Milling Wear Research Articles

Tool wear in dry helical milling for hole-making in AISI H13 hardened steel

Helical milling is a hole-making process which can be applied to achieve high-quality finished boreholes in hardened steels. Due to the drilling process limitations, which are intensified when applied in hardened steels, the helical milling process can be applied on hole-making tasks in moulds and dies industry, since milling have been widely applied in moulds and dies machining to replace high-cost operations like grinding and electrical discharge machining. However, to succeed in achieving high-quality boreholes in hardened parts, which presents high added value due to previous operations, tool wear in the helical milling of hardened steels should be more investigated. In the present study, dry helical milling tool life tests were conducted in AISI H13 hardened steel parts, varying the cutting velocity. The flank wear on frontal cutting edges was progressively measured through optical microscopy, and SEM/EDS was performed in frontal and peripheral worn cutting edges. The wear occurred progressively in the flank of the frontal cutting edges with adhesion and oxidation as main wear mechanisms. In the peripheral edges, coating loss, and adhesion of workpiece material in the tool clearance surface were observed, besides fracture in the tool nose flank with the highest cutting velocity. A nested ANOVA was performed to evaluate the burr height in the borehole exit. The tool life stage was statistically significant in the burr height.

Effect of reverse current on tool wear in micro-electrical discharge milling

An RC-type pulse generator is useful in micro-electrical discharge milling due to its small discharge energy. However, when using this kind of generator, the current between the tool and the workpiece oscillates because of the stray inductance of the circuit. This causes current to flow from the tool to the workpiece in reverse direction to the main discharge current. When the reverse current flows, tool polarity is changed which intensifies tool wear. In this research, the reverse current is eliminated by connecting a MOSFET to a normal RC-type pulse generator. As a result, tool wear was reduced and geometrical accuracy was increased during machining of stainless steel using cemented carbide tool. Tool wear was further reduced through the use of deionized water with low resistivity. However, the use of low resistivity water decreases tool wear but can also reduce geometrical accuracy. The combination of using a MOSFET with low resistivity water therefore reduces tool wear while maintaining geometrical accuracy. The addition of the MOSFET to the RC circuit reduced the relative wear ratio by up to 67%. Thus, removing the reverse current is effective in reducing tool wear in various machining conditions.

Cutting Performance of Different Coated Micro End Mills in Machining of Ti-6Al-4V.

Tool wear is a significant issue for the application of micro end mills. This can be significantly improved by coating materials on tool surfaces. This paper investigates the effects of different coating materials on tool wear in the micro milling of Ti-6Al-4V. A series of cutting experiments were conducted. The tool wear and workpiece surface morphology were investigated by analyzing the wear of the end flank surface and the total cutting edge. It was found that, without coating, serious tool wear and breakage occurred easily during milling. However, AlTiN-based and AlCrN-based coatings could highly reduce cutting edge chipping and flank wear. Specifically, The AlCrN-based coated mill presented less fracture resistance. For TiN coated micro end mill, only slight cutting edge chipping occurred. Compared with other types of tools, the AlTiN-based coated micro end mill could maximize tool life, bringing about an integrated cutting edges with the smallest surface roughness. In short, the AlTiN-based coating material is recommended for the micro end mill in the machining of Ti-6Al-4V.

Tool Wear and Form Accuracy in Ultrasonic-Assisted Milling of Soda-Lime Glass

Machining of hard and brittle materials is inherently involved with tool wear, which influences the dimensional and form accuracy of the machined product. Ultrasonic-assisted machining process is suitable for hard-to-cut materials such as ceramics, glass, and metal matrix composites, etc. In the current study, the mechanism of tool wear is investigated during ultrasonic-assisted milling of soda-lime glass as one of hard and brittle materials. Ultrasonic-Assisted Milling (UAM) combines the material removal mechanism of grinding and the milling kinematics with ultrasonic assistance. The effect of different process parameters, i.e. feed rate, depth of cut, cutting fluid, and ultrasonic vibration assistance on the tool wear behavior are investigated. Form accuracy of the machined slots is also investigated. The results showed that UAM produces less tool wear than conventional milling (CM). However, CM gives less error in the slot dimensions than UAM.

