Difficult Machining Research Articles

Machinability of Ti6Al4V Alloy: Tackling Challenges in Milling Operations

This study extensively elaborates the approach towards making ease in 3D milling of Titanium Alloy Grade 5; by adapting the controlled parameters and specific strategies in cutting tool encroachment in milling. Every manufacturer is anxious about the machinability index (20%) of Ti6Al4V, which affects the machining efficiency proportionally. During machining, Phase alteration above the 8820C produces a Beta lamellar equiaxed microstructure, which is hard; also, limited thermal conductivity allows the generated heat towards the cutting tool to lead the Thermo-assisted wear. Higher temperatures also initiated chemically eagerness of Ti6Al4V and reacted with cutting tool edge and escorts towards catastrophic failure. The difficult Machinability demonstrates the detrimental notable effect on the cutting tool's health and follows the Ti6Al4V surface quality. The Cooling methods can flush out chips and frictional heat with ample lubrication, desirably controlling the worse effect of Machinability to some extent blissfully. The cutting tool material and coating, has chemically inert and excellent thermal conductivity with an aggressive rake angle with higher relief angle, improves the shearing tendency of Ti6Al4V by avoiding smearing, ultimately speculated surface quality with desired Tool life through higher Machining efficiency in milling.

Cyber-Physical Systems for High-Performance Machining of Difficult to Cut Materials in I5.0 Era-A Review.

The fifth Industrial revolution (I5.0) prioritizes resilience and sustainability, integrating cognitive cyber-physical systems and advanced technologies to enhance machining processes. Numerous research studies have been conducted to optimize machining operations by identifying and reducing sources of uncertainty and estimating the optimal cutting parameters. Virtual modeling and Tool Condition Monitoring (TCM) methodologies have been developed to assess the cutting states during machining processes. With a precise estimation of cutting states, the safety margin necessary to deal with uncertainties can be reduced, resulting in improved process productivity. This paper reviews the recent advances in high-performance machining systems, with a focus on cyber-physical models developed for the cutting operation of difficult-to-cut materials using cemented carbide tools. An overview of the literature and background on the advances in offline and online process optimization approaches are presented. Process optimization objectives such as tool life utilization, dynamic stability, enhanced productivity, improved machined part quality, reduced energy consumption, and carbon emissions are independently investigated for these offline and online optimization methods. Addressing the critical objectives and constraints prevalent in industrial applications, this paper explores the challenges and opportunities inherent to developing a robust cyber-physical optimization system.

Thermal effects on wear behavior of additively manufactured NiTi shape memory alloys

NiTi alloys fabricated by laser powder bed fusion (LPBF) additive manufacturing technology not only address the compositional instability resulting from complex processes but also solve the challenges of difficult machining of intricate aerospace structures. However, there are very few reports on the wear behavior of LPBF-NiTi alloys. In the present work, the effects of microstructure and thermal treatment, including heat treatment and frictional heat, on the wear behavior of LPBF-NiTi alloy and 100Cr6 ball were analyzed through a series of tribological experiments with different sliding speeds. As the average sliding speed increases (0.079–0.216 m/s), the wear rate of the as-built and heat-treated samples tends to decrease in the range of 2.69 × 10−3–0.97 × 10−3mm3/m. Although the heat-treated LPBF-NiTi alloy is 46 % harder than the as-built alloy is, the latter has a higher toughness (505 MJ/m3) and greater transformation strain of SIM (0.097). This leads to a coupling effect of heat treatment and sliding speed on the wear resistance. In addition, the wear track morphologies under different sliding speeds are asymmetric due to the 24% greater acceleration at the far end from the motor and the 2.15 mm deviation between the maximum speed position and the geometric center of the track. The wear modes of the as-built and heat-treated samples included adhesive, abrasive and delamination wear. Moreover, the wear morphologies and dominant wear modes change with the frictionally caused heat release induced by the sliding speed.

TITANIUM BLADE MILLING WITH MINIMUM PIECE DEFORMATION BASED ON TOOL ORIENTATION

This article analyses the influence of tool orientation on the geometry and surface finish obtained during the machining of thin-walled curved freeform surface parts on multitasking machining centre. These complex surfaces parts have direct application in blade manufacturing for the aeronautical sector, which has very high quality standards and are difficult to achieve. In addition, the material used is Ti6Al4V which adds a challenge due to its difficult machinability. Tool orientation has a significant effect on the accuracy of multi-axis machining reducing the theoretical force in a 6.17 % have achieved a dimensional improvement of a 7.84 %.

