Effect of sphere configurated particle damper on tribological properties during boring of hardened steel

Tool vibration is the most unfavourable element in the boring operation, as it contributes to poor surface finish, excessive tool wear, and progressive cutting force. Tool vibration mainly occurs due to the overhanging length of the boring tool and to overcome this factor an appropriate mechanism has to be established which helps to increase the production and quality of the product in manufacturing sector. An impact particle damper with variable material spheres, sphere diameter, and sphere location in a boring tool is fabricated in this work. A 27 run experiments were conducted to find the effect of impact particle damping on tribological properties during boring process. The results shows that impact particle damper increases the rigidity of the tool holder which enhances the tribological properties. The sphere in the boring tool will collide with one another thereby suppressing the tool vibration efficiently.

Optimization Research of Machining Parameters for Cutting GH4169 Based on Tool Vibration and Surface Roughness under High-Pressure Cooling

The nickel-based superalloy is widely used in aerospace. It is a typical difficult-to-cut material with poor plasticity. During the cutting process, the fluctuation of the cutting force caused by the change of cutting conditions can aggravate tool vibration, thereby reducing the surface quality of the machined workpiece. However, the emergence of high-pressure cooling technology provides technical support for overcoming the difficulty in superalloy processing. Therefore, it is of great significance to optimize the tool vibration and surface roughness of cutting GH4169 under high-pressure cooling. Taking GH4169 as the research object, the single-factor and orthogonal high-pressure cooling cutting experiments were conducted firstly in this paper. Then, the methods of the main effect diagram and response surface were applied to analyze the impact of cutting speed, feed rate, cutting depth, and cooling pressure on the three-way tool vibration. Next, MATLAB was adopted to draw the frequency spectrum of radial tool vibration at different cutting speeds, and the relationship between chip morphology, tool vibration, and workpiece surface roughness at different cutting speeds was discussed. Based on this, a mathematical model of radial tool cutting vibration and surface roughness related to the cutting amount and cooling pressure was established. Support vector machine (SVM) was applied to make predictions. Meanwhile, the non-dominated sorting genetic algorithm with an elitist strategy was adopted for multi-objective optimization, and the optimization results were verified through experiments. The results indicated that the feed rate and cutting depth had a great impact on the tool vibration and surface roughness. The established mathematical model was accurate and effective for optimizing the cutting parameters. These results are of great significance to improve the cutting stability and the quality of machined surface.

Effects of Process Parameters On Tool Vibration And Force Transmissibility In High-Speed Micro-Milling Machine

High-speed micro-milling is an emerging technology used to produce micro and miniaturized products with smooth surface finish and high dimensional precision. However, tool vibration is a major problem in micro-milling as it directly affects the product accuracy, surface quality and tool life. Inappropriate selection of process parameters increases radial and axial thrust as well as force transmitted to structure during micro-machining which results in rapid tool vibration. This work focuses on the experimental investigation of process parameters (cutting speed and depth of cut) in order to reduce tool vibration due to axial and radial thrust in high-speed micro-milling. The tool used in this experiment is a 2-flute end mill cutter (1 mm cutter diameter) and workpiece is a commercially pure titanium (CpTi) plate. The operation was performed at different depth of cut and varying cutting speeds keeping the chip load constant. Vibration signals were acquired and processed to obtain the vibration thrust of the tool and the force transmitted to the structure. The results indicated that as the depth of cut and cutting speed increases, both axial as well as radial thrust decreases leading to lower vibration amplitude of the cutting tool and reduction in force transmitted to the machine structure.

On Force-Displacement Characteristics and Surface Deformation in Piezo Vibration Striking Treatment (PVST)

This paper presents an experimental study on a novel mechanical surface treatment process, namely piezo vibration striking treatment (PVST), which is realized by a piezo stack vibration device installed on a CNC machine. Unlike other striking-based surface treatments, PVST employs non-resonant mode piezo vibration to induce controllable tool strikes on workpiece surface. In this study, an experimental setup of PVST is implemented. Four types of experiments, i.e., tool-surface approaching, single-spot striking, 1D scan striking, and 2D scan striking, are conducted to investigate the relationships among the striking force, tool vibration displacement, and surface deformation in PVST. The study shows that PVST can induce strikes with consistent intensity in each cycle of tool vibration. Both the striking intensity and striking location can be well controlled. Such process capability is particularly demonstrated by the resulting texture and roughness of the treated surfaces. Moreover, two linear force relationships have been found in PVST. The first linear relationship is between the striking force and the reduction in vibration amplitude during striking. The second one is between the striking force and the permanent indentation depth created by the strike. These linear force relationships offer the opportunity to realize real-time monitoring and force-based feedback control of PVST. This study is the first step towards developing PVST as a more efficient deformation-based surface modification process.

