Speed Of Worktable Research Articles

Study on new magnetorheological chemical polishing process for GaN crystals: polishing solution composition, process parameters, and roughness prediction model

High-quality and high-efficiency processing of gallium nitride (GaN) crystals is urgently required for optoelectronic communications and other major industries. This study proposes a novel high-efficiency non-damage magnetorheological chemical polishing (MCP) process to overcome the existing problems of low efficiency and lattice distortion during processing. The effects of the MCP fluid composition and key processing parameters on the surface roughness and material removal rate (MRR) of GaN crystals were studied experimentally. The results showed that a compounded abrasive containing silica fluid exhibited better polishing effects than a single abrasive. The polishing efficiency could be improved by adding NaOH solid particles, and the MRR reached 13.19 nm min−1 when the pH of the MCP fluid was 10. The MRR increased gradually with an increase in the pole rotation speed and worktable speed and a decrease in the polishing gap. The surface roughness of the GaN crystals was improved from Ra 115 nm to Ra 0.375 nm after polishing for 4 h. The surface and sub-surface damage of the polished GaN crystals was analyzed using scanning electron microscope and transmission electron microscope. The results confirmed that the MCP process can realize the non-damage polishing of GaN crystals. Moreover, a prediction model for the surface roughness of GaN crystals in the MCP process was constructed. The overall difference between the actual and predicted surface roughness values for the model was 11.6%.

Dynamic positioning error analysis and modeling of CNC machine tool guideway system

The dynamic characteristics of the XY worktable are thoroughly analyzed in this study to accurately compensate the measurement errors of on-machine measurement systems caused by the dynamic and static characteristics under multiple factors. The dynamic positioning error model of the XY worktable motion components is established, and the theoretical model of the dynamic positioning error of the XY worktable is derived. The actual parameters of the experimental platform for the correlation error of CNC machine tools are substituted into the model for theoretical calculation and analysis. Results show that the motion speed of the worktable, the weight of the measured workpiece, the installation position of the workpiece, and the friction force are the main factors causing the dynamic positioning error. Dynamic positioning error analysis and verification experiments were conducted to verify the validity of the proposed theoretical model. Experimental results show that a regular change occurs between the dynamic positioning error and the movement speed of the XY worktable, and the actual measurement results are basically consistent with the theoretical calculation results. The research results can lay a good foundation for establishing the measurement error prediction and compensation model of on-machine measurement systems of CNC machine tools and improving its measurement accuracy.

A comparative study of two indirect methods to monitor surface integrity of ground components

One of the major challenges in grinding is to conciliate the material removal rate with components free from damages. Due to the poor thermal conductivity of conventional grinding wheels, most of the heat generated during grinding is transferred to the workpiece surface and subsurface, which can cause thermal damages and impair the performance in service of machined components. Hence, it is very important to monitor the grinding process to ensure the quality of the machined parts. Thus, this work presents an innovative study comparing two indirect monitoring methods in monitoring surface integrity of steel during grinding: the acoustic emission technique and the electromechanical impedance technique. Worktable speed and radial depth of cut were used as input parameters. Visual inspection and scanning electron microscopy images of ground surfaces as well as microhardness were the output variables used to assess surface integrity and to establish a relationship with the acoustic emission and electromechanical impedance techniques. Since the acoustic emission signals are non-stationary in nature, these signals were analyzed in the time–frequency domain by applying the short-time Fourier transform and the continuous wavelet transform. The root mean square deviation index was extracted as feature from the acoustic emission and electromechanical impedance signals. Results showed that both techniques presented similar results. The root mean square deviation index showed a good correlation with alterations in surface integrity under the conditions investigated.

