Reduced Material Removal Research Articles

Electrochemical Performance of Lithium-Ion Pouch Cells Containing Aqueous Processed and Laser Structured Thick Film NMC 622 and Graphite Electrodes

The development of high areal energy density electrodes with layered metal oxide cathode materials is currently a hot topic in research and industry. However, for automotive applications, current research focuses on the merger of two concepts: (i) the “thick-film concept” which enables a high energy density due to a reduced amount of inactive materials, and (ii) the “three-dimensional (3D) battery concept”, which provides a high power density with improved interfacial kinetics at mass areal capacity ≥ 6.5 mAh/cm2. Latter could be realized by applying ultrafast laser patterning of electrodes which in turn includes an advanced 3D electrode design. Briefly, a rapid and homogeneous electrode wetting with liquid electrolyte can be induced, and besides a high capacity retention during long-term cycling. However, the mass loss due to laser patterning needs to be taken into account, since the cathode represents about 50 % of the total material costs of LIBs. Thus, the use of electrode structures with a high aspect ratio as well as a significantly reduced material removal is of great importance. Besides, cost reduction and environmentally friendly production by applying aqueous processing of cathode has been intensively investigated recently. In this work, 150 µm thick-film Li(Ni0.6Mn0.2Co0.2)O2 electrodes were manufactured with both water-based binders and PVDF binder by tape-casting. Both cathodes are anodes were subsequently laser patterned to achieve 3D architectures. Finally, the NMC 622 cathodes were assembled in pouch cells versus graphite anodes for studying the impact of laser patterning and binders on the electrochemical performance by applying rate capability analysis, electrochemical impedance spectroscopy (EIS), and lifetime analysis.

Design and development of spiral grooved grinding wheel and their influence on the performance of vertical surface grinding process

In surface grinding process, the insufficient coolant flow causes the accumulation of dislodged abrasives and chips in the grinding interfaces. It leads to poor performance by increased work-surface scratches and reduced material removal rate (MRR). This can be improved by enhancing the coolant flow in the grinding interfaces by creating grooves on grinding wheels surfaces. In this work, a vertical surface grinding process is employed to emphasize the influence of surface integrity of the work-piece with spiral grooved SiC grinding wheel surfaces. The grinding performance (force, power, MRR, wheel wear and G-ratio) and the surface characteristics (avg. roughness, peak-valley height and pitch value) were investigated by varying the process parameters (i.e., depth of cut = 16, 24, 32 and 40 μm and feed rate = 7 and 14 m/min at a constant speed of 1500 rpm). At first, the spiral grooves of four different patterns (Archimedes, Logarithmic, Fermat=t2 and radius=√t) were designed on wheel surfaces and investigated for the stress distribution with the centrifugal force (157 rad/s) by FEM analysis using ANSYS. It reveals that the stress-distribution was larger than the un-grooved wheel surface, irrespective of groove patterns. However, the stress-distribution was found to be lower in Archimedes spiral groove patterns compared to other patterns. Therefore, the case study on Archimedes spiral groove patterns on grinding wheels were performed and compared with the un-grooved wheels.

Experimental Investigation of Particle Impact Damping On Machine Tools

In machine structure, the boring operations are extensively used for enlarging an existing hole. For large sized workpieces, the overhang length of the boring tool increased, which disturbs the slenderness of the tool (length to diameter ratio) leading to high amplitude vibrations. The tool-workpiece interaction strains the shank and induces vibrations in the workpiece. These vibrations bring along a package of defects such as poor surface finish, dimensional inaccuracy, reduced material removal rate etc. In order to suppress the damping, small metal particles were used. Particle impact damping [6] is a method of achieving high structural damping by using a particle filled enclosure in the region of high displacements. A series of experiments were performed where the closure was attached to the tool at three different locations, the material as well as the size of the particle was changed for obtaining different experimental observations. Further, a particle effectiveness or packing ratio of 25%,50%and 75% was used for experiments. Using NI signal software and LabVIEW we were able to obtain the natural frequency with and without the damper, in an experiment the frequency of vibration was reduced about 15% with the damper