Experimental evaluation on texture of flank face on tool wear in chamfer milling of stainless steel

This paper presents a novel grinding enabled texture, ‘V’ shaped texture (VST), on flank face. To implement the texture on a cutting performance, a set of chamfering experiments of stainless steel materials used as 3C product shell usually are presented. Cutting forces, surface qualities, and tool wear are measured and compared, of which results show that both smallest surface roughness and longest tool life are achieved by using a 30° VST chamfer tool. By comparing the results, a clear conclusion can be drawn that texture types and angles are not independent factors to cutting performance; therefore, a suitable combination of texture types and texture angles can provide a significant improvement of tool life and surface quality.

Investigations on surface microstructure in high-speed milling of Zr-based bulk metallic glass

Bulk metallic glasses (BMGs) are a relatively new group of metallic alloys with amorphous microstructure. BMGs have been increasingly used in industrial applications due to their high strength and high corrosion resistance. The microstructural evolution and the surface generation mechanisms in machining of BMGs and crystalline metal alloys are substantially different. This paper presents the investigations on surface microstructure and progressive tool wear in high-speed milling of Zr-based BMG. The crystallization of originally amorphous BMG material caused by the milling process was examined. The microstructure properties of BMG at amorphous and crystalline phases were determined. The effect of coolant on the progressive tool wear and the constituent element changes of BMG was investigated. The results provide new and comprehensive information on surface microstructure property in response to high-speed milling of Zr-BMG, and can guide the process planning in achieving desired surface property in milling of Zr-BMG components.

Modeling flatness deviation in face milling considering angular movement of the machine tool system components and tool flank wear

The torsional angle, χYDeg, of a machine tool-device-spindle unit is formulated in a face-milling operation. As there is no angular compliance in the technical specifications for the machine tool, a novel method is proposed for the determination of the angular compliance values of a GF2171S5 machine milling system. Deviation from flatness, ΔZfl, is therefore also modeled in this paper, for the first time, by considering the parameters of milling and tool wear. The proposed model performs an acceptable evaluation of various types of flatness deviation for different flank wear values. The face milling and tool-wear parameters and their influence on the torsional angle of the tool-device-spindle unit are calculated. Besides, the effects of different settings on the machining process and the material-cutting speed vc and depth ap, cutting-edge angles kr, and tool slenderness-lo/D in combination with various depths of flank wear VB on the torsional angle of the mill χYDeg and flatness deviation ΔZfl are investigated. This method of determining the angular torsional values can be applied to other milling machines. Moreover, the model can be used to compensate the torsional angle of the mill face, thereby minimizing the flatness deviation.

Notch wear prediction model in high speed milling of AerMet100 steel with bull-nose tool considering the influence of stress concentration

Notch wear is one of the predominant types of tool failure in high speed milling of difficult-to-cut materials. This paper aims to reveal the formation and impact mechanisms of notch wear in bull-nose milling. Tool wear on rake face during dry milling of AerMet100 steel is investigated, severe notch wear is observed in lots of experiments. Based on the comparison of uncut chip thickness variations under two different cutting types, an attempt is made to explain the occurrence of notch wear from the view point of stress concentration. In order to quantitatively characterize the degree of stress concentration at any position on tool edge, a stress concentration factor is defined in this paper. The non-uniform and instantaneous variable characteristics of stress distribution along the cutting edge during bull-nose milling are taken into consideration. Then a predictive model of notch wear depth considering the influence of stress concentration is developed. Series of cutting tests are performed to validate the notch wear depth model, and the results indicate that the proposed model is feasible. In addition, the effects of different cutting parameters on notch wear are discussed. Further, this work can be applied to optimize process parameters for controlling notch wear, improving machining efficiency and reducing production cost.

