Metal Machining Research Articles

A Review: Development of MQL systems applied for metal cutting

Today, there is a remarkable progress to reduce the costs of tooling, production, maintenance and to increase efficiency in metal cutting operations. The practice of machining process under dry cutting has become common in the metal machining industry, but it has weaknesess. To enhance dry cutting, the minimum quantity lubrication (MQL) technique has been introduced. MQL is a very promising solution as an alternative both to replace the conventional flood cooling and to enhance the dry cutting. MQL has been proven to be a superior mechanism with some benefits such as cost effective, worker safety, improved cooling performance, and improved system performance. MQL can be regarded as technology that connecting dry and conventional flood cooling. This study is aimed to discuss MQL including its development and its application in machining processes.

Improving the printing process stability and the geometrical accuracy of the parts manufactured by the additive techniques

Current research is devoted to the computer-aided engineering application for direct modeling of the additive manufacturing process and detailed analysis of the resulting shape of the formed part. The utilized approach is based on the idea that it is possible and efficient to perform a numerical simulation of the process of a layer-by-layer building of the analyzed part, considering all the required mechanical and thermal effects. The results of such simulation should allow obtaining the detailed information about the deformed shape of the printed part before running the printing process itself. Such approach allows avoiding the unsuccessful printing attempts, improve the integral stability of the production process and reduce its cost. The paper presents the methodology of preparing a “digital twin” of the additive manufacturing process performed with AlSi10Mg alloy using one of metal machines and running a simulation of the manufacturing process for a representative structural component. The study has shown that implementation of modeling of the manufacturing process before the printing process leads to significant shape improvements of the parts printed, especially in case of performing additional optimization of the support structures. The research outcomes can be well applied for improving the production processes in the companies working with additive manufacturing in order to increase the stability of the processes and accuracy of the printed parts.

Optimization of process parameters of electrical discharge machining of fabricated AA6082 – ALN

The non-conventional machining methods are used for machining very hard materials and for making difficult shapes. Electrical discharge machining (EDM) process is one of the most commonly used nonconventional machining processes for machining hard, brittle materials like composites. It is commonly used in die making industries for developing complex profiles in dies related to sheet metal work etc., It is commonly used for machining metal matrix composites which are very hard materials. Aluminium based metal matrix composites are widely used in aeronautical and defence parts because of their advanced properties like high strength to weight ratio, etc. At first the material was fabricated using stir casting set up which was the part of research work. The work piece material selected in this study was Aluminium alloy 6082 and 10% Aluminium nitrite based metal matrix composite which was fabricated by stir casting process with the help of newly developed stir casting set up. After fabrication, the characterization of samples was done using SEM and mechanical. The EDM process was selected for machining composite samples with input parameters like gap current (A), pulse on time (μs) and duty factor. In this machining process the output response was material removal rate. The optimization of process parameters was done using Taguchi method with the help of ANOVA test and S/N ratio. Analysis of variance was performed to find the significance of machining parameters in this experimental work.

Machining Performance of Inconel 718 Under Dry, MQL, and Nanofluid MQL Conditions: Application of Coconut Oil (Base Fluid) and Multi-walled Carbon Nanotubes as Additives

The present work intends to investigate the application potential of coconut oil, as cutting fluid, during metal machining of a nickel-based superalloy. In doing so, machining performance of difficult-to-cut aerospace superalloy Inconel 718 is studied under dry, minimum quantity lubrication (MQL), and nanofluid MQL (NFMQL) using uncoated WC–Co tool, operated at varied cutting speeds. MQL environment is created by supplying air-oil mist in which commercially available coconut oil is used as cutting fluid. On the other hand, nanofluid is prepared by dispersing a specific concentration of multi-walled carbon nanotubes within coconut oil. Machining performance as observed in MQL and NFMQL is compared to that of dry machining. The following machining performance indicators are considered herein: cutting force magnitude, tool-tip temperature, and width of flank wear progression. In addition, studies on dominant modes and mechanisms of cutting tool wear, chip morphology (macro/micro), and surface roughness of the machined work part are also carried out. In the purview of machined surface roughness, it is concluded that NFMQL performs better than dry machining and conventional MQL. Flank wear is witnessed more severe during dry machining than MQL/NFMQL. However, beyond 83 m/min cutting speed, conventional MQL outperforms NFMQL (with 0.2 wt% nano-additives concentration) machining, from the viewpoint of flank wear width.

