High-speed Spindle Research Articles

Surface Smoothing of A5083 Aluminum Alloy Plate by Friction Stir Forming

This paper provides a framework for the transcription of the surface of a mirror-finished die onto a metal plate by friction stir forming (FSF). In FSF, a material is put on a die, then friction stirring was conducted on its back surface for the transcription of the profile of the die onto the material. In this paper, a mirror-polished die of JIS SUS304 stainless steel with surface roughness Sz 0.014 mm and a probe-less friction-stirring tool in 18 mm shoulder diameter were employed for the experiment. A5083P-O aluminum plates, 3 mm thick, were utilized as base metals for the transcription. The authors varied tool spindle speed and tool feed rate to evaluate the forming results. Consequently, a mirror-finished surface under the friction-stirring tool was successfully transferred from the die to the aluminum alloy plate. The roughness of the base metal before processing was Sz 0.022 mm and that of the processed metal was Sz 0.012–0.016 mm. Higher spindle speed and faster feed rate resulted in a smoother surface; it is thought that high spindle speed and faster feed rate should be effective for higher contact pressure between a die and a material.

Flow drill riveting of carbon fiber-reinforced polymer and aluminum alloy sheets

As a variation of friction stir blind riveting, flow drill riveting (FDR) is a new one-sided mechanical joining method for similar and/or dissimilar materials without predrilling holes on workpieces. In the FDR process, a blind rivet with a conical mandrel tip rotates at a high spindle speed and penetrates the workpieces due to local softening as a result of high friction between the mandrel tip and workpieces. The FDR process was applied to fabricating dissimilar lap-shear joints of 2.0-mm-thick carbon fiber-reinforced polymer (CFRP) and aluminum alloys (AA6061) with thicknesses of 1.0, 1.5, and 2.0 mm in this work. The effects of the thickness of AA6061 and stack-up sequence of CFRP and AA6061 on the maximum tensile load and failure mode of FDR joints were analyzed and discussed. With the increase of AA6061 thickness, the maximum tensile load increased and the failure mode changed from failure at the AA6061 to failure at the CFRP disregarding their stack-up sequence. It is found that the maximum tensile load and the failure mode are strongly dependent on the relatively weaker one of AA6061 and CFRP workpieces, and the maximum tensile load of the FDR joint is closely related to its failure mode.

Resonance speed measurement of high-speed spindle using an instruction-domain-based approach

Although the manufacturing and assembling technology of the machine tool has become more and more mature, eccentricity of the spindle is still unavoidable and is an important source of spindle vibration. When the spindle rotation frequency is close or equal to the natural frequency of the spindle structure, spindle vibration will increase sharply, causing resonance (resonance speed). The high-speed spindle is more prone to cause resonance speed due to its wide speed range and large amount of centrifugal force. Machining at the resonance speed not only degrades the surface quality but also accelerates the degradation of the spindle performance. Aiming at this problem, this paper presents a G instruction-domain-based resonance speed measurement method. This method realizes the measurement by performing the spindle acceleration signal analysis in the instruction domain, which overcomes the shortcomings of the hammer impact test-based method (complicated operation), it is suitable for in situ application. The effectiveness of the proposed method was verified by hammering modal test and motor vibration test. The influence of resonance speed on the milling surface quality and the influence of different tools on the resonance speed was explored. Based on the proposed method, a portable spindle resonance speed measurement tool and a CNC system resonance speed avoidance module were developed.

Optimization of Machining Parameters for MRR and Surface Roughness for 7024 AL-alloy in Pocket Milling Process

The objective of this work is the investigation of milling process variables which resulting in optimal values of the surface roughness and material removal rate during machining of 7024 Al-alloy. The machining operation implemented on C-TEK CNC milling machine. The effects of the selected parameters on the chosen characteristics have been accomplished using Taguchi’s parameter design approach; also ANOVA had been used to evaluate the contribution of each parameter on the process outputs. Different feed rates are used ranging from (60, 80 and 100) mm/min, found that high feed rates gives a high material removal rates and good surface roughness. On the other hand, using three levels of spindle speeds found that a higher spindle speeds gives better surface roughness with a little effect on MRR. The process results showed that maximum MRR achieved (2.40) mm3/min when machining feed rate (100) mm/min, spindle speed (1000) r.p.m, and depth of cut (0.6) mm while good surface roughness (0.41 µm) when machining feed rate (100) mm/min, spindle speed (1000) r.p.m, and depth of cut (0.2) mm. The level of importance of the machining parameters for material removal rate and surface roughness and is determined by using Taguchi designing experiments and the variance analysis (ANOVA).

