Milled Surface Research Articles

A comprehensive review of free-form surface milling– Advances over a decade

• A comprehensive review (based on 168 papers) of free-form milling is presented. • The advances over a decade (2009–2020) are discussed in five sections. • Experimental, analytical, tool-path and inspection based studies are covered. • The literature is presented and compared concisely in tables and flowcharts. • The prominent findings/observations and scope for future studies are highlighted. The advent of CNC machines resulted in the reduction of machining complexity through efficient programming and increased productivity. The free-form surface milling (FFSM) process comprises several applications in the aerospace and automobile industries that mainly concerned with accuracy of the finished part. Numerous studies were attempted over the years to understand the mechanism involved in FFSM, which reported and facilitated the advances in the overall process. The complex surface milling still poses challenges with continuous change in the tool-workpiece contact that leads to vary an effective tool radius, along with the active cutting speed and cutting forces during machining. Accordingly, the material removal mechanism changes from shearing to plowing (plastic deformation), and vice-versa, which determines the tool wear and overall part quality. This paper presents a review of the research work (a total of 168 papers) published over the past decade considering five main domains in the FFSM process, which leads to enhance accuracy, machinability, productivity, and machining economy. The experimental investigations highlighted the input-output correlations, parametric influence on various machining responses, while analytical models underline the principles and mechanics involved in the process and useful in predicting/estimating the responses. The tool-path generation leads to an efficient tool-path that minimizes the machining time and cost, enhancing the part surface quality, and the surface reconstruction includes an accurate representation of the machined surface in the FFSM. Finally, the part inspection process is implemented for effectively measuring and comparing the accuracy of the machined components is reported. The inclusive knowledge of all five elements of the FFSM process would facilitate a clear understanding of the overall process and useful in developing research objectives and future perspectives.

Increasing the Accuracy of Free-Form Surface Multiaxis Milling.

This contribution deals with the accuracy of machining during free-form surface milling using various technologies. The contribution analyzes the accuracy and surface roughness of machined experimental samples using 3-axis, 3 + 2-axis, and 5-axis milling. Experimentation is focusing on the tool axis inclination angle—it is the position of the tool axis relative to the workpiece. When comparing machining accuracy during 3-axis, 3 + 2-axis, and 5-axis milling the highest accuracy (deviation ranging from 0 to 17 μm) was achieved with 5-axis simultaneous milling (inclination angles βf = 10 to 15°, βn = 10 to 15°). This contribution is also enriched by comparing a CAD (Computer Aided Design) model with the prediction of milled surface errors in the CAM (Computer Aided Manufacturing) system. This allows us to determine the size of the deviations of the calculated surfaces before the machining process. This prediction is analyzed with real measured deviations on a shaped surface—using optical three-dimensional microscope Alicona Infinite Focus G5.

Analysis of Surface Roughness and Flank Wear Using the Taguchi Method in Milling of NiTi Shape Memory Alloy with Uncoated Tools

The aim of this study was to optimize machining parameters to obtain the smallest average surface roughness (Ra) and flank wear (Vb) values as a result of the surface milling of a nickel-titanium (NiTi) shape memory alloy (SMA) with uncoated cutting tools with different nose radius (rε) under dry cutting conditions. Tungsten carbide cutting tools with different rε (0.4 mm and 0.8 mm) were used in milling operations. The milling process was performed as lateral/surface cutting at three different cutting speeds (Vc) (20, 35 and 50 m/min), feed rates (fz) (0.03, 0.07 and 0.14 mm/tooth) and a constant axial cutting depth (0.7 mm). The effects of machining parameters in milling experiments were investigated based on the Taguchi L18 (21 × 32) orthogonal sequence, and the data obtained were analyzed using the Minitab 17 software. To determine the effects of processing parameters on Ra and Vb, analysis of variance (ANOVA) was used. The analysis results reveal that the dominant factor affecting the Ra is the cutting tool rε, while the main factor affecting Vb is the fz. Since the predicted values and measured values are very close to each other, it can be said that optimization is correct according to the validation test results.

