Workpiece Temperature Research Articles

Modeling of plasma temperature distribution during micro-EDM for silicon single crystal

In silicon single crystal micro-electrical discharge machining (Micro-EDM), the plasma channel and workpiece temperature field directly affect the machined parts. For Si single crystal, with short single discharge time and small inter-electrode gap, the temperature cannot be easily measured directly. Based on the theory of energy conservation and heat conduction, combined with Micro-EDM process, in this paper, thermodynamic analysis of plasma in Micro-EDM process is conducted, and a plasma temperature distribution model considering latent heat of fusion is established. Adopting Gaussian distribution heat flux boundary condition and the temperature field distribution of the workpiece surface is simulated by FLUENT. The relationship between material removal rate (MRR) and surface roughness (SR) corresponding to temperature distribution under different peak current and pulse width conditions is analyzed. The results show that plasma temperature has a positive correlation with peak current and pulse width. The increase of peak current and pulse width within the processing parameter range leads to the increase of MRR and SR. The experimental results verify the correctness of the model.

A Finite Element Model for Temperature Prediction in Laser-Assisted Milling of AerMet100 Steel

Laser-assisted milling (LAM) represents an innovative process to enhance productivity in comparison with conventional milling. The workpiece temperature in LAM not only affects the cutting performance of materials, but also the machined surface quality of the part. This paper presents a 3D transient finite element (FE) model for workpiece temperature prediction in LAM. A moving Gaussian laser heat source model is implemented as a user-defined subroutine and linked to ABAQUS. The thermal model is validated by machining AerMet100 steel under different process parameters (laser power, spindle speed and feed per tooth). Good agreement between predicted and measured workpiece temperatures indicates that the FE model is feasible. In addition, the effects of laser spot size and incident angle on workpiece temperature are analyzed based on the proposed model. This work can be further applied to optimize process parameters for controlling the machined surface quality in LAM.

HoT Turning Operation in Finite Element Analysis

There is a requirement for materials of high hardness and protection from cutting. As we probably aware the machining of these materials has dependably been an incredible test. Machining of these composites and materials required for cutting high-quality, which now and again isn't prudent and in some cases even illogical. Also, even the non-ordinary procedures are by and large constrained to the perspective of efficiency. The benefits of simple part assembling of exorbitant hard materials can be considerable as far as decreasing expenses and lead times machined contrasted with the customary one includes the warmth treatment, granulating and manual completing/cleaning. In the hot working at a temperature of work piece is expanded in order to decrease its shear quality. This paper will centre around hot working of high manganese steel with oil fuel. A few parameters, for example, cutting pace, feed, profundity of cut and the temperature of the work piece are taken. An investigation was led. Indeed, even the machining process was reproduced in ANSYS and Disfigure 2D to discover relating distortion, rate of hardware wear, cutting power and the temperature dissemination.

Influences of key process parameters on orbital forging of thin-walled smartphone shell frame of aluminum alloy

Smartphone shell frame is a thin-walled component, which is quite difficult to be fabricated by integral die forging process because of narrow die cavity and high forging load. In this paper, an orbital forging process is proposed to forge the thin-walled smartphone shell frame. Firstly, a FE model on orbital forging of thin-walled smartphone shell frame is developed under Deform-3D platform. By using this model, the influences of initial temperature of workpiece T, tilt angle of swing die γ and feed moment per rotation λ on temperature distribution, equivalent strain distribution and forging load are comprehensively discussed. The results show that final temperature of workpiece compared with initial temperature of workpiece T can be improved with decreasing initial temperature of workpiece T, increasing tilt angle of swing die γ and increasing feed moment per rotation λ. Equivalent strain is positively correlated with tilt angle of swing die γ, negatively correlated with feed moment per rotation λ and almost unaffected by initial temperature of workpiece T. Moreover, forging load can be obviously reduced by increasing initial temperature of workpiece T, increasing tilt angle of swing die γ and decreasing feed moment per rotation λ.

