Cutting force and hole quality analysis in micro-drilling of CFRP

Micro-drilling in carbon fiber reinforced plastic (CFRP) composite material is challenging because this material machining is difficult due to anisotropic, abrasive and non-homogeneous properties and also downscaling of cutting process parameters affect the cutting forces and micro-drilled hole quality extensively. In this work, experimental results based statistical analysis is applied to investigate feed and cutting speed effect on cutting force components and hole quality. Analysis of variance based regression equation is used to predict cutting forces and hole quality and their trend are described by response surface methodology. Results show that roundness error and delamination factor have similar trends to those of radial forces and thrust force, respectively. Non-linear trends of cutting forces and hole quality errors are observed during downscaling of the micro-drill feed value. Optimization results show that cutting forces and hole quality errors are minimum at a feed value which is almost equal to the tool edge radius rather than at the lowest feed value. Therefore, the presented results clearly show the influences of size effects on cutting forces and hole quality parameters in micro-drilling of CFRP composite material.     

Tribological properties and high-speed drilling performance of Zr–C:H:Nx% coatings with different amounts of nitrogen addition

Zr–C:H:N _x% coatings with nitrogen additions ranging from 0 to 29 at.% are deposited on AISI M2 steel substrates and micro-drills using a closed field unbalanced magnetron (CFUBM) sputtering technique. The tribological properties of the coatings are tested against AISI 52100 steel balls under loads of 10 and 100 N, respectively, using an oscillating friction and wear tester. The drilling performance of the coated micro-drills is evaluated by performing high-speed through-hole drilling tests using printed circuit boards as a test material. The wear testing results reveal that the Zr–C:H:N_8% coating has excellent tribological properties, including a low wear depth, a low friction coefficient, and an extended lifetime. Meanwhile, the drilling tests reveal that the Zr–C:H:N_8% coating increases the tool life of the micro-drill by a factor of five compared to an uncoated micro-drill when used for the high-speed through-hole drilling of PCBs and yields a considerable improvement in the machining quality of the drilled hole.     

Environment Friendly Machining of Ni–Cr–Co Based Super Alloy using Different Sustainable Techniques

In order to eradicate the use of mineral based cutting fluid, the machining of Ni–Cr–Co based Nimonic 90 alloy was conducted using environment friendly sustainable techniques. In this work, uncoated tungsten carbide inserts were employed for the machining under dry (untreated and cryogenically treated), MQL, and cryogenic cutting modes. The influence of all these techniques was examined by considering tool wear, surface finish, chip contact length, chip thickness, and chip morphology. It was found that the cryogenically treated tools outperformed the untreated tools at 40 m/min. At cutting speed of 80 m/min, MQL and direct cooling with liquid nitrogen brought down the flank wear by 50% in comparison to dry machining. Similarly at higher cutting speed, MQL and cryogenic cooling techniques provided the significant improvement in terms of nose wear, crater wear area, and chip thickness value. However, both dry and MQL modes outperformed the cryogenic cooling machining in terms of surface roughness value at all the cutting speeds. Overall cryotreated tools was able to provide satisfactory results at lower speed (40 m/min). Whereas both MQL and cryogenic cooling methods provided the significantly improved results at higher cutting speeds (60 and 80 m/min) over dry machining.     

Investigation on cutting mechanism in small diameter drilling for GFRP (thrust force and surface roughness at drilled hole wall)

This study describes the relation between the cutting force and the surface roughness of a drilled hole wall in small-diameter drilling of GFRP for a printed wiring board. In order to investigate the characteristics of small diameter drilling for GFRP, the surface of the drilled hole wall is observed by SEM, and the surface roughness along the feed direction is measured at various edge position angles of the drilled hole. The cutting force during drilling is measured. Moreover, the thrust force is devided into two components (the static component and the dynamic component). It is shown that the dynamic components are related with the surface roughness of the drilled hole wall. In conclusion, it is found that the major cutting edge of the drill is more influential in the quality of the drilled hole wall than the chisel edge of the drill in small diameter drilling of PWB.     

