Shoulder Milling Research Articles

Influence of the Relative Displacements and the Minimum Chip Thickness on the Surface Texture in Shoulder Milling.

The formation of surface texture in milling is a complex process affected by numerous factors. This paper focuses on the surface roughness of X37CrMoV51 steel machined by shoulder milling. The aim of the study was to develop a mathematical model to predict the surface roughness parameter Ra. The proposed model for predicting the surface roughness parameter Ra in shoulder milling takes into account the feed per tooth, fz, the corner radius, rε, and the actual number of inserts involved in the material removal process as well as hmin and D(ξ). The correlation coefficient between the theoretical and experimental data was high (0.96). The milling tests were carried out on a three-axis vertical milling machine using a square shoulder face mill. The geometric analysis of the face mill shows that at a feed rate of 0.04 mm/tooth, cutting was performed by three out of five inserts, and when the feed rate exceeded 0.12 mm/tooth, material was removed by all inserts. The minimum chip thickness parameter and the standard deviation of the relative displacement increased as the feed increased. Over the whole range of feeds per tooth, the displacement increased by 0.63 µm. Higher cutting speeds resulted in lower minimum chip thicknesses and the average standard deviation of the relative displacements for the whole range of cutting speeds was 2 μm.

Role of CO2 cooling strategies in managing tool wear during the shoulder milling of grade 2 commercially pure titanium

As a result of their high hardness, osseointegration and low chemical reactivity titanium alloys have become an invaluable material species for use in medical applications. Unfortunately, many of the material properties which make titanium alloys desirable biomedical materials, also contribute towards difficulties in tool wear and surface quality during machining. Historically, this has been met via the application of robust metalworking fluid (MWF) strategies, e.g. flood, or high-pressure (HP) soluble oil coolant (emulsion). However, this brings with it its own challenges, not least of which the problem of coolant residue contamination. This study describes efforts to minimise and characterise tool wear during the shoulder milling of grade 2 commercially pure titanium (CP–Ti) by using a novel external supercritical CO2 (scCO2) coolant strategy. Whilst the results imply that the sole use of scCO2 coolant contributes to increased tool wear (relative to emulsion), an optimised strategy of combining scCO2 with minimum quantity lubrication (MQL) is shown to support up to a 245% increase in tool life. Despite this, machinability outcomes are found to be highly contingent upon proper selection of trial process variables such as scCO2 mass flow rate and cutting speed, wherein cutting speeds at or below 115 m/min, and 35 kg/h of scCO2 is generally shown to be the most efficacious parameters for this material/operation. Ultimately, scCO2 + MQL is found to be an effective compromise between the cleanliness of scCO2 and the improved function of emulsion.

Machining performance and wear behaviour of polycrystalline diamond and coated carbide tools during milling of titanium alloy Ti-54M

Polycrystalline diamond (PCD) is currently under development as a new generation of cutting tool material for titanium alloy machining applications. The unrivaled high temperature hardness possessed by PCD offers the potential for higher levels of productivity compared to tungsten carbide, the current industry standard tool material, through facilitating higher cutting speeds. This study investigates the performance of various PCD tool grades during square shoulder milling of Ti-54M. The influence of PCD grain size on dominant wear mechanism has been established, revealing that a smaller, sub 1 μm, grain size offers improvements in tool life due to superior fracture toughness compared to larger grained material. For fine grained PCD, loss of tool material through a cyclic process of workpiece adhesion followed by grain pull-out was identified to be the predominant wear mechanism, contrasting the mechanical fracture dominated wear observed for the larger grained PCD grades. The influence of insert microgeometry was also investigated through honing of the cutting edge radii. An increased tendency for edge fracture was demonstrated when machining with larger radii tooling which was attributed to increased cutting forces. Finally, the study has compared the surface integrity response of the workpiece following PCD and carbide machining, revealing considerably lower levels of microstructural damage and cutting forces when machining with PCD. This highlights the potential benefits of PCD in finishing applications, whereby high speed machining can be employed to reduce the impact on component surface integrity.

