Spindle Torque Research Articles

Surface roughness assessment on hole drilled through the identification and clustering of relevant external and internal signal statistical features

Drilling is a continuous cutting process where two or more cutting edges remove the material, to obtain the desired feature. During the chip evacuation, it generally rubs against the generated surface. Thus, the roughness obtained differs from other machining processes such as turning or milling. Therefore, surface roughness can be different from the analytically expected one. In this research work, an analysis of the cutting conditions where a level of roughness is expected to meet specific requirements has been carried out. 600 holes were made with two different tool geometries on steel without modifying the cutting conditions. When analysing the surface generated, certain variability in the roughness profiles obtained can be observed. External signals to the machine tool were acquired with sensors (cutting forces, vibrations, and acoustic emissions) as well as internal signals (spindle power, spindle torque in the Z-axis, spindle current and positions, speeds, accelerations, and jerk of the tool tip in the three axes of the machine). The most representative statistical features of the signals regarding roughness were selected using correlation analysis. Besides that, the hierarchical clustering of statistical features of the external and internal signals of the process was compared with clusters obtained using roughness parameters. Results show that clusters appear using signals highly related to the roughness parameters obtained from the measured profiles, confirming a mapping between the acquired signals during the machining process and the roughness of the holes.

Development of an Automatic Elastic Torque Control System Based on a Two-Mass Electric Drive Coordinate Observer

Development of control system based on digital twins of physical processes is a promising area of research in the rolling industry. Closed-loop control systems are developed to control the coordinates of two-mass electromechanical systems in order to limit the dynamic loads on the equipment of main rolling lines. These control systems are based on observers (digital shadows) that indirectly detect (reconstruct) the roll speed and the elastic torque of the shaft (spindle) in real time. Notably, observers are required to work fast in order to reconstruct transients attributable to shock (impact) loads. Literature review shows that the known observers, which use complex algorithms to compute coordinates, do not respond fast enough. The paper analyzes the kinematic diagram of Mill 5000, a plate rolling mill. It presents oscillograms that prove that the elastic torque does oscillate as the rolls grip the strip dynamically. The authors hereof have developed an observer that reconstructs the coordinates of the uncontrolled mass (the shaft) and the spindle torque from the parameters of the controlled mass, namely the torque and speed of the motor. The paper further rationalizes an approach that consists of simulating the processes on a model to further directly configure them on the object. The authors analyze the transients of the reconstructed two-mass system coordinates, which are associated with the rolls gripping the strip. The paper compares data against oscillograms recorded on the mill itself. The accuracy is satisfactory. The proposed observer has been used to developed a three-loop automatic speed control system for the uncontrolled mass. Controller configurations are substantiated. The paper shows coordinates obtained by simulation modeling as functions of time. It further presents experiments run on Mill 5000; the conclusions are that the amplitude and oscillations of the elastic torque drop significantly. The paper concludes with recommendations on industrial adoption of the observer and the novel electric drive coordinate control system. Study presented herein substantiates and implements a concept of developing algorithms that solve specific problems and are readily implementable on the existing equipment without need for additional computing devices. The contribution of the paper consists of stating and solving the problem of developing and testing an automatic elastic torque control system for the shaft of a heavy-duty rolling mill. This system has been implemented in the form of algorithms that run in the software of the existing industrial controllers (PLCs). It is simple and performs well. It does not need additional sensors or computers to be implemented, nor does it rely on complex computational algorithms. Such algorithms are based on computational tables that require a priori data on numerous process parameters. In our literature review, we have not come across any industrial implementation of such algorithms on hot-rolling mills.