On Applicability of Multilayer Coated Tool in Dry Machining of Aerospace Grade Stainless Steel

The present research work has been undertaken with a view to investigate the influence of CVD multilayer coated (TiN/TiCN/Al₂O₃/ZrCN) and cutting speed on various machining characteristics such as chip morphology, tool wear, cutting temperature, and machined surface roughness during dry turning of 17-4 PH stainless steel. In order to understand the effectiveness of CVD multilayer coated tool a comparison has been carried out with that of uncoated carbide insert. The surface roughness and cutting temperature obtained during machining with chemical vapor deposition (CVD) multilayer coated tool was higher than that of uncoated carbide insert at all cutting velocity. However, the results clearly indicated that CVD multilayer coated tool played a significant role in restricting various modes of tool failure and reducing chip deformation compared to its uncoated counterpart. Adhesion and abrasion were found to be dominating wear mechanism with flank wear, plastic deformation, and catastrophic failure being major tool wear modes.     

The Effectiveness of Multichannel Electrodes on Drilling Blind Holes on Inconel 718 by EDM Process

This study presents an experimental study on making through and blind holes on Inconel 718 by hole drilling electrical discharge machining process. Several holes of Ø2 mm were drilled at specific levels of process parameters using tubular brass electrodes having different channel configurations. Machining performances were analyzed on the basis of material removal and electrode wear. Measurements of depth, diameter, overcut, and taper of holes were performed based on scanning electron microscope photographs to evaluate geometrical and dimensional accuracies of drilled holes. Surface roughness measurements as well as energy-dispersive X-ray analyses were conducted to examine characteristics of machined hole surfaces. The research reveals that drilling holes using multichannel electrodes exhibit superior results in aspects of lower drilling time, better dimensional accuracy, and improved surface quality.     

Performance evaluation of different carbide inserts in turning of newly developed Al-12Si-0.1Sr alloy

An Al-12Si-0.1Sr alloy ingot was manufactured using a permanent mold casting technique. The microstructure and mechanical properties of this alloy were researched. Effects of different cutting conditions (cutting speed-V: 200 m/min, 300 m/min, and 400 m/min and feed rate-f: 0.05 mm/rev, 0.1 mm/rev, and 0.15 mm/rev) on the cutting force (F) and surface roughness (R_a) during machining using uncoated and physical vapor deposition- titanium aluminum nitride coated carbide inserts were also revealed. Microstructure of the alloys consists of α phase, intermetallic δ and Al₄Sr phases, thin spherical eutectic, and irregular coarse-shaped primary silicon particles. Cutting force and surface roughness decreased with the increased cutting speed during turning with uncoated, and titanium aluminum nitride coated inserts while they increased feed rate. A built-up edge and built-up layer were formed in both cutting inserts. The built-up edge and built-up layer decreased with increasing cutting speed and increased feed rate. The cutting force, surface roughness, built-up edge, and built-up layer were lower in uncoated inserts compared to the titanium aluminum nitride coated inserts.     

Performance of alumina-based ceramic inserts in high-speed machining of nimonic 80A

The study of machining forces and cutting tool wear during the machining is important for designing and selection of machining system and improving the productivity. This study reports the machinability of Nimonic 80A superalloy with alumina-based ceramic inserts. The objective is to analyze the reason for higher cutting forces generated during machining and tool wear mechanism on machining parameters. The cutting forces and tool wear are found to be mainly influenced by the cutting speed. The main causes of tool failure while machining Nimonic 80A are adhesion and abrasion. The role of tool wear is more dominant on the surface finish at lower cutting speed. Also, with an increase in cutting speed, thermally activated wear quietly increases at tool surfaces. The mechanistic approach is used to model the main cutting force. Developed cutting force model agrees well with experimental cutting force values.     

Development of ANFIS model and machinability study on dry turning of cryo-treated PH stainless steel with various inserts

This present investigation deals about the machinability comparison of cryogenically treated 15-5 PH stainless steel with various cutting tools such as uncoated tungsten carbide, cryogenic-treated tungsten carbide and wiper geometry inserts. Cryo-treated PH stainless steel is considered as the work material in this investigation and experimental trials were performed under dry turning condition. The machinability aspects considered for evaluation are cutting force (F_z), surface roughness (R_a) and tool wear. The outcomes of experimentation reveal that the tungsten carbide inserts which are cryogenically treated provide improved performance in machining while comparing with conventional and wiper geometry inserts at all machining conditions. The measured cutting force and the observed flank wear were less for the cryo-treated inserts. However, wiper tool produces a better surface finish during machining. An artificial intelligence decision-making tool named Adaptive Neuro Fuzzy Inference System has been evolved to determine the relation among the considered input machining variables and output measures, namely cutting force and surface roughness of the machined surface. An analysis has been performed to compare the results obtained from developed models and experimental results.     