Application of High-speed Spindle in Intelligent High-speed Drilling and Tapping Center Machine Tool

The Concept of intelligent manufacturing has brought about the rapid development of intelligent machine tools, and the development of manufacturing industry has been deeply influenced by such functional components as high-speed spindle. High-speed spindle is the important part of machining center. This article expounds the application of high-speed spindle on intelligent high-speed drilling and tapping center from the aspects of main driving mode and structure of high-speed spindle, and verifies the feasibility of application by means of measurement of temperature rise, measurement of vibration and processing effect of parts.

Joint Formation and Mechanical Performance of Friction Self-Piercing Riveted Aluminum Alloy AA7075-T6 Joints

AA7xxx series aluminum alloys have great potentials in mass saving of vehicle bodies due to pretty high specific strength. However, the use of these high strength materials poses significant challenges to the traditional self-piercing riveting (SPR) process. To address this issue, a novel process, friction self-piercing riveting (F-SPR), was applied to join aluminum alloy AA7075-T6 sheets. The effects of the spindle speed and rivet feed rate on F-SPR joint cross section geometry evolution, riveting force, and energy input were investigated systematically. It was found that the rivet shank deformation, especially the buckling of the shank tip before penetrating through the top sheet, has significant influence on geometry and lap shear failure mode of the final joint. A medium rivet feed rate combined with a high spindle speed was prone to produce a defect-free joint with sound mechanical interlocking. F-SPR joints with the failure mode of rivet shear fracture were observed to have superior lap shear peak load and energy absorption over the joints with mechanical interlock failure. The optimized F-SPR joint in this study exhibited 67.6% and 13.9% greater lap shear peak load compared with SPR and refill friction stir spot welding joints, respectively, of the same sheets. This research provides a valuable reference for further understanding the F-SPR process.

Prediction of Temperature Distribution of the Spindle System by Proposed Finite Volume and Element Method

High-speed machining is one of the emerging cutting processes possessing tremendous potential in the arena of increased metal removal rates as well in achieving improved surface finish, burr-free edges, dimensional accuracy and a virtually stress-free component after machining. However, as known the performance of a machine tool depends on a number of factors of which the most important is the thermal behavior of the high-speed spindle. Thus, the temperature rise and the displacement due to temperature variation in the spindle components will severely affect the thermal characteristics of high-speed motorized spindle. Hence, it is significant to study its thermal behavior, and so in this paper, a coupled fluid–thermal (CFT) of a high-speed spindle is developed to simulate fluid-structural conjugate heat transfer. Based on the proposed model, the thermal characteristic of the high-speed spindle system is studied. The investigation revealed that the proposed CFT analysis for the motor cooling path has shown a minimum deviation in spindle temperature approximating to 7.6% when compared with that of attained experimental results at high speed.

Study on the surface damage mechanism of monocrystalline silicon in micro ball-end milling

This paper investigates the surface damage mechanism of monocrystalline silicon in micro ball-end milling with polycrystalline diamond (PCD) and natural diamond tools. Machining-induced surface damages such as surface fracture, phase transition, and residual stress are studied under different machining conditions. It is found that under a small feed rate and cutting depth and high spindle speed, PCD micro ball-end mill is a potential candidate in manufacturing low-damage surfaces that are distributed uniformly with the amorphous layer of several-nanometer thickness and the average compressive residual stress that does not exceed 150 MPa. Additionally, the influences of feed rate on surface damages in PCD micro milling are more significant than those in micro milling with a natural diamond tool. The experimental results reveal the surface damage mechanism: (i) the current cutting region comprises the subsurface layer after machining in the last tooth period, the previously produced surface/subsurface defects can affect the damages of the current machined surface, (ii) the cutting edge closer to the tool tip acts primarily on amorphous silicon generated in the previous tooth period, part of the amorphous phase remains on the machined surface, and the formation of metastable phases (Si-III, Si-XII, and Si-IV) occurs away from the machined surface.

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Machine tool industry slowdown & remedies; chlorinated paraffin concerns; coolant recycling; high speed spindles; B Elliott companies bought out; largest press brake built in the UK; end of the line for transfer lines; UK gear making; & more

Optimizing Machining Process of E31 Steel for Improved Surface Roughness

End milling (EM) and electric discharge machining (EDM) are frequently used for machining high chromium steel. The superior surface finish is among the key requirements for the improved functional behavior, wear resistance, and fatigue life high chromium steel components. The present work includes optimization of EM (using Taguchi method) and EDM processes (by selecting appropriate electrode) for machining of the high chromium steel keeping high material removal rate (MRR) and superior surface finish as the objectives. Additionally, the effect of coolant on surface roughness was evaluated. For EM, the feed rate was found the most influential parameter and the high spindle speed, small feed rate result-in better surface finish whereas the depth of cut has the insignificant effect on the surface roughness for the selected rages of process parameters. The scanning electron microscope (SEM) micrographs revealed that flood cooling decreases the surface defects and mostly high chromium steel samples were having a lower surface roughness when coolant was used. For EDM, the brass electrode results in a superior surface finish but a lesser MRR than the copper electrode while machining high chromium steel.