Identification of Friction Behavior Variation in the Minor Flank of Square Shoulder Milling Cutters under Vibration

In the milling process, the friction and wear of the tooth minor flank of the square shoulder milling cutter directly affects the machined surface quality and the cutter’s life. The friction of the minor flank of the cutter tooth presents a nonlinear distribution, and its variation cannot be revealed by using a single parameter. It is difficult to identify the dynamic characteristics of the friction of the minor flank of the cutter tooth. In this work, the friction velocity model for the cutter tooth minor flank was developed by using the relative motion relationship between the flank area element and the workpiece transition surface. In accordance with the atomic excitation theory developed under the potential energy field at the friction interface of the cutter, the model for friction energy consumption under the friction velocity and thermal-stress coupling field on the minor flank of the cutter tooth was developed. Based on the mechanism of the interfacial atomic thermal vibration, the model for the friction coefficient under thermal-stress mechanical coupling was developed. Using the instantaneous friction coefficient and normal stress, the instantaneous friction distribution function of the flank was obtained. Finally, an identification method for the friction dynamic characteristics of the shoulder milling cutter tooth flank under vibration was proposed and verified by experiments.

Investigation performance of holders with shape memory dampers against chatter vibration

Chatter phenomenon is usually observed on several machining processes, leading to both poor quality surface and cutting edge chipping. In order to avoid it, this work present one innovative solution: a tool holder fulfilled with a shape memory alloy; these smart materials are being considered as good passive dampers in the construction industry. A comparison between the performance of a commercial tool holder and our proposal in terms of surface integrity was held considering shoulder milling operation of a medium carbon steel. Numerical and experimental results shown that this alternative may be very useful depending on cutting speed employed.

Effect of deep cryogenic treatment on tool life of multilayer coated carbide inserts by shoulder milling of EN8 steel

Effect of deep cryogenic treatment on tool life of multilayer coated carbide inserts by shoulder milling of EN8 steel

Application of Taguchi Technique to Optimize the Shoulder Milling Machining Parameters of Aa6063 T6 Aluminium Alloy

In order to minimize surface roughness, in this paper Taguchi technique is being used for optimizing the shoulder milling process parameters. The shoulder milling was done on VMC milling machine on AA6063 T6 by using M series solid carbide tool. There are following cutting parameters like coolant, speed, feed and depth of cut were considered and the level of these parameters were three except the coolant at two level was considered. The experiments was conducted by using L 18 orthogonal array. Signal to noise ratio were calculated for finding the effects of shoulder milling parameters on surface roughness. And analysis of variance was used for finding the contribution of each parameters. The validation of experimental results was done by the confirmation test. Levels of shoulder milling machining parameters to minimize surface roughness were A 1 B 1 C 2 D 2 i.e. coolant on with a feed of 200 mm/min, depth of cut of 0.25 mm and speed is at 5800 rpm. ANOVA table represented the parameters which mostly affected the surface roughness with 40.18% contribution of feed rate which is maximum followed by speed (21.90.%), depth of cut (16.48%), and affect of coolant 0.81%) is insignificant. The study also shows that this method can effectively improve the surface finish of the shoulder milling process.

Contribution in developing a rapid strategy in assessing hardened steel machining

The present work is a contribution to developing a strategy for rapid analysis of the behaviour of surface roughness and tool wear during machining hardened steel with carbide cemented cutting tools on conventional cutting machines. In agreement with dies and mould manufacturers in East Algeria, the strategy is based on the machining potential of the manufacturers, cutting tools manufacturer’s guidelines and recommendations from literature. The agreement suggested to focus on up and down shoulder finish milling of hardened AISI D3 tool steel using GC1030 insert on a conventional vertical milling machine. The strategy has been developed within five successive steps starting from the analyses of the performance of a machine tool to the definition of an experimental plan to respect. As expected, results show that down shoulder milling is the most suitable process rather than up shoulder milling which must be avoided whatever the hardening condition. In addition, the best performance of down shoulder milling is obtained when machining unhardened steel. In the as-received condition (31.6 HRc) when using down milling the cutting speed can be increased up to the maximum value of 113 m/min, however, the tool life obtained for this value is three times lower than that at Vc = 59 m/min. In 49 HRc hardening condition, milling at Vc = 59 m/min resulted in the good surface finish but with a tool life 6.5 times lower than the tool life when milling in the as-received condition. Vibration measurements provide a time referential data on the evolution of surface roughness together with corresponding tool wear. A time referential data on the evolution of displacement together with the corresponding tool life has been proposed as useful information to meet the needs of dies and moulds manufacturers when milling hardened steels.

