Different Depths Of Cut Research Articles

Effects of depth of cut on the redistribution of residual stress and distortion during the milling of thin-walled part

The distortion of thin-walled part is significantly affected by the residual stress generated after the material is cut away. During this process, the relations between the redistributed residual stress and the distortion are quite complex; as a result the control of distortion of thin-walled part always is being considered tough issues. In this study, an approach of optimizing the profile and magnitude of residual stress is proposed by analyzing the effects of depth of cut on the redistribution of residual stress. Experiments and simulations are conducted to compare the cutting forces, temperature and residual stress. The results show that, in the roughing, by selection of a subsequent depth exceeding prior depth of maximum compressive residual stress, the material which contains the main machined residual stress can be removed in favor of the subsequent machining. Furthermore, in the finishing, different depths of cut are utilized in different cutting stages, resulting in smaller magnitude of maximum machined residual stress and depth of maximum compressive residual stress. In addition, to verify the approach, an aviation thin-walled part is used as the experimental object. The results demonstrate that the magnitude of distortion and residual stress can be decreased and optimized efficiently by controlling and optimizing the depth of cut in the roughing and finishing.

Diffusion Wear Mechanism of Single Crystal Diamond Tool in Machining Die Steels

Ultra-precision diamond cutting of ferrous metals has not been successful in application due to significant tool wear. In this work, numerical simulations and experimental investigations are presented in order to study the interface diffusion between diamond tool and workpiece materials. A diffusion model with respect to carbon atoms from diamond tool penetrating into chips and machined surface was established. The numerical simulation results of the diffusion process reveal that the distribution laws of carbon atoms concentration have a close relationship with diffusion distance, diffusion time and the original carbon concentration of the work material. In addition, diamond face cutting tests of die steels with different carbon content are conducted at different depth of cuts and feed rates to verify the previous simulation results. The wear morphology of rake face and flank face of diamond tool were detected by scanning electron microscopy. Energy dispersive X-ray analysis was proposed to investigate the change in chemical composition of the chips and machined surface. The results of this work benefit for a better understanding on the diffusion wear mechanism in single crystal diamond cutting of ferrous metals.

SIMULATION OF NANO-SCALE CUTTING WITH MOLECULAR DYNAMICS

The simulation of nanometric cutting of copper with diamond cutting tools, with the Molecular Dynamics method is considered. A 2D model of orthogonal nano-scale cutting is presented and the influence of the depth of cut and tool rake angle on chip morphology and cutting forces is investigated. For the analysis, three different depths of cut, namely 10A, 15A and 20A and four tool rake angles, namely 0°, 10°, 20° and 30° are tested. Results indicate that with increasing depth of cut, cutting forces also increase, while with increasing tool rake angle, cutting forces decrease. Furthermore, the effect of Lennard-Jones and Morse potentials on final results of the simulation is studied and discussed. The proposed model can be successfully used for the modeling and simulation of cutting operations that continuum mechanics cannot be applied or experimental and measurement techniques are subjected to limitations or it is difficult to be carried out.

Studies on the formation of discontinuous chips during rock cutting using an explicit finite element model

Predicting the fragmentation process during rock cutting poses significant technical challenges. In this respect, previous research related to rock cutting using various numerical methods was reviewed in detail. A method for simulating the fragmentation process during the mechanical cutting of rock was then introduced using the explicit finite element code LS-DYNA. In the numerical simulations, the base rock material properties were defined using a damage constitutive model. This model simulates the separation of rock chips from the base rock material and the subsequent breakage of the chips into multiple fragments. In the simulations, a rigid steel cutting tool was translated at various sliding velocities (1, 4, 10, 50, and 100 mm/s) against a stationary rock material. For a given sliding velocity, simulations were conducted for various cutting depths (1, 2, 3, and 4 mm). The variation of stresses and the amount of chip formation at different depths of cut and velocities were analyzed. The simulations indicated that the cutting forces and chip morphology were significantly influenced by sliding velocities and cutting depths. Overall, the results indicate that the explicit finite element method was a powerful tool for simulating rock cutting and the chip fragmentation processes, as it was able to predict chip separation behavior from the base rock at different depths of cut accurately.

