Nose radius and cutting speed effects during milling of AISI 304 material

Not only milling parameters, but also cutting tool properties affect the machining performance. Therefore, in the current work, the effect of nose radius and cutting speed on the wear, force, surface roughness and chip morphology in down and up milling of AISI 304 stainless steel was investigated. Machining experiments were conducted with cutting tools with radii of 0.4, 0.8 and 1.2?mm at various cutting speeds in both down and up milling. Experimental results showed that the main tool failure mechanisms and modes were adhesion, abrasion, chipping and fracture during milling with various nose radii. Cutting forces dropped with the increment in nose radius regardless of the cutting speed and milling direction, except for up milling at 100?m/min. From the experimental results, it was found that roughness diminished with increase in both nose radius and speed. Surface roughness and the resultant forces during up milling were found to be lower than that during down milling. It was observed that the increment in nose radius increased the edge serration in chip morphology.     

The Impact of Tool Material and Cutting Parameters on Surface Roughness of a Nickel-Base Superalloy

The objective of the present work, is to assess the effect of tool material and cutting parameters on surface roughness of the supermet 718 Nickel-base superalloy, under dry cutting conditions and a constant nose radius (0.5 mm). The parameters investigated are cutting speed, feed rate, depth of cut and tool material. The tool materials used were the ceramic (Sandvik CC 680) and the CBN (Sandvik CB 50) inserts. These variables were investigated using a 2^k factorial design.

The present work demonstrates a favorable effect for ceramic inserts on surface roughness, when compared with CBN inserts. The work also, showed that the feed rate has the dominant effect among the parameters studied on the surface roughness, irrespective of the tool material used.     

Magnetorheological fluid-based nanotexturing of tool inserts for turning of duplex stainless steel

This paper deals with the study of the nanotexturing process of the cutting tool inserts with the influence of a magnetorheological fluid-based texturing method. The rake and flank surface of the cutting tool inserts were finished with a silicon carbide abrasive mixture of a magnetorheological fluid. Experimentation is conducted with input variables such as voltage, gap width, and polishing time to achieve the desired value of % reduction of surface roughness, polishing rate, andpolishing time. The surface roughness is found to be less than 40?nm for textured and 120?nm for non-textured inserts with a lesser polishing time. A higher polishing rate of the cutting tool inserts is achieved at a working voltage of 36?V and a gap width of 0.75?mm. The machinability characteristics of the nanotextured inserts are based on the cutting force; tool wear is studied for the turning operation of Duplex stainless steel. The tool flank wear is observed to be 0.63?mm, after 13th pass when turned with an unpolished insert and 0.612?mm after the 19th pass with a polished insert. From the results, it is found that the nanotextured inserts could achieve a tool life of 60% higher than the un-textured inserts in machining the duplex stainless steel.     

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.     

On-machine measurement of tool nose radius and wear during precision/ultra-precision machining

The tool state exerts a strong influence on surface quality and profile accuracy during precision/ultraprecision machining. However, current on-machine measurement methods cannot precisely obtain the tool nose radius and wear. This study therefore investigated the onmachine measurement of tool nose radius on the order of hundreds of microns and wear on the order of a few microns to tens of microns during precision/ultra-precision machining using the edge reversal method. To provide the necessary replication, pure aluminum and pure copper soft metal substrates were evaluated, with pure copper exhibiting superior performance. The feasibility of the measurement method was then demonstrated by evaluating the replication accuracy using a 3D surface topography instrument; the measurement error was only 0.1%. The wear of the cutting tool was measured using the proposed method to obtain the maximum values for tool arc wear, flank wear, and wear depth of 3.4 lm, 73.5 lm and 3.7 lm, respectively.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00397-y     

Investigating the Tool Life, Cutting Force Components, and Surface Roughness of AISI 302 Stainless Steel Material Under Oblique Machining

The aim of this work is to investigate the machinability of austenitic AISI 302 stainless steel under oblique cutting. This can be achieved by studying the cutting forces, analysis of tool life, and investigation of the surface roughness at different cutting conditions and nose radius. A factorial experiment and analysis of variance technique are used in which several factors are evaluated for their effects on each level. The machinability experiments are based on design of experiments to obtain empirical equations for machinability values for machining conditions such as speed, feed, depth of cut, and nose radius. The parameters considered in the experiments were optimized to attain maximum tool life using a response graph and a response table. Based on the response models, dual response contours (tool life and surface roughness as a response and metal removal rate) have been plotted in cutting speed-feed planes. Evaluating the effect of the predominant variables influencing the value of tool life is very important for improving the machined product quality.     

