Chip Removal Mechanisms Research Articles

Evaluation of the Surface Topography of Microfinishing Abrasive Films in Relation to Their Machining Capability of Nimonic 80A Superalloy.

This study investigates the surface topography of microfinishing abrasive films and their machining capability on the Nimonic 80A superalloy, a high-performance nickel-based alloy commonly used in aerospace and gas turbine engine applications. Surface analysis was conducted on three abrasive films with nominal grain sizes of 30, 15, and 9 μm, exploring wear patterns, contact frequency, and distribution. To assess the distribution of grain apexes, Voronoi cells were employed. Results revealed distinct wear mechanisms, including torn abrasive grains and cracked bond surfaces, highlighting the importance of efficient chip removal mechanisms in microfinishing processes. Larger grain sizes exhibited fewer contacts with the workpiece but provided more storage space for machining products, while smaller grain sizes facilitated smoother surface finishes. The research demonstrated the effectiveness of microfinishing abrasive films in reducing surface irregularities. Additionally, surface analysis of worn abrasive tools provided insights into wear mechanisms and chip formation, with the segmentation of microchips contributing to efficient chip removal. These findings underscore the significance of selecting appropriate abrasive films and implementing effective chip removal mechanisms to optimize microfinishing processes and improve surface finishing quality in advanced material machining applications. It is worth emphasizing that no prior research has investigated the microfinishing of components crafted from Nimonic 80A utilizing abrasive films, rendering this study truly unique in its contribution to the field.

A New Architecture Paradigm for Tool Wear Prediction during AISI 9840 Drilling Operation

In conventional machining processes based on the chip removal mechanism, the progressive wear of the tool determines a change of the geometric characteristics of the cutting edge. Tool wear is a complex phenomenon and related tool life depends on several factors, such as cutting parameters, lubrication, and tool-workpiece relative trajectories. Tool wear progression affects the quality of the machined parts, making the tool replacement necessary even before its breakage. Moreover, in industrial practice, tool replacement cannot depend on the subjectivity of the operator, thus, the definition of an optimized strategy for cutting tool wear monitoring before tool failure is mandatory. This work compares Random Forest and Neural Network models for predicting tool wear in drilling. For the development of predictive models, tool life tests were performed by drilling through holes on AISI 9840 steel parts, with a coated tungsten carbide drill of 8 mm of diameter and by using constant cutting parameters. Flank wear of the tool was monitored. A set of statistical features computed from the vibration signals, the acoustic emission signals, the power signals and the torque signals constitute the input of the algorithms. The classification accuracy was 88% and 91% for Neural Network and Random Forest models respectively. In order to correctly define the tool replacement policy during production, the developed Random Forest model has been implemented in an industry, through production management software, achieving promising results.

Assessment of Carbon Fiber Reinforced Plastic (CFRP) composites Using COPRAS Method

The influence of concrete strength and between concrete and CFRP composites considering the type of interaction, Exterior of reinforced concrete beams Optimum composition of CFRP composites for reinforcement and is to reach the number of layers. (i) machinability Chip removal mechanisms, cutting force, tool wear, Surface roughness, deformation and uncut of CFRP including properties of fibers; (ii) CFRP Cutting tool requirements for machining; and (iii) recent Industry solutions: cutting tools, coatings and Advanced edge geometry of technologies. CFRP composite, dry carbon fiber adhesive system. Tensile strength, tensile modulus, Air weight. From the result is based on is the result seen and got the Tensile modulus first grade, whereas the Density having the lowest rank. The value of the dataset for CFRP composites in COPRAS method shows that it results in tensile modulus and top ranking.