Surface roughness and vibration analysis in end milling of annealed and hardened bearing steel

This experimental study involves statistical analysis, mathematical modeling and optimization of machined surface roughness (Ra) well as the level of workpièce displacements (D) recorded during the shoulder and contour milling of AISI 52100 bearing steel. Dry end milling of annealed and quenched/tempered condition with TiAlN coated carbide inserts tool. A Taguchi experimental plan of 27 tests was adopted to determine the influence of the cutting parameters (Vc, fz, ae) considered as input factors, surface roughness and level of workpiece throbs/displacements considered as response factors recorded during machining. To show the degree of influence of each cutting parameter on the milled surface roughness and displacements, analysis of variance and mathematical regression models were adopted. The objective of this study is to see the influence of the radial depth of cut ae during shoulder, grooves and contour milling when we have a strong ap and a weak ae. Usually when face milling, we adopt a strong ae and a low ap. The experimental results obtained shown that for two states of steel tested that the cutting speed and feed per tooth is the most influencing factor on the milled surface roughness Ra evolution. Radial depth of cut influences considerably the level of displacements. Multi-objective optimization gave the desired cutting conditions with a desirability function DF ​= ​0.897.

Topic of the issue: Determination of the processing error during face milling of flat surfaces

Using the finite element method and CAD SolidWorks Simulation, the relationship between the geometric parameters of workpieces and the error in processing flat surfaces of levers caused by elastic deformations of the workpiece due to the application of holding force is established. In this paper, we developed a method for determining the error of processing flat surfaces that occurs from fixing, compiled a model for determining the error by the finite element method, and calculated the error of processing flat surfaces that occurs from fixing for workpieces with different geometric parameters. As a result of the study, the relationship between the value of the center distance of workpieces and the error in processing flat surfaces of levers caused by elastic deformations of the workpiece due to the application of holding forces was determined.

Effect of milling on the microstructure and mechanical property of austenite stainless steel

Abstract A milling induced deformation layer of Z3CN20.09M, 304L and 316L austenite stainless steel (SS) was investigated by electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and a nanoindenter. The results indicated that the deformation layer was formed with a depth of about 200 μm, including a nanocrystalline layer within the range of 3 μm at the subsurface and followed by a large amount of persistent slip bands (PSBs). The significant plastic deformation was observed on the cross section of deformation layer with a range of about 80 μm for Z3CN20.09M and 304L SS, while being only about 30 μm for 316L SS. The highest residual stress tested on the milled surface reached about 1000 MPa, which can be attributed to the fact that a deformed martensite phase was formed at the surface during the milling operation. The nanohardness increased by 20-60 % on the cross section of the deformation layer as compared to the matrix.

Effect of milling on the microstructure and mechanical property of austenite stainless steel

Abstract A milling induced deformation layer of Z3CN20.09M, 304L and 316L austenite stainless steel (SS) was investigated by electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and a nanoindenter. The results indicated that the deformation layer was formed with a depth of about 200 μm, including a nanocrystalline layer within the range of 3 μm at the subsurface and followed by a large amount of persistent slip bands (PSBs). The significant plastic deformation was observed on the cross section of deformation layer with a range of about 80 μm for Z3CN20.09M and 304L SS, while being only about 30 μm for 316L SS. The highest residual stress tested on the milled surface reached about 1000 MPa, which can be attributed to the fact that a deformed martensite phase was formed at the surface during the milling operation. The nanohardness increased by 20-60 % on the cross section of the deformation layer as compared to the matrix.

Medium-density fibreboard milling using selected technological parameters

The aim of this study was to investigate the effect of blade type and sharpness angle on blade wear, cutting power, and surface roughness. The study was conducted on medium-density fibreboard (MDF) panels. Two blade types were analyzed (high-speed steel and cemented carbides) along with three variants of sharpness angles (40°, 45°, and 55°). Machining operations were performed on a spindle moulder at a feed rate of 6.3 m/min and rotational speed of 4500 min-1. The blade wear criterion was adopted as the loss of cutter surface area measured on the rake face. Roughness was determined using the Ra parameter, which was measured at three points on the cross-section of the MDF panel. A new, multifaceted approach to the study of cutting a narrow surface of the MDF board was used, thanks to which the interaction of such parameters as blade wear, cutting power, and machining quality as well as the type of material of the knives and their angular parameters were determined. An increase in blade wear and cutting power was recorded with an increase in cutting path, while roughness at the MDF panel cross-section varied. The cemented carbides cutter with the 45° angle may be proposed as optimal, because it showed a relatively low wear and cutting power while providing good quality of the milled surface.