Thermal Analysis of PA66 Grinding

This work focus on studying the temperatures developed during the grinding of polyamides and correlating it to the surface quality of the machined piece. Parts made of natural polyamide 6/6 (PA66) and polyamide 6/6 with 30% of glass fibers (PA66GF30) were ground using aluminum oxide (Al2O3) grinding wheel. Workpiece temperature during the process was measured using an internally placed thermocouple to avoid cutting fluid interference during the acquisition. Experimental results were elaborated, and the main correlations identified.

Technology Optimization for Producing 110G13P Powder Steel by System Analysis Methods

The paper deals with theoretical aspects of optimizing the structure and properties of 110G13P austenitic powder steel using the system analysis method (Pareto method). The optimal sintering temperature of cold-pressed work pieces is selected using the criterion of maximum wear resistance of steel. Microstructures of 110G13P steel in the selected range of sintering temperatures are given. The dependence of the obtained microstructures on the sintering temperature of samples is shown.

Effect of TiO2 and Al2O3-ethylene glycol-based nanofluids on cutting temperature and surface roughness during turning process of AISI 1018

This paper presents the effect of TiO2 and Al2O3-ethylene glycol based nanofluids on cutting temperature and surface roughness during turning process of AISI 1018. Minimum quantity lubrication (MQL) method has been recognized in minimizing the usage of cutting fluid, as a step to achieve cleaner environment and sustainable machining. However, the low thermal conductivity of base fluid in minimum quantity lubrication system caused the insufficient removal of heat generated in cutting zone. Addition of nanoparticles to the base fluid was then introduced to enhance the performance of cutting fluids. In this study, the machinability of AISI 1018 (mild steel) was investigated under dry machining and nanofluid minimum quantity lubrication method. Two types of nanofluids (TiO2 and Al2O3 nanofluid) with concentration 0.05, 0.15 and 0.3 wt.% were used in this study. The experiments were conducted on lathe machine, using tungsten carbide as cutting tool. Three cutting speed (350, 550 and 750 m/min), three depth of cut (0.5, 1.0 and 1.5 mm) and fixed minimum quantity lubrication system nozzle pressure (5 bar) were applied throughout turning operation. To determine the relationship between machining parameters and cutting temperature and surface roughness values were measured. Based on results obtained, the cutting temperature of workpieces with usage of nanofluids in MQL system gave lower value compared to dry machining. The surface roughness of machined parts was also improved under NFMQL methods. In conclusion, when the nanofluid-MQL method was employed, the amount of cutting fluid was reduced and machining performance improved.

Electromagnetic and Thermal Analysis of Cylindrical Aluminum Billet Heated by 1MW HTS DC Induction Heater

In order to improve the efficiency of the conventional AC induction heater, an HTS DC induction heating technology has been proposed. A 1MW HTS DC induction heater has been developed, and the efficiency of the HTS DC induction heater can be more than 80% due to the HTS DC magnet with no AC loss. The electromagnetic and thermal analysis of the HTS DC induction heater is necessary for further optimization of the 1MW HTS DC induction heater. A 3D finite element simulation model for the coupling analysis of electromagnetic and thermal has been built based on the actual 1MW HTS DC induction heater and optimized for accelerating the computing speed by using permanent magnet instead of the HTS magnet. The heating process of the cylindrical aluminum billet has also been simulated and compared with the experimental results. The results show that the simulation results can be in line with the experimental results. What is more, the optimized simulation model can be used to further optimize the device parameters for different workpiece temperature distributions, or design and evaluate the new HTS DC induction heater in the future.