Study on forming process of equal wall thickness metal spiral pipe by single screw pump

To solve the problems of poor high temperature resistance of conventional screw pump stator and difficult machining of screw pump stator with equal wall thickness, this paper created a finite element model of equal wall thickness metal spiral pipe for single screw sump with 42CrMo based on tube hydroforming (THF). In this paper, the forming effects of different processes were evaluated by analysing the average pitch, wall thickness thinning rate and inner contour accuracy. Due to the particularity of design section and irregular plastic flow of material, the wall thickness of internal high pressure forming decreases seriously; on the other hand, because the diameter of the designed section is relatively large, the minimum ratio of D2 to Dmin is 1.12, which shows that wrinkles appear in external high pressure forming. As a result, based on the problems of internal and external high pressure forming, a coupling forming process was proposed. The results show that different parameters of coupling forming have little effect on the average pitch of metal spiral tube, and its maximum deviation is 1.08%; while thickness reduction ratio is proportional to initial diameter and thickness. Besides, when the liquid pressure is 350 MPa, the diameter is 60 mm and the wall thickness is 7.5 mm, the contour matching degree is higher; but the material accumulation and wrinkling will happen when the pipe diameter greater than 60 mm.

Study of electrical pulse heat assisted cutting of titanium alloy TC21 based on the finite element method

Titanium alloys are widely used in various fields because of their high strength, excellent corrosion resistance, and high heat resistance. As a new advanced titanium alloy for aviation, TC21 titanium alloy has high strength and poor machinability. It is of great significance to study the cutting mechanism of this alloy and the methods to improve the machinability of aircraft. In this paper, aiming at the difficult machinability of titanium alloy TC21, EPH online heating assisted cutting method is put forward for the first time. During the cutting experiment, the TC21 alloy sample was heated to a variety of temperatures through the electric pulse thermal heat technique. Chip shape and cutting force under different heating temperatures were obtained by cutting experiments. In order to study the influence of the heat-assisted cutting process on the machining of TC21 alloy, the orthogonal finite element model was proposed to simulate the heat-assisted cutting process of TC21 alloy. Through this simulation, chip formation, cutting force, and cutting temperature variation were all obtained. The chip formed by the simulation was in accordance with the actual chip. The results demonstrate that the influence of heat-assisted machining on chip morphology of titanium alloy is relatively small, but it has a significant influence on cutting force and surface roughness. The results show that when the sample is heated to 600°C, the surface quality is the best and cutting force can be reduced by more than 40%.

Stability analysis of TATWC based on UVA milling method

Difficult machining characteristics of titanium alloy materials and low rigidity characteristics of thin-walled component make Titanium Alloy Thin-Walled Component (TATWC) prone to chatter during machining, resulting in poor surface quality and other defects, which restricts the expansion and application of TATWC in the special industrial field. The appearance of Ultrasonic Vibration Assisted (UVA) milling method provides a new technology to overcome the processing problems of the TATWC. To analyze the stability of the TATWC processed by UVA milling method, first, by introducing a characterization function, a cutting force model of UVA milling method is established; The coefficients of cutting force between milling cutters and TATWC are solved through experiments. The model is verified by comparing the experimental and predicted values of cutting force; Secondly, the stability prediction model of UVA milling method based on full discrete method is established, and the effect of various process parameters on the stability of UVA milling method is researched. Finally, based on theoretical analysis, the modal characteristics of TATWC are measured through modal experiments. The feasibility of the stability prediction model of UVA milling method is verified by cutting TATWC with variable cutting depth.

Impeller Machining Technology Research based on CAXA

The impeller is a kind of contain complex surface more difficult machining parts, often through the UG, Pro/E and CAM software production parts processing program. In this paper, ME2020 domestic CAXA software as a platform, the impeller machining method.In order to improve the machining efficiency of the impeller, and gives the VERICUT software optimization program method.

