Burr Width Research Articles

Shadow zone in MQL application and its influence on lubricant deficiency and machinability during micro-milling

Minimum quantity lubrication (MQL) in metal cutting helps enhancing machinability while ensuring sustainability. In the absence of bulk heating in micro-milling, the cutting fluid needs to be deposited on the tribologically active chip-tool-workpiece region to perceive enhanced lubrication effect. There are few factors that can restrict the oil droplets from depositing on the tool. One such restriction that inherently appears as “Shadow Zone” during end-milling process is reported in this article for the first time. This shadow zone hinders certain percentage of droplets from reaching to the cutting edges resulting in reduced wetting capability of the MQL supply even when the overall oil flow rate remains unchanged. Lubricant deficiency induced solely by this shadow zone during micro-milling under varying parameters is assessed here. For fixed nozzle orientation, detrimental effect of the shadow zone intensifies with an increase in the axial depth of cut and top-burr height. At 50 µm axial depth, the shadow zone restricts 3.7% droplets from depositing on the active cutting edge and thereby compels the MQL assisted cutting process to rotate in incompletely lubrication condition. For unchanged oil flow rate, the corresponding deficiency increases to 16.4% at 200 µm axial depth. When compared with dry micro-milling of Ti-6Al-4 V, shadow zone reduces effectiveness of the MQL supply in controlling tool wear from 25.4 – 5.5% in the entire tool life when axial depth is increased from 50 – 200 µm. Similar degree of reduction in MQL effectiveness towards controlling surface roughness, burr width, and cutting forces is also observed.

Laser cutting of silicon anode for lithium-ion batteries

Lithium-ion batteries (LIBs) are vital in the transportation sector due to their promising technology meeting the future hybrid and electric vehicles requirements. The limited capacities of anode and cathode materials are the obstacle in the current state of LIBs to obtain good performance. Silicon (Si) has the highest capacity compared to the currently used graphite anode. In this study, laser technology was employed to perform cutting of silicon anodes, which previously have not been studied. First, the optical properties of silicon anode are measured, and four types of cutting widths such as top, kerf, clearance, and burr as well as five types of physical cutting phenomena such as excessive fill cutting, proper full cutting, partial cutting, partial melting of the current collector and full ablation of active material were defined and measured. Minimum average cutting power, as well as cutting and energy efficiencies, are established for all parameter groups. The effects of process parameters on the measured cutting widths are studied by developing mathematical models using multivariate regression based on the response surface method (RSM). The process parameters contribution was also analyzed using the analysis of variance (ANOVA). For the formation of kerf width, clearance width, and burr width the cutting speed have the largest contribution with percentages of 53, 55, and 67 respectively. The laser power also has a 65% impact on the formation of the top width.

Performance evaluation of tool coatings and nanofluid MQL on the micro-machinability of Ti-6Al-4V

Micromilling of difficult-to-machine materials like Ti-6Al-4V alloy suffers from drawbacks such as tool wear and catastrophic tool breakage due to the tiny diameter of the micro tool. Hence, in this paper, an effort has been made to prolong tool life and improve surface quality via hybridization of water and CuO nanofluid-based MQL with PVD coated (AlTiN/TiAlN) and uncoated WC micro end-mill in micromilling of Ti-6Al-4V alloy. The results exhibited minimum surface roughness at lower concentration (0.25 vol%) of CuO nanofluids with AlTiN coated WC tool and diminished tool wear and built-up edge formation at higher concentration (1 vol%) water-based CuO nanofluids. Under various environmental conditions, the average size of the top burr width was determined on both the up and down milling sides. The minimum average burr width of 9.93 μm was obtained in up milling using 0.25 vol% CuO nanofluids condition with AlTiN coated tool. In the case of down milling, the minimum burr width was 10.58 μm when using 0.25 vol% CuO nanofluids with TiAlN coated tool. Furthermore, significant improvements in tool life and surface quality have been observed through the hybridized sustainable environments obtained by the combined utilization of MQL and coated tools.