A Study on the accuracy of Thermography-based Temperature measurement in Powder-fed directed energy deposition

Due to continuous development and increasingly deep understanding of the additive process, directed-energy deposition (DED) is becoming more and more interesting for industrial use. However, both the number of influencing factors and the process complexity, still require well-trained operators who can monitor and understand the machine tools. In order to facilitate the operators and to enable longer unattended processes, higher process safety, reliable monitoring systems and closed-loop controller are required. For example, despite a large number of investigations, the monitoring and control of the temperature distribution within the work piece still poses a big challenge.This study focusses on workpiece temperature measurement using a thermal imaging camera that observes the entire machining area. In order examine the measurement error caused by different viewing angles (φ = 0 … 75°), object temperatures (T = 333 … 1073K), surface conditions (welded and milled) and materials (316L, Inconel 718 and CuAl10) commonly used in DED, several approaches were followed using a thermal camera.It was found that surface condition and material cause the greatest measuring errors (up to +325K |−453K).). However, the measuring errors can be significantly reduced by suitable selection of the emissivity, so that it is possible to measure even the milled CuAl10 surface at a known viewing angle with a measuring error of +13.3% |−10.9%.

Final and element modeling of workpiece temperature at the combined grinding

The combined grinding is characterized by simultaneous preliminary and final machining of workpiece on one machine tool without replacement a coarse-grained on a fine-grained grinding wheel, that allows to reduce the main and auxiliary time for performance of technological operation, and, therefore, to increase grinding process productivity. Entry and boundary conditions of computer modeling of the maximum temperature of the processed surface at the combined and traditional grinding are defined. Modeling of surface temperature is carried out in the modern Solid Works software product for simultaneous grinding by wheels with various characteristic of abrasive material, what in scientific-technical literature was not considered earlier. Models of the maximum temperature of the processed surface in a function of removed overmeasure, longitudinal and cross-feed of workpiece, on the basis of which the cutting regime of the combined flat peripheral grinding, providing elimination of thermal damage of the processed blanket, is appointed are established.

Prediction and optimization of work-piece temperature during 2.5-D milling of Inconel 625 using regression and Genetic Algorithm

The estimation of heat distribution during metal cutting is essential, as it contributes in workpiece deflection and quality of the machining. Inconel 625 is a high strength nickel-based superalloy...

A Numerical Model for Heat Transfer in Dry and Wet Grinding Based on the Finite Difference Method and Jet Cooling

AbstractGrinding is a promising machining method for finishing workpieces that need a smooth surface with tight tolerances. Due to the high thermal energy generated in the grinding zone, an accurate prediction of workpiece temperature plays a crucial role in the design and optimization of the grinding process. Finite difference method (FDM) is used for simulating the temperature distribution in a workpiece subjected to shallow grinding using a DuFort–Frankel explicit scheme. Moreover, two simple methods, one for modeling the effect of material removal in shallow grinding and the other for calculating the heat partition, are presented. A semi-empirical correlation of cooling jet is applied to calculate the convection heat transfer coefficient (CHTC) over the grinding surface. Experiments were carried out to verify the simulation results, and a good agreement was observed between the simulation and experimental data. An analysis of the results indicated that the misestimation of workpiece temperature could occur when the effect of the material removal rate is not considered in the simulation. The simulation results showed that the heat flux flow is one-dimensional for a high Peclet number, while a two-dimensional heat flux flow prevails for a low Peclet number. The results revealed that reducing the Peclet number and extending the depth of cut increase the heat partition. The study of wet grinding demonstrated that, for efficient cooling, the coolant should be applied directly to the contact zone. Moreover, using water-based emulsion as a coolant was more effective than palm and sunflower oils.

Thermal analysis and machinability for laser-assisted machining of fused silica

Machining of fused silica to obtain high precision dimension and surface property has been an industry wide problem. In this study, laser-assisted machining (LAM) of fused silica has been introduced with three-dimensional thermal models been built to perform detailed analysis. The accuracy of the model is validated by measuring the temperature of workpiece and poly crystalline diamond (PCD) tool. The appropriate combination of machining parameters has been analyzed, as well as the temperature distribution at material removal layer, cutting zone of workpiece and PCD tool. A uniform temperature distribution is obtained at workpiece surface, with a very small temperature gradient of 20 K at the radial depth range of 100 µm after preheating. Although the temperature at cutting zone of workpiece is 1490 K, it is much lower at nose of tool with a value of 510 K, which is contrary with common belief. In addition, the experiments under higher temperature in LAM and lower temperature in conventional machining (CM) are carried out to study the machinability with respect to subsurface damage, chip morphology and tool wear. The results indicate that the machinability in LAM of fused silica is greatly improved, attributed to the maintenance of excellent performance of the PCD tool, and along with the changes in hardness, strength and viscoplasticity of fused silica.

