Burr Formation Mechanism Research Articles

BURR FORMATION AT THE INTERFACE DURING BI-MATERIAL ORTHOGONAL CUTTING

To reduce the size of exit burrs induced by broaching, it is possible to use a low value martyred part clamped to the functional one on the tool exit side. Thence, this research work deals with an in-situ analysis of the burr formation at a bi-specimens interface in orthogonal cutting configuration. New mechanisms of burr formation at the interface formed by Inconel 718 and cast iron specimens are identified. In addition, a post-machining study is carried out to quantify the burr size obtained with and without the martyred part.

Characteristics and Mechanism of Top Burr Formation in Micro-Milling LF21

Abstract During micro-milling aluminum alloy LF21 process, it tends to produce large top burr usually detected at the top of slot walls. Therefore, the machining accuracy and quality of the micro-parts are difficult to satisfy. To suppress burr and achieve the higher machining quality of machined LF21 micro-parts, this paper using the Johnson–Cook constitutive model establishes a two-dimensional finite element simulation model to obtain a better recognition of burr formation mechanisms and a three-dimensional finite element simulation model to better simulate burr formation process and measure top burr height. Furthermore, effective validation experiments for the proposed models are conducted, good agreements are achieved in the cutting force and top burr height between the experiments and simulation results. The study explores the formation mechanism of top burr in micro-milling LF21 and reveals the influence law of cutting parameters on top burr height based on the simulation and experimental results. The research guides the selection of cutting parameters in micro-milling LF21 process.

Investigation on formation mechanism of the burrs during abrasive reaming based on the single-particle abrasive micro-cutting behavior

Abrasive reaming is a low-speed grinding process, which has been applied in precision machining of fuel nozzle holes of aero-engine. The burrs produced in abrasive reaming always have a great influence on the machining quality. In order to investigate the burr formation mechanism in abrasive reaming, a micro-cutting model of the single-particle abrasive was developed to simulate side burr formation. The model simplified the operation of abrasive reaming process and transformed the helical motion into the linear motion of the abrasive grains. The simulation results were also verified experimentally. The side burrs were characterized by four parameters, e.g., the side burr cross-sectional area S, the burr thickness bg, the burr height h0, and the burr root thickness br. The effects of the position (i.e., the entrance and exit of the nozzle), cutting speed, cutting-edge inclination, cutting depth, and cutting width on the side burrs were discussed. Accordingly, the formation mechanism of side burrs was explored based on the simulation results of single-particle abrasive micro-cutting behavior. Finally, the optimum processing parameters were obtained as follows: cutting speed vs = 0.4 m/s, cutting-edge inclination angle λs = −60°, minor cutting depth aps = 2 μm each time, and little cutting width bps = 2 μm each time. Under such condition, the burr is tiny in thickness, short in length, and easy to be dislodged.

Investigation on the modelling and characterization of top edge burr formation in slotting finned tube

In this study, a three-dimensional finite element model is utilized to analyse the top edge burr formation in orthogonal slotting copper finned tubes. To describe the top edge burr generation, a conceptual model is developed to explain the material shear failure. The normalized Cockroft-Latham criterion is employed for a general understanding of the plastic behaviour and burr formation, and the critical damage value is obtained to qualify the burr geometries by tensile tests. Based on material side flow and the progressive deformation behaviour, the characteristics and mechanism of top edge burr formation are further investigated. The results show that the top edge burr is formed by a combination of material tear and sideward flow. The top edge burr formation process can generally be divided into three phases: the initiation of the deformation bulge, the development of the deformation bulge, and tear formation. The characteristics of the top edge burr also consist of three parts: basal deformation area, tensile area, and top tear area. The three parts of the burr characteristics correspond to the three phases of the burr formation process. Additionally, the influences of rake face, feed rate, and cutting speed on the burr size are studied based on a quantitative method. The study provides a basis for the minimization of top edge burr formation and optimization of machining parameters.

