Built-up Edge Research Articles

Built-up-edge effects on surface deterioration in micromilling processes

Built-up edge (BUE) has been noted as a major cause for surface finish deterioration in micromachining processes—even a trace formation of hardened and brittle structure on the tool edge alters the chip load, creates ad hoc and irregular material flow patterns, and results in deposits and smeared regions on the machined surface. To date, few investigations have addressed the formation and effects of BUE in micromachining. This paper is one of the first experimental investigations of the BUE effects on surface quality and its prediction in micromachining. Experiments were conducted on a Haas OM2 CNC milling system with air bearing spindle. The experiments consisted of micromilling 12mm long thin channels on 316L stainless steel plates (30mm×40mm×0.5mm) using uncoated tungsten carbide micromills (from Performance Micro Tools with flat end and Φ0.406mm diameter) at 16 different settings of carefully selected combination of cutting speed and chip load with minimum quantity lubrication (MQL). The surface morphology including BUE distribution, as well as BUE formation on tool surfaces were studied ex situ via optical and scanning electron microscopy. We introduce two metrics to quantify the severity of BUE, namely, BUE density and its distribution entropy. These metrics capture, respectively, the extent and dispersion of BUE on the surface. We also conducted empirical studies to assess the extent to which these quantifiers can determine the variation in surface finish (Sa). Results suggest that the BUE is the major determinant of surface finish besides the chip load effect in micromachining. Statistical Granger-causality tests suggest also that estimation of the BUE density can help with improving the accuracy (R2) of surface finish Sa prediction from a negative value (poor fit) with conventional model to 0.4, i.e., 40% of Sa variation in the micromachining experiments can be attributed to the BUE effect.

Evaluation of cryogenic cooling and minimum quantity lubrication effects on machining GLARE laminates using design of experiments

The current study investigates the influence of applying cryogenic liquid nitrogen cooling and minimum quantity lubrication (MQL) during drilling of glass aluminium reinforced epoxy (GLARE) fibre-metal laminates. Cutting forces, surface roughness, cutting tool condition and post-machining microhardness of the surface of the upper and lower aluminium sheets near the edge of drilled holes were investigated. The findings are also compared with results from previous dry drilling trials of a similar GLARE grade. An analysis of variance ANOVA was carried out to evaluate the impact of cutting parameters, and cooling conditions, and their percentage contributions when drilling GLARE. The use of MQL and cryogenic liquid nitrogen coolants increased the cutting forces; however, they both reduced the surface roughness of machined holes, adhesions and built-up edge formation on the cutting tool compared to dry drilling. Inspection of post-machining microhardness of the upper and lower aluminium sheets near the hole edges showed that it increased when using both coolants.

Investigating the influence of built-up edge on forces and surface roughness in micro scale orthogonal machining of titanium alloy Ti6Al4V

The edge geometry of cutting tools directly influences the chip formation mechanism in micro-mechanical machining, where the edge radius and uncut chip thickness are in the same order of magnitude. An uncut chip thickness that is smaller than the cutting edge radius results in a large negative rake angle during machining, and built-up edge formation then affects the mechanics of the process. In this study, micro-scale orthogonal cutting tests on titanium alloy Ti6Al4V were conducted to investigate the influence of built-up edge formation on the machining forces and surface roughness. Cutting edges in these tests are engineered using wire EDM technique to have an edge radius of around 2μm and clearance angles of 7° and 14°. It is observed that machining process inputs (uncut chip thickness, cutting speed, and clearance angle) affect the size of the built-up edge, which in turn affect the process outputs. It is observed that built-up edge formation protects the cutting edge from flank and crater wear under micro machining conditions and the influence of built-up edge on the surface roughness varies depending on the cutting speed and uncut chip thickness. Our findings also indicate a close relationship between the minimum uncut chip thickness and the mean roughness depth (Rz) of the machined surface. The minimum uncut chip thickness is found to be around 10% of the edge radius in the presence of built-up edge.