The influence of the crystallographic orientation when micro machining commercially pure titanium: A size effect

Micro machining processes are characterized by the influence of size effects like the influence of the workpiece micro structure on the process and ultimately on the process results. So far, the influence of grain orientation on the process results is state of the art and mostly investigated on single-crystal materials, but the influence of the grain orientation on the process and process results in micro machining of polycrystalline materials with a hexagonal close packed (hcp) crystal structure like commercially pure (cp)-titanium is, to the best knowledge of the authors, not completely understood.Within this research, the correlation between the grain orientation and the surface topography, process forces, and chip formation is researched by orthogonal cutting. This process offers the possibility of clearly linking the cutting behavior with the resulting surface and the influences of the size effect. The results show a clear correlation between the grain orientation and the topography height, the ripping out of material, and the resulting surface. A correlation between the grain orientation and the forces in the X-, Y-, and Z-direction could also be shown. The chip formation and thus the resulting chip thickness differs depending on the grain orientation. In addition, micro milling tests were conducted and influences on burr formation and process forces are shown. At low spindle speeds the burr width or the burr shape are a function of the grain orientation. At high spindle speeds this effect can no longer be observed. With the results of this research, it is possible to compensate the influence of the grain orientation on the process results and to enhance the efficiency and the resulting surface quality of micro machining processes.

Effect of Tool Coating and Cutting Parameters on Surface Roughness and Burr Formation during Micromilling of Inconel 718

Surface roughness and burr formation are among the most important surface quality metrics which determine the quality of the fabricated parts. High precision machined microparts with complex features require micromachining process to achieve the desired yet stringent surface finish and dimensional accuracy. In this research, the effect of cutting speed (m/min), feed rate (µm/tooth), depth of cut (µm) and three types of tool coating (AlTiN, nACo and TiSiN) were analyzed to study their effect on surface roughness and burr formation during the micromachining of Inconel 718. The analysis was carried out using an optical profilometer, scanning electron microscope and statistical technique. Machining tests were performed at low speed with a feed rate (µm/tooth) below the cutting-edge radius for 10 mm cutting length using a carbide tool of 0.5 mm diameter on a CNC milling machine. From this research, it was determined that the depth of cut was the main factor affecting burr formation, while cutting velocity was the main factor affecting the surface roughness. In addition, cutting tool coating did not significantly affect either surface roughness or burr formation due to the difference in coefficient of friction. The types of burr formed during micromilling of Inconel 718 were mainly influenced by the depth of cut and feed rate (µm/tooth) and were not affected by the cutting velocity. It was also concluded that the results for the surface finish at low-speed machining are comparable to that of transition and high-speed machining, while the burr width found during confirmation experiments at low-speed machining was also within an acceptable range.

Experimental Study on the Effect of Cutting Tool Geometry in Micro-Milling of Inconel 718

In this study, the effect of tool geometry on the cutting forces, surface roughness, and burr formation in the micro-milling process is investigated. Three different geometric parameters (helix angle, number of cutting edges, and axial rake angle) that may affect the machining performance are taken into account. Inconel 718 superalloy was used as workpiece material, and the tests were performed under dry cutting conditions. According to the results obtained, the minimum cutting forces were obtained at a helix angle of 45°. The increase in the helix angle causes the forces in the Fz direction to increase. For the new cutting tool, increasing number of cutting edges and axial rake angle has little effect on cutting forces. For the worn tool, the cutting forces are lower in the four-edges cutting tool, and the cutting forces obtained in the negative axial rake angle are also higher. The dominant damage types in the cutting tool are abrasive wear and chipping. Increased cutting distance causes the edge and corner radii of the tool to increase. As a result, cutting forces, surface roughness, and burr formation also increase. Generally, the maximum top-burr width is obtained on the up-milling side for the new cutting tool. Maximum top-burr width occurs on the down-milling side in the worn tools. Increasing helix angle causes burr width to increase. It has been determined that low number of cutting edge and negative rake angle cause smaller burr width.

