Minimum Machining Research Articles

Characterization and Qualification of LPBF Additively Manufactured AISI-316L Stainless Steel Brackets for Aerospace Application

Additive manufacturing or 3D printing is recognized as a revolutionary type of processing to replace the traditionally fabricated components, including castings, wrought products and multiple piece assemblies thereof. 3D printing helps to realize complicated parts within a short time, with minimum material wastage and allowing higher level of design optimization. Two types of brackets in stainless steel AISI-316L grade for aerospace applications were realized through laser powder bed fusion method. Detailed characterization, analysis and structural testing were performed on the powder, test coupons and the component itself to qualify these brackets for the intended application. Significant amount of material removal, excessive machining time and associated problems such as residual stresses and warpage envisaged in the conventional manufacturing route have been avoided. The mechanical properties meet the requirements specified in ASTM F 3184-16 standard and were similar to or better than vis-a-vis that can be achieved through forged route manufacturing. Minor distortion was noticed on thin wall regions which have been avoided in the next hardware by distortion compensation and adding extra stock at thin sections which can be removed by minimum machining. Non-destructive testing was performed by macro CT and brackets were found to be free from defects > 100 µm. Further, there is scope for topology optimization through design for additive manufacturing (DfAM) and achieving weight savings for future requirements.

Improvement in friction and wear characteristics using CaF2 as a solid lubricant at different conditions

During machining, adequate cooling and lubrication is much needed to reduce friction, wear, and temperature by efficient heat dissipation resulting in improved surface quality and longer tool life. The various alternative approach developed to provide lubrication and cooling includes minimum quantity lubrication, cryogenic cooling, and machining with the use of solid lubricants. The efficiency of solid lubricant particles greatly depends on the particle size, the wt% of solid lubricant, and base fluid used to prepare a lubricant mixture. Therefore, an attempt has been made in the present investigation, to evaluate the tribological properties of CaF2 with different grain sizes and weight ratios in a base oil. Results demonstrated the anti-wear and friction ability of CaF2 as a solid lubricant by improving the tribological properties of sliding surfaces. An increase in friction coefficient is observed with larger grain size (30 and 50 μm) with 10 and 20 wt% of CaF2 as compared with 10 μm particle size. Results also showed the ability of solid lubricant particles with smaller particle sizes (10 μm) to maintain a thin film of lubrication. As a comparison, CaF2 mixed with a base oil performed equally well compared to MQL under different loading conditions. The reduction in friction coefficient and wear is observed with solid lubricant application due to its excellent lubricity even at higher load and pressure. The analysis shows the presence of wear on disc surface in the form of visible grooves and wear debris in dry and MQL condition whereas lubricating effects of CaF2 is dominant.

Two-Criterion Optimization of Automatic CNC Grinding Cycles

A new method is proposed for optimizing the automatic cycles for wheel grinding with respect to two criteria: maximum productivity and minimum machining cost. The methoyd is based on structural and parametric changes in the grinding cycle on the basis of optimization by dynamic programming.

EXPERIMENTAL ANALYSIS AND OPTIMIZATION OF THE CONTROLLABLE PARAMETERS IN TURNING OF EN AW-2011 ALLOY; DRY MACHINING AND ALTERNATIVE COOLING TECHNIQUES

The latest trends in machining research show that great efforts are being made to understand the impact of different cooling and lubrication techniques as well as cutting parameters on machining performances. This paper presents the investigation results of different cutting parameters and different cutting environments such as dry machining, minimum quantity lubrication (MQL) and minimum quantity lubrication with compressed cold air (MQL+CCA) on average surface roughness, cutting force and material removal rate. The experiments were designed based on three input parameters and three different cutting environments when turning of EN AW-2011 alloy. Taguchi-based grey relational analysis was used to identify the optimal process parameters by which minimum values of surface roughness, minimum value of cutting force and maximum value of material removal rate will be achieved. The results showed that minimum quantity lubrication in the stream of compressed cold air, in comparison to dry and minimum quantity lubrication machining, gives the best machining performances. Therefore, the use of MQL + CCA method, which reduces the amount of lubricant may represent in the described extent of turning operations an alternative to turning processes most often carried out by wet method that causes considerable costs for purchasing, maintaining and using cutting fluids.

