Study on Performance of PVD AlTiN Coatings and AlTiN-Based Composite Coatings in Dry End Milling of Hardened Steel SKD11

Dry milling of hardened steel is an economical and environmentally friendly machining process for manufacturing a mold and die. Advances in coating technology makes the dry milling a feasible approach instead of a traditional grinding process. However, the cutting condition is particularly severe in a dry machining process. High-performance coating is desired to meet the requirement of green and highly efficient manufacturing. This study concerned the performance of AlTiN-based coatings. The effect of Al content, and the AlTiN composite coating on the cutting performance of tools are investigated in terms of friction force at the tool–chip interface, specific cutting energy, cutting temperature on the machined surface, tool wear pattern and mechanism, and surface integrity. The results show that advanced AlTiN-based coatings reduce the force and cutting energy and protect the cutters from the high cutting temperature effectively. The main wear mechanisms of the coated tools are adhesive wear, chipping induced by fatigue fracture and abrasive wear. In general, the dry milling of hardened steel with AlTiN-based coatings gains a quite satisfactory surface quality. Furthermore, AlTiN-WC/C hard-soft multilayer coating performs well in reducing cutting force, preventing adhesion wear and isolating the cutting heat, being suitable for dry milling of hardened SKD11.

Midterm polls will knock Argentine budget off course

Significance The debate has been delayed by November 14 midterm elections. However, the budget has already been criticised both by the opposition, which considers the forecasts excessively optimistic, and by Vice-President Cristina Fernandez de Kirchner (CFK) and her supporters, who believe fiscal tightening in the first half was responsible for the government’s poor performance in the August open primaries. Impacts The 2021 budget deficit will be narrower than initial expectations thanks to the sharp fiscal adjustment in the first half. Next year’s fiscal adjustment will involve cutting energy subsidies, prompting higher tariffs and inflation. Absent new foreign credit, increased Central Bank transfers to the Treasury could fuel an inflationary spiral.

Design of a Pendulum Prototype for Dynamic Testing of Material Removal Using Picks

The need for large and fast excavations, together with noise and vibration limitations, means that mechanical removal is increasingly used rather than blasting. In mechanical removal, the cutting tools hit the rock and penetrate it, and then move in the direction of cutting, dragging and detaching a portion of rock called chip. Most research on mechanical removal approaches it as a static process without taking into account the speed at which the cutting element impacts the rock. This work presents the design of a pendulum equipment capable of simulating the impact of a cutting element, specifically a pick, against a rock, reproducing the removal in a similar way to how it is carried out in real excavations. Cutting tests are carried out with concrete samples with a cement/sand ratio of 1:1 and 3:1, the volume of material that is removed is calculated using a 3D scanner and images of the tests are collected with a high-speed video camera to facilitate the interpretation of the results. The results confirm the direct relationship between impact energy, chip size and cutting depth, prove the formation of an affected zone that allows to reduce the cutting energy, and empirically obtain the optimum cutting energy with which the maximum performance in mechanical removal would be achieved.

Research on cutting performance and fatigue life of conical pick in cutting rock process

The conical pick is the most crucial tool of roadheader for breaking rock, establishing the conical pick cutting rock and conical pick fatigue life numerical simulation models to investigate the influence of cutting parameters on rock damage, average peak cutting force, specific cutting energy and the conical pick fatigue life. The research results indicate that the width and depth of rock damage increase with increasing cutting depth and cutting speed. The average peak cutting force and the specific cutting energy have the same changing tendency. The changing trend of conical pick fatigue life and conical pick stress is opposite relationship. The optimum cutting angle of the conical pick cutting rock is 45°. Applying the research results for guiding the optimization of the cutting parameters reduces the specific cutting energy and stress and improves the conical pick fatigue life.

Experimental Investigation on Dry Routing of CFRP Composite: Temperature, Forces, Tool Wear, and Fine Dust Emission

This article presents the influence of machining conditions on typical process performance indicators, namely cutting force, specific cutting energy, cutting temperature, tool wear, and fine dust emission during dry milling of CFRPs. The main goal is to determine the machining process window for obtaining quality parts with acceptable tool performance and limited dust emission. For achieving this, the cutting temperature was examined using analytical and empirical models, and systematic cutting experiments were conducted to assess the reliability of the theoretical predictions. A full factorial design was used for the experimental design. The experiments were conducted on a CNC milling machine with cutting speeds of 10,000, 15,000, and 20,000 rpm and feed rates of 2, 4, and 6 µm/tooth. Based on the results, it was ascertained that spindle speed significantly affects the cutting temperature and fine particle emission while cutting force, specific cutting energy, and tool wear are influenced by the feed rate. The optimal conditions for cutting force and tool wear were observed at a cutting speed of 10,000 rpm. The cutting temperature did not exceed the glass transition temperature for the cutting speeds tested and feed rates used. The fine particles emitted ranged from 0.5 to 10 µm aerodynamic diameters with a maximum concentration of 2776.6 particles for those of 0.5 µm diameters. Finally, results of the experimental optimization are presented, and the model is validated. The results obtained may be used to better understand specific phenomena associated with the milling of CFRPs and provide the means to select effective milling parameters to improve the technology and economics of the process.

Experimental technique to analyze the influence of cutting conditions on specific energy consumption during abrasive metal cutting with thin discs

Specific energy consumption is an important indicator for a better understanding of the machinability of materials. The present study aims to estimate the specific energy consumption for abrasive metal cutting with ultra-thin discs at comparatively low and medium feed rates. Using an experimental technique, the cutting power was measured at four predefined feed rates for S235JR, intermetallic Fe-Al(40%), and C45K with different thermal treatments. The variation in the specific energy consumption with the material removal rate was analyzed through an empirical model, which enabled us to distinguish three phenomena of energy dissipation during material removal. The thermal treatment and mechanical properties of materials have a significant impact on the energy consumption pattern, its corresponding components, and cutting power. Ductile materials consume more specific cutting energy than brittle materials. The specific cutting energy is the minimum energy required to remove the material, and plowing energy is found to be the most significant phenomenon of energy dissipation.

A Systematic Method of Optimization of Machining Parameters Considering Energy Consumption, Machining time and Surface Roughness with Experimental Analysis

For improving energy efficiency of machining process, extensive studies have focused on how to establish energy consumption model and optimize cutting parameters. However, the existing methods lack a systematic method to promote the widespread use of energy efficiency methods in the industry. This paper proposes a systematic method integrating energy model, experiment design, and multi-objective optimization model. Firstly, the energy model is established considering cutting energy and non-cutting energy. Then, the orthogonal experiment is designed with the three levels of four factors of spindle speed, feed speed, cutting depth, and cutting width in the X and Y cutting directions. The data of energy consumption, surface quality and machining time are obtained to study the effects of different cutting elements and cutting directions. Meanwhile, the standby, spindle idling, feed, SEC, material cutting and idling feed models of the CNC machine tools are established based on the experimental data. In addition, for verifying the accuracy of the established energy consumption model, five sets of experimental data are tested that show the prediction accuracy can reach 99.4%. Finally, a multi-objective optimization model for high efficiency and energy saving of processing process is establishes to optimize the cutting parameters from the three perspectives of energy consumption, processing time and surface quality. Combining the case of milling with constraints including machine tool performance, tool life, processing procedures, and processing requirements, the Pareto solution set is used to solve the Pareto of the target model. Through drawing a three-dimensional needle graph and two-dimensional histogram, the optimal cutting parameter combination for rough machining and semi-finish machining are provided, assisting in promoting the application of the sustainable techniques in the industry.