Study on optimization of surface processing technology of silicon nitride bearing ring

Based on the difficult machining characteristics of silicon nitride materials, this manuscript focuses on optimizing the precision machining process of silicon nitride bearing components and improving the machining efficiency and quality of silicon nitride bearing components. Firstly, the mechanism of crack formation and propagation in hard and brittle materials under the action of abrasive particles is discussed in this paper, and based on this, a kinematic model of single abrasive grain cutting on hard and brittle materials is established. The effect of workpiece linear velocity, grinding wheel linear velocity, grinding wheel oscillation velocity and feed velocity on inner surface roughness of Si3N4 ring was discussed through grinding test. The experimental results show that the surface roughness can reach about Ra0.20 ∼Ra0.33 μm through a large number of grinding experiments by adjusting the combination of process parameters μm. On this basis, use the optimized process parameters calculated by the surface quality prediction model constructed in this manuscript to conduct grinding test again, and the surface roughness value reaches about Ra0.19 ∼Ra0.23 μm. The purpose of optimizing the process parameters is realized. Finally, the surface roughness can be further reduced and maintained at Ra0.05 ∼Ra0.06 μm by further superfinishing the surface after the process optimization with an oilstone. The research work of this manuscript realized the optimization of precision machining process of silicon nitride bearing ring and the rapid optimization of machining process through the established prediction model, which improved the precision machining efficiency of ceramic bearing components. Through the study of this manuscript, a process route of controllable processing of inner surface quality of Si3N4 ring is formed, from preliminary selection of process parameters by optimization model to precision grinding and then to ultra-finishing of whetstone, which provides theoretical reference for efficient and precise manufacturing of practical bearing components.

Experimental investigation on simultaneous machining of EDM and ECM of Ti6Al4V with different abrasive materials and particle sizes

In view of the difficult machining characteristics of titanium alloys and the limitations of sequential EDM/ECM machining, taking NaNO3 salt solution with low conductivity as the working fluid, the simultaneous machining of EDM and ECM (SEDCM) assisted by abrasive particles was carried out. Firstly, the effects of the electrical conductivity of the working fluid, the abrasive material, and particle size on material removal rate (MRR), tool wear rate (TWR), surface roughness (Ra), and surface morphology of SEDCM were investigated. Then, SiC abrasive with particle size of 50 μm was selected to add in the working fluid of SEDCM, owing to the unique properties of SiC in comparison with Al and Cu abrasive particles. The effect of process parameters, such as peak current, pulse on time, abrasive concentration, and gap voltage, was optimized using Taguchi-based grey relational analysis. The multi-objective optimization of MRR, TWR, and Ra was converted into the optimization of a single grey relational grade. Finally, based on the grey relational grade, the optimal combination of peak current, pulse on time, abrasive concentration, and gap voltage was predicted and verified by experiments. The results show that the comprehensive machining effect is better when the conductivity of working medium is 300 μS/cm, as long as other electrical parameters and experimental conditions are the same. Compared with Cu and Al abrasives, SiC abrasive has the lowest tool wear rate and the best surface quality, even with the worst material removal rate. Moreover, MRR, TWR, and Ra were obviously improved at the optimal parametric combination of peak current 1.5A, pulse on time 15 μs, abrasive concentration 5 g/L, and gap voltage 40 V by implementing Taguchi-based grey relational analysis.

A Review on Surface Roughness Measurement using Image Processing

In industries like aerospace, automotive, and other manufacturing industries, machining has become one of the major tasks, which involves turning, drilling, milling, etc. Drilling is one of the most difficult machining processes in the aerospace industry because millions of holes have to be drilled to assemble the parts. In another way, it is also a difficult machining process because the quality of drilling should be good, otherwise it may cause crack propagation and lead to the failure of the entire aircraft. The quality of the machining is predicted based on surface roughness. The contact method which involves the physical contact between the surface of the material and the measuring instrument, is used to measure the surface roughness, which has the major drawback of damaging the surface of a workpiece. To avoid this drawback, a non-contact method of measuring the surface roughness has been developed. This research paper thoroughly reviews the recent development and research by many researchers on image processing, which is one of the non-contact methods used to find the roughness value.

Removal mechanism of SiC/SiC composites by underwater femtosecond laser ablation

Silicon carbide Ceramic matrix composites (SiC matrix with SiC fibers, abbreviated as SiC/SiC composites) are widely used in aerospace and energy applications due to their excellent resistance to high temperatures, corrosion, wear, and low density. However, the difficult machinability and surface oxidation of SiC/SiC composites are the main factors restricting their further application. To address these issues, this paper explores a novel method for underwater femtosecond laser ablation of SiC/SiC composites to obtain high cleanliness, low-oxidation microporous surfaces. This paper systematically analyses the changes in hole depth, material removal rate (MRR), surface morphology, and material components during underwater femtosecond laser ablation of SiC/SiC composites, and explains the formation of typical features such as induced cones, small banded pits, fiber debonding and shedding. Our work provides new research ideas for understanding the removal mechanism and surface oxidation resistance of SiC/SiC composites.