Sustainable Turning of Biocompatible Materials Using Eco Nano-Mist Technique

In today’s industrial scenario, the requisite for elevated efficiency, better economic viability and higher quality asks for immense improvements in the cutting process stability. Such machining at higher cutting speeds and cutting depths causes an immense amount of heat generation at the work tool interface. The industry makes utilization of cooling techniques to contravene these ill-effects. These techniques make utilization of chemical coolants which are non-biodegradable in nature and consumed in immense quantities. In this study the role of minimum quantity lubrication (MQL) or green machining was experimentally evaluated when utilizing nanoparticle enriched coolants. The effect on the wear and roughness values while turning commercially pure Titanium (Grade 3) was analyzed. Experimentation was performed in two phases. In the first phase, the comparison in dry, flood and MQL process was made. The experimental design was composed factorially and 16 experiments were performed. Analysis was carried out utilizing ANOVA and the results were compared. In the second phase, a graphical cognation was established between the coolant application rate with both surface roughness and flank wear values. It was concluded that the nanoparticle enriched coolant i.e. the “eco nanomist”technique was more efficacious when machining the biocompatible Titanium grade 3.

Design and optimum process parameters for unique production cost

In the present study textured tungsten carbide cutting tool was used to machine on stainless steel 316 bar stock. Cutting velocity and feed rate with the range of 70–170 m/min and 0.1–0.5 mm/rev respectively were chosen as input process parameters. The tool life and machining time are considered as responses for the proposed experiments. Unit production cost (USD) was calculated with standard assumptions. The investigation reports maximum tool life and minimum machining time required for defined volume of metal removal. Evolutionary algorithm was adopted to optimize the input parameters for minimum production cost. The optimal process parameter is 164.58 m/min cutting velocity, 0.5 mm/rev feed rate, 14.99 min tool life, 12.27 machining time were found for minimum unit production cost (9.26 USD).

An approach to calculate grinding wheel path for complex end mill groove grinding based on an optimization algorithm

Applying complex groove with variable helical angle, rake angle, core radius or groove width along tool axis is an essential way to improve the cutting performance of solid end mills. However, the usage of complex groove is limited due to the lack of an effective way to calculate wheel path for its machining, because the previous envelope theory or trial-and-error method that used for simple constant groove can no longer be used for complex groove. In this paper, a general model is established to calculate the wheel path for complex groove machining based on a mathematical optimization model, which have three constraints and one objective. First, the complex groove is defined by four curves, namely the edge curve, rake curve, core curve and flank curve, so that the variable helical angle, rake angle, core radius and groove width can be expressed by mathematical formulas. Second, the grinding wheel path is expressed as a series of its position vectors, including three location parameters and three posture parameters. Then, these vectors are calculated by searching the minimum machining error of groove width with three constraints: contact constraint to meet the rake and core radius requirements, groove width constraint to prevent the overcut with the adjacent edge and non-interfere constraint to prohibit the interfere with the current edge. Finally, the accuracy and efficiency of the model are validated by five experiments with different designed complex grooves.

Plateau honing of a diesel engine cylinder with special topography and reasonable machining time

Deep valleys and flattened peaks are essential characteristics of the finished cylinder bore surface, which is known as the plateau surface. Generally, a honing process is done in three steps to achieve a plateau surface, which is costly and time-consuming and acts as a bottleneck for cylinder block machining line. The real challenge is to select optimum levels of honing process parameters to achieve desired surface characteristics with minimum machining time. The aim of this study is to examine the influence of the input parameters of the honing process on the surface texture of diesel engine cylinder bore. The Rk family parameters are used for surface roughness evaluation and the honing crosshatch angle, in accordance with engine design requirements, which was fixed for all experiments. Optimization by means of the desirability function technique allowed determining most appropriate conditions to desirable roughness (surface quality) and/or minimize machining time (productivity). Based on the findings of this study the conventional three-stage honing process has been replaced by the two-stage process. Using the proposed two-stage honing process the intended plateau surface in cylinder bores are achieved and a remarkable reduction in the honing process time is obtained. Consequently, the process efficiency is improved significantly.