High efficiency orientated milling parameter optimization with tool wear monitoring in roughing operation

High efficiency milling is one of the main goals of CNC machining. Although roughing operation has low requirement for machining accuracy, the milling parameter selection usually need to consider the cutting force, milling stability, spindle torque and power. Besides, the tool wear in difficult-to-cut material machining is another very prominent problem. Therefore, how to achieve the high efficient milling parameters under the multi-constraint condition has been a severe challenge in the field of CNC machining. In this paper, a milling parameter optimization method for efficient rough machining is proposed by combining the off-line optimization and real-time monitoring. Firstly, a mathematical model of the optimization problem is established, which takes the machining efficiency as the objective, the spindle speed, radial and axial depth of cuts as the variables, and considers the multi-constraint, such as the basic parameter feasible region, cutting force, stability, spindle torque and power. Secondly, the quantitative relationship between the spindle three-phase current and milling force is established to realize the real-time estimation of cutting force coefficients. Furthermore, a numerical optimization method based on the random vector search is proposed, and the overall optimization procedure is given. Finally, a series of experimental verifications on the titanium alloy Ti5Al5Mo5VCrFe machining has been carried out, and the case study results show that the proposed parameter optimization method can greatly improve the machining efficiency, which proves the validity of the method.

Experimental Investigation of Suitable Cutting Conditions of Dry Drilling into High-Strength Structural Steel.

Dry machining is one of the main ways to reduce the environmental burden of the machining process and reduce the negative effect of the cutting fluid and aerosols on operators. In addition, dry machining can reduce overall machining costs and, in the case of large workpieces, reduce the extra work associated with removing residual cutting fluid from the workpiece and adjacent area. For high-strength structural steel products, it is typical to drill holes with larger diameters of around 20 mm. Therefore, this work is devoted to the investigation of the dry drilling process carried out on a workpiece made of S960QL steel with a helical drill with a diameter of 21 mm. The aim was to find suitable cutting conditions for dry drilling with regard to process stability and workpiece quality. An experiment performed with a coolant served as a comparison base. A dry drilling experiment was performed with cutting speeds from 30 to 70 m·min−1 and feeds from 0.1 to 0.3 mm·rev−1, and with the results of this experiment, the same experiment with flood cooling was performed. During the drilling process, spindle torque values were recorded using the indirect spindle current recording method. The macroscopic chip morphology was studied to understand the cutting process. The chip thickness ratio was measured, as well as the maximum diameter of spiral chips. On the final workpiece, the qualitative and dimensional parameters of the holes were evaluated, such as the diameter, cylindricity and surface roughness, depending on the change in the cutting conditions and cutting environment. Evaluation of the obtained data led to the following conclusions. When drilling the S960QL material, there is only a very small increase in the drilling torque during dry drilling compared to drilling with cutting fluid. The increase in friction demonstrated by the chip thickness coefficient is significant. The influence of the environment on the dimensional accuracy showed a tendency for a slight increase in the holes’ diameters during dry machining. In comparison, the cylindricity of the dry-drilled holes shows a lower deviation than the holes drilled with cutting fluid. The surface roughness of the holes after dry drilling is affected by the increased friction of the outgoing chips, despite the resulting parameters being very good due to the drilling technology standards. This work provides a comprehensive view of the dry drilling process under defined conditions, and the results represent suitable cutting conditions to achieve a stable cutting process and a suitable quality of drilled holes.

Регулирование координат электромеханической системы прокатного стана на основе наблюдателя упругого момента

The paper considers the electromechanical system of the reversing stand of the plate rolling mill 5000 of PJSC “Magnitogorsk Metallurgical Plant” (PJSC “MMK”). The performed experimental studies of transient processes in the mode of gripping metal by rolls allowed establishing unacceptable dynamic loads of an oscillatory nature and a loss of controllability of the electric drive. This confirms the need for the development of control methods that limit the motor and spindle torques. It is noted that the known control systems for the speed modes of an electric drive, which decrease the elastic moment due to the preliminary closing of the angular gaps, are, in essence, open-loop speed control systems. This does not provide for the controlled regulation of coordinates in dynamic modes. The paper proposes the development of a closed system for automatic control of coordinates of a two-mass electromechanical system with an observer of the moment of the elastic shaft and the speed of the second mass. An observer of the unmeasurable parameters of a two-mass rolling mill system has been developed. It provides an indirect determination (recovery) of the roll speed and the spindle torque in on-line mode. It is based on a system of equations in the state space. By comparing the reconstructed and experimentally obtained transient processes, the satisfactory accuracy of the results has been confirmed. Based on the proposed observer, the authors developed an automatic control system (ACS) of the roll speed with subordinate contours of the elastic shaft moment, speed and engine torque. The setting of closed-loop regulators has been substantiated. Transient processes of moments and velocities are considered at impact application of a load with increased speed of the second mass speed control loop. The analysis of the LAFC and LPFC confirmed the stability of the developed system in the frequency range. The analysis of experimental data substantiated a conclusion about the influence of the angular gap on the accuracy of the elastic moment recovery in the mode of metal capture by rolls. Prospects for the introduction of developments at mill 5000 and other rolling mills operating with shock load are noted.