Investigation on the Behavior of Austenite and Ferrite Phases at Stagnation Region in the Turning of Duplex Stainless Steel Alloys

This paper investigates the deformation mechanisms and plastic behavior of austenite and ferrite phases in duplex stainless steel alloys 2205 and 2507 under chip formation from a machine turning operation. SEM images and EBSD phase mapping of frozen chip root samples detected a build-up of ferrite bands in the stagnation region, and between 65 and 85 pct, more ferrite was identified in the stagnation region compared to austenite. SEM images detected micro-cracks developing in the ferrite phase, indicating ferritic build-up in the stagnation region as a potential triggering mechanism to the formation of built-up edge, as transgranular micro-cracks found in the stagnation region are similar to micro-cracks initiating built-up edge formation. Higher plasticity of austenite due to softening under high strain is seen responsible for the ferrite build-up. Flow lines indicate that austenite is plastically deforming at a greater rate into the chip, while ferrite shows to partition most of the strain during deformation. The loss of annealing twins and activation of multiple slip planes triggered at high strain may explain the highly plastic behavior shown by austenite.

Experimental Investigations on Effect of Ceramic B4C Particulate Addition on Cutting Forces and Surface Roughness during Turning of 6061Al Alloy

ABSTRACTAluminium matrix composites are of great interest for researchers in recent years because of their excellent combinations of engineering properties over traditional materials. The machinability of these aluminium matrix composites has become vital for manufacturing industries. During machining of aluminium matrix composites, the cutting forces and surface roughness are dependent on machining parameters (feed rate, cutting speed and depth of cut) and manufacturing parameters (size of the particles, volume fraction, porosity, hardness). With this backdrop, the present work is aimed at investigating the effect of machining parameters, viz. cutting speed, feed rate and depth of cut on the cutting force components, namely, feed force (Ff), radial force (Fd), cutting force (Fc) and surface roughness. The experiments were performed on 0, 5, 7 and 9 wt% B4C particulate of 88 µm size reinforced composite specimens. The prepared specimens were subjected to turning operation on a conventional lathe machine using polycrystalline diamond (PCD) tool to evaluate the effect of B4C particulate addition with varying percentages on cutting forces and surface roughness. Results reveal that the cutting force components decrease with the increase in the wt% of ceramic B4C particulate reinforcement, which can be attributed mainly to increase in porosity, hardness and dislocation densities. SEM image obtained from composite having low wt% of ceramic B4C particulates (5 wt%), which is machined at higher cutting speed and higher depth of cut, has clearly shown the presence of built-up edge (BUE) at the tip of polycrystalline diamond tool. Further, cutting forces increased with increase in feed rate and depth of cut for both 6061Al matrix and 6061Al-B4C composites. It is observed that the surface quality is significantly improved when the cutting speed is increased, and depth of cut and feed rate are decreased.

The Effect of Different Modifiers in AlSi7Mg0.3 Alloy on Built-up Edge Formation in Machining

Aluminium and silicon alloys are widely used in practice. But there is increasingly more emphasis placed on the research and development of these materials. The aim of this article is to analyse modified aluminium alloy AlSi7Mg0.3. The paper is focused on the effect of particular modifiers in AlSi7Mg0.3 alloys on built-up edge formation in machining. Four variants of castings (unmodified alloy and alloy modified by chemical elements - strontium, calcium and antimony) were used. All alloys were compared with non-modified alloy. There were moulded castings from each modified variant and the casting of non-modified alloy. It was casted using a gravity-die casting into a metal mould with a thermal insulation.