Analytical model and experimental verification of Poisson burr formation in ductile metal machining

Previous investigations on the theoretical model to predict burr dimensions have normally been confined to a single geometric model, and the findings that have been proposed rarely take into account the influence of multi-physics factors on burr formation in the complex machining process. This paper proposes an analytical model to reveal subsurface plastic deformation behavior in machining of ductile material. This model is developed based on coupled thermo-mechanical factors. More importantly, the material property and tool edge arc are taken into consideration. According to the proposed model, the two approaches are presented to predict Poisson burr height and root thickness. Moreover, the material flow and burr formation mechanism are further investigated at great length. The effects of machining parameters and material properties on burr formation are analyzed and discussed in terms of plastic deformation behavior. The results show that this proposed model can describe burr morphology and predict burr size accurately. Poisson burr generation has a great sensitivity to machining parameters, as well as material property, and the transition of burr morphology is caused by severe lateral material flow owing to material softening effect at high temperature. There is the synchronous interaction between machining parameters and material property influencing burr formation. As a result, this study provides a valuable theoretical reference and basis for the deburring energy minimization, high surface quality, and machining parameters optimization.

Burr formation and surface roughness characteristics in micro-milling of microchannels

Microchannels are attractive for their widespread applications in electronics, biological, chemical, and energy areas. Micro-milling provides an ideal method to fabricate microchannels, whereas problematic burr formations and inherent rough surfaces of microchannel bottom and sidewalls are still far from sufficiently known. In this study, micro-milling process of rectangular copper microchannels was conducted by a two-flute tungsten carbide micro-end mill. Burr formation mechanism was studied via 3D finite element simulation together with experiment observations. Surface quality of microchannels, i.e., burr size and surface roughness, was studied in different spindle speeds, feed rates, and depths of cut. It was found that the top burr sizes on the down-milling side of microchannels were much larger than those on the up-milling side. The top burr size on the down-milling side and surface roughness on bottom and both sidewalls of microchannels presented a monotonic decreasing trend when the spindle speed increased, and an increasing trend with increasing depth of cut. Nevertheless, they firstly decreased due to the plowing and extruding effect together with elastic recovery when the feed rate was smaller than the tool cutting edge radius, and then changed to increase due to the shearing and cutting process after the feed rate exceed the tool cutting edge radius. High spindle speed, small depth of cut, and moderate feed rate close to the tool cutting edge radius seem to be favorable to improve surface quality of micro-milled microchannels.

THE BASIC CONCEPTS OF MICRO-MILLING PROCESS AND ITS REVIEW IN TERMS OF DISTINCTIVE PARAMETERS

The micro-milling process is relating to the production of miniature parts, and it is one of the significant micromachining processes. The size of parts produced by micromachining is smaller than millimeters and in the range of a few microns. In the last years, the demand for needs to minimal parts in industries, such as biomedical, communication, and aerospace have been increased. To encounter this need, one of the proper solutions is the micro-milling process. In this study, a review of the micro-milling process was achieved in terms of the important common terms and some concepts. Terms like size effect, minimum chip thickness, and ploughing phenomenon were evaluated with respect to literature. These terms can be taken into account to distinguish a major difference between micro and macro cutting processes. In addition to, surface quality is an important required factor for machined parts. In this work also the surface roughness and burr formation mechanism were showed because they represent an inevitable result in the micro-cutting process. In addition to the micro-milling process have been assessed in terms of important factors used in determining the quality of workpieces such as surface quality, burr formation, and cutting forces. In conclusion, this study investigated the important parameters in the micro-milling process and provided general information to compare the micro-milling with conventional milling.