Plasma electrolytic oxidation of Ti-6Al-4V alloy and its influence on the machinability during micro-milling

With the aim to modify the micro-milling behaviors of Ti6Al4V alloy for engineering application, a novel processing method of plasma electrolytic oxidation assisted micro-milling (PEOAM) was proposed in this paper. Ti6Al4V alloy was treated by plasma electrolytic oxidation (PEO) with an electrolyte mainly containing KH2PO4 and Ca(CH3COO)2, so that a low-strength oxide film that could be easily removed grew in-situ on the alloy surface. The oxide film was then subjected to micro-milling. The structure and composition of the oxide surface layer and sub-surface layer were characterized by scanning electron microscope and X-ray spectrometer. The cutting force of micro-milling applied to the oxide film was detected by dynamometer. Meanwhile, the milled surface roughness and top burrs were measured and analyzed by white light interferometer. The results indicated that PEO could promote the in-situ growth of 19 μm-thick loose and porous titanium oxide film on the surface of Ti6Al4V alloy. Compared with non-oxidation specimens, the microhardness and elastic modulus of the oxide surface layer were decreased by 34.5% and 47.1%, respectively. With the same micro-milling parameters, the cutting forces Fx and Fy were decreased by 51.4% and 71.4% respectively in down milling, and 36.2% and 88.4% in up milling. The surface roughness Ra was decreased by 26.7%.

Comparison of surface integrity of Ti6Al4V titanium alloy manufactured by laser deposition and traditional method after end milling

Ti alloy has been widely applied in aerospace due to its high strength, good corrosion resistance, and excellent high-temperature performances. The quality and usability of Ti alloy parts are closely related to surface integrity. In this study, a comparative analysis of the milling surface integrity between laser deposition manufacturing and traditional Ti6Al4V samples was conducted. End milling surfaces of additive and traditional Ti6Al4V samples were observed with an orthogonal experiment under different milling parameters from the perspectives of cutting force, surface morphology, surface roughness, subsurface damages, and microhardness. Results demonstrate that the additive Ti6Al4V sample has a slightly higher cutting force and surface roughness relative to traditional Ti6Al4V. This is related to the higher hardness and plasticity of the additive Ti6Al4V sample. There are unmelted powder particle defects on the milling surface of the additive Ti6Al4V sample and serious cracking defects on the subsurface of the additive Ti6Al4V sample. The microhardness of the work hardening layer and base of the additive Ti6Al4V sample is higher than that of traditional Ti6Al4V. Moreover, the additive Ti6Al4V sample presents higher work hardening and a larger depth of the hardening layer. These findings demonstrate that material properties and manufacturing processes can influence surface integrity significantly.

Improving the facade element surface processing of MDF case furniture

A lot of enterprises engaged in the production of MDF case furniture face the problem of milled plate surface quality. It ensures the production of facing paper and synthetic film or finishing liquid paints and varnishes to improve the facade element surface processing quality of MDF case furniture. The experiments to study the roughness of MDF plates milled surface have been carried out, depending on the feed rate and tool rotation frequency. The work has been carried out using hard-face end mill tools manufactured in accordance with the patent for the utility model (Russian Federation), which enables to improve the quality of machined surfaces by performing finishing milling in one pass and increasing equipment productivity. The determination of the roughness parameter has been carried out in accordance with the requirements of 15612 State Standard. As a result of experimental processing, the dependences of milled surface roughness on the factors under study in the form of regression equations have been obtained. The mathematical dependencies are the results of this work. It enables to set regime parameters for profile milling of MDF surface plates to obtain the required roughness. The optimal milling mode has been determined improving surface finish facade element quality of MDF case furniture.