Investigation of Power Consumption in the Machining of S960QL Steel by Finite Elements Method

Armor steels have good strength and corrosion resistance; however, due to their difficult machinability, high power consumption occurs. High power consumption increases the cost in machinability studies. Therefore, minimizing power consumption is important for sustainable and cleaner production. In order to minimize power consumption during machining, factors such as workpiece material, cutting tool material and geometry, machining conditions and cutting parameters must be compatible with each other. For this reason, power consumption modeling was carried out in the milling of S960QL structural steel material according to the finite elements method, depending on the cutting parameters. In this context, simulation processes were carried out at three levels for each factor: cutting speed, lateral depth, axial depth and feed rate. The most effective parameter in power consumption was the axial deep of cut. There was a 476% change between the highest and lowest power consumption. It is concluded that finite element modeling is feasible in order to determine the effect of processing parameters on power consumption.

Atomic simulation of textured silicon carbide surface ultra-precision polishing

In view of increasing accuracy requirements and difficult machining characteristics of silicon carbide materials, this paper proposes new machining method with ultra-high precision. Based on improvement of ultra-precision machining quality by textured surface, specific nano texture was machined on silicon carbide surface. Effects of different texture parameters on polishing force, polishing temperature, potential energy, dislocation, stress and friction coefficient were analyzed. Two typical textures (grooves and pits) with different sizes were compared. Simulation results show that surface morphology, polishing force and friction coefficient are improved with the increase in groove depth and pit depth. The smaller the groove spacing, the better the polishing quality and polishing behavior. In addition, groove texture can effectively inhibit the growth of dislocations and defect atoms during polishing. Compared with non-textured surface, textured silicon carbide surface can improve polishing conditions. It is found that groove texture has more beneficial effect on polishing quality than pit texture with the same size.

Investigation of the friction weldability of an AlSi10MnMg-alloy reinforced with 30 Vol.-% silicon carbide particles with the adequate monolithic material

Due to their positive properties, AMC materials represent a current trend in industrial applications and thus a major research focus. But currently their difficult machinability limits a full establishment. Therefore, suitable joining processes are needed which allow a targeted and punctual use of the AMC-materials and thus minimize the machining effort.This paper presents a feasibility study of a direct material bond between an AlSi10MnMg-alloy reinforced to 30 Vol.-% with silicon carbide particles and the adequate monolithic material by using friction welding. For this purpose, in addition to the general feasibility, the achievable strengths are evaluated and the underlying material behavior as well as metallurgical processes are analyzed.As a result, the principle friction weldability of the used AMC material is demonstrated. Essentially, the joint results from a material bond between the aluminum alloy and the matrix material. The reinforcing phase contained in the latter remains unaffected by the joining process. The test results show neither transport nor mechanical comminution of the silicon carbide particles. It is proven that the quality of the produced material joint as well as the process stability depend on the setting of the variable process parameters. In particular, the ratio between frictional and forge pressure as well as the burn-off length are shown to have a major influence on the joint quality. The intensity of the individual influences is illustrated by the presentation of the parameter main and interaction effects as well as predominant significances. Because the used AMC material is softened by process- and material-related annealing effects, a large proportion of the weld specimens fail outside the joining zone. On the part of the unreinforced aluminum alloy, the absence of such temperature-induced softening is demonstrated. As a consequence, the investigated friction welding process can unusually not be aligned with the lower-strength material.

Tool development for hybrid finishing milling of iron aluminides

The importance of high-temperature materials made of iron aluminides (FeAl) has been increasing in light weight applications, e.g., airplane turbines, due to the high material’s specific strength. However, the highly economic production by means of permanent mold casting involves special microstructures for Fe26Al4Mo0.5Ti1B alloy components leading to difficult machinability for subsequent finishing milling and low surface qualities. Major effects of tool and machining parameter variation incorporating ultrasonic assistance on the milling process and surface integrity are shown. Loads for tool and component surface are significantly adjustable to enable an economic process chain regarding the surface integrity of safety-relevant components.