Tool wear of corner continuous milling in deep machining of hardened steel pocket

Pocket molds are widely applied, whose pockets usually contain many transition corners. The machining efficiency of pocket mold can be improved significantly through deep milling. However, tools are subject to quick wear and damage during corner deep milling. Corner rounding along tool path by different approaches has great influence on the tool wear in deep milling of hardened steel pocket mold. Therefore, conducting related researches on tool wear is of practical significance. Firstly, continuous cutting pocket molds were designed for typical corners of different corner rounding approaches as per the basic theory of tool engagement angle in milling, and then hardened steel was subject to deep milling and the tool was inspected and analyzed; afterwards, tool wear process and mechanism, etc. were studied. The results showed that during the deep milling of hardened steel, adhesion, oxidation, and diffusion wear appeared gradually since the stabilization of tool wear and further aggravated along with the cutting process, which led to wear and peeling of coating as well as highly possible tool damage like tipping and chipping of tool nose in later period. It was easy to generate high tool-chip interface temperature and great tool load in the high-speed deep milling of hardened steel with small corner rounding radius. In this case, the cutting edge was under considerable thermal fatigue and mechanical shock and thus subject to extensive abrasion wear, adhesion wear, and diffusion wear. The tool wear could be reduced notably by increasing the corner rounding radius.

On sustainable manufacturing titanium alloy by high-speed EDM milling with moving electric arcs while using water-based dielectric

Abstract In order to solve the environmental pollution and low machining efficiency of conventional EDM process, a sustainable manufacturing method of high-speed EDM milling while using water-based dielectric is proposed. Firstly, the machining principle of moving electric arcs was investigated. Then, models were established and utilized to explain the characteristics of high-speed EDM milling with moving electric arcs. Experiments on machining titanium alloy with this method were carried out to analyze the machining characteristics. The experimental results showed that the material removal rate (MRR) was significantly improved. The maximum MRR was almost five times greater than that of conventional EDM. Moreover, the lower tool-electrode wear in high-speed EDM milling was obtained, which can be attributed to the high-speed rotation of tool-electrode and protective layer formation on the tool-electrode surface caused by sputtering and deposition of Ti-6Al-4V.

Modeling and optimization of tool wear in MQL-assisted milling of Inconel 718 superalloy using evolutionary techniques

The Inconel 718 alloy, a difficult-to-cut superalloy with an extensive demand on aircraft and nuclear industries, being a low thermally conductive material exhibits a poor machinability. Consequently, the cutting tool is severely affected, and the tool cost is increased. In this context, an intelligent solution is presented in this paper—investigation of minimum quantity lubrication (MQL) and the selection of best machining conditions using evolutionary optimization techniques. A series of milling experiments on Inconel 718 alloy was conducted under dry, conventional flood, and MQL cooling modes. Afterward, the particle swarm optimization (PSO) and bacteria foraging optimization (BFO) were employed to optimize the cutting speed, feed rate, and depth-of-cut to minimize the flank wear (VBmax) parameter of a cutting tool. Though both the PSO and BFO models performed well, the validated results showed the superiority of PSO. Furthermore, it was found that the MQL performed better than the dry and flood cooling condition with respect to the reduction of the tool flank wear.

Machining characteristics and removal mechanisms of moving electric arcs in high-speed EDM milling

Low machining efficiency is the major challenges of conventional electrical discharge machining (EDM). To resolve this problem, a novel machining method of high-speed EDM milling with moving electric arcs was developed, which can remove material continuously without discharge intervals of pulse power supply and achieve extremely low tool-electrode wear for the direct-current power supply employed. An EDM milling equipment was devised to explore machining characteristics and removal mechanisms of moving electric arcs in high-speed EDM milling process. Firstly of all, the motion characteristics of moving electric arcs were investigated. The theoretical analysis shows that the arcs maintain an independent movement relative to the tool-electrode and workpiece. Then, the plasma channels were captured by high-speed video camera, which contributed to develop the model of removal mechanisms of moving electric arcs. Finally, the machining experiments were carried out based on titanium alloy, which verified that a much higher material removal rate could be easily achieved by moving electric arc. Moreover, the tool-electrode wear in high-speed EDM milling is much lower than conventional EDM due to the protective layer formation.

