An integrated toolpath and process parameter optimization for high-performance micro-milling process of Ti–6Al–4V titanium alloy

Double‐vacuum‐bag (DVB) process, as an effective out‐of‐autoclave (OoA) technology, can manufacture composite materials with low void content and high mechanical properties. Therefore, this paper aimed to achieve low void content, the effects of pressure difference between inner and outer bags, dwelling temperature, and dwelling time on the void of composite laminates were studied based on orthogonal experimental method. The void content and morphology of laminates were statistically analyzed, by observing the microscopic images of the samples on cross‐section. The results show that the pressure difference between the inner and outer bags has a significant impact on the void content and morphology, while the dwelling temperature and dwelling time have little effect. In addition, with the variance analysis and extreme difference analysis, the optimal process parameters were determined as follows: pressure difference between inner and outer bags was 0 MPa, dwelling temperature was 110°C, and dwelling time was 15 min. The void content of composite laminates manufactured under these parameters is 0.07%, less than 1% requirement for aerospace components, and interlaminar shear strength (ILSS) is 110 MPa, which is 54.93% higher than the single‐vacuum‐bag (SVB) process. Generally, the void content and ILSS reached the level of hot press process with 0.6 MPa. Highlights Influence of different DVB process parameters on void were studied. Void content manufactured with the optimal DVB process parameters was less than 1%. ILSS of laminate with the optimal DVB process parameters was equal as hot press process.

Optimizing process parameters for hot forging of Ti-6242 alloy: A machine learning and FEM simulation approach

Effect of progressive tool wear on the functional performance of micro milling process of injection molding tool

Effects of machining parameters, ultrasonic vibrations and cooling conditions on cutting forces and tool wear in meso scale ultrasonic vibrations assisted end-milling (UVAEM) of Ti–6Al–4V under dry, flooded, MQL and cryogenic environments – A statistical analysis

This article aims to investigate the means to obtain optimal hot stamping process parameters and the influence of the stochastic variability of these parameters on forming quality. A multi-objective stochastic approach, integrating response surface methodology (RSM), multi-objective genetic algorithm optimization non-dominated sorting genetic algorithm II (NSGA-II) and the Monte Carlo simulation (MCS) method is proposed in this article to achieve this goal. RSM was used to establish the relationship between the process parameters and forming quality indices. NSGA-II was utilized to obtain a Pareto frontier, which consists of a series of optimal process parameters. The MCS method was employed to study and reduce the influence of a stochastic property of these process parameters on forming quality. The results confirmed the efficiency of the proposed multi-objective stochastic approach during optimization of the hot stamping process. Robust optimal process parameters guaranteeing good forming quality were also obtained using this approach.

The effects of cooling/lubrication techniques on cutting performance in micro-milling of Inconel 718 superalloy

Titanium alloys are widely used in important manufacturing sectors such as the aerospace industry, internal components of motor or biomechanical components, for the development of functional prostheses. The relationship between mechanical properties and weight and its excellent biocompatibility have positioned this material among the most demanded for specific applications. However, it is necessary to consider the low machinability as a disadvantage in the titanium alloys features. This fact is especially due to the low thermal conductivity, producing significant increases in the temperature of the contact area during the machining process. In this aspect, one of the main objectives of strategic industries is focused on the improvement of the efficiency and the increase of the service life of the elements involved in the machining of this alloy. With the aim to understand the most relevant effects in the machinability of the Ti6Al4V alloy, an analysis is required of different variables of the machining process like tool wear evolution, based on secondary adhesion mechanisms, and the relation between surface roughness of the work-pieces with the cutting parameters. In this research work, a study on the machinability of Ti6Al4V titanium alloy has been performed. For that purpose, in a horizontal turning process, the influence of cutting tool wear effects has been evaluated on the surface finish of the machined element. As a result, parametric behavior models for average roughness (Ra) have been determined as a function of the machining parameters used.