Tailoring Surface Integrity of Biomedical Mg Alloy AZ31B Using Distinct End Mill Treatment Conditions and Machining Environments

Magnesium alloys are identified as the new generation degradable biomaterials in the biomedical industry. They can prevent secondary operation for the removal of the inserted implant. Nowadays, sustainable manufacturing is promoting the use of low-temperature machining environments over the traditional means. Surface integrity characteristics of the machined surface and tool wear have always been some of the key interests of the researchers. In this research, aluminum titanium nitride-coated cemented carbide end mills were employed in an untreated and cryo-treated condition to machine the biomedical magnesium alloy AZ31B. The experiments were designed using one-factor-at-a-time (OFAT) approach, and milling operations were conducted under three different machining environments, namely wet, cryogenic, and hybrid. Spindle speed, feed rate, and depth of cut were chosen as the input control variables for a comparative study to achieve lowest surface roughness and highest surface microhardness. The results displayed an improvement in the outcome at higher spindle speed (2800 rpm) and lower feed rate (80 mm/rev) and depth of cut (0.5 mm) produced by untreated end mill during cryo-milling. However, the treated end mill performed best with hybrid machining environment (simultaneous application of LN2 and cutting fluid) during milling. Moreover, in this case, the accumulated oxides were found to form the most uniform and thinnest passivation layer over the milled surface. Higher spindle speed in cryo-milling achieved 27.45 and 19.56% better surface finish than wet and hybrid-milling, respectively. Moreover, higher spindle speed in cryo-milling achieved 14.46 and 8.72% higher surface microhardness than wet and hybrid-milling, respectively. Higher spindle speed in hybrid-milling achieved 14.89 and 6.97% better surface finish than wet and cryo-milling, respectively. Furthermore, higher spindle speed in cryo-milling achieved 7.69 and 4.10% higher surface microhardness than wet and cryo-milling, respectively.

Effect of milling parameters on HSLA steel parts produced by Wire and Arc Additive Manufacturing (WAAM)

Abstract Additive manufacturing is considered a motivator for the development of the industrial world. Recent advances show that Wire and Arc Additive Manufacturing (WAAM) has the potential to become a relevant method for the fabrication of large complex-shaped metallic components. In this study, we address one of the most important post-processing methods for WAAM parts to be used in structural applications, milling. In this work, thin-walled high strength low alloy steel parts were manufactured by WAAM and their microstructure was characterized. Then, a milling strategy which considered the microstructure and local mechanical properties of each part was employed. The results show that the mechanical behavior of the as-built parts does not yield a significant influence on the milling process. Overall, it was ascertained that the quality of the milled surfaces improves, that is, has lower roughness, with the increase of cutting speed and with the decrease of feed per tooth. Nevertheless, we highlight the need for more attention to be dedicated on post-process machining operations after WAAM, to establish the best strategies aiming at decreasing tool wear, while maintaining both high surface quality and production rates.

Effects of Cryogenic Milling on Stress Corrosion Cracking Resistance of AISI 316L Austenitic Stainless Steel

The stress corrosion cracking (SCC) susceptibility of 316L austenitic stainless steel milled with cryogenic cooling and conventional cutting fluid cooling is investigated and compared. The milled subsurface properties are characterized in terms of microstructure, residual stress and microhardness. The SCC susceptibility of the milled surfaces is evaluated in boiling MgCl2 by examining the density and depth of the SCC microcracks. Results show that the cryogenic milling increases the SCC susceptibility of 316L austenitic stainless steel. The increase of SCC susceptibility is attributed to the higher residual tensile stress level and the larger volume fraction of slip band produced in the cryogenic milling process in comparison with the conventional cooling milling.

