Spindle Motor Research Articles

Theoretical prediction and experimental verification of the unbalanced magnetic force in air bearing motor spindles

Dynamic vibrations of air bearing motor spindles have significant influence on the surface quality in ultra-precision machining. In this article, the influence of the vibration caused by the unbalanced magnetic force on the diamond turning is investigated on the basis of the theoretical and experimental method. A permanent magnet motor model (10 poles and 12 slots) is built and then simulated to gain a periodic unbalanced magnetic force. The effects of unbalanced magnetic force on the inclination of the spindle shaft is analyzed, which would affect the surface quality of the workpiece, and the surface topography of the workpiece is predicted during an unbalanced magnetic force acting on air bearing motor spindle. The theoretical analysis and experimental turning results validate that the angle between the direction of unbalanced magnetic force and the feed direction has a certain relationship with the profile of the machined surface. Also, under different turning speeds and directions, the surface topography of the machined workpiece shows a 10-cycle-per-revolution pattern, which has good agreement with the simulations of periodic unbalanced magnetic force. This research work provides a theoretical foundation for the fault diagnosis of air bearing motor spindle caused by motor rotor eccentricity and its effect on surface generation in turning.

Near-field vibro-acoustic transfer function prediction of small close fit enclosure with multiple rotating components

The 2.5-inch Hard Disk Drive (HDD) has been used widely in many consumer electronic devices including laptop computers. It consists of multiple rotating components such as a spindle motor, a voice coil motor, and other mechanical components, that are enclosed in an extra small close fit enclosure. The conventional approach of using frequency analysis is unable to identify the sound source at the near-field of the small HDD enclosure. A vibroacoustic transfer function (VATF) for HDD near-field for random read/write operation was proposed. The VAFT was developed using finite element method (FEM) and compared with the experimental results at specific frequencies. Good agreement in the results was found between the numerical and experimental data. The method will enable optimization for acoustic at the design stage or an existing device.

Predictive Maintenance of Machine Tool Systems Using Artificial Intelligence Techniques Applied to Machine Condition Data

Often, manufacturing equipment is utilized without a planned maintenance approach. Such a strategy frequently results in unplanned downtime, owing to unexpected failures. Scheduled maintenance replaces components frequently to avoid unexpected equipment stoppages, but increases the time associated with machine non-operation and maintenance cost. The emergence of Industry 4.0 and smart systems is leading to increasing attention to predictive maintenance (PdM) strategies that can decrease the cost of downtime and increase the availability (utilization rate) of manufacturing equipment. PdM also has the potential to foster sustainable practices in manufacturing by maximizing the useful lives of components. In this paper, the AI-based algorithms for predictive maintenance are presented, and are applied to monitor two critical machine tool system elements: the cutting tool and the spindle motor. A data-driven modeling approach will be described, and it will be utilized to investigate the tool wear and the bearing failures.

A Digital Twin for Grinding Wheel: An Information Sharing Platform for Sustainable Grinding Process

Emerging re-industrialization demands the fusion of the physical and the digital world for the development of sustainable manufacturing processes. Sustainability in manufacturing aims at improving the resource productivity by identifying the environmental challenges as opportunities. In the present era of the fourth industrial revolution or digital manufacturing, manufacturers strive to gain value through every bit of data collection throughout the product lifecycle. Integration of the collected information as knowledge to improve the productivity and efficiency of the system is required to realize its benefits. In the present work, a digital twin for grinding wheel as a product integrated and web-based knowledge sharing platform is developed. It integrates the data collected in each phase of the grinding wheel from the manufacturing to the conditioning phase. The developed digital twin is implemented on the surface grinding machine. The methods for the abstraction of the production information from the manufacturer and the process information while grinding are presented. The development of a predictive model for redress life identification and computation of dressing interim period using spindle motor current data is developed and integrated. The quantifiable benefits from the digital twin for productivity and efficiency are discussed through a case study. The case study scenario evident that the implementation of the digital twin for grinding wheels increases energy and resource efficiency by 14.4%. This clearly depicts the usefulness of the digital twin for energy and resource efficiency toward the sustainable grinding process.