A review on localised and multi-point aerosol application in minimum quantity lubrication machining

A review on localised and multi-point aerosol application in minimum quantity lubrication machining

MQL machining of high strength steel: A case study on surface quality characteristic

The present paper highlights investigation on hard turning of high strength EN24 steel using multilayer coated carbide insert (TiN/TiCN/Al2O3/ZrCN) under minimum quantity lubrication environment for surface roughness. Measured surface values are found to be less than 1 µm which is much below the surface roughness criteria of 1.6 µm. It indicates that quality components can be obtained during MQL assisted machining of high strength EN 24 steel. This indicates proper cooling and lubrication of machining zone occurred due to application of pressurized oil mist. Developed regression model has been found to be significant because determination coefficient i.e. R2 close to unity (0.9) and p-value is less than 0.05 at 95% confidence level. Hence, environmental friendly minimum quantity lubrication machining can be effectively utilized for production of quality components in industrial shop floors for ecological and economical benefits.

A review on localised and multi-point aerosol application in minimum quantity lubrication machining

The minimum quantity lubrication (MQL) is prominent among the environmentally friendly machining techniques. Localised cooling and lubrication at multiple locations in the cutting zone is the latest development to improve efficacy and further trim down the consumption of metalworking fluid. The paper consolidates the strategies to use the MQL cutting fluids at the specific locations, vis-a-vis rake face, flank face and back of the chip. A critical analysis is made on cutting fluids, cooling strategies, process parameters, and their effect on quality. The latest developments and future directions in the framework of the hybrid lubrication method, hybrid cutting fluid and numerical modelling are presented.

Investigation of surface roughness and chip morphology of aluminum alloy in dry and minimum quantity lubrication machining

Aluminum alloys are used in different sectors due to their lightness, high strength ratio, corrosion resistance, and heat conduction, and electrical conduction, non-magnetic and non-toxic properties. Despite these properties, determination of surface quality is a critical factor for improving the functional properties of aluminum alloys such as high fatigue strength, corrosion behavior, and wear resistance. In this study, the effect of high-speed machining of Al7075-T6 aluminum alloy on the surface quality of Al7075-T6 alloy was investigated. Besides, the effect of different conditions on-chip formation was studied. The experiments were carried out in three different cutting parameters in dry and minimum quantity lubrication (MQL) conditions. It was found the surface quality of the Al7075-T6 alloy workpiece was improved when the test results performed in the MQL condition were compared to the dry condition. When the chip structure is examined, longer chip formation occurs in the MQL environment than a dry environment. It was observed that there was no significant difference in surface quality and chip morphology of the Al7075-T6 workpiece at different cutting speeds.

Effect of micro-EDM machining parameters on the accuracy of micro hole drilling in Zr-based metallic glass

Micro drilling of metallic glass is a technologically important research due to recent development of metallic glass and their technological niche applications in field of micro nozzles, micro-electro mechanical systems (MEMS) and bio-implants. Micro drilling of metallic glass is a challenging work because of in situ crystallization of resultant workpiece due to localized high heat generation during machining. However, micro-electrical discharge machining (Micro-EDM) eludes the limitations of conventional machining methods and offers precise machining of metallic glass with good surface properties. Micro-EDM machining parameters exerts a big influence on the machined features and their surface properties. A study of effect of micro-EDM machining parameters on machined geometry’s features and optimization of machining parameters for accurate machining of metallic glasses are very essential owing to the recent advancements in the applicability of Micro-EDM for processing of metallic glass parts. In present work micro-EDM is used for precision drilling of micro holes in metallic glasses. The levels of input micro-EDM machining parameters such as capacitance, voltage, tool revolutions per minutes (RPM) for optimum accuracy of micro holes and minimum machining time are identified. Resultant of present work culminated to the establishment of micro holes with exceptional accuracy using micro-EDM. The tool RPM is found to be a key parameter for increasing hole accuracy as well as reducing machining time. Outcome of present work may pave application of metallic glasses products based on precision engineering.