Numerical, Mechanical, and Metallurgical analyses of an innovative lightweight titanium conrod additively manufactured

This study presents findings of an investigation on the reduction of the weight of a critical engine component manufactured by means of additive manufacturing technologies. The component under examination is a Ti6Al4V connecting rod (conrod) having a non-conventional optimized structure produced with SLM. Thanks to the capabilities of the AM technologies, the innovative near net shape design allows: the manufacturing of a lightweighted part, the reduction of some difficult machining operations, and the integration of conformed cooling channels into the part. To take full advantage of these potential benefits, a careful work is necessary to carefully consider all the aspects connected with the product development to ensure the feasibility of replacing the traditional and consolidated manufacturing methods for serial production in the automotive field. In this work we present a summary of the research activities carried out and in progress to assess the innovative conrod design, including selection of heat treatment after experimental characterization of mechanical properties, finite element analyses of the component and fatigue tests on a full-scale prototype, integrated with metallurgical investigations and fracture surface analyses. These activities helped to identify critical locations for fatigue performance, which could pave the way to potential future improvements (i.e. post-processing and re-designing specific component regions based on local methods for fatigue prediction).There is currently very limited literature about the development and testing of actual SLM Ti6Al4V parts and the results of the present work are also a first test bench toward the definition of procedures for the fatigue assessment of real additively manufactured full-scale components.

Comparison between the machinability of different titanium alloys (Ti–6Al–4V and Ti–6Al–7Nb) employing the multi-objective optimization

Titanium and its alloys are amongst the most important metallic materials used by many industries, such as those pertaining to the aerospace, automotive, and biomedical sectors. This is due to the reliability and functionality of titanium components, in addition to their high strength-to-weight ratio and corrosion resistance. Thus, titanium and its alloys are of great importance to the challenging operations of these sectors. The manufacturing of titanium requires great accuracy to ensure that resulting products meet quality requirements, due to its difficult machinability. In this study, the cutting forces and surface roughness of the turning were analysed to compare different titanium alloys, Ti–6Al–4V and Ti–6Al–7Nb, with CVD-coated and uncoated inserts. The effect of control factors on the response variables was measured using ANOVA. Response surface methodology was applied to the creation of a model of responses and to a bi-objective optimization process via the normalized normal constraint method. The Pareto-optimal sets of both alloys were achieved, which may be applied to practical situations to achieve optimal results for these responses. The models and optimization results confirmed the similarity of machinability values between the Ti–6Al–4 V and Ti–6Al–7Nb alloys. The uncoated inserts yielded the best surface roughness and cutting force results when used with both titanium alloys.

Numerical and experimental study of injection step, separation, and imbalance filling in low pressure injection molding of ceramic components

In recent years, widespread use of advanced ceramics in vast areas of the industries such as medical technology and automotive industries has led to the growth of the advanced ceramics market. Due to the difficult machining processes and the difficulty of forming complex parts, manufacturing of ceramic components has been restricted. Powder injection molding can be used to overcome these restrictions. In this paper, SiC feedstock was injected at various temperatures and flow rates. Numerical and experimental results of injection step and imbalance filling were studied. As well as the separation of powder and binder was simulated and verified by experimental tests. Thermogravimetric analyzer and rotational rheometer were employed to evaluate the separation in the green parts and rheological properties of the prepared feedstocks, respectively.

Accurate preparation of mesoscopic geometric characteristics of ball end milling cutter and optimization of cutting performance

According to the difficult machinability of titanium alloy, the research shows that the surface micro-textured technology can reduce the friction force and cutting temperature in the cutter-workpiece contact area. Starting with the precise preparation of micro textures by laser processing technology, this paper takes ball-end milling cutter milling titanium alloy as the research object, studies the influence of laser processing parameters on micro-textured size parameters, and optimizes the laser processing parameters as follows: laser power P = 40 W, scanning speed V = 1700 mm/s, scanning times N = 7 times, and spot diameter D = 40 μm. The distribution of temperature field and stress field during laser processing is analyzed, and the accuracy of the influence rule of laser processing parameters on micro-textured size parameters is verified, thus realizing the purpose of accurately preparing micro textures. The interactive influence of mesoscopic geometric features on the cutting performance of ball-end milling cutter is analyzed, and the genetic algorithm is used to optimize the parameters. The results show that the main factor affecting the force-heat characteristics of the tool is the blunt edge radius, and the interaction between the blunt radius of the cutting edge and the distance from blade is obvious. The optimized mesoscopic geometric parameters are as follows: the blunt edge radius is 20 μm, and the distance from blade is 110 μm, the micro-textured diameter is 30 μm, and the micro-textured spacing is 175 μm. The research content of this paper lays a foundation for efficient cutting of titanium alloy materials.