Experimental and numerical investigation of heat generation and surface integrity of ZrO2 bioceramics in grinding process under MQL condition

Zirconia bioceramics has tremendous potential in medical applications owing to biocompatibility and high mechanical properties. Meanwhile, thermal damage and surface defects limit the grindability to achieve the desired properties. Therefore, this research provides an investigation of various grinding parameters on heat generation and surface morphology using a diamond wheel. In addition, a triangular and parabolic moving heat flux is used for heat distribution analysis based on FEM-model. The parabolic model more corresponds to experimental compared to the triangular heat flux, with an average deviation of <5% and 6.5% under dry and MQL, respectively. The response surface methodology is applied to extract a statistical representation of inputs and outputs. Dry grinding temperature obtained in range of 200–540 °C, which by applying MQL, it decreased by 16–35%. Increasing cutting depth would worsen the MQL efficiency in force and temperature. Results indicate the impact of cutting depth on temperature and force is greatest, followed by the effect of feed-rate, and that of wheel speed is the least. Thus, the increasing feed-rate should be utilized to preserve the high removal rate. SEM images indicate material removal mechanism is accomplished by plastic and brittle mode. Furthermore, MQL and a combination of low depth of cut could effectively decline the surface roughness and defects formation by decreasing the brittle material removal mechanism in one step. MQL reduced surface roughness by 46% compared with dry grinding, so that its performance increase in higher cutting depth. Because at higher cutting depths, the MQL changes the prevailing chip removal mechanism from brittle to ductile-regime grinding.

Effect of water medium on material removal and sub-surface defect evolution in nano-cutting of single-crystal γ-TiAl alloy

ABSTRACT In this paper, molecular dynamics (MD) simulation has been applied to study the influence of water medium on the nano-cutting process and the evolution of sub-surface defects of single-crystal γ-TiAl alloy. The effect of water medium in the result of cutting force and cutting temperature have been analysed and discussed in the machining process, while the function of common neighbour analysis (CNA) method has been used to research the chip removal mechanism, sub-surface defects and crystal structure changes. The results showed that the extrusion and shear effects of tool removed atoms from the surface of the workpiece. In the meantime, the cooling and lubricating effect of the water medium reduces the cutting temperature and cutting force. Especially, the temperature of the workpiece has a diffusion effect in the cutting process in the absence of the water medium. Some heat was taken away by the water medium, which lead to insufficient nucleation and migration of the dislocation, and high compressive stress was formed during cutting of water-bearing medium.

Research on chip removal mechanism of pulse fluid negative pressure in deep hole machining

The processes of deep hole parts is prone to chip blocking due to its large length-to-diameter-ratios. Aiming at this problem, this paper designs a pulse negative pressure chip removal device based on a negative pressure chip removal system, which realizes the supply of pulsed chip removal fluid, and establishes the pulse fluid mathematical model of the device, and analyzes the effect of pulse supply fluid on the effect of chip removal. The simulation test of its chip removal effect is carried out by the Fluent software, and the results show that the pulsed oil supply device can make the chip produce relaxing combined suction force in the chip drain channel and alleviate the occurrence of chip blocking phenomenon.

Performance augmentation of machining centers by improving the overall equipment effectiveness in subsystems

The demand for increase in performance of the manufacturing units is increasing day by day. This project work aims at improving the Overall Equipment Effectiveness (OEE) of a Hardinge 600 II series Vertical Machining Centre (VMC) machine by modification of its subsystems. The problems related to higher power consumption and decreases in the units produced per unit hour were taken for analysis. By analyzing the earlier conditions it was found that the productivity of the VMC machine was found to be limited because of low OEE. The installation of an accumulator in the hydraulic system of work holding device and a simplification of the chip removal mechanism was proposed on the VMC subsystem. Also these changes were only possible to be done effectively by removing the existing conveyer belt and introducing tray disposal system. After the suggested changes were made the machine was again investigated to check for any possible increase in the OEE. An increase of 40% in OEE was achieved after implementation of the suggested changes. The improvement in OEE could be followed in similar machines such as HMC machines, FMS setups and other machines through proper steps for better productivity of the manufacturing facility.

Analysis of the influence of tool radius on single crystal silicon cutting process based on Molecular dynamics

In this paper, a molecular dynamics method is used to construct a simulation model for cutting single crystal silicon with a tool. Through the analysis of phase transition, instantaneous atomic position, temperature, Wigner-Seitz defect and other variables, the influence of tool radius on material deformation is studied. The results show that in the process of cutting single crystal silicon, the contact area between the cutting edge and the single crystal silicon workpiece is the main area of cutting heat generation, and the phase change process from the atomic crystalline state to the amorphous state is reflected in the cutting process of different tool radii The difference is that the amorphous atoms are removed in the form of chips during the cutting process of the sharp-angle tool, while the amorphous atoms are further compressed directly under the tool in the round-angle tool, causing subsurface damage. The chip removal mechanism of sharp tools is shear, and the chip removal mechanism of round tools is shear and extrusion. As the radius of the tool increases, the more atoms are compressed directly below the tool, the worse the surface quality of the machined surface.