Characteristics of array holes with large aspect ratio in aluminum-based cast alloy

Array holes were obtained by machining methods or nontraditional machining methods, and casting process was rarely used in the preparation of array holes. In this experiment, stainless steel thin rods coated with alcohol group graphite paint were chosen as cores to prepare array holes on aluminum-based cast alloys, and the roughness and roundness of holes were analyzed. The results show that array holes cast with 2?mm pitch of holes, 0.54?mm diameters, and large aspect ratio of 100 were obtained. The roundness and roughness of holes were influenced by consumption of carbon element from surface of hole core and wettability between molten metal and hole core surface; the lower roughness and the better roundness could be acquired under these experimental conditions. And roughness of holes (R_a) was about 6.3?µm, which is close to that obtained by machining, and the value of hole shape factor (K, characterizing the roundness of the hole) was above 0.7; the shape of the hole approached a circular shape.     

Cryogenic turning of the Ti–6Al–4V alloy with modified cutting tool inserts

Productivity in the machining of titanium alloys is adversely affected by rapid tool wear as a consequence of high cutting zone temperature. Conventional cutting fluids are ineffective in controlling the cutting temperature in the cutting zone. In this research work, an attempt has been made to investigate the effect of liquid nitrogen when it is applied to the rake surface, and the main and auxiliary flank surfaces through holes made in the cutting tool insert during the turning of the Ti–6Al–4V alloy. The cryogenic results of the cutting temperature, cutting forces, surface roughness and tool wear of the modified cutting tool insert have been compared with those of wet machining. It has been observed that in the cryogenic cooling method, the cutting temperature was reduced by 61–66% and the surface roughness was reduced to a maximum of 36% over wet machining. The cutting force was decreased by 35–42% and the flank wear was reduced by 27–39% in cryogenic cooling over that of wet machining. Cryogenic cooling enabled a substantial reduction in the geometry of tool wear through the control of the tool wear mechanisms. The application of liquid nitrogen to the heat generation zones through holes made in the cutting tool insert was considered to be more effective over conventional machining.     

Modeling and Optimization of Machining Nimonic C-263 Superalloy using Multicut Strategy in WEDM

In recent years, wire-electrical discharge machining (WEDM) has gained popularity in the industry due to its capability to generate complicated shapes in exotic materials, irrespective of their hardness. Conventional machining of Nimonic C-263 superalloy is an extremely difficult and costly process due to its high hardness and tool wear rate. The present research work investigates the influence of the WEDM process parameters on different performance measures during machining of Nimonic C-263 superalloy. A mathematical model for all four important performance measures, namely, cutting rate, surface roughness, spark gap, and wire wear ratio, was developed and the responses were used for studying the interrelationship between performance measures and process parameters. The optimal settings of operating conditions were predicted using desirability function. The effectiveness of multicut strategy was also investigated in the article.     

Comparison of tool life and surface characteristics of uncoated,coated carbide and ceramic tools during machining of SiC reinforced ZA43 alloy MMC

Abstract

In the present investigation, machinability issues of zinc–aluminium (ZA43) alloy reinforced with silicon carbide particles (SiC) were evaluated. The fabrication of composite was done through liquid metallurgy technique. Metal matrix composite (MMC) was subjected to turning using conventional lathe with three grades of cutting tools, namely, uncoated carbide tool, coated carbide tool and ceramic tool. Surface roughness and tool wear were measured during the machining process. Results reveal that roughness increases with increase in the reinforcement concentration and particle size. Feed has direct influence on roughness, i.e. surface deteriorates with higher feeds. Depth of cut has very minimum effect on the surface roughness, while inverse effect of cutting speed on the roughness was observed (i.e. increase in the cutting speed leads to better finish on the specimen). Tool wear was studied during the investigation, and it was noticed that MMC with higher reinforcement concentration and particle size cause severe wear on the flank of the cutting tool. Increase in the cutting speed, feed and depth of cut also increases the flank wear on the tool. Out of all the three grades of tools, coated carbide tool outperformed uncoated carbide and ceramic tools.     