Relationship of microstructure, mechanical properties and titanium cutting performance of TiAlN/TiAlSiN composite coated tool

Research on the relationship of microstructure and properties of coated tools such as TiAlN and TiAlSiN plays a key role in obtaining the needed cutting performance in titanium machining. In this study, three kinds of coatings of TiAlN, TiAlSiN monolayer and TiAlN/TiAlSiN composite multilayer have been fabricated by magnetron sputtering method. It is found that the coating structure changes from columnar growth to nanocrystal growth by doping Si element. The TiAlN/TiAlSiN coating is composed by a coarse columnar TiAlN bottom layer and a fine nanocrystalline TiAlSiN top layer. Premature spalling problem (Lc2) is improved by forming the TiAlN/TiAlSiN multilayer structure. Titanium cutting experiment shows that the major wear mechanism of these coated tools is adhesive wear and chipping. The TiAlSiN coated tool has the longest cutting distance at various cutting speeds in these three kinds of coatings. This is because less built-up edge and chipping are generated at the cutting edge due to the dense nanocrystal structure, high hardness and good oxidation resistance of TiAlSiN coating. Therefore, the TiAlSiN coating with dense structure, high hardness and good oxidation resistance is recommended to use in high speed turning titanium.

純鉄および低炭素機械構造用鋼S10Cの切削面と構成刃先の創成メカニズム

Machined surface and chip formation mechanism in pure iron with a single phase and low C structural steel (S10C) with dual phases is discussed, using the Quick Stop Test (QST). On the machined surfaces, chip surfaces and built-up edges of the QST samples, many elongated dimples are found and the dimples suggested that the fracture occurred on both the rake side and flank side of the tool. These results suggested that the chip, surface and Built-up Edge (BUE) formation of pure iron and S10C are formed by accumulation of many fine ductile fractures. Therefore BUE formation is affected by microstructure, because the ductile fracture property is affected by microstructure of steels.

Application of Combined Taps for Increasing the Shaping Accuracy of the Internal Threads in Aluminium Alloys

The main difficulties of shaping of internal treads with the required accuracy in aluminium alloys caused by a built-up edge were studied in this paper. A new design of deforming-cutting taps which allows the increase of the accuracy of internal threads was proposed. The difference of the new design from the existing ones is that each land of tap has both deforming and cutting teeth. An operation principle of the proposed tap is based on the preliminary plastic deformation with the following cutting of the workpiece material. In order to compare the proposed tap with existing designs of deforming and cutting taps, the comparative experimental study was carried out. The results of this experiment have shown that utilization of the proposed tap can essentially increase the quality of internal threads and prevent BUE formation.

Reduction of built-up edge formation in machining Al- and cast iron hybrid components by internal cooling of cutting inserts

In parallel machining of aluminium and cast iron hybrid components, like in precision boring of crankshaft bearing bores, a tribo-chemical reaction occurs on the rake face of a cutting insert and comes along with significant built-up edge formation. Cooling strategies (external, internal) and the cutting fluid quality show significant influence. The determination of the temperature dependency of the intermetallic compound formation velocity (Fe-Si-C) gives a better understanding of this particular tribo-chemical process. An internal cooling of the cutting insert allows a reduction of the built-up edge effect by reducing the temperature on the rake face.

A Study on the Orthogonal Cutting Mechanism Based on Experimental Determined Displacement and Temperature Fields

This paper presents a new methodology to study the orthogonal cutting mechanism based on the displacement and temperature fields obtained by the particle image velocimetry technique and thermal infrared imager, respectively. With the displacement and temperature fields as inputs, the thermo-elasto-viscoplastic constitutive model is adopted to calculate the orthogonal cutting strain and stress fields. The formation of built-up edge is detected using the velocity fields. The geometries of the primary shear zone for two different cutting speeds are determined by the strain rate field. The shear stress distributions along the shear plane are obtained according to the calculated results.

Simultaneous Machining of a Material Combination with an Internally and Externally Cooled Cutting Insert

This paper discusses the machining of cylinder running faces of aluminum engine blocks with reinforced, arc-sprayed cylinder walls. Such special material combinations and, therefore, processing conditions are common in the automotive sector, where the load-oriented material use induces a significant reduction of fuel consumption. The machining of such a material combination comes along with several challenges including notch wear on the main cutting edge as a result of the arc-sprayed cylinder walls or a built-up edge formation on the main cutting edge because of the aluminum. Promising approaches by means of an internally and externally cooled cutting insert are presented in this paper and compared to common external cooling.