Artificial Intelligence Applications for Friction Stir Welding: A Review

Advances in artificial intelligence (AI) techniques that can be used for different purposes have enabled it to be used in many different industrial applications. These are mainly used for modeling, identification, optimization, prediction and control of complex systems under the influence of more than one parameter in industrial applications. With the increasing accuracy of AI techniques, it has also obtained a wide application area on friction stir welding (FSW), one of the production methods developed in recent years. In this study, commonly used AI techniques for FSW, results, accuracy and superiority of AI techniques are reviewed and evaluated. In addition, an overview of AI techniques for FSW in different material combinations is provided. Considering the articles examined; It is seen that welding speed, rotational speed, the plunge depth, spindle torque, shoulder design, base material, pin design/profile, tool type are used as input parameters and tensile strength, yield strength, elongation, hardness, wear rate, welding quality, residual stress, fatigue strength are used as output parameters. As can be seen from the studies, it made important contributions in deciding what input parameters should be in order to have the output parameter at the desired value. The most common used materials for FSW are Al, Ti, Mg, Brass, Cu and so on. When FSW studies using artificial intelligence techniques were examined, it was seen that 81% of the most used materials were AL alloys and 23% of them were made with dissimilar materials. The most commonly utilized AI techniques were said to be artificial neural networks (ANN), fuzzy logic, machine learning, meta-heuristic methods and hybrid systems. As a result of the examination, ANN was the most widely used method among these methods. However, in recent years, with the exploration of new hybrid methods it was seen that hybrid systems used with ANN have higher accuracy.

Effect of traverse speed on microstructure and mechanical properties of friction-stir-welded third-generation Al–Li alloy

The aim of the study is to investigate the consequences of tool traverse speed on force and torque distribution of friction-stir-welded third-generation Al–Cu–Li alloy joints. The microstructure and corresponding mechanical properties of the joints are investigated on force and torque perspective. Thus, the contribution of the present work lies in establishing the relation between traverse speed and mechanical properties of the AA2050-T84 joint. Four welds have been considered at varying traverse speeds from 1 to 4 mm/s at constant tool rotational speed and tool tilt angle of 1400 rpm and 2°, respectively. A tool of H13 steel having a tapered screw-threaded pin profile was used. The investigation reveals that with the increase in traverse speed, longitudinal force (X-force), vertically downward force (Z-force) and spindle torque also increase. The grain size of the nugget zone reduces from 19.84 to 14.86 µm as traverse speed increases. It has been found that the mechanical strength of the joint increases as the traverse speed increases. The Vickers microhardness value increases from 115 HV0.1 to 131 HV0.1 in the nugget zone as traverse speed increases from 1 to 4 mm/s. The maximum tensile strength, % elongation and joint efficiency are 403.2 MPa, 7.2% and 75.5% for traverse speed of 4 mm/s. The tensile fracture samples are analyzed by scanning electron microscope and reveal ductile mode of fracture.

Finite element modelling of the filler wire feeding in the hybrid metal extrusion & bonding (HYB) process

HYB is a new solid-state joining method for metals and alloys that utilises continuous extrusion as a technique to enable aluminium filler metal additions. In the present paper a finite element (FE) model for the filler wire feeding inside the HYB PinPoint extruder has been developed and implemented within the commercial software package Deform 3D ™. Based on a comparison with experimental data for the extruder housing temperature, the drive spindle torque and the wire feed rate, it is concluded that the FE model is sufficiently relevant and comprehensive to be used in future developments of the HYB process. In addition to improved wire feeding control, a model-based approach will make it possible to reduce the engineering time and costs involved in case a modification of the design is needed to optimise the extruder performance in a real joining situation.