Analytical model and experimental verification of Poisson burr formation in ductile metal machining

Previous investigations on the theoretical model to predict burr dimensions have normally been confined to a single geometric model, and the findings that have been proposed rarely take into account the influence of multi-physics factors on burr formation in the complex machining process. This paper proposes an analytical model to reveal subsurface plastic deformation behavior in machining of ductile material. This model is developed based on coupled thermo-mechanical factors. More importantly, the material property and tool edge arc are taken into consideration. According to the proposed model, the two approaches are presented to predict Poisson burr height and root thickness. Moreover, the material flow and burr formation mechanism are further investigated at great length. The effects of machining parameters and material properties on burr formation are analyzed and discussed in terms of plastic deformation behavior. The results show that this proposed model can describe burr morphology and predict burr size accurately. Poisson burr generation has a great sensitivity to machining parameters, as well as material property, and the transition of burr morphology is caused by severe lateral material flow owing to material softening effect at high temperature. There is the synchronous interaction between machining parameters and material property influencing burr formation. As a result, this study provides a valuable theoretical reference and basis for the deburring energy minimization, high surface quality, and machining parameters optimization.

The Effect of Environmental Parameters on Nondestructive Control of Metal Machine Parts by the Contact Potential Difference Method

This article is devoted to improvement of a nondestructive control of metal machine parts by the contact potential difference method. The results of experimental studies of the effect of environmental parameters on the contact potential difference measurements with a Kelvin probe on the surface of metal samples from Al, Ti, and Ni are presented. The measured dependence of the contact potential difference on the surface of metals on the environmental parameters has been explained. Practical recommendations for measuring the contact potential difference on the surface of parts have been given. The results can be used in production, operation, and repair of metal machine parts.

Influence of cutting insert (uncoated and coated carbide) on cutting force, tool-tip temperature, and chip morphology during dry machining of Inconel 825

During metal machining, tool material (substrate as well as coating) plays an important role to influence machinability of any work material. Dry machining performance of ‘difficult-to-cut’ aerospace superalloy Inconel 825 is studied herein. Machining experiments are conducted at different cutting speeds using uncoated carbide, and MT-CVD TiCN-Al2O3 coated carbide inserts. Machining performance is assessed in purview of magnitude of cutting force, approximate tool-tip temperature, and quantitative chip morphological parameters. Performance of coated tool is compared to that of uncoated insert. It is estimated that coated tool causes 39.79% reduction in tangential cutting force (at cutting velocity ∼121 m/min) when compared to uncoated counterpart. Higher tool-tip temperature of the coated insert caused higher chip curling. Shear band microhardness of chip (obtained by using coated tool) appear higher than that of uncoated insert.

Surface Texture Transformation in Micro-Cutting of AA6061-T6 with the Rehbinder Effect

The Rehbinder effect (R-effect) on microcutting has been successful to augment machinability of ductile metals; however, there is a lack in understanding of its influence on texture evolution in the machined surfaces. This study validates the R-effect on AA6061-T6 and characterises the influence of the R-effect on the texture transformation in the machined surface. Microhardness tests reveal that the R-effect produces softer surfaces (87–96 HV) as compared with the surfaces produced conventionally (96–108 HV), which is attributed to the differences in grain types. A large fraction of substructured grains (96.4%) exists in the surfactant-affected subsurface while a higher proportion of deformed grains (42.8%) forms during conventional microcutting. In addition, the main texture components of the conventionally produced surface are Cube, Goss and S textures, which differ from the dominant volumes of Copper and R textures under the R-effect. The differences are results of the stress states induced during microcutting, which is exemplified through numerical simulations that consider the reduction in fracture toughness of the material with the R-effect. The advanced understanding of the R-effect better positions the use of surfactants as a cleaner near-dry metalworking fluid.