An experimental study on tool wear behaviour in micro milling of nano Mg/Ti metal matrix composites

With the development of metal matrix composites (MMCs), the mechanical properties of MMCs with a small volume fraction of nano-sized particles were found to be even superior to that with a larger content of micron-sized particles. However, the improved mechanical properties of MMCs bring tremendous challenges such as premature tool failure in Ti machining process. This study exhibits an investigation on tool wear in micro milling of magnesium-based MMCs reinforced with 1.98 Vol.% of nano-sized titanium particles using 0.5-mm diameter two-flute tungsten carbide micro endmills. The tool wear was characterised both quantitatively and qualitatively by observing tool wear patterns and analysing the effect of cutting parameters on flank wear, reduction in tool diameter, cutting forces, surface roughness, and burr formation. A finite element model was established to understand matrix deformation and interaction between tool-particle and further explain the tool wear phenomena observed. Additionally, cutting performance using AlTiN coated and uncoated was also investigated. The results indicated that the main wear mechanisms were identified as flank wear and edge chipping due to abrasive wear and chip adhesion in uncoated micro endmills. These wear mechanisms were confirmed by chip formation process produced by finite element modelling (FEM). It was also observed that the largest tool wear occurred at the smallest feed per tooth (0.75 μm/tooth) and smallest wear occurred at the largest feed per tooth (3 μm/tooth). Also, the effect of BUE on tool wear and surface generation was studied.

A hybrid approach to multi response optimization of micro milling process parameters using Taguchi method based graph theory and matrix approach (GTMA) and utility concept

Nowadays, it is required to produce micro products with high dimensional accuracy to use them in different applications like aerospace, electronic and optics. The objective of this study is to investigate influence of process parameters on surface roughness (Ra and Rq), tool wear and cutter vibration in micro milling of AISI304 stainless steel. According to orthogonal array of L27, twenty-seven experiments were conducted on the workpiece with carbide end mill cutter at different levels of spindle speeds, feeds and depth of cuts. A hybrid approach of Taguchi method based graph theory and matrix approach (GTMA) and utility concept was used for multi response optimization of process parameters. The GTMA was used to calculate weightage of four responses as per user’s opinion or preference. The utility concept was used to calculate utility value of four responses using preference scale. Mean utility values of responses are analyzed with Taguchi method and analysis of variance. The optimum process parameters for the minimization responses were found to be 6000 rpm of spindle speed, 95 µm/teeth of feed and 50 µm of depth of cut. The predicted responses at optimal process parameters are Ra = 0.534 µm, VB = 70.861 µm, Amp = 54.395 µm and Rq = 0.894 µm. A confirmation test was also carried out to verify the results.

Experimental investigation on tool wear and measurement method in micro milling with carbide tools

In this paper, the carbide tool wear in micro milling is investigated and a new tool wear measurement method is proposed. Al7075 alloy and C45 steel is used as the work-piece materials due to their common application. The cutting tools with different machining time are obtained by experiments and the states of tool wear with different work-piece materials are compared. The influence of tool wear on micro milling forces and surface topographies is studied through experiments. The traditional tool wear measurement methods based on the tool edge radius, tool diameter and flank wear width are introduced. For a more complete explanation of the tool wear, a new tool wear measurement method based on the wear area is proposed. The carbide tool wear values based on the tool edge radius, tool diameter, and flank wear width and wear area are measured and the tool wear process is obtained. Compared with the traditional methods, the new tool wear measurement method based on the wear area can explain the tool wear process more reasonable.