Characterization of tribological conditions within direct hot stamping

Abstract The aim of this study is to create a detailed process understanding regarding the tribological conditions within direct hot stamping. Hot stamping has established as a common technology for manufacturing safety-relevant components in modern car bodies. However, due to the high forming temperatures within hot stamping applications, no suitable lubricants have been developed yet. As a consequence, high friction and severe wear occur during the forming. This affects the tool wear as well as the resulting part quality. For improving the robustness and the efficiency of industrial hot stamping processes, future measures to reduce the tribological loads have to be found. The key to the development of such measures is a detailed process understanding of the tribological conditions. Within this study, friction and wear are analyzed for different workpiece and tool temperatures, relative velocities and contact pressures. Based on the experimental results, detailed knowledge of the critical cause-effect relations between process parameters and tribological behavior is acquired. The friction behavior is analyzed via strip drawing experiments under hot stamping conditions. The amount of wear is determined via confocal microscopy measurements before and after the experiments. The results of this study help to improve the process understanding of the tribological conditions within the hot stamping process and to develop future measures for reducing tool wear.

Atmospheric pressure plasma jet and minimum quantity lubrication assisted micro-grinding of quenched GCr15

High-strength alloys have significant application values in aerospace industry due to their excellent mechanical properties. However, grinding of these alloys, which is generally used for precision machining, suffers from problems like high grinding temperature and poor surface quality. Having relatively lower grinding temperature and smaller grinding force, micro-grinding is a high-efficient manufacturing method for precision machining of difficult-to-cut materials. Nevertheless, the side effects induced by current composite grinding methods, such as temperature gradient and chatter marks, tend to be more obvious in the micro-machining process. Atmospheric pressure plasma jet (APPJ) can effectively improve metal surface wettability without changing surface structures. On the other hand, minimum quantity lubrication (MQL) can more efficiently cool and lubricate the grinding area. Here, we propose to induce APPJ and MQL cooling media into the micro-grinding area, and adjust the cooling and lubricating characteristics. Quenched GCr15 workpieces are machined under five different conditions (dry micro-grinding, nitrogen jet assisted micro-grinding, APPJ assisted micro-grinding, MQL assisted micro-grinding, and APPJ+MQL assisted micro-grinding), and grinding temperature, grinding force, surface roughness, and surface morphology of workpieces in each group are investigated and analyzed. The results indicate that APPJ can reduce grinding force and that APPJ+MQL micro-grinding can obtain surfaces with much better surface quality. Tensile experiments demonstrate that APPJ can reduce material elongation rate and promote material fracture, which contributes to its positive effect on the micro-grinding process. The environmentally-friendly method is expected to have promising application potentials in machining of difficult-to-cut materials.

Response optimization using VIKOR while machining on lathe under dry and minimum quantity and lubrication conditions – A case study

Multi-response optimization is frequently used in metal cutting research for determining cost and time effective machining parameter combinations. Apart from it, eco-friendly machining on other hand had gained greater importance. Hence this paper deals in multi-response optimization of process factors using VIKOR method on surface roughness, tool and workpiece temperatures. Process factors like cutting speed, tool feed and tool depth of cut in dry and minimum quantity cooling and lubrication (mqcl) conditions as eco-friendly machining are adopted in turning operations on AISI 316L workpiece material. This paper shows novelty of comparison between two different machining environments on same workpiece material with same process factors and design of experiments. Analysis of Variance and Regression analysis for compatibility of process factors with responses is also been carried.