Molecular Dynamics Simulation Study of Grinding Process of Mg-Al Alloy

A molecular dynamics simulation considered of chip deformation and force analysis for grinding process of Mg-Al alloy is presented. Hybrid potentials including embedded atom method (EAM) potential and Morse potential are applied in this model. The activities among atoms of Mg-Al Alloy material is described by EAM potential which is very suitable for metal materials. Morse potential is used to realize the interaction between Mg-Al alloy and abrasive grain made of diamond. Simulations of Different depths of cut (0.6nm, 0.8nm and 1.0nm) and different cut speeds (50m/s, 100m/s and 200m/s) are given. The experience result shows that with the same nanometric depth of cut, there is a little difference of ratio of the cut potential to the cutting speed. Moreover, with the same cutting speed, the cut potential is increased linearly with the depth of cut while reaching to stable cutting regime.

Investigation of Tool Life in Turning of AISI D6 Steel

In this study, AISI D6 cold work tool steel was machined on lathe by using the CBN tools. AISI D6 work pieces hardness before heat treatment was 22 HRc. Heat treatments were implemented to the work piece at 860-880°C for 40 minutes and it was cooled in oil. In addition the work piece was applied tempering procedure for three times at intervals of 3 hours. The hardness of the work piece after heat treatment was 62 HRc. Experiments were conducted under different depth of cuts, cutting speeds and feed rates by using factorial experimental design on a lathe. The cutting speed of 50, 100 and 150, feed rate of 0.1, 0.15 and 0.2 mm/rev, depth of cut of 0.2, 0.4 and 0.6 125 mm were chosen as the experimental conditions. According to the obtained experimental, it was seen that when the cutting speed, feed rate and depth of cut increases and tool life decreases fast.

Effects of Cutting Conditions on the Machinability of Stainless Steel Formed by Laser Cladding

The paper investigates the effects of cutting conditions on the machinability of stainless steel coatings manufactured onto AISI 1045 steel by laser cladding technology. Two kinds of CBN (cubic boron nitride) tools with different corner radius and two different depths of cut were adopted in the experiments. Cutting force during machining, surface roughness and microhardness of machined surface were measured and analyzed. The results show that both the cutting force and surface roughness increase with the increase of depth of cut. When the other cutting parameters are identical, the surface roughness decreases with the increase of tools corner radius while the variations of different cutting force components present different tendencies. The microhardness of the machined surface and its varied gradient in the direction of depth of cut increase with the increase of tools corner radius. The experiment results will provide valuable suggestions for optimization of cutting performance for laser cladding coatings in order to obtain excellent surface quality.

Experimental Investigation of Effect of Tool Length on Surface Roughness during Turning Operation and its Optimization

In the turning operation, vibration is a frequent problem, which affects the result of the machining and in particular the surface finish. Tool life is also influenced by vibrations. Severe acoustic noise in the working environment frequently results as a dynamic motion between the cutting tool and the work piece. In all cutting operations like turning, boring and milling vibrations are induced due to deformation of the work piece. In the turning process, the importance of machining parameter choice is increased, as it controls the surface quality required. Tool overhang is a cutting tool parameter that has not been investigated in as much detail as some of the better known ones. It is appropriate to keep the tool overhang as short as possible; however, a longer tool overhang may be required depending on the geometry of the work piece and when using the holeturning process in particular. In this study, we investigate the effects of changes in the tool overhang in the external turning process on both the surface quality of the work piece and tool wear. For this purpose, we used work pieces of AISI 1050 material with diameters of 20, 30, and 40 mm; and the surface roughness of the work piece were determined through experiments using constant cutting speed and feed rates with different depth of cuts (DOCs) and tool overhangs. We observed that the effect of the DOC on the surface roughness is negligible, but tool overhang is more important. The deflection of the cutting tool increases with tool overhang. Two different analytical methods were compared to determine the dependence of tool deflection on the tool overhang. Also, the real tool deflection values were determined using a comparator. We observed that the tool deflection values were quite compatible with the tool deflection results obtained using the second analytical method.