Subsurface defect evolution and crystal-structure transformation of single-crystal copper in nanoscale combined machining

ABSTRACT In the paper, molecular dynamics simulation is applied to study the evolution and distribution of subsurface defects during nanoscale machining process of single-crystal copper. The chip-removal mechanism and the machined-surface-generative mechanism are examined through analysis of the dislocation evolution and atomic migration of the workpieces. The findings show that under different stresses and temperatures, the difference of the binding energy leads to a zoned phenomenon in the chip. Owing to elastic deformation, some of the dislocations could be recovered and form surface steps; moreover, the work hardening of the workpiece can be achieved on account of generation of twin boundaries, Lomer-Cottrell dislocations, and stacking fault tetrahedra (SFT) by plastic deformation. A process of evolution of an immobile dislocation group containing stair-rod dislocations into SFT is discovered, which is different from the traditional Silcox-Hirsch mechanism. Furthermore, a growth oscillation phenomenon, which corresponding stacking fault planes growth and retraction during the formation of the stable SFT, is discussed.

Evolution of the surface integrity while turning a fillet radius in a martensitic stainless steel 15-5PH

Abstract Surface integrity induced by longitudinal turning has been widely investigated in the literature. On the contrary, few works have aimed at investigating the surface integrity induced during turning of geometric singularities such as fillet radii. This paper investigates the surface integrity generated while turning a fillet radius in a martensitic stainless steel (15-5PH). The induced residual stresses, microstructure and mechanical properties have been characterized. Then, a geometrical analysis has revealed that the chip removal mechanisms vary continuously along the fillet radius, which, as a consequence, modify the cutting phenomena responsible of surface integrity modifications along the fillet radius. The study has highlighted that the microstructure remained stable but the residual stresses profiles differed especially regarding the compression peak intensity and the affected depth.

Study on chip removal mechanism of PCD ball-end milling (1st report) cutting simulation by orthogonal cutting

ABSTRACT A polycrystalline diamond (PCD) ball-end mill is effective for processing molds made of hard and brittle materials, such as cemented carbide and ceramics and having fine and complex shapes with a high aspect ratio. The PCD ball-end mill has a distinctive feature of its cutting edge, which it has a simple spherical shape without sharp cutting edge found on conventional cemented carbide and cubic boron nitride (cBN) ball-end mills. The rake angle varies depending on the depth of cut. In cutting using the PCD ball-end mills, flow type chips are observed and mirror finish surface without micro fracture can be realized by adopting the ductile-cutting mode. However, the mechanism of chip generation in this cutting with the PCD ball-end mills has not been fully clarified. In this study, to simulate the cutting mechanism of the PCD ball-end mill, an orthogonal cutting experiment was conducted using an ultrafine PCD cutting insert having nose radius similar to that of the PCD ball-end mill, for basically understanding the chip formation mechanism of the PCD ball-end mill. Consequently, we designed an experimental setup with a spring constant force for applying simulation of thrust force of the PCD ball-end mill. As a result, the chips could be generated at down to −75° of rake angles and the relationship between the negative rake angles and the chip generation mechanisms were clarified.

An Experimental Study on Cutting Forces in Ultrasonic Assisted Drilling

This paper presents the effect of imposing ultrasonic vibration on conventional drilling. The cutting force was compared between conventional drilling (CD) and ultrasonic assisted drilling (UAD). With numerical calculations and analytical software (Ansys), the test structure and the horn were designed and also the vibratory behavior of the parts was predicted to have vibrations with longitudinal mode and in the direction of the tool feed, reaching to the peak at the tip of the tool. The results show a considerable improvement in drilling process due to transformation of cutting process and chip removal mechanism: In ultrasonic assisted drilling the average of the drilling thrust force along the axis of the tool decreased noticeably.