PERHITUNGAN SISTEM HIDROLIK UNTUK PENGGERAK PISAU PADA MESIN PENGHAPUS MARKA JALAN

<p>One of very important and vital tool in road marking is road mark erasing machines. In general, the machine used to repair road markings is a road marking erasing machine that is pushed manually. However, this machine has a disadvantage that requires a long time in the process of erasing the road marking, so making it less efficient. Therefore, the truck road mark erasing machine is one of the options to replace the erasing machine that is pushed manually. The machine uses a grinding system with a vertical blade eraser position and hydraulic power to drive the blades as it is able to withstand shock loads and thrust upwards due to the removal process, having overload protection, and the size of components are not large. The study started with doing observation to the existing manual erasing machine, then determining the required blades and calculating as well as selecting the required components of the hydraulic system. Based on the calculation, the blade specification was obtained and selected, i.e <em>surface milling cutter</em> of type WFX12200R from Sumitomo Electric Hardmetal Corporation having rotation speed 750 rpm, hydraulic motor from Danfoss of type OMR-80 having torque 136 Nm dan displacement 80.3 cc/rev., and using hydraulic pump from Parker of type 0210 having displacement 21 cc/rev. From the test result in the field, this machine is three times faster than the manually pushed machine, less number of the blade used, and the engine as a resource on the machine is more durable. <strong></strong></p>

GaAs milling with neon focused ion beam: Comparison with gallium focused ion beam milling and subsurface damage analysis

This study explores the usage of a neon focused ion beam (Ne FIB) as an alternative to the traditional gallium focused ion beam (Ga FIB) for the task of milling into the III-V compound semiconductor material, GaAs. While the Ga FIB is more commonly available, it is known to produce undesired artifacts such as the formation of gallium rich droplets distributed randomly on the milled surfaces. We reproduce this effect and compare directly with the Ne FIB at a comparable energy and current. Although Ne FIB mills slower, it does not produce the residual gallium rich droplets. At high energies (25 to 30 keV), the Ne FIB is observed to produce a porous texture on the milled surfaces, while at a low beam energy (10 keV), a smooth surface is created with no evidence of pores. We also find that at lower energies neon produces much less subsurface damage from transmission electron microscopy images. With this new learning, we were able to use neon at low energies to mill trenches, as small as 20 nm wide with high fidelity, less damage, and no evidence of the droplet artifacts commonly encountered when using the conventional Ga FIB.

Experimental investigations on the surface characteristics of abrasive waterjet-milled pockets in aluminium 6061-T6 alloy

ABSTRACT Abrasive waterjet (AWJ) milling is suitable for generating pockets in difficult-to-machine ductile materials as the material removal is through local erosion with the exertion of minimal forces. However, the surface generated is non-uniform. The surface quality characterisation based on 2D profile parameters is insufficient to characterise the whole-milled surface. In this work, a region-wise surface characterisation approach is proposed and validated on Al6061-T6 material. The varying depth at jet start/stop (region 1), and jet traverse direction change (region 2) are qualitatively analysed. Following this, relatively flat central surface (region 3) is quantitatively characterised by 2D/3D surface roughness and waviness parameters. From the qualitative analysis, the mean depth at region 1 and region 2 is observed higher than the mean depth at region 3. The quantitative analysis at region 3 reveals that the surface quality improved in terms of surface waviness by ten times at lower waterjet pressures (P) and by two times at higher jet traverse rates (vf ). The surface roughness improved by 2.5 times at lower P, and roughness parameters found less sensitive to vf . Finally, from the results, it is concluded that the 3D characterisation with surface waviness as parameter suits better for AWJ milled surfaces.

Effects of different contact film thicknesses on the surface roughness evolution of LY2 aluminum alloy milled surface subjected to laser shock wave planishing

Laser shock wave planishing technology (LSWP) was adopted to treat a milled surface of LY2 aluminum alloy in the present research. The effects of different contact films thicknesses on the surface roughness and surface profile of the milled surface were investigated. Experimental results indicated that the milling removal rate was related to the contact film thickness, and the thinner contact film, the higher removal efficiency. When a contact film of suitable thickness was used, the surface roughness of the workpiece was minimized, and surface subsidence and edge effects were not noticed after single LSWP, multiple LSWP, and overlapping LSWP. The roughness of the coarsest surface decreased from 2.56 μm to 1.16 μm after single LSWP. However, the roughness of this coarse surface decreased notably to 0.47 μm after multiple LSWP, and its surface profile precision were also guaranteed.