Highly Dynamic Spindle Integrated Magnet Actuators for Chatter Reduction

This paper presents a novel approach for active chatter reduction using a motor spindle with integrated magnet actuators. Based on the results of previous studies the design of an active damped prototype is described. The system performance as well as the benefits and drawbacks of this solution are discussed. In order to eliminate the known drawbacks a novel actuator design is introduced. The novel approach integrates the actuator windings into the stator core. Next, strategies for electric and magnetic decoupling of the actuator and motor windings are presented. Subsequently the actuator design is discussed. The force generation and distribution of the damping actuator are calculated via analytical and finite elements analysis (FEA). With the novel approach the mechanical integration of the active damping actuators is simplified significantly. Additionally, the maximal attainable spindle power is increased up to 150% in relation to the previous solution.

Cell Division: Here Comes the Kinesin Cavalry

A new study finds that a spindle motor makes an unexpected contribution to kinetochore-microtubule attachments and chromosome segregation.

Stochastic Modeling and Analysis of Spindle Power During Hard Milling With a Focus on Tool Wear

The rapid development of modern science and technology brings with it a high demand for manufacturing quality. The surface integrity of a machined part is a critical factor which needs to be considered in the selection of the appropriate machining processes. Surface integrity is also tightly linked with tool wear. Tool wear is one of the most significant and necessary parameters to be considered for machining sustainability. By monitoring and predicting tool wear, it is possible to improve sustainability by reducing the scrap rate due to poor surface integrity. In this work, data-dependent systems (DDS), a stochastic modeling and analysis technique, was applied to study the power of spindle motor during a hard milling operation. The objective was to correlate the spindle power to tool wear conditions using DDS analysis. The spindle power was monitored, and the time series trends were decomposed to study the frequency variation with different severities of tool wear conditions and processing parameters. Analysis of variance (ANOVA) was also used to determine factors significant to the power by a spindle motor. Experiments indicate that low-level frequency of spindle power is correlated with the amount of tool wear, cutting speed, and feed per tooth. The results suggest that effective tool wear monitoring may be achieved by focusing on low-level frequencies highlighted by DDS methodology.

Mechanical Heterogeneity and Roles of Parallel Microtubule Arrays in Governing Meiotic Spindle Length

Metaphase spindles are arrays of microtubules whose architecture provides the mechanism for regulated force generation required for proper segregation of chromosomes during cell division. Whereas long-standing models are based on continuous antiparallel microtubule arrays connecting two spindle poles and overlapping at the equator, spindles typically possess a more complex architecture with randomly arranged short filaments. How these heterogeneous multifilament arrays generate and respond to forces has been mysterious, as it has not been possible to directly measure and perturb spindle force while observing relevant filament motility. Here, we combined microneedle-based quantitative micromanipulation with high-resolution microtubule tracking of Xenopus egg extract spindles to simultaneously examine the force and individual filament motility in situ. We found that the microtubule arrays at the middle of the spindle half are considerably weak and fluid-like, being more adaptable to perturbing forces as compared to those near the pole and the equator. We also found that a force altering spindle length induces filament translocation nearer the spindle pole, where parallel microtubules predominate, while maintaining equatorial antiparallel filaments. Molecular perturbations suggested that the distinct mechanical heterogeneity of the spindle emerges from activities of kinesin-5 and dynein, two key spindle motor proteins. Together, our data establish a link between spindle architecture and mechanics, and highlight the importance of parallel microtubule arrays in maintaining its structural and functional stability.