An experimental investigation of control parameters in five-axis hybrid parallel kinematic machine in milling of aluminium 6061-T3

Surface roughness is an important factor in predicting performance of any machining operation. The experiment has been performed in milling a V-shaped pocket on aluminium 6061-T3 by Exechon parallel kinematic machine using carbide tool. Three different segmented surfaces are selected on V-block and the effect of control parameters were investigated over it. In this research, Taguchi method is used to identify the optimal combination of spindle speed, feed, and depth of cut. To analyse the effect of the control parameters for fine surface finish, Taguchi L9 orthogonal array, signal-to-noise (S/N) ratio and analysis of variance (ANOVA) are employed. Control parameters such as high spindle speed, low feed rate and low depth of cut plays a decisive role in the result of surface roughness. Also, the obtained results from PKM were compared to that of CNC machining, and the surface topologies were examined under optical and scanning electron microscope.

Optimization of surface roughness and delamination factor in end milling of graphene modified GFRP using response surface methodology

Abstract Glass fibre reinforced polymer (GFRP) composites are used in most of the applications like aerospace industries, marine, sport goods due to its better mechanical properties with high strength to weight ratio. Application of nanoparticle in matrix material has increased the mechanical and thermal properties of GFRP. In this study, end milling operation is conducted on neat GFRP and GFRP modified with different weight % of graphene using solid carbide end mill. Experimental parameters like feed rate and spindle speed with weight % of graphene were taken as input parameters. Response surface method was used to optimize these input parameters and analyze the surface roughness and delamination factor. Conducted experiment showed that weight % of graphene was the most influenced parameter for both delamination factor and surface roughness. Result concluded that low feed rate and high spindle speed with high weight % of graphene within used range of parameters value provided less surface roughness and delamination damage.

Identification of spindle dynamics by receptance coupling for non-contact excitation system

The identification of spindle dynamics plays a crucial role in accurate prediction of the stability diagrams for high speed machining operations. In this study, variations of the mode shapes of the tool-spindle assembly at high spindle speeds are examined using numerical models and hypotheses are formulated. An identification method of spindle dynamics is proposed, dedicated to non-contact excitation system; from which only cross FRF can be obtained (instead of tool tip FRF classically). Then, spindle dynamics is calculated using inverse Receptance Coupling (RC) method. Proposed method enables the identification of the speed dependent spindle dynamics in the full frequency range. The approach has been verified with the Finite Element Model (FEM) of a spindle-bearing assembly. The prediction by RC of the dynamics of another tool has been successfully compared to the FEM simulation.

Convergence Analysis of the Multi-Frequency Approach around a Variable-Helix Instability Island

Variable helix tools are known to have unusual regenerative chatter stability behaviour that can be difficult to predict. This paper explores the convergence and accuracy of a multi-frequency approach (MFA) to stability prediction. An island of instability was identified using the MFA, and the stability boundary was compared to predictions from the semi-discretisation method (SDM) and experimental data. A convergence study for the MFA and SDM showed that the SDM approach was very slow to converge for this specific case, in contrast to its performance at higher spindle speeds. The MFA approach exhibited fast convergence which led to orders of magnitude improvements in the computational speed of the predictions.

Fundamental analysis on thermal characteristics of high-speed aerostatic spindle

Fundamental analysis on thermal characteristics of high-speed aerostatic spindle

Fundamental design study of high-speed aerostatic spindle with built-in motor and shaft-bore water cooling structure for improving thermal stability

Fundamental design study of high-speed aerostatic spindle with built-in motor and shaft-bore water cooling structure for improving thermal stability

An Integro-Differential Equation with Variable Delay Arising in Machine Tool Vibration

We rigorously derive an integro-differential equation as a model for the possible onset of regenerative chatter during a turning process using a lathe. The cut is made parallel to the axis of rotation of the spindle. The model allows the spindle speed to continuously vary with time, which results in the presence of a variable time delay determined from a threshold condition. We present a number of conditions sufficient for the elimination of chatter; these emphasize sufficiently low feed rate or sufficiently high spindle speed. Numerical simulations cast light on the effect of a sinusoidally varying spindle speed, a feature of some modern lathes. Spindle speed variation can cure chatter but does not necessarily do so and can fail at higher values of the tool feed rate.

