure. We report a case of a 28-year-old male who sustained a mangled hand injury that was successfully extricated from an industrial grinding machine, thereby allowing preservation of precious length of the limb during surgery. This case highlights the importance of adhering to safety precautions at the workplace to reduce the risk of potential occupational hazards when dealing with machinery equipment.

Potential of Mechanochemically Activated Sulfidic Mining Waste Rock for Alkali Activation

Sulfidic mining waste rock is a side stream from the mining industry with a potential environmental burden. Alkali activation is a promising method for transforming mining waste into construction materials. However, the low reactivity of minerals can be a sizeable challenge in alkali activation. In the present study, the reactivity of waste rock was enhanced by mechanochemical treatment with a LiCl-containing grinding aid. X-ray diffraction (XRD) and diffuse reflectance infrared Fourier transform (DRIFT) analysis were utilized to display the structural alteration of individual minerals. A schematic implication of the grinding mechanism of mica was provided according to the results of transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The alkaline solubility displayed the enhanced chemical reactivity of the waste rock, in which Si and Al solubility increased by roughly 10 times and 40 times, respectively. The amorphization of aluminosilicate is achieved through chemical assisted mechanochemical activation. Sulfidic waste rock, as the sole precursor in alkali activation, achieved a 28-day compressive strength exceeding 10 MPa under ambient curing conditions. The simulation of the upscaled grinding process was conducted via the HSC Chemistry® software with a life-cycle assessment. The results showed that mining waste rock can be a promising candidate for geopolymer production with a lower carbon footprint, compared to traditional Portland cement. Graphical Abstract

Experiment study on the corrosion resistance of the surface metamorphic layer of grinding

Workpiece will face corrosive problems during its application after the manufacturing process. As the common final process, grinding can generate special metamorphic layer on the surface of workpiece and change the initial corrosion resistance of workpiece. In order to study the corrosion resistance of workpiece after grinding process, the paper carries on combining experiment of grinding and electrochemical corrosion. The characteristic of corrosion resistance of grinding is revealed based on the association of grinding mechanism and electrochemical theory. The corrosion potential of workpiece after grinding is higher than matrix, which shows the grinding surface is difficult to begin to corrode. Electrochemical impedance spectroscopy (EIS) shows the grinding surface has large phase angle, impedance and capacitance characteristic because the metamorphic layer of grinding has good obstructive ability. They reveal that grinding improves the surface corrosion resistance of workpiece. Then the mechanism of the corrosion resistance of grinding is revealed. The special grain boundary formed in grinding with much C element, large clusters and complex shape prolongs the corrosion channel, which reduces the corrosive speed. While, the sensitive hardening structure generated in grinding hardening with much free energy is easy to form the corrosion cell, which will accelerate the corrosion.

Active Compliant PID Learning Control for Grinding Robots

This article proposes a Proportional, Integral, and Derivative (PID) learning controller for rigid robotic disk grinding mechanism. It has been observed that the stiffness of the robotic arm for a grinder has a direct correlation with the sensitivity of the grinding forces. It is also drastically influenced by the end-effector path tracking error resulting in limited accuracy of the robot. The error in robot’s accuracy is also increased by external interferences, such as surface imperfections and voids in the subject material. These errors can be mitigated via efficient feedback. In the proposed methodology, the controller gain is tuned by implementing a learning-based methodology to PID controllers. The learning control for the robotic grinding system helps by progressively decreasing error between the actual grinded paths and required trace. Experimental results demonstrate that as the grinder machines the required path iteratively, its grinding accuracy improves due to the learning algorithm.

Preparation and Properties of Sustainable Brake Pads with Recycled End-of-Life Tire Rubber Particles

Sustainable composite brake pads were processed by employing recycled end-of-life tire (ELT) rubber particles obtained by means of cryogenic grinding and ambient grinding. The effect of the grinding mechanism and concentration of ELT rubber particles was then reported. From the friction result test, better behavior in terms of coefficient of friction (COF) was obtained when 3% of ELT rubber particles were introduced into the composite. It was demonstrated that the size of the particles is not as determinant as the friction mechanism in the wear properties of the sustainable brake pads. Whereas, while increasing the ELT rubber particle size acts as detrimental to the COF either in the ambient or cryogenic grinding, at high friction distances, the better adhesion of the particles because of the rough surface of the particles subjected to ambient grinding enhances the long-life behavior of the composite brake pads.

Special Issue on Advances in Abrasive Technology

As abrasive technologies are currently indispensable for production processes in the automotive, aerospace, optics, telecommunications, and healthcare industries, among others, it is essential that the application of abrasive processing to production be optimized and improved. To those ends, it is necessary to understand how to approach the task, as there are many processing factors to consider. However, priority is given to understanding the abrasive processing mechanism that determine finishing results, as well as the relationship between the processing factors and individual conditions. Measurement, analysis, and evaluation technologies are also important. Furthermore, the development of new abrasive tools or machining fluids and the active use of physicochemical phenomena are key to the development of advanced abrasive technologies. Cutting-edge studies focusing on advanced abrasive technologies were collected for this special issue, which includes 12 papers covering the following topics: - Quantitative evaluation of surface profile of grinding wheel - Elucidation of grinding mechanism, based on grinding force - Novel grinding wheel - High-efficiency and high-accuracy grinding of difficult-to-cut materials - Polishing technology using magnetic fluid slurry - Application of ultrasonic waves or ultra-fine bubbles to coolants, and their effects on them - Planarization technology for single-crystal silicon carbide This issue is expected to help its readers to understand recent developments in abrasive technologies and to lead to further research. We deeply appreciate the contributions of all authors and thank the reviewers for their incisive efforts.