Investigations on burr formation mechanisms in micro milling of high-aspect-ratio titanium alloy ti-6al-4 v structures

Micro-scale features with high aspect ratios are used extensively in aerospace parts and biomedical implants. However, burrs produced during the micro-milling process seriously affect surface quality and performance of high aspect ratio structures. In this paper, micro slots with 1.5:1 and 3:1 aspect ratio are fabricated, and burr types and morphology are obtained through experiments. Then burr formation mechanisms were comprehensively investigated from a theoretical and experimental perspective, with the assistance of simulation. The quantitative evaluation of the top burr and sidewall burr dimension is conducted to analyze the effect of aspect ratio on the burr formation in the micro-milling of high-aspect-ratio structures. Moreover, the results suggest that burrs generated during machining can be classified into six categories according to the location: sidewall, entrance, top, exit, the bottom edge of the sidewall, and slot base. And the dimension size of top and sidewall burr is around 30 μm and 40 μm respectively. The burr formation process in high aspect ratio structures has a significant relationship with the limitation of the sidewall, tearing failure, and extrusion of chip materials. Furthermore, the aspect ratio has a positive effect on the top and sidewall burr generation. The adoption of sharper cutting edge can obtain a reduction of the top and sidewall burr dimension.

Burr Formation in Casting Using Vertical-Type High-Speed Twin-Roll Caster

The mechanism and region of burr formation in casting using a vertical-type high-speed twin-roll caster were investigated using a side-dam plate with a window. A383, an aluminum alloy typically used for casting due to its excellent fluidity at semisolid condition was used. The solid fraction of the semisolid metal ejected from the window was low. When solid metal was ejected from the window, no burr formed. The results suggest that a burr formed when the semisolid metal was ejected in gap between the side-dam plate and the side surface of a roll. The semisolid metal was ejected near the point where the semisolid metal on the two rolls met.

Exit burr height mechanistic modeling and experimental validation for low-frequency vibration-assisted drilling of aluminum 7075-T6 alloy

The burr influences the surface quality and the performance of the part. Nowadays, vibration-assisted drilling (VAD) is used to decrease the exit burr size. However, further analysis of the VAD burr formation mechanism is required. A mathematical burr prediction model of low-frequency VAD is proposed for the aluminum 7075-T6 alloy cutting. This model includes material deformation mechanisms, multi-region thrust force, and VAD kinematic characteristics. In the material deformation process of VAD, the Johnson-Cook model and fracture model are considered. The results indicate that the experimental burr height is consistent with the model prediction values, and the deviation is less than 8%. The average burr height of VAD decreases by 49.5 %–52.6 % compared with conventional drilling (CD). The parameter analysis shows that the vibration amplitude had the highest sensitivity to the burr height. In the Multivariate regression analysis (MRA), the regression coefficient sum of vibration-related parameters’ absolute values (0.676) approximates the sum of other parameters’ absolute values (0.817).

Analytical and experimental investigation of improved burr morphology prediction at the top edge in metal machining

Previous research on analytical models used to predict burr size in machining operations has usually been limited to simple geometries and mechanics models. This paper investigates the material side-flow and Poisson burr formation mechanism. An improved analytical model is developed to describe the surface (subsurface) plastic deformation and Poisson burr morphology. First, the theoretical model is established based on mechanical, geometrical, and material property considerations. Then, machining experiments are performed on high-purity copper, and the proposed model is validated by comparing the predicted burr height and thickness to the experimental measurements. The results show that the developed model provides two new methods to predict burr dimensions with considerable accuracy and that this model is suitable for ductile materials. Additionally, this article offers a basis for minimizing the energy required during deburring, suppressing the formation of burrs, and optimizing the machining parameters.

Research on Burr Formation of Aluminum Alloy Frame of Mobile phone by Milling

The characteristics and mechanism of burr formation in the milling of aluminum alloy mobile phone frame and the influence of cutting conditions on burr formation were studied. The 3D model of milling is established by DEFORM, and the mechanism of burr formation is analyzed. A three-edge end mill with a diameter of 6 mm was used to mill the aluminum alloy 6061 mobile phone frame, and the influence of cutting conditions on burr formation was analyzed. The results show that the burr size decreases with the increase of cutting speed, the decrease of feed speed and the decrease of cutting width. The burr formation is more stable and smaller in the down milling than in the up milling.