A study of viscosity and thermal conductivity of vegetable oils as base cutting fluids for minimum quantity lubrication machining of difficult-to-cut metals

The properties of environmentally friendly, sustainable, and renewable cutting fluids are very important to effective machining of difficult-to-cut materials under minimum quantity lubrication (MQL). This paper presents the experimental investigation of viscosity and thermal conductivity of three vegetable oils for use as base cutting fluids: modified high oleic soybean oil (HOSO), refined low oleic soybean oil (LOSO), acculube LB2000 (LB2000) oil, and mineral oil–based emulsion cutting fluid (EC) as benchmark and at temperature from 25 to 70 °C. The results show that viscosity of all vegetable oils decreases exponentially with temperature, and are significantly higher than that of EC. HOSO shows an enhanced viscosity of 6.03% compared to LB2000, 25.69% compared to LOSO, and 4688.30% compared to EC at 30 °C temperature. Thermal conductivity of soybean oils and LB2000 is similar, decreases gradually from 0.192 to 0.179 W/mK, not significantly affected by temperature and very low compared to EC. EC increases from 0.698 to 1.857 W/mK between 25 and 50 °C and decreases from 1.857 to 0.762 W/mK between 50 and 70 °C. Critical temperature of EC is around 50 °C. Shear stress–shear rate plots of vegetable oils show linear relation typical of Newtonian fluids. The R-square of HOSO was greater than 0.99 at all investigated temperature and better than the observed values for LB2000, LOSO, and EC. HOSO with higher oleic fatty acid composition shows the most significant viscosity enhancement and oxidation stability, and is recommended as alternative to EC and based-cutting fluid for MQL machining.

Efficient and Precise Micro-Injection Molding of Micro-Structured Polymer Parts Using Micro-Machined Mold Core by WEDM.

In this paper, micro-structured polymer parts were efficiently and accurately fabricated by micro-injection molding using a micro-structured mold core machined by wire electrical discharge machining (WEDM). The objective was to realize low-cost mass production and manufacturing of micro-structured polymer products. The regular micro-structured mold core was manufactured by precise WEDM. The micro-structured polymer workpieces were rapidly fabricated by micro-injection molding and the effects of the micro-injection molding process parameters on replication rate and surface roughness of micro-structured polymers were systematically investigated and analyzed. It is shown that the micro-structured polymer can be rapidly and precisely fabricated by the proposed method. The experimental results show the minimum size machining error of the micro-structured mold core and the maximum replication rate of micro-formed polymer were 0.394% and 99.12%, respectively. Meanwhile, the optimal micro-injection molding parameters, namely, jet temperature, melt temperature, injection velocity, holding pressure and holding time were 195 °C, 210 °C, 40 mm/min, 7 Mpa and 5 s, respectively. The surface roughness Ra at the groove bottom and top of the micro-structured polymer workpieces achieved minimum values of 0.805 µm and 0.972 µm, respectively.

Cutting force prediction in milling CFRPs with complex cutter geometries

The ability to predict the cutting forces for an arbitrary cutting tool is essential for selecting process parameters that would result in minimum machining damage. This activity is also important for improving existing cutting tool geometries and developing new ones. This work utilizes the mechanistic modeling approach in combination with neural networks data fitting for simulating the cutting forces in the milling of unidirectional carbon fiber-reinforced polymers (UD-CFRP). A method is proposed for predicting the cutting forces for tools of complex geometry by transforming the specific cutting energies from orthogonal cutting to the oblique cutting and accounting for the effects of rake angle and edge radius. It is shown that the method developed is capable of predicting the cutting forces in slot milling of unidirectional composites with a segmented flute cutter and over the entire range of fiber orientations from 0° to 180°. Model predictions were compared with experimental data and were found to be in good agreement. The effect of varying tool geometry on cutting forces was also investigated.