Experimental investigation on fine particle emission during granite polishing process

Environmental, occupational health and safety regulations are pushing manufacturers towards reducing of manufacturing hazards including aerosol and fine particles. Granite shaping, cutting, and polishing are some of these processes producing large amount of dust containing silica that must be controlled. At the same time, the machining conditions must remain competitive and cost-effective and lead to quality parts. The goal of this work is to address these issues by determining the factors governing the dust emission during granite polishing in order to reduce the risk of exposition while producing quality parts. To do so, experimental polishing tests were carried on a vertical CNC machining center using an adaptable tool holder which controlled the contact pressure during the tests. Diamond polishing tools with different grit sizes were used. The workpiece tested were two granites, one with high silica content (white granite) and another with low silica content (black granite). The output responses studied include the surface finish, the forces, and the fine particle emission and dispersion. The experimental results led to establishing relationships between the surface finish, dust emission, and cutting forces on one hand and the abrasive sizes and polishing conditions on the other hand. It was found that the polishing tool grit size governs not only the granite surface finish but also the fine particle emission and the chip removal mechanism.

An Experimental Study on the Dynamic Behavior of Grinding Wheels in High Efficiency Deep Grinding

The design and material of the grinding wheel hub determine its static and dynamic behaviors which, in turn, play significant roles in grinding performance. This can be of special interest in high efficiency deep grinding (HEDG) process, in which the wheel is subjected to extremely high centrifugal and grinding forces. On the other hand, controlling the dynamic behavior of the grinding wheel through an in-process monitoring and a post-process measurement seems an appropriate approach to optimize the grinding process. This paper addresses the effects of the Carbon fiber-reinforced polymer (CFRP) hub body on the grinding process efficiency through comparing the results of the experiments carried out by two CBN vitrified bonded wheels with different hub materials, CFRP and steel. The experiments were conducted using a new in-process measurement system. It was proved that the dynamic behavior of grinding wheels can affect the chip removal mechanism, and in turn, influences the finished surface roughness. Furthermore, using the CFRP as the hub material leads to a reduction in the wheel radial expansion during the operation and grinding forces. High amplitudes and frequencies have been measured when using the steel grinding wheel, while they can be damped by employing CFRP hub material.

High-Speed Milling of Tool Steel Dies for Aluminium Extrusion: Surface Roughness, Dimensional Tolerance and Chip Removal Mechanisms

Die finishing has a fundamental importance to ensure a good quality of aluminium extruded parts and involves important economic effects due to the vastness of metalworking industry and the relatively short tool life in this field. Maximum machining efficiency is thus crucial. The research addresses optimization of finishing performances on tool steel extrusion dies. Milling tests are carried out on semimanufactured parts to ensure adherence to standard industrial technological chain, varying cutting parameters towards the field of high-speed machining (HSM). Dimensional tolerance is determined on die lands. Land surface roughness is measured through a multiscale approach and modelled as a function of cutting speed and feed. The above methodology enables a correlation between macroscopic process outcomes and chip removal mechanisms in the microscale.

Grinding Micromechanisms of a Sintered Friction Material

New brake-pad materials are inhomogeneous compounds with a variety of metallic and ceramic phases, whose interaction with the tool during the grinding operation is not fully understood. Yet, ground surface quality strongly influences the bedding-in phase. This research surveys how grinding operation affects the pad surface. The purpose is pursued by adopting an investigation protocol merging macroscopic outcomes with the study of chip-removal mechanisms and of the ground surface morphology in the microscale. A specific set of grinding tests is carried out on the friction material under different kinematic conditions. Macroscopic indicators of the process performances are measured and modeled. At a closer look, the ground surface shows a complex morphology that cannot be completely described by roughness values, but depends on how the various phases are distributed in the material and how they are affected by the tool during abrasion. A multiscale inspection procedure is proposed to assess the performances of a machining operation on complex materials, where the descriptive power of standard technological tests becomes inadequate.