Numerical analyses of molten pool evolution in laser polishing Ti6Al4V

Abstract As one advanced manufacturing process, laser polishing has been widely used in precision machining of metal or nonmetal materials. However, the evolution mechanism of molten pool formed during polishing process has not been thoroughly studied. This paper studies the polishing process of Ti6Al4V with a continuous wave (CW) fiber laser under the top-hat distributed heat source. A two-dimensional (2D) axisymmetric numerical transient model is established to simulate the formation process of the surface of Ti6Al4V after laser heating to form a molten pool and then cooling. It reveals that the evolution mechanism of physical processes involved in heat transfer, heat radiation, heat convection, melting and solidification during the polishing process. Particularly, the capillary and thermocapillary regimes (Marangoni flow) play a key role in smoothing the free-form surface of molten pool. The freedom surface can be smoothed effectively before the solidification of molten pool. In order to verify the correctness of the simulation model and explore the influence of laser irradiation duration on the material, the surface topography of the polished sample was investigated. It is found that the errors of the depth and width of the remelting zone are respectively less than 8 % and 22 % by the comparison of simulation and experimental results. Likewise, the depth and width of molten pool expand with the laser radiation duration increasing. Meanwhile, the polished surface topography becomes smoother.

Towards Dry Machining of Titanium-Based Alloys: A New Approach Using an Oxygen-Free Environment

In the current study, the potential of dry machining of the titanium alloy Ti-6Al-4V with uncoated tungsten carbide solid endmills was explored. It is demonstrated that tribo-oxidation is the dominant wear mechanism, which can be suppressed by milling in an extreme high vacuum adequate (XHV) environment. The latter was realized by using a silane-doped argon atmosphere. In the XHV environment, titanium adhesion on the tool was substantially less pronounced as compared to reference machining experiments conducted in air. This goes hand in hand with lower cutting forces in the XHV environment and corresponding changes in chip formation. The underlying mechanisms and the ramifications with respect to application of this approach to dry machining of other metals are discussed.

Comparison of lightweight and solid milling cutter capabilities

Milling is one of the oldest methods of metal machining. This technology has been developed over a long time. The last milestone is the use of composite materials for the construction of cutting tools. However, there are other pos-sibilities for improvement offered by new production methods such as Metal Additive Manufacturing. The paper deals with machining experiments using a lightweight milling cutter with a lattice structure. The results of machin-ing are compared to the capabilities of a solid milling cutter. The evaluated parameters are: cutting forces, blade wear and surface roughness of the workpiece. Based on these parameters, it was not possible to confirm the benefit of the lightweight version for machining.

Effects of lubricant on cutting performance in single-point diamond turning of ferrous metal NAK 80

In the ultra-precision machining field, ferrous metal machining is an important and practical research topic. However, lubricant effects, especially in tool wear reduction, have yet to be researched regarding the single-point diamond turning of ferrous metals. In this research, tool wear patterns, chip characteristics, and surface topography are investigated through cutting experiments that implemented two lubricant conditions, ordinary dry machining (ODM) and machining with minimum quantity lubrication (MQL), to determine the eco-friendly cutting condition effects on cutting performance in the diamond turning of NAK 80. Results show that MQL conditions achieve a higher tool wear rate than ODM. Furthermore, tool selection and lubricant components are also explored. The results, which tool wear was significantly worse under the MQL conditions than under the ODM conditions, are neither accidental nor related to the lubricant composition. Under the ODM conditions, the machined surface micro-hardness is higher and the cutting chips are both more complete and stable. Results suggest that chemical aspects caused the essential tool wear under the MQL conditions and that chemical tool wear is greater under the MQL conditions than under the ODM conditions. This indicates that the presence of lubricant is the root cause of catastrophic tool wear under the MQL conditions.