Effect of the alumina nanofluid concentration on minimum quantity lubrication hard machining for sustainable production

The use of vegetable oil-based nanofluids for minimum quantity lubrication hard machining has become a new research trend, proven to bring out very promising results and attained much attention to reduce the negative effects of using cutting fluids on the environment. The enhancement of thermal conductivity and viscosity of nanofluids helps to reduce the values of the friction coefficient, and the cooling lubricant properties are significantly improved when compared to the base fluids. In this paper, a set of optimized minimum quantity lubrication hard milling parameter combinations is obtained by using response surface methodology. Based on the optimized results, the study of the concentration effect of Al2O3 soybean oil-based nanofluid used for minimum quantity lubrication hard milling performance of 60Si2Mn hardened steel is investigated to validate and make further observations. It is noted that the appropriate nanoconcentration (1.0–1.5 wt%) and cutting conditions are observed to improve the cutting performance using soybean oil-based nanofluid. Increasing the nanoparticle concentration enhances the thermal conductivity and viscosity of the base fluids, which lead to reduce the cutting temperature and cutting forces and prolong the tool life from 80 to 115 min (increasing about 43.8%). Especially, the surface roughness ( Ra, Rz) improves and remains stable during hard cutting. Hence, the application of soybean oil-based nanofluid in minimum quantity lubrication hard machining is enlarged without losing anti-toxic, economic, and environment-friendly properties.

Modeling and Optimization of Machining Parameters Using Regression and Cuckoo Search in Deep Hole Drilling Process

This study presents the modeling and optimization of the machining parameters in deep hole drilling process using statistical and soft computing technique. Regression analysis is used for modeling and Cuckoo Search, CS algorithm is used for the optimization process. Design of Experiment (DoE), have been carried using a Full Factorial design with added centre point that comprises of machining parameters (feed rate (f), spindle speed (s), depth of hole (d) and minimum quantity lubrication, MQL (m)) and machining performance which is surface roughness, Ra. Next, the mathematical models (Multiple Linear Regression, MLR and 2-factor interaction, 2FI) are developed for the experimental results of Ra and Analysis of variance, ANOVA are used to check the significance of the models developed. The results showed that both of mathematical models (MLR and 2FI) have outperformed the minimum Ra value compared to the experimental result.

An empirical evaluation and optimization of performance parameters of wire electrical discharge machining in cutting of Inconel 718

Wire electrical discharge machining is an alternative vying and innovative non-traditional machining process. This paper focuses on the experimental investigation of wire electrical discharge machining while cutting Inconel 718 material. Pulse on time, pulse off time, cutting voltage, flushing pressure, and wire feed are considered as process parameters; and machining time and surface roughness are taken as performance parameters. In improving the machining productivity and surface characteristic, machining time and surface roughness play a crucial role respectively. Therefore, it is necessary to analyze these response parameters in correlation with the input parameters. The objective of this work is to obtain minimum machining time, minimum surface roughness and to identify significant input parameters which influence these response parameters by statistical modeling. The experimental design has been accomplished by the L27 orthogonal arrays with three different levels of each machining parameters and experiments are performed. The scanning electron microscope has been employed for measuring the kerf of machining. In this research work, evaluation of observed data has been carried out by adopting the Taguchi method, analysis of variance and response surface methodology. It has been found that pulse on time is the most significant parameter which influences both the response parameters.

Multi-objective optimisation for minimum quantity lubrication assisted milling process based on hybrid response surface methodology and multi-objective genetic algorithm

Parametric modelling and optimisation play an important role in choosing the best or optimal cutting conditions and parameters during machining to achieve the desirable results. However, analysis of optimisation of minimum quantity lubrication–assisted milling process has not been addressed in detail. Minimum quantity lubrication method is very effective for cost reduction and promotes green machining. Hence, this article focuses on minimum quantity lubrication–assisted milling machining parameters on AISI 1045 material surface roughness and power consumption. A novel low-cost power measurement system is developed to measure the power consumption. A predictive mathematical model is developed for surface roughness and power consumption. The effects of minimum quantity lubrication and machining parameters are examined to determine the optimum conditions with minimum surface roughness and minimum power consumption. Empirical models are developed to predict surface roughness and power of machine tool effectively and accurately using response surface methodology and multi-objective optimisation genetic algorithm. Comparison of results obtained from response surface methodology and multi-objective optimisation genetic algorithm depict that both measured and predicted values have a close agreement. This model could be helpful to select the best combination of end-milling machining parameters to save power consumption and time, consequently, increasing both productivity and profitability.