Experimental investigation on tool wear and measurement method in micro milling with carbide tools

In this paper, the carbide tool wear in micro milling is investigated and a new tool wear measurement method is proposed. Al7075 alloy and C45 steel is used as the work-piece materials due to their common application. The cutting tools with different machining time are obtained by experiments and the states of tool wear with different work-piece materials are compared. The influence of tool wear on micro milling forces and surface topographies is studied through experiments. The traditional tool wear measurement methods based on the tool edge radius, tool diameter and flank wear width are introduced. For a more complete explanation of the tool wear, a new tool wear measurement method based on the wear area is proposed. The carbide tool wear values based on the tool edge radius, tool diameter, and flank wear width and wear area are measured and the tool wear process is obtained. Compared with the traditional methods, the new tool wear measurement method based on the wear area can explain the tool wear process more reasonable.

Machining Mechanisms and Characteristics of Moving Electric Arcs in High-speed EDM Milling

A novel machining process of high-speed EDM milling with moving electric arcs was developed, which can remove material continuously without discharge intervals of pulse power supply and achieve extremely low electrode tool wear for the direct-current power supply employed. An EDM equipment was devised to explore machining characteristics and removal mechanisms of moving electric arc in high-speed EDM milling process. Firstly, the motion characteristics and resistance properties of moving electric arc were investigated. The theoretical analysis shows that the arcs maintain a relatively independent movement between the electrode and workpiece. Then, the plasma channel of electric arc was captured by high-speed video camera to explore the machining mechanisms of the moving electrical arc. Finally, the machining experiments were carried out based on titanium alloy, which verified the above mechanisms and a much higher material removal rate could be easily achieved by moving electric arc. Moreover, the tool electrode wear in high-speed EDM milling is much lower than conventional EDM due to the protective layer formation.

Taguchi analysis of tool wear and delamination in milling of GFRP composite using coated K10 end mill

Taguchi analysis of tool wear and delamination in milling of GFRP composite using coated K10 end mill

Taguchi analysis of tool wear and delamination in milling of GFRP composite using coated K10 end mill

Modern composite materials constitute a significant proportion of the engineered materials market ranging from everyday products to sophisticated niche applications. While composites have already proven their worth as weight -saving materials, the current challenge is to make them machinable with minimum tool wear. In this study an attempt has been made to fabricate Glass fibre reinforced composites using hand moulding techniques and test its machinability based on delamination and tool wear using Ti-Nimate Coated Carbide and Ti-Carbonitride K10 end mill. The experiment was conducted in Vertical Machining Centre using Taguchi L8 orthogonal array. The test results showed that Ti-Carbonitride causes less damage to material during milling of glass fibre reinforced plastics (GFRP), whereas Ti-Nimate Coated Carbide has less tool wear at high speed, feed and depth of cut.

Assessment of the effect of borax and boric acid additives in cutting fluids on milling of AISI O2 using MQL system

The present study assesses the effects of eco-friendly cutting fluids prepared on cutting performance and tool wear in hard milling of AISI O2 cold work tool steel applying the minimum quantity lubrication (MQL) technique for sustainable manufacturing. Boron compounds such as boric acid (BA) (5% wt.) and borax (BX) (5% wt.) as additives were added to ethylene glycol (EG) of base fluid. For the purpose of comparison, commercial boron oil was utilized in addition to the dry machining as a benchmark using MQL method. The lowest surface roughness value (0.411 μm) was reached in the cutting fluid containing BA. Compared with the dry condition, the surface roughness value was determined to be improved as 52 and 38% in cutting fluids containing BA and BX, respectively. The highest tool life was measured as a cutting length of 3.15 m in the cutting fluid containing BX. According to the experimental results, a raise of tool life occurred in cutting fluids prepared using both BA and BX. Compared with dry condition, tool life was increased by 110% with cutting fluid prepared by BA and by 50% by cutting fluid prepared by BX. The cutting forces decreased with cutting fluids containing both boron compounds. After milling process, the wear type and mechanism of the cutting tool were analyzed by scanning electron microscopy (SEM) aided with energy dispersive spectroscopy (EDS). Furthermore, it has been found that the diffusion and abrasion are dominant wear mechanisms on cutting tools, all the cutting fluids studied. Consequently, the promising results were obtained by adding boron compounds, which are harmless and non-toxic to human and environmental health, to cutting fluid-based EG for improving machinability of AISI O2 cold work tool steel.