Fabrication of high aspect ratio microgroove on Ti6Al4V by laser-induced oxidation assisted micro milling

High aspect ratio microstructures based on titanium alloys have a become driving demand for various fields such as aerospace, biomedicine, and turbine blades due to their high strength, low density, biocompatibility, and corrosion resistance. However, high aspect ratios in micro-machining domains come up with low material removal rate, poor machined microstructure quality, premature tool failures, and slow machining efficiency. In this paper, a novel hybrid processing method of laser-induced oxidation assisted micro milling (LOMM) is proposed to solve the aforementioned problems. The oxidation behavior of Ti6Al4V under nanosecond laser irradiation, cutting force, machined surface quality, burr formation and tool wear mechanisms were investigated. A microgroove on Ti6Al4V alloy with a width of 0.5 mm and an aspect ratio of 5.4 was fabricated successfully by LOMM. For comparison, the conventional micro milling (CONV) was also carried out to fabricate a high aspect ratio microgroove under the same cutting parameters. Under laser irradiation, a loose oxide layer and relatively dense sub-layer were formed. The thicknesses of the oxide layer and sub-layer were 18.2 μm and 2.3 μm, respectively. The cutting force and tool wear rate in LOMM were tremendously low in removing the oxide layer compared to those in CONV. The surface quality machined by LOMM was superior to that produced by CONV. The tool wear mechanisms observed in LOMM was coating spalling, while in CONV tool nose breakage, coating spalling and adhesive wear were observed. Compared to CONV, the tool service life in LOMM was prolonged significantly.

Investigations on exit burr formation mechanisms based on digital image correlation and numerical modeling

Requirements on burr height and burr amount on machined parts are getting stricter. This leads to method development from manufacturing companies to predict burr distribution and its size along part edges. A deeper understanding of burr formation mechanisms will assist to more accurate model development. This study aims to analyze the exit burr formation, which is formed during orthogonal cutting of a brittle cast aluminum alloy. A customized digital image correlation (DIC) system with the help of a high-speed camera was used to measure the displacements fields. It calculates strain fields during burr initiation and development in orthogonal cutting of T7 heat-treated cast aluminum alloy ENAC-AlSi7Mg0.3 as well. Those results are then qualitatively compared with a numerical model of the burr with chamfer formation developed and simulated using a finite element method, to ensure a good correspondence between experiments and simulation. This model is used to complete the DIC study of burr with chamfer formation mechanisms during crack propagation leading to chamfer formation. The analysis of numerically obtained stress triaxiality fields and of DIC observations from experiments are compared to the assumptions made from analytical models. Finally, necessary improvements of an existing burr formation analytical model are proposed.

Numerical and experimental investigation on grinding-induced exit burr formation

Exit burrs are easily generated on workpiece edges. In grinding process, particularly, exit burrs could deteriorate the highly required precision and even affect the functionality of components. Therefore, to understand the burr formation mechanism and control it in grinding process is of great significance. To this end, this paper investigates the features and mechanism of exit burr formation, as well as the influence of grinding conditions including grinding speed, grinding depth, wheel granularity, and grinding pass sequences on the exit burr formation of 12CrMoV stainless steel using the Al2O3 grinding wheels. A 3D finite element (FE) model of single-grit scratching process was developed for explaining the exit burr formation procedures. The effects of different grinding conditions on the exit burr sizes were analyzed, and the characteristics of the exit burr sizes and hardness were observed via experiments. It was found that the whole procedure of exit burr formation during grinding could be divided into six stages: steady-state grinding, pre-initiation, appearance of the fourth deformation zone, formation of plastic deformation band, burr development, and finish of burr formation. The burr sizes were strongly determined by the wheel granularity and grinding depth, rather than the grinding speed. For the same required grinding depths, using whether single pass or multiple passes of the grit has a very small impact on the exit burr sizes. The hardness of the burr root part is relatively stronger than that of the burr rollover part, while the burr hardness would increase when decreasing the grinding depth.

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.