Studies on Machining Parameters While Milling Particle Reinforced Hybrid (Al6061/Al2O3/Gr) MMC

In this article, response surface methodology has been used for finding the optimal machining parameters values for cutting force, surface roughness, and tool wear while milling aluminum hybrid composites. In order to perform the experiment, various machining parameters such as feed, cutting speed, depth of cut, and weight (wt) fraction of alumina (Al₂O₃) were planned based on face-centered, central composite design. Stir casting method is used to fabricate the composites with various wt fractions (5%, 10%, and 15%) of Al₂O₃. The multiple regression analysis is used to develop mathematical models, and the models are tested using analysis of variance (ANOVA). Evaluation on the effects and interactions of the machining parameters on the cutting force, surface roughness, and tool wear was carried out using ANOVA. The developed models were used for multiple-response optimization by desirability function approach to determine the optimum machining parameters. The optimum machining parameters obtained from the experimental results showed that lower cutting force, surface roughness, and tool wear can be obtained by employing the combination of higher cutting speed, low feed, lower depth of cut, and higher wt fraction of alumina when face milling hybrid composites using polycrystalline diamond insert.     

Investigation on Some Machinability Aspects of Inconel 825 During Dry Turning

In the current study, attempt has been made to investigate the influence of cutting speed (Vc) (51, 84, and 124 m/min) on various machining characteristics like chip morphology, chip thickness ratio, tool wear, surface, and sub-surface integrity during dry turning of Inconel 825. Comparable study was carried out using uncoated and commercially available chemical vapor deposition multilayer coated (TiN/TiCN/Al₂O₃/ZrCN) cemented carbide (ISO P30 grade) insert. Chip morphology consists of chip forms obtained at different cutting conditions. Serrated chips were observed when machining Inconel 825 with both types of tool with more serration in case of uncoated insert. The chip thickness ratio increased as cutting speed was increased. Use of multilayer coated tool also resulted in increase in chip thickness ratio. Rake and flank surfaces were examined with scanning electron microscope and optical microscope. Abrasion, adhesion, and diffusion wears were found to be dominating tool wear mechanism during dry machining of Inconel 825. The beneficial effect of coated tool over its uncoated counterpart was most prominent during machining at high cutting speed (Vc = 124 m/min). The surface and sub-surface integrity obtained with coated tool were superior to that while machining Inconel 825 with uncoated tool.     

Application of Analytical Simulation on Various Characteristics of Hole Quality during Micro-Drilling of Printed Circuit Board

Achievement of good surface quality remains a concern during the micro-drilling of printed circuit board (PCB). Although a great deal of work is reported on the micro-drilling of PCB, information on the effect of drilling parameters like feed rate on different characteristics of hole quality is relatively scarce. It is known that stresses during micro-drilling of PCBs are critical issues. However, their correlation with hole quality is yet to be reported. The current work utilizes finite element analysis (FEA)-based simulation of deformation and stresses to explain various parameters of hole quality such as diameter, delamination factor and burr thickness. Effect of feed rate on these parameters has also been established. Results indicated that stresses play a vital role in influencing the hole quality of PCB. Increase in feed rate resulted in a reduction in hole diameter, whereas delamination factor and mean burr thickness increased with feed rate. The study is, therefore, expected to be of help in the proper selection of feed rate in order to achieve acceptable hole quality after micro-drilling of PCB.     