Effect of cutting speed on the carbide cutting tool in milling Inconel 718 alloy

Abstract

Analysis of Chip Removal Operations via New Quick-Stop Device

Machining is obviously indispensable to industrial manufacture, a process whereby a workpiece takes its planned shape after proper chip removal. The type and the size of a chip from such a process are determined by a set of factors, the analysis of which can provide valuable insights into the cutting process. In this study, a new quick-stop device (QSD) for chip removal was designed, manufactured, and employed in an analysis of chip formation in chip removal with cutting tool at varying cutting speeds. The samples competently illustrate the differences in the formation of chips at various cutting speeds. Depending on material and cutting conditions, a chip may be continuous or discontinuous. Employing metallographic techniques, the present study analyzed the orthogonal cutting of aluminum 5000 with cutting tool. During the experiments, the built-up edges (BUEs), the surface quality, and the interactions among machining parameters were observed. At the end, a frozen chip with a BUE was divided into seven sections. The results show that the new QSD is effective and BUEs have a direct effect on the quality of a workpiece's surface and additionally can increase the penetration depth and machining forces.

Evaluation of cutting force and surface roughness in the dry turning of Al–Mg2Si in-situ metal matrix composite inoculated with bismuth using DOE approach

Al–Mg2Si particulate metal matrix composites (PMMC) has recently received wider attention because of its improved properties, however there is a lack of knowledge about machinability characteristics of these composites especially with bismuth addition. The purpose of this study is to evaluate the machining parameters and modifier element effects on cutting force (Fc) and surface roughness (Ra) when dry turning Al–Mg2Si with a coated carbide tool (K10U). The experimental trials are designed using the multi-level factorial design (DOE) and their results are analyzed using Analysis of Variance (ANOVA). Statistical models are developed to represent the relationship among machining parameters as independent variables, surface roughness and cutting force as response variables. For each experiment, a new cutting insert is used to encourage accurate reporting of the cutting force and surface roughness. The statistical observation revealed that the main effect of cutting speed, feed rate and modifier element influenced the cutting force and surface roughness. Moreover, there are no interaction effects of variables. Built-up-edge (BUE) formation was observed at every combinations of cutting speed and feed rate which affected the surface quality negatively. The proximity of predicted results and experimental results provide evidence that the DOE method has successfully derived the predictive models. The addition of Bi as modifier reagent results in lower cutting force and better surface roughness due to the formation of Bi compound and modifies the morphology of Mg2Si reinforcement particle. Our findings showed that the Bi is a promising element to improve the machinability of Al–Mg2Si composite.

Influence of High-Cycle Fatigue on Crater Wear Characteristics of Cemented Carbide Tool

Recently, in order to make positively use of the effect of adhesive layer, which works as Build-up edge or Belag on the tool surface during machining operation, there have many investigations on the technique to reduce the wear of cutting tool. However, the mechanism of wear on the rake face is unknown and the reason why the adhesive layer can resist the abrasion is also unclear.This study aims to propose a new crater high-cycle fatigue wear model depending on the tool adhesion model established by the surface cluster on the interface between the Tool-Work Piece. By using this model we can elucidate the mechanism of adhesive layer. When the chip flows on the rake face, the commensurate phase occurs in the surface cluster on the interface, and the surface cluster slides in the similar form of dislocation. At the same time, the strong chemical bonding among the surface clusters becomes the repeat force which can result in the fatigue failure on the tool, and the tool crater wear happens. The energy dissipation process associates with the vibration of cluster, which increases the tool temperature rapidly. Therefore, the crater wear is a damage process on the tool with the high-temperature and high-cycle fatigue.In this study, the mechanism of crater wear when the cemented carbide cut the carbon steel was investigated using the adhesion cluster model, and the crater wear model was proposed to estimate the properties of the adhesive layer.