Development of surface texture evaluation system for highly sparse data-driven machining domains

ABSTRACT Dimensional, geometrical and surface texture tolerances are significant issues to be addressed by manufacturing industries. Dimensional and geometrical tolerance estimation systems are used by several machining industries, whereas surface texture tolerance estimation systems are rare. In general-purpose machines, several machining operations are performed and huge machining data are required for the development of surface texture tolerance estimation model. The necessity for sparse data modeling is the need of the hour and such modeling techniques reduce costly trial and error approaches. Shoulder milling operations are performed on mild steel workpieces. Experimentation is performed at diverse cutting conditions, and surface texture tolerances of the machined components are measured. Big data computation is being accomplished by contemporary tools compared to sparse data evaluation. The novelty of this work is to develop a system capable of surface texture tolerance evaluation from highly sparse learning data, as big data generation involves cost and time for experimentation. Flower Pollination Algorithm (FPA) models are developed for the highly sparse data for surface roughness estimation. Two different FPA techniques, namely, Maximum (Max) and Average (Avg) are used, and a comparison between the methods mentioned above is made. An operator-friendly adaptive performance enhancement system is developed to evaluate the corresponding surface texture tolerance for the given operating parameters.

Investigation of cutting conditions on tool life in shoulder milling of Ti6Al4V using PVD coated micro-grain carbide insert based on design of experiments

Tool life prediction is generally of great importance in all metal cutting processes, including milling titanium. In this paper, tool life testing was performed based on full factorial design. The cutting speed and width varied between 100 and 120 m/min, and 10 and 70 percent of tool diameter, respectively. All cutting tests were performed in Ti6Al4V under wet conditions using Physical Vapor Deposition (PVD) coated milling inserts. The wear limit was set to 0.2 mm. The data were analyzed using multiple regression analyses, where the method of least squares was applied. A mathematical tool life model was established. Roughly, for each one percent increase in cutting width, tool life decreases on average by one percent, and an increase in cutting speed by a percent leads to a decrease in tool life by four percent. The adequacy of the model was verified using analysis of variance at 95% confidence level. Tool life contour in cutting width and speed was generated from the model. The results can be used for selecting optimum cutting parameters for providing a desired tool life or maximum metal removal rates for a favored tool life.

Meso-scale tool breakage prediction based on finite element stress analysis for shoulder milling of hardened steel

In this article, finite element method (FEM) based tool stress analysis and breakage prediction are advanced for meso-scale shoulder milling of hardened stainless steel. Rather than using simplified line loads or uniformly distributed loads, the tool stress analyses are conducted with realistic chip load predicted by the previously developed 3D coupled Eulerian-Lagrangian (CEL) FEM model. A reliable distribution of contact forces obtained with a continuous tool-chip contact region is transferred to a static FEM model for tool stress analysis and breakage prediction at each angular location of an end mill. The simulation results are validated through dedicated cutting experiments with short cutting distances under various cutting conditions. The developed FEM models are found to be capable of making accurate predictions of tool breakage. Some key features of feed rate-related tool breakage are identified. It is found that the maximum tensile stress in the tool does not coincide with the maximum resultant cutting force in terms of cutter rotation. The tensile stress in the tool is not positively correlated with the resultant cutting force. In down milling, the maximum tensile stress is found to occur just after the tool starts to contact with the workpiece. It is also observed that the tensile stresses of the tool are much smaller in up milling configuration compared to down milling processes.

Multi Performance Optimizationof Shoulder Milling Process Parameters of AA6063 T6 Aluminium Alloy by Taguchi Based GRA

In this paper, a grey relational analysis method based on Taguchi is proposed to improve the multi-performance characteristics of VMC shoulder milling process parameters in the processing of AA6063 T6. Taking into account four process parameters such as coolant, depth of cut,speed and feed, there are three level of each process parameter in addition to two levels of coolant. 18 experiments were used by L18 orthogonal array using the taguchi method. Multi-performance features like surface roughness and material removal rate are used. Grey Relational Analysis method is used to obtain the Grey Relational Grade, and the multiperformance characteristics of the process are pointed out. Then, the Taguchi response table method and ANOVA are used to analysis data. In order to ensure the validity of the test results, a confirmation test was conducted. The study also shows that this method can effectively improve the multi-function characteristics of shoulder milling process.In his work microstructure and mechanical properties of AA6063 T6before and after shoulder milling have been investigated.

Cutting parameter optimization in shoulder milling of commercially pure molybdenum

Due to its superior properties such as high melting point (2617 °C), high thermal conductivity and low thermal expansion at higher temperatures, molybdenum is a refractory metal and is used for making critical parts in defense, space, electronics and nuclear industries. High cost of molybdenum makes the selection of suitable cutting conditions imperative in machining operations in order to obtain the required surface quality and dimensional accuracy. In this study, suitable cutting tools and cutting parameters were aimed to be determined in terms of cutting forces (Fc) and average surface roughness (Ra) when shoulder milling commercially pure molybdenum. The milling tests were carried out at 0.05, 0.1, 0.15, 0.2 mm/tooth feed rates and 75, 100, 125, 150 m/min cutting speeds using four different cutting tools. The Taguchi’s experimental design (L16 orthogonal array) technique was implemented. Analysis of variance was used to determine the effects of cutting tools and cutting parameters on Ra and Fc. The results showed that the feed rate is the most influential parameter for Fc while the cutting speed is for Ra.