FACTORS AFFECTING SURFACE ROUGHNESS IN FINISH TURNING OF GRAY CAST IRON

The objective of this study was to ascertain the effect of tool wear on surface roughness and develop a more thorough understanding of the process variables affecting surface roughness. Experimental data from a finish turning operation on gray cast iron with uncoated tungsten carbide tools was used to develop a model for surface roughness as a function of cutting speed, feed rate, nose radius of the tool and the amount of wear on the tool. The experiment was statistically designed to minimize the number of runs. Tool wear was treated as a variable notwithstanding the fact that it is one of the responses of the process. The results showed that surface roughness is significantly affected by tool wear and the interactions between tool wear and other variables like cutting speed, feed rate and nose radius. The results also provide better insight into the problem of “adaptive” process control for finish turning operations.     

Investigation of the influential parameters of machining of AISI 304 stainless steel

Austenitic stainless steels are hard materials to machine, due to their high strength, high ductility and low thermal conductivity. The last characteristic results in heat concentration at the tool cutting edge. This paper aims to optimize turning parameters of AISI 304 stainless steel. Turning tests have been performed in three different feed rates (0.2, 0.3, 0.4 mm/rev) at the cutting speeds of 100, 125, 150, 175 and 200 m/min with and without cutting fluid. A design of experiments (DOE) and an analysis of variance (ANOVA) have been made to determine the effects of each parameter on the tool wear and the surface roughness. It is being inferred that cutting speed has the main influence on the flank wear and as it increases to 175 m/min, the flank wear decreases. The feed rate has the most important influence on the surface roughness and as it decreases, the surface roughness also decreases. Also, the application of cutting fluid results in longer tool life and better surface finish.     

Investigations on hard machining of Impax Hi Hard tool steel

In this paper, experimental investigations are carried out by end milling process on hardened tool steel, Impax Hi Hard (Hardness 55 HRC) a newly developed tool steel material used by tool and die making industries. Experiments are performed with an aim to study performance investigations of machining parameters such as cutting speed, feed, depth of cut and width of cut with consideration of multiple responses viz. volume of material removed, tool wear, tool life and surface finish to evaluate the performance of PVD coated carbide inserts and ball end mill cutters. It has been observed through scanning electron microscope, X-ray diffraction technique (EDX) that chipping and adhesion are active tool wear mechanisms and saw-toothed chips are formed while machining of Impax Hi Hard steel. It is also noticed out that tool life is not enhanced while machining with minimum quantity lubricant than dry machining. From the investigations, it is observed that hard machining can be considered as an alternative to grinding and EDM, traditional methods of machining difficult-to-machine materials i.e. hardened steel with hardness greater than 50 HRC with a scope of improved productivity, increased flexibility, decreased capital expenses and reduced environmental waste.     

Cuttability Investigation of Coated Carbides

The cutting performance of CVD-Ti(C,N)/Al₂O₃(Tl), CVD-Ti(C,N)/Al₂O₃/ TiN(T2) and PVD-TiN(T3) coated inserts was investigated in the dry turning of a low alloy steel. The PVD-TiN single-layer coated insert presented a better cutting performance based on wear and material removal indices than the CVD multilayer coated inserts at low feed rate. At high feed rate, it was the CVD-Ti(C,N)/Al₂O₃ coated insert that gave the best cutting performance. While excessive nose wear and plastic deformation limited the tool lives of Tl and T2, it was chipping/fracture for T3. Cutting temperature was deduced to have more effect on chip serrations than did degree of work hardening; with PVD-TiN inducing the highest degree of work hardening and lowest cutting temperature. Microstructural evidence also suggested brittle deformation and dissolution/diffusion as the wear mechanisms on T3, and plastic deformation, interfacial, and surface fatigue cracks were the observed phenomena for Tl and T2.     

Wear monitoring of single point cutting tool using acoustic emission techniques

This paper examines the flank and crater wear characteristics of coated carbide tool inserts during dry turning of steel workpieces. A brief review of tool wear mechanisms is presented together with new evidence showing that wear of the TiC layer on both flank and rake faces is dominated by discrete plastic deformation, which causes the coating to be worn through to the underlying carbide substrate when machining at high cutting speeds and feed rates. Wear also occurs as a result of abrasion, as well as cracking and attrition, with the latter leading to the wearing through the coating on the rake face under low speed conditions. When moderate speeds and feeds are used, the coating remains intact throughout the duration of testing. Wear mechanism maps linking the observed wear mechanisms to machining conditions are presented for the first time. These maps demonstrate clearly that transitions from one dominant wear mechanism to another may be related to variations in measured tool wear rates. Comparisons of the present wear maps with similar maps for uncoated carbide tools show that TiC coatings dramatically expand the range of machining conditions under which acceptable rates of tool wear might be experienced. However, the extent of improvement brought about by the coatings depends strongly on the cutting conditions, with the greatest benefits being seen at higher cutting speeds and feed rates. Among these methods, tool condition monitoring using Acoustic Techniques (AET) is an emerging one. Hence, the present work was carried out to study the stability, applicability and relative sensitivity of AET in tool condition monitoring in turning.     