Investigation on Machining Performance of Inconel 718 under High Pressure Cooling Conditions

The paper deals with the experimental investigation on machinability of Inconel 718 in conventional and various high pressure cooling conditions. The experiments designed based on Taguchi L18 orthogonal array at three different cutting speed, feed rate and pressure levels and two different depth of cuts. The cutting forces and tool flank wear were measured, while turning of Inconel 718 with (Ti,Al)N+TiN coated CNMG0812. In order to determine the importance of cutting parameters on tool flank wear and cutting forces, ANOVA (Analysis of variance) was employed. Moreover, with regression analysis, multi regression equation which indicating relation between tool flank wear, cutting forces and cutting parameters were obtained. The experiment results have proven that the tool flank wear and cutting forces considerably decrease with the use of high pressure coolant. ANOVA results also indicate that high pressure cooling has significant beneficial effect on tool flank wear.

小径エンドミルの二次元モニタリング計測システムと工具挙動 (第2報)

This study presents a two-dimensional monitoring system for precise process control of end milling processes that involve the use of small-diameter tools. This system enables the measurement of tool deflections and cutting forces in two directions : the cutting or tangential direction and the feed or normal direction. Furthermore, this monitoring system makes it possible to estimate periodic changes in tool deflection during a given turn. In this study, this system was applied to side-milling using a small-diameter end-mill. The experiment was performed by end milling a steel plate at different depths of cuts and different radial depth of cuts, and feed rates. Tool behavior in side- milling was examined by this system, and it was compared with the tool behavior examined in slotting. In addition, the relation between the machined form of workpiece and the examined tool behavior was considered. The results of the in-process measurement of tool deflection in side- milling suggest that periodic changes in tool deflection during a given turn are related to the rotation angle of the tool and the number of tool edges. Furthermore, prediction of the machined form of workpiece was found to be possible by estimating tool deflection.

A Force Torsor Analysis for a Turning Process in the Presence of Self-Excited Vibrations

A testing device in turning including, a six-component dynamometer, is used to measure the complete torsor of the cutting actions in the case of self-excited vibrations. For the tests, the insert tool used is a TNMA 160412 type carbide not coated, without chip breaker. The machined material is a chrome molybdenum 42CrMo24-type alloy. The test workpieces are cylindrical and have a diameter of 120 mm and a length of 30 mm. For the first time, we present an analysis of forces and moments for different depths of cut and different feed rates.

MOLECULAR DYNAMICS SIMULATION OF NANOMETRIC CUTTING

Molecular Dynamics (MD) simulations of nanometric cutting of single-crystal copper were conducted to predict cutting forces and investigate the mechanism of chip formation at the nano-level. The MD simulations were conducted at a conventional cutting speed of 5 m/s and different depths of cut (0.724–2.172 nm), and cutting forces and shear angle were predicted. The effect of tool rake angles and depths of cut on the mechanism of chip formation was investigated. Tools with different rake angles, namely 0°, 5°, 10°, 15°, 30°, and 45°, were used. It was found that the cutting force, thrust force, and the ratio of the thrust force to cutting force decrease with increasing rake angle. However, the ratio of the thrust force to the cutting force is found to be independent of the depth of cut. In addition, the chip thickness was found to decrease with an increase in rake angle. As a consequence, the cutting ratio and the shear angle increase as the rake angle increases. The dislocation and subsurface deformation in the workpiece material were observed in the cutting region near the tool rake face. The adhesion of copper atoms to the diamond tool was clearly seen. The same approach can be used to simulate micromachining by significantly increasing the number of atoms in the MD model to represent cutting depths in the order of microns.