A method for evaluating dynamic viscosity of alloys during friction stir welding

The constitutive laws for dynamic viscosity, used today in CFD-models for the analysis of viscous flows during friction stir welding, aggregate data obtained from diverse standard mechanical trials (including, among others, hot compression, tension, torsion, etc.). However, the real stress–strain condition in the stir zone during FSW is that the metal dwells in the condition of overall, multiaxial deformation at high strain rates. Therefore, a method for determining the dynamic viscosity of alloys via spot-FSW trials has been proposed. The method is based on the measurements of the forge force and spindle torque of a pinless tool during the spot-FSW trials as well as the thickness of the stir zone. The results of the measurements are then processed by means of a computational procedure, which reproduces: the temperature field in the workpiece based on the torque and forge force data; strain rate in the stir zone based on its thickness; dynamic viscosity based on the strain rate and temperature. The method has allowed the calculation of a variety of discrete values of the dynamic viscosity for aluminum alloy AA5083 in dependence on the temperature and strain rate at various locations of the stir zone boundary. These discrete data have finally been approximated to receive a corresponding temperature-and-strain rate dependent polynomial.

Prediction of the surface quality of friction stir welds by the analysis of process data using Artificial Neural Networks

Friction stir welding is an advanced joining technology that is particularly suitable for aluminum alloys. Various studies have shown that welding quality depends significantly on the welding speed and the rotational speed of the tool. It is frequently possible to detect an unsuitable setting of these parameters by examining the resulting surface defects, such as increased flash formation or surface galling. In this work, Artificial Neural Networks were used to analyze process data in friction stir welding and predict the resulting quality of the weld surface. For this purpose, nine different variables were recorded during friction stir welding of EN AW-6082 T6 sheets: the forces and accelerations in three spatial directions, the spindle torque, and temperatures at the tool shoulder and tool probe. In Case 1, the welds were assigned to the classes good and defective on the basis of a human visual inspection of the weld surface. In Case 2, the welds were categorized into the two classes on the basis of a surface topography analysis. Subsequently, three different major Artificial Neural Network architectures were tested for their ability to predict the surface quality: Feed Forward Fully Connected Neural Networks, Recurrent Neural Networks and Convolutional Neural Networks. The highest classification accuracy was achieved when Convolutional Neural Networks were used. Thus, the evaluation of the force signal transverse to the welding direction yielded the highest accuracy of 99.1% for the prediction of the result of the human visual inspection. The result achieved for the prediction of the topography analysis was an accuracy of 87.4% when the spindle torque was evaluated. Using all nine different process variables to predict the topography analysis, the accuracy could be improved slightly to 88.0%. The sampling rate of the spindle torque was varied between 40 Hz and 9600 Hz and no significant influence was determined. The findings show that Convolutional Neural Networks are well suited for the interpretation of friction stir welding process data and can be used to predict the resulting surface quality. In future work, the results are to be used to develop a parameter optimization method for friction stir welding.

An experimental investigation to the influence of traverse speed on microstructure and mechanical properties of friction stir welded AA2050-T84 Al-Cu-Li alloy plates

5 mm thick AA2050-T84 plates were joined successfully with four different traverse speed (from 1 mm/s to 4 mm/s) by friction stir welding (FSW). Other process parameters were kept constant such as tool rotational speed (TRS) 600 rpm and tool tilt angle (TTA) 1.5° during FSW. A non-consumable, left-hand taper threaded tool made of H13 steel was used in the experiment. The present study revealed that with an increase in TTS, the average forces (X-force and Z-force) and spindle torque increases. The grain size of the nugget zone (NZ) decreases from 17.9 µm to 10.5 µm with increasing TTS. The mechanical properties improve with increasing TTS. The maximum tensile strength of 388.6 MPa, % elongation of 9.19%, and joint efficiency 70.2% was observed at higher TTS 4 mm/s.