An experimental analysis of minimum chip thickness in micro-milling of two different titanium alloys

Micro-milling is a micro-mechanical cutting method used to obtain complex and three-dimensional micro geometries. Micro-cutting tools are used in the manufacturing of micro-components and the type of workpiece is also important for good surface quality and minimum burr. In this study, micro machinability of Ti6Al4V alloy which is used most frequently in micro-component production is compared with Ti5553 alloy. Micro-milling of Ti5553 alloy and comparison of the minimum chip thickness with Ti6Al4V were performed for the first time in this study. Using different cutting parameters, the variation of surface roughness, burr width, and cutting forces were investigated. The cutting tests were carried out on a specially designed and high-precision micro-milling test system using a TiCN-coated two-flute end mill of 0.6 mm diameter. According to the results, minimum chip thickness is approximately 0.3 times the edge radius of the cutting tool and does not vary with the alloy type. At feed rates smaller than the minimum chip thickness, both the cutting forces increase and the surface quality decreases. For both alloys, reduced feed rate and increased depth of cut lead to increased burr width. The burr widths in Ti6Al4V alloy are higher. At the end of the study, the limits of the cutting parameters where plowing occurred for the both alloys are clearly determined. In addition, the limits of the cutting parameter causing plowing have been confirmed by cutting forces, surface roughness, and burr formation.

Micro-end milling of biomedical Tz54 magnesium alloy produced through powder metallurgy

In this study, micro machinability of Mg5Sn4Zn (TZ54) alloy produced by a hot-pressing process (one of the powder metallurgy methods) is investigated. For this purpose, micro-milling experiments were carried out, considering different cutting parameters. In order to determine the appropriate cutting parameters, the variation of cutting forces, surface quality and burr width were investigated. The cutting forces obtained in micro-milling of the TZ54 alloy are relatively small compared to other biomedical materials. In terms of both cutting forces and surface roughness, the minimum chip thickness is between 7% and 34% of the tool edge radius. However, compared to alloys such as Ti6Al4V and 316 L, the burr width is about 80% smaller. An important contribution of the study is that the minimum chip thickness (0.1 μm) has been confirmed in terms of both cutting force and surface roughness. In addition, even at high material removal rates, the minimum cutting forces are important findings of the study. The predominant wear mechanism in the cutting tool is abrasive wear. In view of tool life, surface roughness and burr formation, it is envisaged that the TZ54 alloy can be an easy machinable, alternative biomedical material.

Study of High-Speed Mechanical Micro Drilling Process Fundamentals for Small Holes

High-speed mechanical micro drilling would be a promising process for small hole fabrications with high productivity and high quality. But there are limited studies on this topic. Fundamental questions such as the minimum undeformed chip thickness (MUCT) due to the size effect in microcutting, burr size, cutting force, and optimal parameters are discussed for high-speed mechanical micro drilling in this paper. Based on finite element method (FEM) modelling, the MUCT is identified as 0.86 μm for copper C26000 with the cutting edge radius of 5 μm from both chip generation and force variation analyses. The ratio of MUCT to the cutting edge radius is 0.17, which is smaller than that (usually 0.2 or 0.25 for copper) in micro shaping and micromilling processes. This result has been successfully verified by experiments with the drill with a diameter of 1 mm and the spindle speed of 80,000 min-1. Burr width at the hole entrance reaches the maximum value when the undeformed chip thickness (UCT) is smaller than the MUCT. Experimental optimizations with the integrated considerations of cutting forces and burrs have been conducted. The optimal high-speed micro drilling parameters have realized a material removal rate (MRR) of 25% increasement compared with conventional micro drilling.