Molecular dynamics simulation of chip formation mechanism in single-crystal nickel nanomachining

Nanometric machining simulations of single-crystal nickel were performed using molecular dynamics. The atomic displacement vector method was applied to study the relationship between defect displacement vectors and the crystal slip system during different deformation stages as well as the displacement trend characteristics of workpiece atoms under different deformations. The arrangement characteristics of atoms in the machining region, relative density of atoms at different machining zones, and proportion of different atoms were investigated in detail. In addition, the atom shunt phenomenon was observed by studying the displacement trend of the atoms adjacent to the machining tool, and a method for determining the location of the shunt point was determined. Moreover, direct evidence of crystal transition caused by temperature was obtained. The effects of machining depth on workpiece damage, surface flatness, and workpiece temperature were investigated. With increasing machining depth, the chip gradually changed from spherical to strip-shaped, the damage depth of workpiece gradually increased, but the atomic arrangement of the machined surface became neater. Simultaneously, the dislocation reaction of subsurface defects was studied, and the rationality of the reaction was analyzed using an energy criterion. Furthermore, the overall temperature of the workpiece increased, but the temperature of the chip part gradually decreased.

An investigation of surface topography and workpiece temperature in whirling milling machining

Surface topography and workpiece temperature are the foremost characteristics for the service performance of the workpiece. The main objective of this paper is to develop a surface topography (including scallop height and waviness) model and a workpiece temperature model for the optimal machining strategy in ball screw whirling milling. The geometry of the tool and workpiece during the machining are analyzed to reveal the process of the chip generation, cutting tool trajectory and relative motion of the tool-workpiece. Furtherly, theoretical models for predicting the surface topography and temperature of the workpiece are developed, in which the cutting conditions, tool geometry, un-cut chip thickness and area are taken into consideration. The effectiveness of the proposed models is verified by cutting experiments on a whirling milling machine. The analysis of sensitivity factors indicates that the maximum depth of cut makes a great influence on surface topography, while the cutting velocity and maximum depth of cut make a great influence on workpiece temperature. Moreover, the optimal machining strategy to minimize the workpiece temperature and achieve a certain surface topography is proposed in the process of ball screw whirling milling.

FAST AND COST EFFICIENT MEASURING OF GEOMETRY AND TEMPERATURE FOR OPEN-DIE FORGING

In open-die forging it is state of the art to use simulation tools for creating forging plans and setpoint values for the forging press and the automated part manipulator. These forging plans define required positions and forces. Therefore, the process can be fully automated. However, even small variations of not considered influence parameters lead to different forging results and thus to a discontinuous process. Influencing factors are, e.g. material parameter deviations, uncertainties in force measurements or variations in the part temperature due to varying environmental conditions. This paper presents an approach for a fully automatic open-die forging process with respect to actual conditions, based on a parallel measurement of the workpiece geometry and temperature and a “process-real-time” adaptation on the controller system. The focus of this work is the development of a measuring strategy and an according sensor setup for the combined temperature and geometry measurement of the workpiece. In addition, the structure, the characteristic features of the components and the beam path of the sensors scanning units are shown. Furthermore, first experimental results for the alignment of the beam path are presented. In the outline, the setup and calibration strategy of the measurement system are stated.

Precision Core Temperature Measurement of Metals Using an Ultrasonic Phase-Shift Method

Temperature measurement is one of the most important aspects of manufacturing. There have been many temperature measuring techniques applied for obtaining workpiece temperature in different types of manufacturing processes. The main limitations of conventional sensors have been the inability to indicate the core temperature of workpieces and the low accuracy that may result due to the harsh nature of some manufacturing environments. The speed of sound is dependent on the temperature of the material through which it passes. This relationship can be used to obtain the temperature of the material provided that the speed of sound can be reliably obtained. This paper investigates the feasibility of creating a cost-effective solution suitable for precision applications that require the ability to resolve a better than 0.5 °C change in temperature with ±1 °C accuracy. To achieve these, simulations were performed in MATLAB using the k-wave toolbox to determine the most effective method. Based upon the simulation results, experiments were conducted using ultrasonic phase-shift method on a steel sample (type EN24T). The results show that the method gives reliable and repeatable readings. Based on the results from this paper, the same setup will be used in future work in the machining environment to determine the effect of the harsh environment on the phase-shift ultrasonic thermometry, in order to create a novel technique for in-process temperature measurement in subtractive manufacturing processes.