3D coupled Eulerian-Lagrangian finite element analysis of end milling

In this article, a 3D coupled Eulerian-Lagrangian (CEL) finite element method (FEM) model is presented for simulation of end milling processes based on Abaqus/Explicit. In the proposed model, the chip formation process does not rely on the degradation of material or continuous remeshing algorithms to achieve chip separation. The processes under investigation are the slot and shoulder milling of Al6061-T6. A linear motion of the workpiece is adopted as a simplification of the trochoidal motion of the end mill. The workpiece is given a sinusoidal profile to achieve a varying uncut chip thickness in the cutting process. With a stationary tool and a confined region of mesh refinement, the computational cost of the model can be minimized, which makes the proposed model compatible for parametric studies. The model demonstrates good accuracy in cutting force predictions. The prediction error of the resultant cutting forces can be controlled within 12% over various milling conditions. The proposed model also gives accurate predictions in terms of the morphology of chips. The excessive curling of chips in the early stages of chip formation can be predicted which has been compared with the shape of the actual chips collected during machining.

Trochoidal milling: investigation of a new approach on uncut chip thickness modeling and cutting force simulation in an alternative path planning strategy

Trochoidal milling is an alternative tool path strategy which has been shown to increase productivity, improve tooling life, and reduce resultant cutting forces. While the advantages of trochoidal milling over conventional slot or shoulder milling were previously reported, the complexity of trochoid tool path makes developing an analytical force model highly complicated. In this work, a numerical algorithm to construct the uncut chip thickness model in trochoidal milling is introduced, which is based on the geometrical relation of self-intersection and cross-intersection points of the tool path curve. In addition, an extensive series of experiments is carried out in slot and trochoidal-milling operations in order to investigate the dependency of cutting pressure coefficients on tool path parameters and to develop a model to relate the two. Furthermore, the performance of the developed model for uncut chip thickness and the cutting pressure coefficients are evaluated in predicting cutting forces; it is shown that the model predicts the maximum cutting force in the feed direction and between all the testing sets with 8% total average error, while 17% total average error is observed in predicting maximum cutting force in the lateral direction. This demonstrates the potential of the proposed approach in offline simulation of the cutting forces which is a critical step in selecting proper tooling and process parameters to increase productivity of the cut.

Ergonomic Risk Assessment of Distal Upper Extremities by Job Strain Index in Carpet Weavers

Background: Distal upper extremities musculoskeletal disorders (DUEMSDs) is considered as the main cause of working lost time, increased labor costs, and human injuries. This study was conducted to assess the risk factors of DUEMSDs in carpet weavers. Methods: This descriptive cross-sectional study was conducted on 143 carpet weavers located in Qom city. For quantifying the prevalence of signs or symptoms of DUEMSDs, the customized nordic musculoskeletal questionnaire (NMQ) was used. Next, carpet weaving jobs were analyzed by hierarchical task analysis (HTA). All risk factors that caused DUEMSDs were determined and risk assessment of DUEMSDs was done by the Job Strain Index (JSI). Results: Nordic musculoskeletal questionnaire results (NMQ) showed that the most prevalent of disorders was related to the upper back (62.2%), lower back (60.1%), wrist (55.9%), and shoulders (37.2%), respectively, during the last year. Also, JSI results showed that sub-tasks of knot tying and cutting, milling, shoulder milling headband, and the sub-tasks paid in the area were placed in the hazardous category. Among the parameters of the strain index, duration of exertion, effort in minutes, and hand/wrist posture had the most important effect in the creation of the risky level knot (W4), cutting the knots (W5), and combing (T6) sub-tasks. Also, duration of exertion and hand/wrist posture had the most important effect in the creation of the risky level in head band milling (R1) and combing (R7) sub-tasks. Conclusions: Knot and cutting sub-tasks in the task of weaving, as part of carpet weaving jobs, were the most hazardous sub-tasks. Implementation of ergonomic interventions focused on reducing the duration of exertion, efforts in minute, and correction of hand/wrist postures may improve workstations and reduce distal upper extremities musculoskeletal disorders risk factors in carpet weaving workers.