Study on tool wear and chip shapes in deep drilling OF AISI 4150 steel

Deep drilling process is widely used in the manufacturing of diesel injection components such as the injection holder, used to transport fuel from the high-pressure pipe to the combustion chamber of the engine. The material used in the manufacturing of these components is low-alloy steel AISI 4150. This high percentage chrome (~1 %) and molybdenum (~0.2 %) steel attains its high resistance through heat treatment (quenching and tempering), which allows this material for working with high injection pressures up to 2300 bar. However, it presents problems in deep drilling operations. This is due to the high rate of drill bit breakage, high tool wear and ribbon-like chips. This work studies deep drilling of AISI 4150 steel by analyzing through the method of design of experiment, the influence of the following machining factors: cutting speed, feed-rate and tool coating. Tool wear, machining drilling torque and shape of the machined chips were considered for the analysis. Evidences were found that the uncoated tool shows a cyclical wear mechanism of adhesion removal workpiece material on the tool, where material is welded onto the cutting edge forming the built-up edge. The results showed that TiNAI-coated tool did not present this wear mechanism and it outperformed the uncoated tool.

Effect of reinforcement on the cutting forces while machining metal matrix composites–An experimental approach

Hybrid metal matrix composites are of great interest for researchers in recent years, because of their attractive superior properties over traditional materials and single reinforced composites. The machinabilty of hybrid composites becomes vital for manufacturing industries. The need to study the influence of process parameters on the cutting forces in turning such hybrid composite under dry environment is essentially required. In the present study, the influence of machining parameters, e.g. cutting speed, feed and depth of cut on the cutting force components, namely feed force (Ff), cutting force (Fc), and radial force (Fd) has been investigated. Investigations were performed on 0, 2, 4, 6 and 8 wt% Silicon carbide (SiC) and rice husk ash (RHA) reinforced composite specimens. A comparison was made between the reinforced and unreinforced composites. The results proved that all the cutting force components decrease with the increase in the weight percentage of the reinforcement: this was probably due to the dislocation densities generated from the thermal mismatch between the reinforcement and the matrix. Experimental evidence also showed that built-up edge (BUE) is formed during machining of low percentage reinforced composites at high speed and high depth of cut. The formation of BUE was captured by SEM, therefore confirming the result. The decrease of cutting force components with lower cutting speed and higher feed and depth of cut was also highlighted. The related mechanisms are explained and presented.

Tool Life and Wear Mechanism when Machining LM6 Aluminium (MMC) with Coated and Uncoated High Speed Steel

This paper aims to study the tool life of coated and uncoated high speed steel (HSS) when machining LM6 aluminium. The experiment was carried out in dry condition with spindle speed of 5000 rpm and 6000 rpm, and feed rate of 90 mm/min and 120 mm/min. Axial and radial depth of cut remain constant at 0.5 mm and 1.0 mm, respectively during the experiment. Throughout the experiments, coated HSS showed higher tool life as compared to uncoated HSS due to the coating layer of titanium aluminium nitride (TiAlN) provides protection from rapid wear during machining. For both cutting tools, the optimum cutting parameter was recorded at 5000 rpm spindle speed, 90 mm/min feed rate, 0.5 mm axial depth of cut and 1.0 mm radial depth of cut. Some evidence of built up edge (BUE) formation were observed at most of cutting tools, showing the dominant wear mechanisms appear to be adhesive wear.

An Experimental Study of Wear Mechanism on High Speed Machining of FC300 Gray Cast Iron Using TiAlN Coated Carbide Cutting Tool

This paper presents an experimental study of wear mechanism on high speed milling of FC300 gray cast iron using TiAlN coated carbide cutting tool. The experiment was carried out under dry cutting condition with different cutting speed (95-143m/min) and feed rate (4000-7000 mm/min). The cutting tool for machining FC300 gray cast iron is a ball nose end mill ø32 mm coated with TiAlN. Wear mechanism was analyzed at VB 0.08mm after 60 minute machining. The flank wear increased when the spindle speed and feed rate increased caused by the generated high shearing force and high cutting temperature. The dominant wear mechanisms appear to be the abrasion, adhesion, chipping and delaminating of coating at the contact surface of cutting tool. Formation of built-up edge (BUE) was evidence for most of the cutting trials.