Development of a Self-Heated Friction Stir Welding tool for welding of polypropylene sheets

The present investigation is focused on the development of a new FSW tool for polymer welding. The newly developed Self-Heated Friction Stir Welding (FSW) tool as well as a conventional FSW tool was employed to join 3-mm polypropylene sheets at different traverse speeds. The spindle torque and various forces exerted on the tool pin during welding were studied. The weldments obtained from both the tools were tested in order to analyse the weld morphology and tensile strength. SEM analysis of the stir zone revealed that the Self-Heated FSW tool had significant influence on the material flow and consequently resulted in defect-free welded joints. Also, the relationship between weld quality and tool axial and transverse forces on tool pin was established. The Self-Heated FSW tool was able to produce durable weld with superior mechanical property in terms of tensile strength compared to the conventional FSW tool.

An experimental investigation of the effect of tool rotational speed on the force, torque and mechanical behaviour of friction stir welded PVC sheets

In this investigation, an attempt has been made to join the polyvinyl chloride (PVC) sheet of 3mm thickness with a taper cylindrical pin tool. They are butt welded under different weld parameters by Friction Stir Welding. This study is focused on the effect of tool rotational speed on the force, torque and mechanical behaviour of friction stir welded polyvinyl chloride sheets. The welding parameters are the tool rotational speed; varied between 1500 and 1800 RPM and the traverse speed; varied between 0.3 and 0.7 (mm/sec) with a constant tilt angle of 1°. It is observed that the spindle torque is first increasing then decreasing with increasing tool rotational speed whereas in some cases the spindle torque is also found to decrease with increase in traverse speed. Z-force is found to reduce as the tool rotation speed increases. With a change in traverse speed inconsistent variation of Z-force is observed causing disturbed material flow and weld irregularities. Minimum micro-voids and blisters are observed in Scanning Electron Micrographs of the nugget zone of the specimen welded at 1600 RPM and 0.3 mm/sec traverse speed. The specimen with least micro-voids also exhibits highest ultimate tensile strength.

A method for determining the constant DC/AC motor power range and main technological spindle unit parameters

The article offers an original method for determining the constant DC/AC motor power range and basic technological parameters of the main spindle unit for multifunctional machine tools at the design stage. The method allows them to be determined, both in terms of the strength characteristics of the gearbox (or the strength characteristics of the system “machine-equipment-tool-work piece”) and in order to obtain the maximum spindle torque needed to ensure maximum machine productivity. The graphical interpretation of the method can be used both for designing new and for operating existing machines.

Thermal Characteristics of Spindle Supported with Water-Lubricated Hydrostatic Bearings

Characteristics of a spindle supported with water-lubricated hydrostatic bearings were experimentally investigated. In particular, this paper focuses on the thermal characteristics of the spindle. The flowrates of water as the lubricating fluid were measured separately for the radial and thrust bearings, in relation to the supply pressure. Fluid power losses owing to pressure losses of the lubricating fluid were then introduced. Furthermore, the power losses owing to the water viscosity were determined by measuring the spindle torque and angular velocity. The experiments revealed that the total power loss of the spindle is approximately 300 W. The cooling effect of the lubricating water was then examined by introducing a temperature increase between the supply and drain water. The experimental results verified that the water temperature increased by approximately 0.8°C, at a spindle speed of 3000 min-1. Based on the temperature increase of the water, the power removed from the spindle by the water flow was estimated. By comparing the generated total power loss and the power transferred by the water flow, the cooling efficiency of the flow of lubricating-water was defined in this paper. If the cooling efficiency is 100%, the temperature change of the spindle can be zero regardless of the power loss, achieving ideal thermal stability of the spindle. Experimental results revealed that the cooling efficiency of the tested spindle was over 80%. This indicates that the flow of water as a lubricating fluid removes generated heat from the spindle effectively, and achieves improved thermal stability of the spindle.