Study on surface roughness and top burr of micro-milled Zr-based bulk metallic glass in shear dominant zone

As a novel class of versatile advanced materials with excellent mechanical, physical, and chemical properties, bulk metallic glasses (BMGs) are promising materials for micro-molds and micro-components. In this paper, the influence of feed rate, rotation speed, and axial depth of cut on surface roughness and top burr size of Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass in a shear dominant zone was investigated by micro-milling with coated two-tooth cemented carbide tools. Initially, the shear dominant zone was identified by analyzing milling force, specific cutting force, surface roughness, and top burr width under different feed rates. Then, a surface morphology model considering the effect of runout was established to study the surface formation process and the influence of runout on surface roughness. Finally, the effects of rotation speed and axial depth of cut on surface roughness and burr size were investigated by an experimental approach. This study proved that, under the optimized parameters, excellent surface quality (Ra around 0.1 μm) and small burr width (below 20 μm) could be obtained by micro-milling Zr-based bulk metallic glass.

Evaluation of size effect and improvement in surface characteristics using sunflower oil-based MQL for sustainable micro-endmilling of Inconel 718

The increased demand for smaller features leads to miniaturization of components in many areas such as aerospace, biomedical, and electronic industry. Since the tribological performance of the machined components is highly influenced by surface characteristics, the analysis of environmental-friendly lubrication techniques such as minimum quantity lubrication (MQL) using vegetable oil is an important area of interest for the sustainable machining. MQL is a promising technique that minimizes the usage of lubricant, thus enhancing sustainability. This work aimed at studying the size effect and improvement in surface characteristics of sunflower oil-based MQL-assisted micro-endmilling of Inconel 718 with respect to dry machining. Chip analysis was also conducted to confirm the findings. Effects of feed/tooth on surface roughness, chip formation, top burr height, and top burr width for both dry and MQL conditions were studied. The size effect was found to be up to a feed/tooth value near to the cutter edge radius (3 µm). Minimum uncut chip thickness was found to be near to 0.3 times the cutter edge radius. It was found that almost 32% average reduction in areal surface roughness, 36% average reduction in top burr width, and 37% average reduction in top burr height were observed for sunflower oil-based MQL-assisted micro-endmilling of Inconel 718 compared to dry condition. Finally, it was concluded that the application of sunflower oil-based MQL enables micro-endmilling of Inconel 718 for higher feed/tooth range with good surface quality.

Modeling of Top Burr Formation in Micro-End Milling of Zr-Based Bulk Metallic Glass

Abstract In this study, an analysis is presented for the formulation of a model in top burr formation to estimate the width of the top burrs formed in micro-end milling process. In this analysis, the width of the top burrs, considered to be the measure of burr size of top burrs, represents the extent of burr formation. The model is applied to quantify the burr formation in Zr-based bulk metallic glass, an amorphous metallic alloy. In this study, micromilling experiments were carried out on the bulk metallic glass work material at different levels of feed rate, axial depth of cut, and cutting speed to compare the experimental values of top burr width with the predicted values. Analysis is carried out to characterize top burr formation based on the experimental results of burr sizes in the up-milling and down-milling side edges, and the influential effects of the cutting parameters on the burr formation are analyzed.

Experimental investigation of top burr formation in high-speed micro-milling of Ti6Al4V alloy

Miniaturization with superior quality product of super alloy is the demand of the industry. Ti6Al4V is the demanding super alloy due to its excellent material properties, although this super alloy is known for poor machinability in terms of burr formation, low tool life, and poor surface finish. Therefore, being a popular super alloy, it comes under the difficult-to-cut material. In the current work, burr formation on the machining of Ti6Al4V has been studied. Experimental investigation and characterizations of top burr formation on Ti6Al4V alloy using end milling process were carried out. A scanning electron microscopy identifies the burr formed on the machined surface. A new technique has been introduced to measure the top burr width (i.e. equivalent width) accurately. Equivalent burr width calculated as the ratio of total area of burr generated to the total height. It was observed that equivalent burr width in up milling was increased by 120%, while in down milling, it was decreased by 50% as the speed varies from conventional to high speed. Furthermore, the effects of different cutting parameters and tool parameters on top burr formation have been analyzed to establish correlation among them.