INVESTIGATION OF SINGLE-POINT DRESSING OVERLAP RATIO AND DIAMOND-ROLL DRESSING INTERFERENCE ANGLE ON SURFACE ROUGHNESS IN GRINDING

This paper investigates the effect of both single-point and diamond-roll dressing techniques on the workpiece surface roughness in grinding. Two empirical surface roughness models are studied – one that incorporates single-point dressing parameters, and another that incorporates diamond-roll dressing parameters. For the experimental conditions used in this research, the corresponding empirical model coefficients are found to have a linear relationship with the inverse of the overlap ratio for single-point dressing and the interference angle for diamond-roll dressing. The resulting workpiece surface roughness models are then experimentally validated for different depths of cut, workpiece speeds and dressing conditions. In addition, the models are used to derive a relationship between overlap ratio for single-point dressing, and interference angle for diamond-roll dressing such that both dressing techniques produce a similar surface finish for a given material removal rate.

The dependence of tool overhang on surface quality and tool wear in the turning process

Intheturningprocess,theimportanceofmachining parameter choice is increased, as it controls the surface quality required.Tooloverhangisacuttingtoolparameter thathasnot been investigated in as much detail as some of the better known ones. It is appropriate to keep the tool overhang as short as possible; however, a longer tool overhang may be required depending on the geometry of the workpiece and when using the hole-turning process in particular. In this study, we investigate the effects of changes in the tool overhang in the external turning process on both the surface quality of the workpiece and tool wear. For this purpose, we used workpieces of AISI 1050 material with diameters of 20, 30, and 40 mm; and the surface roughness of the workpiece and tool wear were determined through experiments using constant cutting speed and feed rates with different depth of cuts (DOCs) and tool overhangs. We observed that the effect of the DOC on the surface roughness is negligible, but tool overhang is more important. The deflection of the cutting tool increases with tool overhang. Two different analytical methods were compared to determine the dependence of tool deflection on the tool overhang. Also, the real tool deflection values were determined using a comparator. We observed that the tool deflection values were quite compatible with the tool deflection results obtained using the second analytical method.

Distinct element modeling of laser assisted milling of silicon nitride ceramics

Laser assisted milling (LAMill) of ceramics shows some complicated characteristics such as discontinuous chips, crack formation, propagation and coalescence. In this paper, numerical simulation is conducted to explore the machining mechanism of LAMill. The distinct element method (or discrete element method, DEM) is applied to model the microstructure of a β-type silicon nitride ceramic. Clusters are used to simulate the real grain shape of the silicon nitride ceramic and parallel bonds are employed to represent the connections between intergranular glass phase and grains. Numerical tests (compression, bending and fracture toughness tests) are performed to evaluate the macroproperties of the synthetic material, thus matching the corresponding physical properties of the real silicon nitride. Moreover, a temperature-dependent synthetic DEM specimen is created and then used in simulations of LAMill. The DEM model is validated through comparing the simulation results with the experimental ones in terms of the cutting forces and subsurface damage under different depths of cut. It is shown that the model can successfully predict the subsurface damage in LAMill.

Up-milling and down-milling wood with different grain orientations – the cutting forces behaviour

Peripheral milling of wood with up milling and down milling techniques is very well known from a geometrical point of view. However, in processing anisotropic materials such as wood, these geometrical aspects imply relevant differences when machining. In fact, milling of anisotropic material leads to different cutting geometries when up- or down-milling and when increasing or decreasing the depth of cut resulting in different grain orientations depending on the adopted process. In this paper, tests performed when processing Douglas Fir with different depths of cut and grain orientations are described. The cutting forces were measured, and the dependence of the cutting forces with respect on the cutting geometry are analysed and discussed.