Numerical Simulation of Material Flow and Analysis of Welding Characteristics in Friction Stir Welding Process

Friction stir welding (FSW) material flow has an important influence on weld formation. The finite element model of the FSW process was established. The axial force and the spindle torque of the welding process were collected through experiments. The feasibility of the finite element model was verified by a data comparison. The temperature field of the welding process was analyzed hierarchically. It was found that the temperature on the advancing side is about 20 °C higher than that on the retreating side near the welding seam, but that the temperature difference between the two sides of the middle and lower layers was decreased. The particle tracking technique was used to study the material flow law in different areas of the weld seam. The results showed that part of the material inside the tool pin was squeezed to the bottom of the workpiece. The material on the upper surface tends to move downward under the influence of the shoulder extrusion, while the material on the lower part moves spirally upward under the influence of the tool pin. The material flow amount of the advancing side is higher than that of the retreating side. The law of material flow reveals the possible causes of the welding defects. It was found that the abnormal flow of materials at a low rotation speed and high welding speed is prone to holes and crack defects. The forming reasons and material flow differences in different regions are studied through the microstructure of the joint cross section. The feasibility of a finite element modeling and simulation analysis is further verified.

Thermo-mechanical interaction between aluminum alloy and tools with different profiles during friction stir welding

Abstract The influence of the tool profiles on the thermo-mechanical interaction between AA6061-T6 workpiece and tool during friction stir welding was investigated. A customized experimental setup was employed to measure the feature points temperature and tool spindle torque in the process of FSW. Microstructure and tensile properties of stir zone (SZ) were characterized. Results indicate that the shoulder and pin geometries were responsible for the heat generation, tool torque variation at the plunging stage as well as the cross section contour of SZ, respectively. Finer grains in SZ resulted from flutes on shoulder and grooves on pin. Flat faces on the pin resulted in inhomogeneous grain size. Weld with higher 0.2% yield strength of 173 MPa was obtained by using the cylindrical pin tool while higher elongation weld of 32.0% was produced with triflat threaded pin tool.

High-efficiency gear hobbing technics based on fuzzy adaptive control of spindle torque

In this paper, the problem of relatively low efficiency of the current gear hobbing process is addressed through fuzzy adaptive control of the cutting force. The paper studies the influencing factors of the cutting torque of gear hobbing, and the relationship between the feed rate and the cutting torque is established. Based on the relationship and the fuzzy adaptive control method, a high efficiency gear hobbing method is designed. A methodology using the static spindle torque rather than the dynamic one as the feedback signal of the fuzzy controller is also presented, which can deal with the severe cutting torque fluctuations during gear hobbing. The input and the output scaling factors of the fuzzy controller can also be tuned online to adapt to different types of gears or various cutting conditions. The key issue of determining the reference value of the spindle torque is also resolved through analysis of the spindle torque data in a trial cut. The proposed method is simulated and implemented on a numerical control gear hobbing machine, which cuts spur gears and helical gears. The simulation and experimental results are in a good consistency. The efficiency is improved considerably, which saves as high as 40% and 30% cutting time of the gear hobbing process in the first and second set of experiments, respectively.

Investigation on effect of pin shapes on temperature, material flow and forces during friction stir welding: A simulation study

Tool pin geometry plays an important role in the weld strength of friction stir welding process. In the current work, a thermo-mechanical model is developed to study the effect of three different pin shapes, namely, cylindrical, square and triflat, during friction stir welding process. The developed model is validated with the temperature, force and spindle torque at different welding conditions. Among the three geometries, triflat pin produced higher temperature, and strain rate. Material deposition for the square pin is stretched toward the advancing side while it is uniformly distributed for the triflat pin. Material rotates multiple times with the flat surfaced pin as compared with cylindrical pin.

Shear Assisted Processing and Extrusion (ShAPE™) of AZ91E Flake: A Study of Tooling Features and Processing Effects

Charges of melt-spun AZ91E flake were indirectly extruded into tubes using Shear Assisted Processing and Extrusion (ShAPE™). The effect of instrument parameters and tool features on densification and microstructural evolution was studied. At a constant extrusion ratio, the tool rotational velocity varied from 75 to 300 rpm and was demonstrated to reduce the forge force by a factor of four. Modification of the extrusion die face with successively more aggressive scrolled features was found to enhance material flow into the extrusion orifice which led to a 30% reduction in spindle torque. Microstructure, texture and hardness are reported for the range of rpm and scroll geometries investigated. It was observed that the ShAPE™ process is able to retain the average grain size of the as-spun flake (2.5-4 μm) while simultaneously imparting strong textural alignment in the resultant tube.