Experimental analysis of system parameters for minimum cutting fluid consumption when machining Ti-6Al-4V using a novel supply system

This paper presents the development of a new controlled cutting fluid impinging supply system (Cut-list) to deliver an accurate quantity of cutting fluid into machining zones through precisely oriented coherent round nozzles. The performance of the new system was evaluated against a conventional system during the step shoulder milling of Ti-6Al-4V using a water-miscible vegetable oil-based cutting fluid, which was phase 1 in this comprehensive study. The use of Cut-list resulted in a significant reduction up to 42% in cutting fluid consumption as well as reductions in cutting force, tool flank wear, average surface roughness (Ra) and burr height (Gariani et al. in Appl Sci 7(6):560, 2017). This paper details phase 2 of the study which was aimed to investigate the effects of working conditions, nozzle positions/angles and impinging distances on key process measures including cutting forces, workpiece temperature, tool wear, burr formation and average surface roughness of the machined surface. Feed rate showed a significant effect on mean values of cutting force, burr formation and surface roughness, whereas average workpiece temperature and flank wear values are very sensitive to cutting speed. Nozzle position at a 15° angle in the feed direction and 45°/60° against feed direction assisted in minimising workpiece temperature. An impinging distance of 55/75 mm is also necessary to control burr formation, workpiece temperature and average surface roughness. It can be concluded that Cut-list gave promising results compared to conventional flood cooling systems in terms of the evaluated machining outputs. Therefore, the new system can be considered as a feasible, efficient and ecologically beneficial solution, giving less fluid consumption in machining processes.

Surface Structure Analysis of Syntactic Metal Foams Machined by Milling

In the automotive and aerospace industries the engineers are encouraged to develop new materials, having special features mainly for the purposes of mass reduction, favourable (specifi) mechanical properties, appropriate strength, heat resistance, and environmental impacts, becoming even more critical technically. The matrix of the metal matrix composite, being the subject of our research, is an AlMgSi1 aluminum alloy: it contains 50-55 volume per cent of Al2O3 particles as reinforcement, having an average diameter of 100 - 150 μm. After machining, the surface of materials, having such large particles, is divided by open cavities, therefore other methods have to be used in order to describe and characterise the surface structure than in the case of steel or aluminum components, having a homogeneous structure. In our present article the aim is to analyse the microgeometrical properties of the surface of metal matrix composite materials, produced to the tests and machined with shoulder milling; furthermore, the measures, being able to evaluate the produced surface in an exact way, will be determined.

Evaluation of a Novel Controlled Cutting Fluid Impinging Supply System When Machining Titanium Alloys

Following a comprehensive review on titanium machining and methods of cutting fluid application, this paper presents a new Controlled cutting fluid impinging supply system (Cut‐list) developed to deliver an accurate amount of cutting fluid into the machining zone via wellpositioned coherent nozzles based on the calculation of the heat generated. The performance of the new system was evaluated against a conventional flood cutting fluid supply system during step shoulder milling of Ti‐6Al‐4V using vegetable oil‐based cutting fluid. The comparison was performed at different cutting speeds and feed rates. Comparison measures/indicators were cutting force, workpiece temperature, tool flank wear, burr formation and average surface roughness (Ra). The new system provided significant reductions in cutting fluid consumption of up to 42%. Additionally, reductions in cutting force, tool flank wear and burr height of 16.41%, 46.77%, and 31.70% were recorded, respectively. Smaller Ra values were also found with the use of the new system.

The definition of cutting forces in square shoulder milling by 3D

The paper presents the 3D square shoulder milling study of modeling, using Smooth Particles Hydrodynamics methodology that also illustrate specific challenges and solutions. The aim of the study – define the cutting forces and to compare them to analytical models. The milling is discontinuous cutting and by each turn the chips are formed depending on the milling tool width and number of teeth. Then the simplification of complex cutting tools to one-point tool is not so informative and understandable for the numerical analysis. The main advantage of presented SPH methodology – less artificial numerical criterions needed for numerical solution. Also, shorter calculation time comparing to FEM and „natural“ chip removal process due to Kernel function. SPH metodology alloowed to use real 3D milling cutter and to perform the calculation according to feed rate, cutting speed and tool rotation. In order to provide the numerical simulation the simplified numerical tests were performed, according to the density of smooth particles and artificial bulk viscosity parameter. The model demonstrated satisfactory coincidence of computed results against the theoretically obtained data. Calculated tangential cutting force is in satisfactory correlation with theoretical Hulle hypothesis. Tne numerical instabilies seen in graphics of results coud be eliminated with SPH metodology, by using higher cutting speed (deformation rate). DOI: http://dx.doi.org/10.5755/j01.mech.21.3.12203