Study of angular cutting conditions using multiple scratch tests onto low carbon steel: An experimental-numerical approach

Multiple parallel scratches are often analyzed to understand the material removal mechanisms due to abrasion. However, successive scratches with different orientations may represent better the conditions found in machining processes, such as honing and belt finishing. The objective of this work was to analyze the cutting forces and the phenomena of material removal due to abrasion, arising from angular scratches in low carbon steel. Experimental and numerical techniques were considered. In both, analyses considered the presence of an initial set of parallel scratches, followed by a second set of scratches with different orientations (10, 20 or 30°) with respect to the previous one. The cutting action was performed by a tool representing an abrasive particle, which had a cono-spherical geometry with 235 µm tip radius and 30° apex angle. The cutting settings were: 50 m/min scratch velocity and 100 µm depth of cut. In the experimental part, scratches were conducted using a shaper machine tool equipped with a tungsten carbide (WC-Co) stylus. Tests were conducted on a Kistler platform, which allowed force measurement. Surfaces were later analyzed with an optical profilometer. The numerical simulations considered a ductile damage model with element deletion to provide the material removal during the scratches. Experimental and numerical results showed that the angle affects the cutting forces, especially when one scratch crosses a previously scratched region. The 20° case was the most critical, especially in terms of the cutting forces, due to the accentuated material strain-hardening for this condition. Likewise, this fact was corroborated by numerical results, which indicated a higher energy necessary to plastic deformation, and a reduced material removal at 20°.

Manufacturing of carbide tools by Selective Laser Melting

Application fields of electrical discharge machining (EDM) are limited due to given process conditions. When producing structures of high aspect ratios or using multi-axis machining, removed particles assemble at the machining zone, leading to process instabilities and increasing tool wear. A promising approach to improve EDM process conditions is the utilization of flushing channels in the tool electrode. However, with increasing complexity of the electrode geometry and the local integration of the mentioned flushing channels, conventional electrode manufacturing reaches its limitations. By applying Selective Laser Melting (SLM), these limitations are eliminated. An additional benefit is the efficient use of material during SLM, where nearly no waste is produced, because remaining powder can be used for the next SLM-process. The appropriate integration of flushing channels, even for complicated electrode geometries, improves process conditions during EDM in a variety of applications, leading to a higher material removal rate VW and reduced tool wear ϑ compared to machining without flushing. Additionally, the number of required tool electrodes can be reduced, as SLM enables an efficient integration and miniaturization of all features in a single electrode, what results in a far more sustainable process chain. Of particular interest in the field of EDM is carbide. Because of its wear resistance and stability, it is an ideal electrode material, which is commonly applied in µEDM. Tungsten carbide-cobalt is representative for this group of materials, which is already used in tool manufacturing. Several tests show a general suitability of carbide tool electrodes made by SLM for EDM-processing. However, the SLM process parameters and the composition of the carbide-cobalt show significant impact to the EDM results. A lower proportion of cobalt leads to reduced material removal rates, whereas the level of tool wear remains at a similar level. In order to benefit from the advantages of additive manufactured carbide tool electrodes, this investigation aims at decreasing waste of material and the number of required tool electrodes.

Application of Additive Manufactured Tungsten Carbide Tool Electrodes in EDM

Application fields of electrical discharge machining (EDM) are limited due to given process conditions. When producing structures of high aspect ratios or using multi-axis machining, removed particles assemble at the machining zone, leading to process instabilities. A promising approach to improve EDM process conditions is the utilization of flushing channels in the tool electrode. However, with increasing complexity of the electrode geometry and the local integration of the mentioned flushing channels, conventional electrode manufacturing reaches its limitations. By applying Selective Laser Melting (SLM), these limitations are eliminated. The appropriate integration of flushing channels, even for complicated electrode geometries, improves process conditions during EDM in a variety of applications, leading to a higher material removal rate VW and reduced tool wear ϑ compared to machining without flushing. Additionally, the number of required tool electrodes can be reduced, as SLM enables an efficient integration and miniaturization of all features in a single electrode.Of particular interest in the field of EDM is carbide. Because of its wear resistance and stability, it is an ideal electrode material, which is commonly applied in μEDM. Tungsten carbide-cobalt is representative for this group of materials, which is already used in tool manufacturing. Several tests show a general suitability of carbide tool electrodes made by SLM for EDM-processing. However, the SLM process parameters and the composition of the carbide-cobalt show significant impact to the EDM results. A lower proportion of cobalt leads to reduced material removal rates VW and rising tool wear.