Linear stone cutting tests with chisel tools for identification of cutting principles and predicting performance of chain saw machines

Different natural stone quarries are visited for collection of stone samples, determination of geological conditions, specifications and operational conditions of the chain saw machines and recording machine cutting performance with a data acquisition system. The samples are tested with a linear cutting test rig using chisel-type cutting tools with 0°, 15°, 30° and 45° sideways angles at different depths of cut and tool spacings, to determine stone cuttability, cutting characteristics of chain saw machines and effect of unsymmetric and symmetric sideways angles and different cutting patterns on cutting performance (tool forces, specific energy, optimum cutting geometry). A deterministic model is suggested for predicting performance of chain saw machines using the results of linear stone cutting experiments, and the laws of kinematics. The results of experimental studies and in-situ investigations indicate that the cutting action of chain saw machines can be successfully simulated by linear cutting experiments and the suggested model is proven, though requiring some additional study, to be a useful and reliable tool for selection, design, and performance prediction and optimization of chain saw machines.

Up-milling and down-milling wood with different grain orientations – theoretical background and general appearance of the chips

Peripheral milling with up-milling and down-milling techniques is very well known from a geometrical point of view. However, in processing anisotropic materials such as wood these geometrical aspects imply relevant differences when machining. In fact milling anisotropic materials leads to different cutting geometries when up-milling or down-milling and when changing the depth of cut. This results in a relative orientation of the grain depending on the process adopted. In this paper the geometrical interactions between tool and wood grain have been analysed theoretically and supported by experimental evidence. To achieve this result, Douglas fir has been processed with different depths of cut and grain orientations, the resulting chips have been collected and analysed. The experiments show how a shift of the cutting phenomenon and the chip type can be observed to support the theoretical background.

On the temperature field during superficial grinding: an experimental study

Grinding is a mechanical process that involves a great amount of energy per unit volume of removed material. This energy is almost all converted into heat, causing a significant rise of the temperature, mainly on the surface of the workpiece. Therefore, locally, the surface of the workpiece will experience high increases in temperature during small periods of time, while the rest of the part remains at a low temperature. In this work we describe an experimental process to determine the temperature distribution on the workpiece, during a grinding operation. The forces acting on the workpiece and the temperature are measured simultaneously during the grinding process. Two different materials and three grinding wheels were used at three different depths of cut. It is possible to conclude that the high temperatures generated in the surface of the piece depend (among other factors) on the type of the piece material and on the physical characteristics of the used grinding wheels. Additionally, for steels, CBN wheels are the most suitable whenever high superficial temperatures must be avoided since alumina wheels produce temperatures substantially higher. This is a part of a broader work involving finite element method simulation of the grinding process.

EFFECT OF WHEEL WEAR ON CONTACT LENGTH, UNCUT CHIP THICKNESS AND FORCES FOR A DEFORMABLE GRINDING WHEEL AND WORKPIECE

In this paper, contact length, uncut chip thickness, and contact forces were studied as the wheel wore during dry surface grinding of 4130 normalized steel for three different depths of cut (0.0025, 0.005, 0.0075 mm). An aluminum oxide grinding wheel (Norton 38A46HVBE) was used for all the experiments and the work and wheel speeds were 0.22 and 32.3 mis, respectively. In each experiment, the wear flat area, the cutting edge density, the cutting edge width and length were determined using an automated optical measurement system. The grinding forces were measured using a force dynamometer. The contact length was determined using rigid-body, smooth­ body and rough-body contact assumptions. The uncut chip thickness was determined using a continnity analysis. In this approach, the average volume of material is lJrSt determined by dividing the total material removal rate by the number of cutting edges. Then an assumption of the shape of the chip is made. In this work, the uncut chip was assumed to have a triangular profile and a rectangular cross-section. The uncut chip thickness can then be determined by dividing the average chip volume by the average contact length and chip width. In the experiments, grinding forces, wear flat area, cutting edge density increased and uncut chip thickness decreased as a result of wheel wear. In addition, the wheel wear increased the contact length significantly in the rough-body assumption, marginally in the smooth-body. assumption but not in the rigid-body assumption. The normal contact pressure was determined by dividing the normal force by the product of the percent wear flat area and contact area. This result suggested that the rough body assumption represented the data most accurately.