Effect of tool wear on microrods fabrication using reverse μEDM

Arrayed microrods are used to drill array of microholes in workpieces by Micro electrical discharge machining (μEDM). In comparison to a single microrod, the use of an array of microrods enables drilling of multiple microholes in lesser time, and hence it offers a higher productivity. The present work focuses on the effect of tool wear on the dimensions of the machined array of microrods through reverse micro electrical discharge machining (R-μEDM). The effects of the input parameters such as voltage, capacitance and feed rate on the obtained length and diameter of the microrods have been investigated. This study introduces a simple analytical model to evaluate the amount of tool wear and material removal from a bulk rod. As the levels of voltage and capacitance increase from lower to higher, the tool wear increases by 574%. At lower levels of voltage and capacitance, a straight array of microrods with a longer length of about 1.961?mm is obtained. On the other hand, at higher levels of voltage and capacitance, the obtained microrods are found to have a shorter length of 1.725?mm but with taper. Scanning electron microscope (SEM) and optical microscope images are also analyzed for describing the effects of tool wear on the shape and size of the fabricated microrods.     

Investigation on tool wear and tool life prediction in micro-milling of Ti-6Al-4V

Short tool life and rapid tool wear in micromachining of hard-to-machine materials remain a barrier to the process being economically viable. In this study, standard procedures and conditions set by the ISO for tool life testing in milling were used to analyze the wear of tungsten carbide micro-end-milling tools through slot milling conducted on titanium alloy Ti-6 Al-4 V. Tool wear was characterized by flank wear rate,cutting-edge radius change, and tool volumetric change. The effect of machining parameters, such as cutting speed and feedrate, on tool wear was investigated with reference to surface roughness and geometric accuracy of the finished workpiece. Experimental data indicate different modes of tool wear throughout machining, where nonuniform flank wear and abrasive wear are the dominant wear modes. High cutting speed and low feedrate can reduce the tool wear rate and improve the tool life during micromachining.However, the low feedrate enhances the plowing effect on the cutting zone, resulting in reduced surface quality and leading to burr formation and premature tool failure. This study concludes with a proposal of tool rejection criteria for micro-milling of Ti-6 Al-4 V.     

Cost-effective way of hard turning with newly developed HSN2-coated tool

EN-31 (AISI 52100, hardness 55 HRC) is one of the difficult-to-cut steel alloys and it is commonly used in shafts and bearings. Nowadays, it is becoming a challenge to the cutting tool material for economical machining of extremely tough and hard steels. In general, CBN and PCBN tools are used for machining hardened steel. However, machining cost using these tools becomes higher due to high tool cost. For this purpose, carbide tool using selective coatings is the best substitute having comparable tool life, while its cost is approximately one-tenth of CBN tool. In this work, the newly developed second-generation TiAlxN super nitride (i.e., HSN²) is selected for PVD coating on carbide tool insert and further characterized using thermogravimetric analysis and differential scanning calorimetry for oxidation and thermal stability at high temperature. Later, HSN²-coated carbide inserts are successfully tested for their sustainability to expected tool life for turning of AISI 52100 steel. In the present study, forces, surface finish, and tool wear are used as a measure to appraise the performance of hard turning process. Experimentally, it is found that speed, feed rate, and depth of cut have considerable impact on forces, insert wear, and surface roughness of the machined surface.     

Effects of friction stir welding on microstructure and mechanical properties of extruded secondary aluminum 6061 alloy

Experiments were carried out to determine the effects of friction stir welding on microstructure and properties of recycled Aluminum 6061 alloy, whose alloy content varied from that of primary alloy. The alloy was processed at tool speed and feed ranges of 530 rev/min–1320 rev/min and 40 mm/min–100 mm/min respectively. Microstructure examination; tensile test and Vickers microhardness evaluation were carried out. Microstructure of the alloy was in four zones including: base metal, heat affected zone, thermo-mechanically affected zone and stirred zone. Average grain size of unprocessed material was 93 μm. Processing the alloy at 530 rev/min and 100 mm/min resulted in grains of average size 93 μm, 183 μm and 7 μm; in base metal, heat affected zone and stirred zone respectively. Tensile failure occurred in heat affected zone; that was exposed to high heat. The alloy hardness decreased to a minimum in heat affected zone, followed by a brief rise in thermo-mechanically affected zone, to another maximum in stirred zone. Processed zone hardness was inversely proportional to tool speed and directly proportional to feed rate. Increase in the speed and decrease in feed, increased heat which deteriorated the properties.     