Nowadays, titanium alloys are achieving a significant interest in the field of aerospace, biomedical, automobile industries especially due to their extremely high strength to weight ratio, corrosive resistance, and ability to withstand higher temperatures. However, titanium alloys are well known for their higher chemical reactive and low thermal conductive nature which, in turn, makes it more difficult to machine especially at high cutting speeds. Hence, optimization of high-speed machining responses of Ti–6Al–4V has been investigated in the present study using a hybrid approach of multi-objective optimization based on ratio analysis (MOORA) integrated with regression and particle swarm approach (PSO). This optimization approach is employed to offer a balance between achieving better surface quality with maintaining an acceptable material removal rate level. The position of global best suggested by the hybrid optimization approach was: Cutting speed 194 m/min, depth of cut of 0.1 mm, feed rate of 0.15 mm/rev, and cutting length of 120 mm. It should be stated that this solution strikes a balance between achieving lower surface roughness in terms of Ra and Rq, with reaching the highest possible material removal rate. Finally, an investigation of the tool wear mechanisms for three studied cases (i.e., surface roughness based, productivity-based, optimized case) is presented to discuss the effectiveness of each scenario from the tool wear perspective.

Titanium and Ti alloys are popular materials used in aviation and biomedical field due to their excellent strength-to-weight ratio and corrosion resistance properties. Micromilling is a common mechanical machining process used in the production of microscale features. The micro-tool has very low stiffness and even small forces can lead to catastrophic tool failure. High speed micromachining can be used to address the issue because of lower chip loads at higher rotational speeds. Consequently, high speed micromilling can be used for micromachining of hard metals/alloys which are difficult to accomplish at lower speeds. Nowadays high speed micromilling is gaining popularity due to its high material removal rate and good surface finish. In many cases, the machined product does not need an additional finishing process. However, the burr formation in the mechanical machining process is the most important problem which becomes more critical for a microscale feature. Removal of micro-size burr is much more difficult than its macro counterpart. The current work is focused on the characterization of the burr formation in high speed micromilling. Influence of various process parameters, viz., spindle speed, feed rate, depth of cut, tool diameter and number of flutes of the micromilling tool has been analyzed on the burr size and on the quality of the machined surface via measuring the surface roughness.

The effect of process parameters namely peak current, pulse on time and flushing pressure on electrical discharge machining (EDM) of titanium alloy (Ti–6Al–4V) were investigated by using three different tool electrode materials namely copper, brass, and aluminium. Kerosene is used as dielectric. The process parameters for machining Ti6Al4V are varied at three levels by using Taguchi's orthogonal array table. The responses such as Metal Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (SR) are measured and the most significant parameter was confirmed by ANOVA (Analysis Of Variance). The test result shows that copper electrode material possesses higher MRR, less TWR as compared to brass and aluminium. Brass and copper tools has good surface finish as compared with aluminium. The finest electrode material for machining of Ti6Al4V alpha beta alloy in EDM process was in the order of copper, brass and aluminium.

ABSTRACT. Functional graded magnesium matrix composites (FGMMCs) are widely employed for biomedical, aerospace and thermal barrier applications because of their better mechanical properties, biocompatibility and bioactivity. In this study, AZ91D-wt. %Ti (x = 0, 4, 8, 12 and 16) composites are fabricated by ex-situ centrifugal casting method. The NaCl based solution is sprayed on all fabricated magnesium composites for 72 hours at the 1 kg/cm3 pressure spray and 6.9 pH value in salt spray chamber. The microhardness and flexural strength of fabricated composites are determined. The corrosion resistance of AZ91D-wt. %Ti fabricated composites is determined for 21 days immersion. The AZ91D -12wt. %Ti exhibits higher microhardness, flexural strength and corrosion resistance than other produced AZ91D-Ti composites. The optimization on micro machining process parameters is done on the AZ91D-12wt. %Ti with the help of Technique for order of preference by similarity to ideal solution (TOPSIS).The input process parameters are selected as cutting rate, feed rate, depth of cut and tool type and the response parameters are selected as feed force, normal force, tool wear rate, burr height and surface roughness. The computed optimal micro milling process parameters are at 120 m/min cutting speed, 0.5 µm feed rate, 0.15 mm depth of cut and the TiB2 coated tool.
 