Fabrication of a micro-pin array with high density and high hardness by combining mechanical peck-drilling and reverse-EDM

To fabricate circular cross-section micro-pin array with high hardness and high density in a fast and efficient way, a combined method of mechanical peck-drilling and reverse electrical discharge machining (reverse-EDM) is proposed in this research. First, a ball-cone-hole-magnet (BCHM) method is applied in high vibration cantilevered platform (HVCP) and quick release holder/jig to produce highly precise, fast and elastic positioning. Second, a micro-hole array with high density and different types of holes on a workpiece (brass material) is produced by a vibration-assisted mechanical peck-drilling (VAMPD), which includes the high vibration of workpiece created by HVCP and mechanical peck-drilling of micro-drill. This VAMPD can drill up to 1600 single-stage or multi-stage micro-holes, and the aspect ratio of the drilled one-stage micro-holes of Ø60 μm is up to ten. Finally, reverse-EDM is used to fabricate the micro-pin array made of tungsten carbide. In this process, the effects of the chip removal mechanism, the various micro-hole types, and the density of the micro-holes on the electrodes are investigated. The results indicate that the combination of multi-stage micro-hole electrodes and three chip removal methods (working fluid spraying, vibration-assisted electrode and shake-down type workpiece) can produce a 1600-micro-pin array with an average diameter below Ø30.00 μm, a length of 625.0 μm, and a pitch of 100 μm. Consequently, the proposed method of combining mechanical peck-drilling and reverse-EDM can fabricate a micro-pin array with high hardness, high density, high quantity, and uniform diameter in a fast and efficient way.

Mechanics and Dynamics of the Circular Milling Process

Circular milling operations are used to enlarge die and mold cavities, cylinder bores and machine airframe pockets. The tool attached to the rotating spindle follows a circular trajectory with a machining feed rate, while gradually moving forward in the direction of global axis with a step over feed. This paper presents the mathematical model of chip removal mechanism by predicting time varying cutter-part intersection as the cutter travels along the circular path. The vibration free cutting forces are predicted and experimentally verified. The dynamics of the process are modeled by considering vibrations of the end mill in two directions. The chatter stability of circular milling is modeled both in frequency domain and with a numerical model based on time finite element analysis which considers time varying immersion and directional factors. The resulting stability solutions are compared against experimental results.

Micromachining selected metals using diamond coated cutting tools

Micro and nanotechnology is becoming increasingly important to the needs of society. Therefore, the need to create devices from selected metals becomes more apparent. High-speed milling has been shown to provide a great deal of promise in creating microstructures and in nanotexturing surfaces in engineering materials. Cutting tool rotation is expected to reach 1,000,000 rpm (revolutions per minute) compared with conventional cutting speeds of around 30,000 rpm. Rotating the tool this quickly reduces cutting forces, which produce a high quality of cut so that post-processing is not required. Clearly, strain rates imparted to the workpiece at these speeds are very high and this influences initial chip formation and chip removal mechanisms. High strain rates imparted cause distinct chip formations in certain metals to occur which are similarly observed in other materials. Certain soft metals such as aluminium do not machine very well because the material adheres to the cutting tool. However, high strain rates tend to overcome these limitations. This paper examines high strain rate initial chip formation in metals, compares these results to other materials and shows that an initial chip curl model can be applied to describe high strain rate machining phenomena at the microscale.

High strain rate induced initial chip formation of certain metals during micromachining processes

As microtechnology and nanotechnology become increasingly important to the needs of society, the need to create devices in engineering materials becomes more apparent. High speed milling has been shown to provide a great deal of promise in creating microstructures and in nanotexturing surfaces in engineering materials. Cutting tool rotation is expected to reach 1 000 000 revolutions per minute (rev min−1) compared with conventional cutting speeds of around 30 000 rev min−1. Rotating the tool this quickly reduces cutting forces, which produces a higher quality of cut so that post- processing is not required. Clearly, strain rates imparted to the workpiece at these speeds are very high and this influences initial chip formation and chip removal mechanisms. High strain rates imparted cause distinct chip formations in engineering materials to occur which are similarly observed in other materials, most notably biological materials such as cancellous bone. Certain soft metals such as aluminium do not machine very well because the material adheres to the cutting tool. However, high strain rates tend to overcome these limitations. This paper examines high strain rate initial chip formation in metals, compares these results to other materials, and shows that an initial chip curl model can be applied to describe high strain rate machining phenomena at the microscale.