Cutting Edge Tool Monitoring

While Ceratizit’s reputation is that of a leader in the development and provision of hard material solutions for metal machining and wear protection, it is also a pioneer in machining process digitalisation. Machinery explains further

Process Planning in Industry 4.0—Current State, Potential and Management of Transformation

The implementation of the Industry 4.0 concept enables the flexibility, modularity and self-optimization of the manufacturing process. Process planning, placed in the value chain between construction and physical manufacturing, therefore, also demands digital transformation, while management of the transformation towards the new digital framework represents one of the most demanding challenges. Continuing the research on its structure and role within the smart factory, the main motivation for this work was to recognize the potential of the digital transformation of process planning elements, and to define the key dimensions that are essential for the readiness factor calculation and later transformational strategy formation, but also to recognize the current level of awareness of the Industry 4.0 concept among the process planners, along with the current use of its elements and key priorities for the transformation. The research has therefore been conducted in 34 Croatian metal machining companies, within which the influence of company size, level of education and familiarity with Industry 4.0 on final results and the stage of development have been investigated. The results have shown that the company size has a significant influence on the development stage and the use of certain elements wherein small and medium enterprises (SMEs) have already implemented certain digital elements, while they also tend to have a better fundamental infrastructure when using complex process planning methods, unlike others, which are still highly traditional. Organization and human resources have been ranked with the highest priority for change, while target goals for hardware and software have been set, with the managerial challenges of transformation defined and discussed.

An analytical modeling with experimental validation of bone temperature rise in drilling process

Predicting the bone thermal response in a surgical operation remains a major challenge. In the previous works, metal machining theory has frequently been used to predict bone temperature in drilling process. However, several experimental studies demonstrate that the chip formation process is very complex compared to metal cutting. In the present study, a simplified analytical model based on the moving heat source approach combined with the method of image sources is developed. The heat source due to the drill-bit tip was supposed to be proportional to the cutting energy. The friction at the tool-hole contact was also considered. An experimental study was performed on fresh femur pig bone for cutting speeds from 2 to 20 m/min. Temperature rise, drilling forces and bone volume fraction were measured. The experimental validation showed that the model reproduces satisfactorily the increase in temperature up to the maximum value while it overestimates the temperature during the cooling stage. A parametric study (thermal boundary conditions, lateral friction) was also performed. From the predicted results, it appears that the model can be improved by considering the effects of the bone volume fraction which can present a significant variation in the bone sample.

EFFECT OF CUTTING SPEED IN THE TURNING PROCESS OF AISI 1045 STEEL ON CUTTING FORCE AND BUILT-UP EDGE (BUE) CHARACTERISTICS OF CARBIDE CUTTING TOOL

In the machining of metal cutting, cutting tools are the main things that must be considered. Using improper cutting parameters can cause damage to the cutting tool. The damage is Built-Up Edge (BUE). The situation is undesirable in the metal cutting process because it can interfere with machining, and the surface roughness value of the workpiece becomes higher. This study aimed to determine the effect of cutting speed on BUE that occurred and the cutting strength caused. Five cutting speed variants are used. Observation of the BUE process is done visually, whereas to determine the size of BUE using a digital microscope. If a cutting tool occurs BUE, then the cutting process is stopped, and measurements are made. This study uses variations in cutting speed consisting of cutting speed 141, 142, 148, 157, 163, and 169 m/min, and depth of cut 0.4 mm. From the results of the study were obtained that the biggest feeding force is at cutting speed 141 m/min at 347 N, and the largest cutting force value is 239 N with the dimension of BUE length: 1.56 mm, width: 1.35 mm, high: 0.56mm.