Al2124 Alüminyum Alaşımının Frezeleme Performansı Üstüne Takım Kaplamasının Etkisi

This study investigated the effect of various coated carbide inserts and depth of cut on some machining criteria such as surface roughness, tool wear, top burr width and milling forces during milling of Al2124 aluminium alloy. Monolayer TiCN, AlTiN, TiAlN and two layers TiCN + TiN, AlTiN + TiN deposited by physical vapour deposition coated inserts were utilized in the milling experiments. From experimental results, it was concluded that flank wear, milling forces, surface roughness and top burr width increased with the increment in the depth of cut for all coatings. The main wear mechanisms for all coated inserts were found to be adhesive and abrasive wear. As a result, coated inserts with two layers (TiCN + TiN and AlTiN + TiN) and TiCN coated inserts gave better machining performance with respect to AlTiN and TiAlN coated inserts in milling of Al2124 aluminium alloy.

Experimental study of micromilling burrs of 304 stainless steel

Stainless steel is a well-known difficult-to-machine material with high toughness, low thermal conductivity, and high work hardening characteristics. Burrs generated in micromilling of the stainless steel seriously affect the performances of the fabricated high-accuracy miniaturized geometrical features. Aiming at reasonable control of burrs in micromilling of the 304 austenitic stainless steel, single-factor analyses, multi-factor optimization, and further post processing procedures are introduced in the paper. First, the axial depth of cut ap, feed per tooth fz, spindle speed n, and radial depth of cut ae are investigated by single-factor micromilling experiments. It shows that burrs generated in up milling are smaller than that in down milling. The minimum burr widths of 171.93 μm can be achieved, and the overall trend of micromilling force is in accordance with the burr widths. Then, multi-factor orthogonal experiments have been carried out to optimize micromilling parameters based on the Taguchi method. It shows that the significance sequence of key parameters for burr widths from large to small is ap, n, ae, and fz. The optimized minimum burr width is 83.69 μm with micromilling parameters ap of 45 μm, fz of 1.0 μm/z, n of 48,000 min−1, and ae of 200 μm. To further reduce the burrs, ap of 0 is set for post processing experiments. It shows that the radial depth of cut affects burr sizes greatly. The optimized radial depth of cut is 500 μm, and burr widths have been finally reduced to 14.3 μm. The study provides an effective method to reduce burr sizes in micromilling of very ductile materials.

Study on laser-induced oxidation assisted micro milling of Ti6Al4V alloy

The micro-scale machining of titanium alloy has many problems such as severe tool wear, low machining efficiency, and poor machined surface quality. This paper presented a novel processing method of laser-induced oxidation assisted micro milling (LOMM). The morphology and phase compositions of the surface layer and subsurface layer under laser irradiation, as well as the morphology of the machined microgroove, were investigated. The effects of micro milling parameters on cutting force, surface roughness, and top burr width were studied in detail. The burr formation mechanisms and tool wear mechanisms were revealed. A comparison study of LOMM and conventional micro milling in terms of cutting force, machined surface quality, and tool wear was conducted. A porous oxide surface layer and relatively dense subsurface layer were formed under laser irradiation. The cutting force and tool wear in removing the oxide surface layer was extremely low compared with those in removing the substrate material. Feed per tooth had a significant effect on the cutting force, surface roughness, and top burr width. For the investigated range of parameters, the optimal feed per tooth and cutting depth were 3.5 μm/z and 6 μm, respectively. The tool wear mechanisms in LOMM were coating spalling, and in conventional micro milling were tool nose breakage, coating spalling and adhesive wear. Under the same cutting parameters and cutting length, LOMM effectively decreased the cutting force, slowed the tool wear, and prolonged the service life of tool.