Investigating the effects of broad ion beam milling to sedimentary organic matter: Surface flattening or heat-induced aromatization and condensation?

Previous work has proposed transfer of kinetic heat energy from low-energy broad ion beam (BIB) milling causes thermal alteration of sedimentary organic matter, resulting in increases of organic matter reflectance. Whereas, other studies have suggested the organic matter reflectance increase from BIB milling is due to decreased surface roughness. To test if reflectance increases to sedimentary organic matter (vitrinite) caused by BIB milling were related to molecular aromatization and condensation, Raman and Fourier transform infrared (FTIR) spectroscopies were used to evaluate potential compositional changes in the same vitrinite locations pre- and post-BIB milling. The same locations also were examined by atomic force microscopy (AFM) to determine topographic changes caused by BIB milling (as quantified by the areal root-mean-square roughness parameter Sq). Samples consisted of four medium volatile bituminous coals. A non-aggressive BIB milling approach was used with conditions of 5 min, 4 keV, 15°incline, 360° rotation at 25 rpm and 100% focus (1.5 kV discharge; ∼100 μA). This gentle BIB milling caused vitrinite reflectance (VRo) increases of 12 to 36% of the original values determined optically before milling (average 26% increase). When molecular proxies from FTIR (A- and C-factor, branching ratio) were plotted against each other for the same vitrinite locations pre- and post-milling, mean data points for each sample generally lie within error of a 1:1 line. Likewise, mean Raman thermal proxy [full-width half maximum of G-band (G-FWHM), Raman band separation (RBS) and D1/G band intensity ratio] values were similar for pre- and post-milled locations, also plotting within error of a 1:1 line. AFM confirms the majority (24 of 36) of pre- and post-ion milled surface pairs were smoother (lower Sq values) after BIB milling. These results are interpreted to indicate VRo increase induced by the gentle BIB milling conditions used in this study is an effect of decreased diffuse reflectance due to flatter surfaces, causing more photons to reflect directly back to the detector. Little evidence was observed for molecular aromatization and condensation of vitrinite molecules following BIB milling (with the conditions used). The presence of milling-induced artifacts, including differential milling effects dependent on location and the development of self-organized patterned structures, indicate much work remains in standardization of BIB milling before its promulgation as a routine sample preparation technique for organic petrography. These results provide better understanding of anthropogenic-induced changes to geological samples caused by the now widespread adoption of BIB milling as a disruptive innovation in sample preparation.

Tool path selection for high-speed ball-end milling process of hardened AISI D2 steel based on fatigue resistance

This paper aims at revealing how tool paths influence the fatigue resistance of high-speed ball-end hard milled surfaces and proposing corresponding tool path selection methods. Three kinds of tool paths (tool paths A, B, and C with angles relative to the length direction of cuboid workpiece 0°, 90°, and 45°, respectively) were utilized during high-speed milling process of hardened AISI D2 steel. The fatigue resistance of samples for different tool paths was evaluated through three-point bending fatigue tests. Results shows that tool paths have significant effect on fatigue resistance, and the maximum discrepancy in fatigue life can reach about 37.6% for different tool paths. Samples for tool path C shows the longest fatigue life when radial depth of cut ae = 0.1 mm. However, with the further increase of ae, samples for tool path A have the best fatigue resistance, followed by tool path C and B. Microscopic stress concentration and effective residual stress are the main ways by which tool paths influence the fatigue resistance. Changing tool paths leads to the difference in surface topography orientation and then in degree of microscopic stress concentration. Moreover, the effective residual stress (residual stress component in direction parallel to cyclic tensile stress) is also directly determined by tool paths. Tool path selection methods are put forward based on the aforementioned influence mechanisms. This study indicates that improving the fatigue resistance of high-speed ball-end hard milled surfaces suffering given cyclic tensile stress is feasible by choosing appropriate tool paths.