Investigations on wear characteristics of Stellite coating by micro-plasma transferred arc powder deposition process

This paper reports on investigations of wear characteristics of the Stellite 6 coating on AISI 4130 steel substrate using micro-plasma transferred arc (µ-PTA) powder deposition process. Effects of plasma power, powder mass flow rate and travel speed of worktable have been studied in terms of secondary dendritic arm spacing, microstructure, dilution, line scan analysis and microhardness for enhancement of wear resistance of the Stellite coating. Travel speed of worktable was found to be the most important parameter affecting wear characteristics of Stellite coating. Its higher value gives smaller secondary dendritic arm spacing (SDAS) value and minimum dilution with almost no transfer of iron to Stellite coating. Analysis of microstructure, energy-dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD) patterns revealed that the produced Stellite coating had a lamellar structure consisting of α-Co and ε-Co phases, chromium-rich carbides (Cr23C6 and Cr7C3) and tungsten-containing compounds (W2C). These carbides are responsible for imparting the higher hardness and wear resistance to the Stellite coating. Analysis of microhardness and wear found that higher travel speed of worktable also results in a lower coefficient of friction, specific wear rate coefficient and wears volume and higher microhardness. It can be concluded from this work that micro-PTA process has a capability to selectively deposit a thin and sound quality coating of Stellite on metallic substrates thus providing the techno-economic solution to their wear problems.

ELID grinding characteristics of SiCp/Al composites

In this study, electrolytic in-process dressing (ELID) grinding experiments were conducted on SiCp/Al composites, and the effects of grinding depth and feed speed of work table on grinding force, surface roughness, and surface morphology were investigated. The experimental results showed that the fluctuation range of grinding force and grinding force ratio Cf under ELID condition were smaller than that of the same grinding parameters under wet grinding condition. Additionally, ELID grinding is effective in providing the uniformly grit protrusion and chip storage space. SiC particles were removed in ductile mode, and the brittle fracture of SiC particles were reduced substantially. The high integrity surface of the SiCp/Al composites could be obtained under ELID condition.

Mirror Grinding Process Parameter Selection and Design

Mirror grinding mainly depends on the precision of the machine tool, cutting and grinding amount and wheel selection and dressing. This paper mainly studies the MG1432 high-precision universal cylindrical grinder, exploring the impact on the workpiece roughness through selection and design of various process parameters in grinding, such as changing work table speed in dressing the grinding wheel and grinding, workpiece linear velocity and excessive feeding. The experimental conditions were: Using resin binder white corundum graphite grinding wheels, workpiece: GCr15 (HRC60); dressing tool: sharp single particle diamond correction pen, and ultimately achieving mirror grinding process results.

Simulation of Temperature Distribution in HFCVD Diamond Films Growth on the End Surfaces of Seals

The uniform temperature flied of substrates is a key factor to deposit high-quality diamond films on milling tools by the hot filament chemical vapor deposition (HFCVD). In this study, a 3-D computational model is established to simulate the temperature distribution on the substrates. Thereafter, the influence of the rotational speed of worktable n and the water flux of water-cooled worktable Q are investigated. The simulation results show that the increasing of the rotational speed of worktable is suitable to grow homogeneous diamond films and gently decrease the even temperature of seals. What’s more, the deceasing of the water flux will significantly increase the overall temperature of seals.

Distribution of the Convection Heat Transfer Coefficients of Grinding Fluids along the Contact Zone in High Speed Grinding

The local distribution of the convection heat transfer coefficient (CHTC) of grinding fluids along the wheel-work contact zone under high speed grinding conditions has been investigated. A new approach has been proposed to derive the distribution of CHTCs along the contact zone by using the measured grinding temperatures and linking the distribution of local heat flux and heat partitioning to the workpiece, wheel and grinding chips. It has been found that the worktable speed is the key factor affecting the pattern of CHTC distribution, whilst the grinding speed strongly affects the overall magnitudes of the CHTCs. Down grinding mode is beneficial for achieving effective cooling under creep-feed conditions. The distribution of CHTC under faster worktable speeds shows a rather different pattern, which has to be considered when selecting the grinding mode and grinding fluid supply strategy.Keywords: Grinding, Fluid, Convective heat transfer coefficients, Temperature, High speed

Application of artificial neural network for the prediction of laser cladding process characteristics at Taguchi-based optimized condition

This paper presents an investigation on the optimization of multiple performance characteristics during CO2 laser cladding process considering clad width and clad depth as performance characteristics. This optimization for multiple quality characteristics has been done using Taguchi’s quality loss function. The process model for laser cladding operation using various techniques like artificial neural network (ANN) has rarely been found in the literature review. In the present work, a number of experiments have been performed to establish the interrelationship between process variables and response variables using the back propagation method of ANN. The essential input process parameters are identified as laser power, scan speed of work table, and powder feed rate. Moreover, the analysis of variance is also employed to determine the contribution of each control parameter on clad bead quality. In order to validate the predicted result, an experiment as confirmatory test is carried out at the optimized cladding condition. It is observed that the confirmatory experimental result is showing a good agreement with the predicted one. However, it has been found that the optimum condition of the cladding parameters for multi-performance characteristics varies with the different combinations of weighting factors.