Experimental investigation on wire electric discharge machining (WEDM) of Nimonic C-263 superalloy

Nimonic C-263 superalloy offers a wide range of outstanding properties, namely, high-temperature resistance, high specific strength, high thermal fatigue, and hot corrosion resistance. The concern of the present study is mainly focused on the effect of wire electrical discharge machining (WEDM) process parameters namely, spark energy, spark frequency, and peak current on surface roughness, average cutting rate, and surface integrity aspects of Nimonic C-263 superalloy by using one-parameter-at-a-time (OPAT) approach. Surface roughness and average cutting rate were showing the increasing trend with the spark energy and peak current and reverse trend with the spark frequency. Surface integrity aspects of Nimonic C-263 such as surface topography, surface morphology, recast layer thickness, elemental composition, and phase analysis have been also considered in this study. Scanning electron microscope (SEM) micrograph of the machined surface shows the presence of micro-voids, discharge craters, micro-globules, and droplets of molten material. A recast layer of minimum thickness, with less transfer of foreign atoms (Mo, C, and O) from dielectric fluid and molybdenum wire, has been formed at lower spark energy compared to higher spark energy. The various compounds of Ni, Fe, Al, and Ti such as Fe_1.2Ni_0.8, Fe_1.5Ni_0.5, Co_0.06Fe_0.94, and Al_o.29Ni_0.27Ti_0.44 were formed on the machined surface identified through analysis of XRD peaks.     

Electric discharge hole grinding in hybrid metal matrix composite

Moving toward a hybrid approach, a hybrid process, electric discharge hole grinding (EDHG) was used to machine a hybrid metal matrix composite (MMC) (Al6063/SiC/Al₂O₃/Gr). Here, holes were drilled and ground in a single step process (EDHG) using a novel tool electrode. The experiments were designed using response surface methodology (RSM). The objective of this study was to investigate the effect of electric discharge diamond hole grinding operation on the surface roughness (SR) of the hole. The input process parameters were current, duty factor, tool speed and flushing pressure. It was found that the process is very effective in producing a finished hole. A comparison of surface roughness was made between electric discharge drilling (EDD) and electric discharge diamond hole grinding, thereby showing the effectiveness of the electric discharge diamond hole grinding process. The grinding action of the process is clearly visible in the scanning electron microscopic (SEM) image. It was observed that the craters, globules of resolidified material and micro cracks, which are normally seen on surfaces machined by electric discharge machining (EDM), are completely ground off by electric discharge diamond hole grinding.     

Investigation on laser drilling of AA6061-TiB2/ZrB2 in situ composites

Laser beam machining is considered as economic machining process to machine the composite materials. AA6061-TiB₂/ZrB₂ in situ composites are drilled by using Ytterbium fiber laser machine with input parameters as laser trepanning speed, laser power, and standoff distance. Entry diameter, exit diameter, and taper are responses which are to be measured by metallurgical microscope. The contribution of the paper is to analyze the influence of reinforcement ratio of the composites and machining parameters on the responses. Analysis of the results shows that the entry and exit diameters and taper of unreinforced alloy are less than the composites for all the experimental conditions. Increase in laser trepanning speed decreases the entry and exit diameters whereas increases the taper of the laser drilled hole. Increase in laser power enlarges the entry and exit diameters but reduces the taper of the hole. The increase in the standoff distance reduces the entry and exit diameters of the hole. This investigation helps to find the suitable machining parameters for attaining the desired accuracy of laser drilled holes.     

Thrust force model for ultrasonic-assisted micro drilling of DD6 superalloy

As a typical refractory material, the DD6 nickel-based single-crystal superalloy has important applications in the aviation industry. Ultrasonic-assisted drilling is an advanced machining method that significantly improves machining of refractory materials. The drilling thrust force influences the hole surface quality, burr height, and bit wear. Therefore, it is necessary to predict the thrust force during ultrasonic-assisted drilling. However, there are few reports on the modeling of the thrust force in the ultrasonic-assisted drilling of micro-holes. A thrust force prediction model for ultrasonic-assisted micro-drilling is proposed in this study. Based on the basic cutting principle, the dynamic cutting speed, dynamic cutting thickness, and acoustic softening effect caused by ultrasonic vibrations are factored into this model. Through model calibration, the specific friction force and specific normal force coefficients were determined. The model was verified through ultrasonic-assisted drilling experiments conducted at different feed rates, spindle speeds, frequencies, and amplitudes. The maximum and minimum errors of the average thrust force were 10.5% and 2.3%, respectively. This model accurately predicts the thrust force based on the parameters used for ultrasonic-assisted micro-hole drilling and can assist in the analysis and modeling of DD6 superalloy processing.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-021-00381-y