Analysis of burr formation mechanisms when drilling CFRP-aluminium stacks using acoustic emission

Multimaterial composites are increasingly gaining importance in the design of aircrafts due to the demand for lightweight design in the aerospace industry. Riveting is used here as an important joining technique of individual structure components in aircrafts and requires the drilling of holes into the multimaterial composites. However, the individual layers in the stack place in part contrary demands on the optimum machining process and the design of drilling tools. To guarantee a sufficient drill hole quality, it is useful to safeguard the cutting process by monitoring the drill hole quality already during machining so that the reject rate of components may be reduced. Previous research works had shown that structure-borne sound could be used successfully for an online monitoring of drilling processes. Based on these investigations, this paper is focused on examining the burr formation mechanisms in CFRP-aluminium materials during the exit of the drill. By analysing patterns in the frequency spectra, it was shown that fundamental burr formation mechanisms could be detected by means of patterns in structure-borne sound signals. In addition, it was possible to infer the burr height produced in drilling from the analysis of the characteristic patterns in the structure-borne sound spectrum.

Improved analytical prediction of burr formation in micro end milling

In the fields of aerospace, bio-medicine and other optical devices, micro end milling is widely used to fabricate miniature parts and features which require a high quality of machining. Generally, the accurate prediction of burr formation is one significant factor to improve the quality of machined parts and performance of micro components and features. This paper investigates the burr formation mechanism in micro end milling by considering the minimum chip thickness, as well as the size effect of cutting edge radius. The improved analytical model is developed to predict the size (height and width) of Poisson burr and exit burr. The proposed model is validated by the micro end milling experiments with different cutting parameters, where the error percentage of comparison results is limited to 16.8%. Furthermore, the effects of spindle speed, feed per tooth and axial depth of cut on the burr size are analyzed based on the prediction model and experimental results. The proposed analytical method offers a basis for the control and minimization of burr formation as well as cutting parameters optimization.

Fundamental study of exit burr formation mechanisms during orthogonal cutting of AlSi aluminium alloy

Burr formation during machining is an important issue in industry. It causes an additional deburring operation, which is time consuming and has a negative economic impact.This study aims to analyse burr formation mechanisms and its accumulation in successive passes during orthogonal cutting of a cast aluminium alloy. A customized experimental setup was developed, which includes a high speed imaging system and a laser profilometer. A design of experiments using the setup mentioned previously is carried out and a methodology for geometric burr characterization is developed and applied. Furthermore, statistical representation of the obtained results is performed, which allows the understanding of the geometric heterogeneity influence associated to burr formation mechanisms and to work material microstructure.Based on the exit burr analysis, new geometrical criteria are proposed for the characterisation and the definition of two main burr formation mechanisms.The influence of cutting parameters on burr morphology along the workpiece exit edge is investigated in depth. The results show that two types of burrs can be produced simultaneously along the workpiece exit edge due to the work material microstructure heterogeneity. The results present as well the influence of low uncut chip thickness that leads to a higher proportion of burrs without chamfer. This type of burr is higher and more propice to burr accumulation. After performing several cutting passes, these burrs may be eliminated and replaced by a burr with chamfer.

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

The wastes and emissions from machining processes have negative effects on the environment and human health. Therefore, the use of environmentally friendly cooling or lubrication systems has increased recently. Ethanol is an ideal coolant for high-speed machining because it has lower viscosity than those of oil-based coolants. Ethanol’s low evaporation temperature makes it an efficient cooling technique and also eliminates the need for disposal and recycling. The effects of different cooling/lubrication techniques (minimal quantity lubrication (MQL), ethanol, and oil-water emulsion) on tool wear, surface roughness, and burr formation were investigated in micro-milling of Inconel 718 superalloy. After cutting tests, 3D profilometer and scanning electron microscopy (SEM) analyses were carried out to determine surface roughness, burr formation and tool wear mechanisms. Better surface quality was obtained in the cutting processes under MQL and dry conditions. Minimal tool wear was obtained in the cutting process with MQL. The decrease in tool diameter was at a maximum level in the cutting process with ethanol. When assessed in terms of surface roughness, the ethanol method exhibited a more stable state than the cutting process with conventional cutting fluid.