Experimental Study of Grinding Characteristics on SiCp/Al Composites

This paper deals with the grinding performances of SiCp/Al composites with higher volume fraction and larger SiC particle. The effects of the grinding parameters on the grinding force, removal mechanisms of SiC particles have been investigated. The grinding tests were carried out by using diamond wheel on surface grinding machine. The results indicate that the feed speed of worktable has more significant effect on the grinding forces than that of grinding depth. The scanning electron microscopic images of the machined surfaces indicate that the material removal of SiC particles was primarily due to the failure of the interface between the reinforcement and matrix, and resulting from microcracks along the interface and many fracture or crushed SiC particles on the ground surface.

Brittle-Ductile Transition in the Two-Dimensional Ultrasonic Vibration Grinding of Nanocomposite Ceramics

Based on impulse theories and indentation fracture mechanics, the motion model of the contact between abrasive particle and workpiece in workpiece two-dimension ultrasonic vibration grinding (WTDUVG) was analyzed, and the critical condition of ultrasonic vibration grinding brittle-ductile transition was analyzed theoretically, furthermore the critical cutting depths of a grain under different grinding conditions were obtained by Matlab programs. In this work, the ultrasonic vibration and conventional diamond grinding of Al2O3/ZrO2 nanoceramics were performed in order to investigate the effect of workpiece ultrasonic vibration on the brittle-ductile transition mechanism, the effect of grit size, worktable speed and grinding depth on the critical depth of cut were studied by grinding experiments. the micro-topography of the grinding surface was observed by AFM and SEM. Experiment indicated that only when the grinding depth less than critical grinding depth, ductile regime grinding of ceramics can be realized, the appropriate grinding parameter on surface finish are suggested.

Experiment Research on Temperature Field in Ultrasonic Assisted Grinding Engineering Ceramics

As one of the key factors grinding heat has a significant effect on the ground surface quality in grinding engineering ceramics using diamond grinding wheel. Differences between mechanical and physical performances of ceramic materials and grinding parameters have important influences on the surface temperature distribution. In the present research, experiments with/without ultrasonic assistance were carried out to study the temperature characteristics in the grinding field by thermocouple in grinding ZrO2 and Al2O3 engineering ceramics respectively. Moreover, the theoretical analysis and the experiment confirmation for the relationship between grinding parameters and temperature have been discussed. The results show that the further the heat source keeps against grinding surface, the lower the peak value of temperature, and the surface temperature increases with the grinding depth, grinding speed and work table speed. According to the results of orthogonal experiments on grinding parameters, the grinding depth is the most important factor affecting the grinding temperature on the workpiece surface.

Grinding temperature within contact arc between wheel and workpiece in high-efficiency grinding of ultrahard cutting tool materials

This paper describes the grinding temperature characteristics during creep-feed grinding of cermet (Ti(C,N) alloy), which shows extreme difficulty in grinding. Creep-feed grinding is one of the high-efficiency grinding methods, and has inherent thermal problems because there is a long contact arc between wheel and workpiece. Furthermore, as cermet has low thermal conductivity, the grinding temperature tends to rise dramatically. Therefore, measurements of the grinding temperature distribution within the contact arc were made using a thermocouple method. Changes in the temperature distribution during grinding were also examined. It was found that when the grinding temperature within the contact arc reaches 150 °C or more, burnout occurs and the temperature suddenly increases to over 400 °C. The burnout starts from the rear of the contact arc and extends almost throughout the contact arc as grinding progresses. In other words, even if grinding fluid is being supplied, a phenomenon similar to dry grinding occurs in the contact arc in such circumstances. The optimum conditions of wheel and worktable speed were found in order to improve the cooling effects.