Electromagnetic actuator for determining frequency response functions of dynamic modal testing on milling tool

Machine tools are the main driving forces of industrialization of a country. However, poor machinability because of chatter vibration results in poor surface quality, excessive noise, and reduced material removal rate. Modal testing is a useful method to investigate dynamic properties of a cutting tool system and improve material removal rate. However, at present, modal testing using impact hammer is limited by certain problems. This paper developed a non-contacting electromagnetic actuator (EMA) to determine frequency response functions (FRFs) under amplitude and speed dependencies of cutting milling tools. The geometry was designed using magnetic circuit analysis and generalized machined theory before finite element analysis was conducted using magnetostatic-ansys software. Next, EMA was used as a contacting and non-contacting exciter of a conventional milling machine to determine the FRFs and dynamic properties of milling tool with amplitude and speed dependencies including comparison with static FRFs. Subsequently, dynamic properties and FRFs are used to establish stability lobe diagram. Stability lobe diagram also shows an improvement of up to 5% of depth of cut at lower spindle speed. In conclusion, by generating force that applies to static and dynamic modal testing, an EMA can determine dynamic properties and stability lobe diagram for increasing material removal rate and production rate.

In-process tool point FRF identification under operational conditions using inverse stability solution

Self-excited vibrations of machine tools during cutting result in process instability, poor surface finish and reduced material removal rate. In order to obtain stability lobe diagrams to avoid chatter vibrations, tool point frequency response function (FRF) must be determined. In classical machine tool studies, tool point FRF is obtained experimentally or analytically for the idle state of the machine. However, during cutting operations, discrepancies are frequently observed between the stability diagrams predicted by using the FRFs measured at the idle state and the actual stability of the process. These deviations can be attributed to the changes in machine tool dynamics under cutting conditions which are difficult to measure. In this study, a new identification method is proposed for the identification of in-process tool point FRFs. In this method, experimentally determined chatter frequency and corresponding axial depth of cut are used in order to identify tool point FRF. The proposed method is applied to a real machining center and by using chatter tests it is demonstrated that the tool point FRF can be accurately identified under operational conditions.

Mathematical Model for Chip Serration Frequency in Turning of Stainless Steel with Magnetic Damping from Bottom of Tool Shank

Chatter, a violent and often unpredictable relative oscillatory motion between the tool and work-piece, is a serious concern in turning operations. Its occurrence is usually associated with a loud monotonous sound and usually results in increased surface roughness, reduced material removal rates, shortened tool life, and damaged machine-tool bearings. The established theories for chatter are very limited in scope and are often contradicted by empirical evidences. Therefore, chatter avoidance in the past has relied on inefficient techniques like limiting material removal rates or expensive setups such as actuators and ultrasonic vibration damping systems. However, a deeper investigation into chatter formation reveals that chip morphology and segmentation play a significant role during the incidence of chatter. The novel Resonance theory of chatter combines the concept of mode coupling of the machining setup and serrated chip formation, to explain and predict chatter. To validate the postulates of this theory, models for chip serration frequency are essential. At the same time, a reliable and economical chatter control method is required. With this goal, the current research work has developed an empirical mathematical model of chip serration frequency in turning of stainless steel AISI 304 using Response Surface Methodology (RSM). Also, it investigated the influence of damping provided by magnetic field from a permanent ferrite magnet placed beneath the tool shank. The developed chip serration model is in good accord with the experimental data, demonstrating that the empirical model could be used for further chip morphology and chatter analyses.