 KEY WORDS: AZ91D -Ti, TOPSIS, Surface roughness, Tool wear loss, Cutting force
 
 Bull. Chem. Soc. Ethiop. 2023, 37(1), 77-89. 
 DOI: https://dx.doi.org/10.4314/bcse.v37i1.7

Chapter 25 - State-of-the-art in additive manufacturing of Ti–6Al–4V: recent progress and insights into future developments

Micro-milling is a suitable technique for manufacturing of microstructures with high aspect ratios and intricate geometries. The application of the micro-milling process in cutting hardened tool steel is particularly challenging. The low strength of the miniaturized end mills implies accurate control of the chip load in order to prevent the tool break and product dimension errors, which requires high positioning accuracy. It is known that the application of cutting fluids can improve the performance of machining operations. However, the supply of cutting fluids in a conventional way is not appropriate for miniature machine tools due to the plentiful electronic components used to construct micro-scale machine tools. Minimum quantity lubrication (MQL) presents itself as a possible alternative for micro-cutting with respect to the minimum impact on the electronic components as well as low tool wear, better heat dissipation, and machined surface quality in metal cutting. This study compares the mechanical performance of MQL to completely dry condition for the micro-milling of SKD 61 steel based on experimental measurements of tool wears and surface finish. The effect of MQL on the burr formation is also observed. Results indicate that the use of MQL leads to reduced tool wears, better surface roughness, and less burr formation.

The machining of Titanium alloy, Ti–6Al–4V has got an extensive attention from industries like aerospace, medical, and biomedical plants due its unique properties like high strength at elevated temperature and better strength to weight ratio. Still, properties like reduced thermal conductivity, affinity to react with the tool and work hardening make difficult to cut it by conventional turning process. Ultrasonic vibration-assisted turning (UVAT) is one of the advanced turning method in which tool is allowed to vibrate with ultrasonic frequency (~ 20 kHz) with small amplitude and hence converting the continuous cutting to an intermittent cutting process. In the present work a horn (acts as an amplifier as well as a tool holder) with inserted tool tip is designed and FEM analysis has been done for its suitability for the process. The dynamic analysis has also been performed to find out the stress distribution in both parts under cyclic loading conditions. It enables to locate the highly stressed nodal regions. Experimental investigation has been carried out for both conventional turning (CT) and UVAT processes to demonstrate effects of various inputs on the output responses like cutting forces, surface roughness, tool wear and temperature rise in UVAT. Additionally, a 3D finite element model for UVAT and CT has been prepared. The simulation results like force and steady state tool tip temperature have also been validated with the experimental results and found to be in good agreement. The advantages of UVAT process have been discovered in terms of reduction in the cutting forces and surface roughness for the used Ti–6Al–4V workpiece.

Hastelloy X exhibits outstanding thermal fatigue resistance, making it a promising material for repairing 50CrVA landing gear via directed energy deposition (DED). However, the substantial differences in composition and thermophysical properties between 50CrVA and Hastelloy X pose challenges by affecting interfacial microstructure and surface quality. This study investigates the effect of DED process parameters (laser power p, powder feed rate f, scanning speed v, and overlap rate) on the dilution ratio (η), microscopic morphology, surface flatness (ζ), and porosity of Hastelloy X claddings on a 50CrVA substrate. An optimization methodology integrating thermal–flow coupled simulation models and orthogonal experiments is developed to fabricate high-quality claddings. Furthermore, the corrosion–wear performance of the claddings is evaluated. The results indicate that the η of a single track increases with higher p or lower f, while it first increases and then decreases with the increase in v. Ablation marks tend to occur at excessive p or insufficient f, while low v causes surface ripples. The ζ of a single layer initially improves and subsequently deteriorates with increasing overlap rate. Porosity is significantly influenced by p and f. The optimal p, f, v, and overlap rate are 1600 W, 2.4 g/min, 240 mm/min, and 55%, respectively. The wear resistance of the cladding is nearly identical to that of the substrate, while corrosion resistance is significantly improved. This work provides a theoretical foundation for high-performance repair of 50CrVA landing gear in aircraft.