Особливості формування професійної компетентності майбутніх фахівців машинобудівної галузі під час вивчення теми «Безпечне конструювання високошвидкісних шпиндельних вузлів на пневматичних опорах»

The article analyzes the learning process of the students of the machine-building industry. It is established that engineering thinking occupies a special place among professional competences needed for the successful professional activity of a technical specialist. The aim of the article is to analyze the peculiarities of forming the professional competence of future specialists of the machine-building industry during the study of the topic "Safe construction of high-speed spindle units on the pneumatic supports". Studying of this topic provides acquiring by the students the knowledge and skills of designing of efficient and safe elements of the mechanical equipment. First of all the stress is made on the safety of the machines and mechanisms for metal working, being designed. This stipulates the proposal to use pneumatic supports for spindle units, which are designed for high-speed machine-tools of high precision and allow to increase the rigidity and technological capabilities of the spindle at its high efficiency and satisfy the requirements of electrical, explosion and fire-safety, allowing students to form the culture of safety, which is decisive for the formation of professional competence. We believe that the proposed method of calculating the pneumatic supports with the required static stability of its equilibrium position ensures their efficient and safe use, as well as generates technical thinking and professional competence of future specialists. In addition, this technique of forming technical thinking while studying the topic of safe construction of high-speed spindle units on pneumatic supports, in the conditions of the reduction of time for training of future specialists of the machine-building industry, allows moving from the reproductive training to searching training.

Характеристики конічних підвісів з поздовжніми глухими мікроканавками постійної ширини і різним профілем по глибині

Gas bearings with longitudinal grooves are successfully used in high-speed spindle units of drilling and grinding machines, processing equipment for processing crystals and precision instruments. But a small viscosity and compression of gas requires a detailed study of all factors that affect their work. The reliability of gas bearings depends on the compliance of the calculated values of the lifting force, the moment of reaction and the rigidity of the working gas layer from the external load, and the economy — on the gas flow. Engineers and scientists constantly search for structures and methods for calculating gas bearings with maximum power characteristics with minimal gas consumption. This is achieved using external chokes, a combination of external and internal throttling of the gas flow. The use of gas bearings with longitudinal grooves is determined by the manufacturability of their manufacture and high reliability in operation. But bearings of this type are significantly inferior in their characteristics to bearings with pressure regulators outside the carrier gas layer with a relative bearing length of l £ 3. To improve the characteristics of bearings with longitudinal grooves, it is necessary to reduce costs and harmful circular flow of gas in the working gap from the section of increased pressure to the lower side. This is achieved by using variable profile grooves with a maximum depth of grooves in the compressed gas supply zone for working of gas bearings. The proposed application of stepped longitudinal micro-grooves and micro-grooves, the depth of which varies according to the linear law with the maximum depth at the line of pressure of compressed gas into the working gaps of the conical bearing, leads to an increase in the efficiency of Eε (Kε*/Q* ratio) of the use of tapered bearings in spindle units, devices and etc. from 13,9 to 16,8 % for α = 2° and from 1,2 to 16,5 % for α = 6° and reduces the radial displacement of the axis of the shaft with the coaxial with the body of the position by 17…27 % compared with the bearings with the micro-grooves constant depth (with the same external load), which increases the reliability of the work of the spindle units. The profile of longitudinal micro-grooves has an insignificant effect on the angular and axial stiffness of the bevel bearing and greatly affects the radial stiffness.

Research on Vibration Characteristics of a Ceramic Spindle Based on the Reverse Magnetic Effect

The electromagnetic radial force about a ceramic spindle affects the spindle dynamic, which determines the quality of processing. Using a Timoshenko beam unit to build the dynamic model for the ceramic spindle, the dynamic characteristic of an angular contact ball bearing is analyzed using a nonlinear bearing model. The electromagnetic magnetization model was established based on Maxwell’s theory to calculate electromagnetic magnetic density and radial force. The influence about the reverse magnetic field characteristic of the ceramic rotating shaft and dynamic stiffness of the contact ball bearing on the dynamic phenomena of the spindle is analyzed, which is verified by experiments. The results show that the magnetic effect produced by the reverse magnetic of ceramic rotation shaft has a great influence on the electromagnetic radial force. Compared with the paramagnetic effect of the metal shaft, the dynamic characteristics of the spindle can be significantly improved. Considering the coupling relationship between the radial force of the magnetic field and the bearing contact force, dynamic stiffness, and other factors, the accuracy of the model simulation is highly consistent with the test results. In particular, the ceramic spindle model has been successful in predicting with high accuracy and is suitable for multiple extreme working conditions. The parameters, such as initial eccentricity of the rotor, bearing preload, and rotating speed, can be adjusted to restrain the vibration of spindle. The ceramic spindle model provides a theoretical basis for the dynamics development of a high‐speed spindle.