Review of Intermediate Strain Rate Testing Devices

Materials undergo various loading conditions during different manufacturing processes, including varying strain rates and temperatures. Research has shown that the deformation of metals and alloys during manufacturing processes such as metal forming, machining, and friction stir welding (FSW), can reach a strain rate ranging from 10−1 to 106 s−1. Hence, studying the flow behavior of materials at different strain rates is important to understanding the material response during manufacturing processes. Experimental data for a low strain rate of <101 s−1 and a high strain rate of >103 s−1 are readily available by using traditional testing devices such as a servo-hydraulic testing machine and the split Hopkinson pressure bar method, respectively. However, for the intermediate strain rate (101 to 103 s−1), very few testing devices are available. Testing the intermediate strain rate requires a demanding test regime, in which researchers have expanded the use of special instruments. This review paper describes the development and evolution of the existing intermediate strain rate testing devices. They are divided based on the loading mechanism; it includes the high-speed servo-hydraulic testing machines, hybrid testing apparatus, the drop tower, and the flywheel machine. A general description of the testing device is systematically reviewed; which includes the working principles, some critical theories, technological innovation in load measurement techniques, components of the device, basic technical assumption, and measuring techniques. In addition, some research direction on future implementation and development of an intermediate strain rate apparatus is also discussed in detail.

Kekasaran permukaan pada pemesinan frais mikro Ti 6Al- 4V ELI (extra low intertitial)

One of the ingredients that are popular now is titanium, but titanium is a material that is difficult to process using conventional milling machining because of the poor thermal conductivity of the material so that the high-temperature machining process produced in the cutting zone causes plastic deformation in cutting tools and increased chemical reactivity in titanium. High-speed micro-milling machining can be used for micro machining of hard metals or alloys that are difficult to achieve at low speeds. Micro milling machining in titanium material 6Al-4V ELI with variations in milling tool diameter 1 and 2 mm, spindle speed 10.000 and 15.000 rpm, feed 0,001 and 0,005 mm/rev, depth of cut 100 and 150 μm, which then do data processing using the method taguchi full factorial and theoretical analysis. The results showed that the diameter of the tool and into the depth of cut the most effect on surface roughness, the greater the tool diameter of the milling produced a smaller roughness value, this is inversely proportional to the depth of the cut. The lowest roughness value is 0,26 and the highest roughness value is 0,9. Keywords: Micro milling machining, titanium 6Al-4V ELI, surface roughness.

Tool Wear Analysis of Coated Carbide Tools on Cutting Force in Machining Process of AISI 4140 Steel

In manufacturing industries specifically in metal machining, the use of the cutting tool is important to consider. The use of the cutting tool has not been used optimally, as well as cutting parameters. In the cutting process, the wear of the cutting tool and cutting force has a very close relationship. This research was carried out to analyze the wear of coated carbide cutting tool and cutting forces produced in turning AISI 4140 steel workpieces. This study was conducted with a variation of five cutting speed levels consisting of 180 m/min, 220 m/min, 260 m/min, 300 m/min, 340 m/min and depth of cut 0.7 mm. To observe the tool wear, every 5 minutes with a maximum limit value of VB of 0.3 mm and for the cutting force values taken every 1 minute. From the results of the study obtained: The increase in the value of the cutting force is affected by the increase in wear that occurs in the cutting tool due to a change in tool geometry due to wear on the cutting tool. The highest feeding force value is at the cutting speed (Vc) 340 m / min at 368 N and the greatest cutting force value is at the cutting speed (Vc) 340 m / min at 371 N.

An approach to modeling self-oscillations during metal machining based on a finite-element model with small amount of computing resources

A novel approach to the simulation of self-oscillations by the finite-element method is proposed in this paper. It is based on studies of self-oscillations during machining. It allows to study different-scale dynamic phenomena using a model made with small amount of computing resources. The results are consistent with the results of full-scale experiments, analytical calculations and modeling.