Effect of indirect cryogenic cooling on the machining accuracy and tool vibration in the turning of polysulfone

Cutting deformation and cracks are common problems during the machining of precise polymer parts. This paper aims to explore the effect of different conditions on the contour profile of machined surfaces and tool vibration. Turning experiments of polysulfone (PSU) were performed under three conditions: dry, conventional flood cooling, and indirect cryogenic cooling. Then the formation mechanism of machined surfaces contour profile under different cutting conditions was clarified by the Eyring equation from the perspective of molecular chains relaxation time. Furthermore, extension models of crazing and cracks were proposed through the microscopic morphology of machined surfaces and the discriminant formula of crazing generation to explain the differences in tool vibration. The results indicated that the indirect cryogenic cooling condition with the internally cooled cutting tool could significantly improve the machinability of polysulfone, and have an excellent performance on the contour profile of machined surfaces with and the inhibition of crazing. Compared with dry and conventional flood cooling, indirect cryogenic cooling could reduce the mean of the Contour profile (Ra) by 40.3% and 30.1% and the machining accuracy error by 41% and 83%. The indirect cryogenic cooling method proposed in this work provides a reference for the cryogenic machining for polymers.

Study On Cutting Force and Tool Vibration For Optimization of Depth of Cut in Ultra-Precision Planing Process of the Master Mold For Retro-Reflection Film

The micro-triangular pyramid patterns are widely used in advanced optical components with retro-reflection characteristic. The performance of the retro-reflection is affected by an effective area, and it can be maximized by machined surface without defects such as edge blunt, burr, surface roughen. The ultra-precision planing process is well-known that can fabricate superior surface when the depth of cut (DOC) is applied to minimum depth above the critical value to prevent the size effect. However, it was very difficult to determine a DOC without comparing of quality of machined surfaces through the ultra-high magnification measuring instrument such as SEM. In this study, the critical DOC which is key parameter was analyzed using cutting force and tool vibration signals. These signals were converted to specific cutting resistance and frequency spectrum, respectively. As a result, spectrum frequency signal was more effective and accurate than specific cutting energy, and critical DOC was determined to 1µm. This proposed process was validated by comparing the quality variation of the machined surfaces with analysis result based on cutting signals. Finally, a master mold with area of 250mm2 for fabrication of the retro-reflection film was manufactured by applying optimized DOC, and the retro-reflection film was fabricated by press molding process. This retro-reflection film was clearly recognized at a distance of 100m from light source with low power.

Effect of Vibration Direction of Ultrasonic Vibrating Cutting Edge on Internal Stress Fluctuation of Workpiece

The aim of this study is to investigate the dynamic phenomenon of ultrasonic vibration-assisted cutting by utilizing a stress distribution visualization system. The vibrating cutting-edge is considered to be a cause of dynamic changes in the cutting force at ultrasonic frequencies. However, many researchers have explained the effect of ultrasonic vibration-assisted cutting by evaluating the time-averaged cutting force, because existing dynamometers are unable to measure the dynamically changing cutting force at ultrasonic frequencies. There are some reports that the vibration direction of cutting edge strongly affects tool wear. However, in practical ultrasonic cutting, the vibration of the cutting edge has yet to be measured in a production environment. In this study, the instantaneous stress distribution on the workpiece was visualized by a photoelastic method that combines a pulsed laser emission synchronized with tool vibration. The developed photographic system can capture 360 frames in one ultrasonic vibration period. The dynamic cutting force was calculated by Flamant’s stress distribution theory. It was experimentally confirmed that the stress distribution under vibration-assisted conditions showed periodical changes synchronized with vibration. Because these results are compatible with well-known vibration-cutting theories, the imaging system was able to show the periodic changes in stress distribution in the ultrasonic frequency band. This indicates that the dynamic change in cutting force during the ultrasonic vibration period affects intermittent cutting conditions. In this report, the vibration direction was adjusted from −9.5° to +9.5° along the cutting direction. When the tool moved in upwards for the cutting phase and downwards for withdrawal phase, the stress distribution was continuously observed over one tool vibration period; no intermittent cutting was observed. The locus of the cutting force vector was affected by the ultrasonic vibration direction and rake angle of the cutting tool. A negative rake angle showed that the direction of the cutting force vector shifted toward the workpiece side near the most advanced position of the cutting edge.