IDENTIFICATION OF DYNAMIC RIGIDITY FOR HIGH SPEED SPINDLES SUPPORTED ON BALL BEARINGS

The widespread use of high-speed machining in recen t decades has led to a significant area of research on issues that limit its productivity. Regenerative chatter is a well‐known machining problem that results in unstable cu tting process, leads to the poor surface quality, reduced material removal rate and damage on the machine tool itself. The main require ment for the stability of system dynamics is the information of tool tip frequency r esponse functions (FRF’s).The present work consider ed a coupled model of spindlebearing system by using the angular contact ball be aring forces on stability of machining. Using Timos henko beam element formulation, the spindle unit is analyzed by includ ing the gyroscopic and centrifugal terms and the be aring contact forces are arrived from Hertzian contact theory. Then, the model is us ed for studying the effects of viscous damping to o btain the tool point FRF for the dynamic spindle.

Disturbance of material removal in laser-chemical machining by emerging gas

Using laser-chemical machining allows a localized and precise processing of metallic work pieces. The temperature distribution on the surface is the primary factor of this selective and gentle machining method. Investigations regarding temperature and material removal related surface effects like locally induced gas bubbles and reduced material removal are shown. It is shown that the processing feed rates only have a negligible impact on the resulting temperature field and thus the width of the cavity, while laser intensity appears to be the dominant parameter. Furthermore, it is shown that emerging gas bubbles caused reduced material removal resulting in irregular cavities.

Post-Processing Effect on the Fatigue Behavior of Three Titanium Alloys under Simulated SPF Conditions

This experimental study investigates a post-Superplastic Forming (SPF) processing method with reduced material removal requirements and its effect on high-cycle fatigue behavior. Comprehensive high-cycle fatigue experiments were conducted on three titanium alloys in part to validate the proposed post process and in part to provide baseline properties for evaluating additional materials. High-Cycle Fatigue results indicated that lower temperature superplastic forming conditions allow more efficient use of titanium material. Manufacturing process designers needing to predict the best SPF conditions and establish design allowables for titanium alloys may find the results of this research useful.

Analytical modeling of spindle–tool dynamics on machine tools using Timoshenko beam model and receptance coupling for the prediction of tool point FRF

Regenerative chatter is a well-known machining problem that results in unstable cutting process, poor surface quality and reduced material removal rate. This undesired self-excited vibration problem is one of the main obstacles in utilizing the total capacity of a machine tool in production. In order to obtain a chatter-free process on a machining center, stability diagrams can be used. Numerically or analytically, constructing the stability lobe diagram for a certain spindle–holder–tool combination implies knowing the system dynamics at the tool tip; i.e., the point frequency response function (FRF) that relates the dynamic displacement and force at that point. This study presents an analytical method that uses Timoshenko beam theory for calculating the tool point FRF of a given combination by using the receptance coupling and structural modification methods. The objective of the study is two fold. Firstly, it is aimed to develop a reliable mathematical model to predict tool point FRF in a machining center so that chatter stability analysis can be done, and secondly to make use of this model in studying the effects of individual bearing and contact parameters on tool point FRF so that better approaches can be found in predicting contact parameters from experimental measurements. The model can also be used to study the effects of several spindle, holder and tool parameters on chatter stability. In this paper, the mathematical model, as well as the details of obtaining the system component (spindle, holder and tool) dynamics and coupling them to obtain the tool point FRF are given. The model suggested is verified by comparing the natural frequencies of an example spindle–holder–tool assembly obtained from the model with those obtained from a finite element software.

Electrical discharge machining of carbon fibre composite materials

An investigation has been made into the feasibility of using Electrical Discharge Machining (EDM) as a means of machining carbon fibre composite materials. Machining was preformed at various currents, pulse durations and with different tool materials and polarities. There exists an optimum material removal rate with peak current and the pulse-on time. However, electrical discharge machining of carbon fibre composite materials should be done at low current density as high current density would cause the epoxy resin to smear over the surface leading to reduced material removal rate and rapid deterioration of the EDM surface. It is found that copper electrodes perform better than graphite electrodes in terms of tool wear, and tools with positive polarity give higher material removal rate and lower tool wear ratio.