工艺参数对基于3D打印支撑模具板料双点渐进成形性能的影响

目的 提高基于3D打印支撑模具的板料双点渐进成形的成形性能,获得更好的成形参数。方法 选择工具头直径、加工步长、进给速度3个工艺参数为因素,设计单因素实验,加工支撑模具半径为45 mm的球冠,获得成形破裂角度,得到成形性能较好的工艺参数范围,确定成形性能较高的双点渐进成形方案。结果 通过实验数据对比并综合表面质量、加工时间及成形精度等因素考虑,最佳工艺参数工具头直径为 10 mm（实验选择8, 10, 12 mm）,垂直层进给量为0.5 mm（实验选择0.2, 0.5, 1 mm）,加工进给速度为 400 mm/min（实验选择300~500 mm/min）。结论 一定区域内工具头半径越小,垂直层进给量越大,工具头进给速度越大,板料成形性能越好。     

Boron containing combination tool coatings—characterization and application tests

The requirements for durable tool coatings continuously increase. In many cases, tool coatings combining different phases or several layers could provide an improvement in tool life. The broad range of mechanical properties of materials in the B–C–N and Ti–B–N ternary systems, from very soft to superhard, presents many possibilities to generate various combination coatings. Such coatings were prepared using reactive sputter techniques with different target materials. An outstanding example is a superhard 3 μm thick coating system with a 0.5 to 0.8 μm thick cBN top layer deposited on cutting inserts. Soft coatings like hexagonal boron nitride were found to be essential for machining operations under dry conditions. The coatings were characterized with respect to hardness, abrasive wear rate and friction coefficients. The correlation between properties and composition was revealed. Application test results of B–C–N and Ti–B–N coating systems on tools obtained under near production conditions will be reported. Specifically, turning tests performed with cemented carbide cutting inserts coated with a superhard coating system with a cBN top layer will be discussed.     

Prediction and optimisation models for turning operations

Selection of process parameters has very significant impact on product quality, production costs and production times. The quality and cost are much related to tool life, surface roughness and cutting forces which they are functions of process parameters (cutting speed, feed rate, depth of cut and tool nose radius). In this paper, empirical models for tool life, surface roughness and cutting force are developed for turning operations. The process parameters (cutting speed, feed rate, depth of cut and tool nose radius) are used as inputs to the developed machineability models. Two data mining techniques are used; response surface methodology and neural networks. The data of 28 experiments have been used to generate, compare and evaluate the proposed models of tool life, cutting force and surface roughness for the selected tool/material combination. The resulting models are utilized to formulate an optimisation model and solved to find optimal process parameters, when the objective is minimising production cost per workpiece, taking into account the related boundaries and limitation of this multi-pass turning operations. Numerical examples are given to demonstrate the suggested optimisation models.     

Tool life and cutting forces when machining XC 45 steel

Machinability equations have been developed for prediction of tool life when machining XC 45 steel with P 10 and P 30 carbide inserts. A marked difference in cutability was observed between separate batches of P 10 inserts. A new criterion of tool life is suggested.

Equations are developed relating cutting forces to cutting conditions and to tool wear measurements. It is suggested that the percentage increase of the feed force may be suitable as a monitor of tool performance. The effect of cratering upon feed force is discussed and it is concluded that cratering should not necessarily affect feed force.

A slight positive correlation between cutting force and cutting speed has been observed for the radial and feed forces but not for the vertical cutting force.     

A study of the tool life of TiC and TiC plus Al2O3 chemical vapour deposited tungsten carbide tools

Tool life characteristics were investigated for tungsten carbide cutting tools coated with TiC and with TiC plus Al₂O₃. A low carbon steel workpiece was turned on a lathe at a feed rate of 0.206 to 0.410 mm rev^–1 and a depth of cut of 0.1 to 0.5 mm for cutting velocities between 100 and 250 m min^–1. Data were analysed using both Taylor's tool life equation and Wu's tool life method. Results were similar for both methods but Wu's method seemed to give more consistent results. Compared to an uncoated tungsten carbide tool, the tool life of both the coated tools were from 5 to 7 times longer and the improvement was greater at higher cutting speeds. The TiC plus Al₂O₃ coated tool was slightly superior to the TiC coated tool. The wear mechanism and a possible explanation of increased tool life for the coated tools are discussed.