Overhang length effect during micro-milling of Inconel 718 superalloy

The accuracy of machining force relies on the accuracy of the cutting force coefficients which are determined by calibration experiments and are related to cutting tool–workpiece material couple. To this end, a mechanistic model was established to anticipate machining forces that occurred during micro-milling under different tool overhang lengths. This study assumed that the cutting force coefficients varied with the tool overhang length, and this assumption was proved by some micro-milling experiments. Force coefficients were computed by linearly fitting the experimental force data. In the current work, also wear on tool and burr formation were observed as functions of feed per tooth and overhang length. The overhang length of 15 and 20 mm significantly reduced the diameter of the micro-tool as compared to the overhang length of 10 mm. The obtained results showed that cutting forces and top burr width increased with the increasing overhang length. It was also found that the values of cutting and edge coefficients differed with the overhang length.

Performance evaluation of micro-dimple formation on a Ti-6Al-4V alloy by using electrical discharge drilling

Micro-dimple formation improves the tribological behavior of a material. This study investigates dimple formation on a titanium (Ti-6Al-4V) alloy by using electrical discharge drilling. Input parameters, namely capacitance (C), pulse-on-time (Ton), and voltage (V), were varied to measure the output quality responses including dimple depth, burr height, and burr width. The experimental results indicated that the quality of the dimple is determined based on the spark energy and rate of material removal. A regression analysis was performed for each output response. The developed model confirmed the fitness at a 95 % confidence interval. The contribution of each factor and its significance was determined by using analysis of variance (ANOVA). Further, the optimum drilling condition was predicted by using desirability analysis (C = 10000 pF, Ton = 100 μs, and V = 180 V). The microscopic view of the dimple array and the micro-dimple geometry were analyzed by using scanning electron microscopy images.

Evaluation of wear-induced plastic deformation at the trimmed edge of DP980 steel sheets

In order to increase the use of advanced high strength steel (AHSS) for automotive light-weighting, the significant trimming-induced wear damage that AHSS sheets cause to the trim dies should be reduced so as to decrease die maintenance costs and deterioration of the quality of sheared edge. In this research, the wear characteristics in the upper AISI D2 die inserts used for trimming DP980-type AHSS sheets and the wear-induced plastic deformation at the sheared edges of DP980 were studied. Observation of wear profiles at the edge of the upper trim die revealed that material abrasion was the main damage feature. The trimmed edge quality of DP980 deteriorated with the number of strokes, as indicated by an increase in burr width. Plastic strains near the surface of the sheared edge estimated using the displacements of martensite plates, increased from 2.9 at 2.5 μm below the trimmed edge after 40,000th cycles, to 55 after 80,000th cycles. Micro-hardness tests performed to estimate the local flow stresses in the shear affected zone (SAZ) indicated that the flow stress at a distance of 4.5 μm below the trimmed edge increased with the number of trimming cycles to 1.73 GPa in the 80,000th trimmed part.

Optimization of process parameters for micro milling of Ti-6Al-4V alloy using Taguchi-based gray relational analysis

In this study, the effects of the cutting parameters on the surface quality and burr width were investigated in the micro milling of Ti-6Al-4V alloy. Spindle speed, feed per tooth and depth of cut are selected as the control factors. Taguchi-based gray relational analysis was used in the optimization of the cutting parameters for minimal burr width (for up and down milling operations) and surface roughness (Ra). The contribution percentages of the control factors were determined by using analysis of variance (ANOVA). According to the obtained results, it was determined that the feed rate value for the best surface quality was 0.25 μm/tooth. At lower feed rate values, ploughing takes place and the surface quality deteriorates. On the other hand, it was found that it is more appropriate to use values ap of 0.1 mm and n of 10,000 rev/min to produce minimal Ra. The burr width on the down milling side is higher than that on the up milling side. A lower feed rate and greater depth of cut lead to an increase in burr width. In addition, higher spindle speeds increased the burr width due to rapid tool wear.