Calculation and analysis of critical speed of high speed motor spindle rotor system

The traditional transfer matrix method used to calculate the critical speed of high-speed spindle motor rotor system will produce large errors. Taking the 170SD30 electrospindle as the analysis object, a high-speed electric spindle dynamics theoretical model was established based on the Riccati method, using Matlab to program and calculate the kinetic parameters of the first three critical speeds and natural frequencies of the high-speed spindle. Finally, the simulation data was compared with experimental data. The results show that the Riccati transfer matrix method is 2.3% more accurate than the traditional transfer matrix method, and it verifies the accuracy and feasibility of the Riccati transfer matrix method, and is of great significance to effectively guide the analysis and design of high-performance and high-speed motor spindle.

Origami Microfluidic CD

Employing the centrifugal force for liquid displacement in bioanalytical compact discs (CDs) is becoming more popular for academic and industry applications. Pseudo forces that are controlled by a low-cost spindle motor enables the simultaneous manipulation of several liquids on the microfluidic CD. For this reason, centrifugal microfluidic platforms are considered more robust for extreme point of care (ePOC) applications when compared to stationary microfluidic systems that work with mechanical liquids pumps (e.g., syringe pump). However, the fabrication of microfluidic CDs requires expensive and bulky equipment (e.g., router or laser CNC) that cannot be implemented at ePOC and point of need (PON). To cope with this limitation, we have introduced a rapid microfluidic CD fabrication technique using only a low-cost cutter plotter [1]. The CDs were made through assembly of thin PVC and double-sided pressure sensitive adhesive (PSA) layers that were cut by the plotter machine. However, the technique yet required careful assembly of several disc layers, and the double-sided PSA is an expensive material and not widely available. In this article, we introduce a new origami CD fabrication process using only one type of material, a cutter plotter and a laminating machine. The origami CDs fabrication process prevents the need for PSA film and the tedious/sensitive CD assembly procedure. Therefore, the origami CDs facilitates onsite development of automated diagnosis test at ePOC and PON with minimum and widely available material and equipment. In addition to the origami CD fabrication process, this study includes the characterization of different microchannels made by the cutter plotter blade. Finally, as an application of the CD fabrication technique we developed an origami CD for automated serial dilution that is required for a wide range of bioanalytical applications such as microbial counting and multiplexed assay. [1] M.M. Aeinehvand, P. Magaña, M.S. Aeinehvand, O. Aguilar, M.J. Madou, S.O. Martinez-Chapa, Ultra-rapid and low-cost fabrication of centrifugal microfluidic platforms with active mechanical valves, RSC Adv. 7 (2017) 55400–55407. doi:10.1039/C7RA11532F.

Carbon Iso-Dielectric Separation (CIDS) on Centrifugal Microfluidic Platforms

Centrifugal microfluidic platforms employ pseudo forces controlled by a spindle motor to automate bioanalytical assays on a single fluidic disc with no need for several syringe pumps [1]. Recently, we employed a portable cutter-plotter to fabricate microfluidic discs with active valves at point of need [2]. To address a healthcare issue of global interest, we developed a microfluidic disc to automate a sTREM-1 immunoassay for the detection of sepsis at late stages of the disease. To enable sepsis detection and monitoring at early stages, recently a gold iso-dielectric separation (GIDS) chip is develop that separates activated and non-activated leukocytes from blood serum [3]. However, the GIDS chip requires several syringe pumps and an off-chip manual step for sample preparation i.e., blood serum separation. As an alternative to GIDS, in this study we have developed 3D carbon IDS (CIDS) chips to reduce the cost of device fabrication. To prevent the need for the syringe pumps and external piping networks, we have integrated the CIDS on a microfluidic disc to automate the whole bioanalytical process from sample preparation to characterization of thousands of particles and cells. The main objective of developing the integrated microfluidic platform is the separation of activated and non-activated leukocytes for automated early sepsis detection at point of care (POC). However, as an early proof of the practicality of CIDS-on-disc, in this study we employed the hybrid centrifugal microfluidic system for separating various sizes of polystyrene microbeads as well as different bacteria. [1] M.M. Aeinehvand, F. Ibrahim, S.W. Harun, A. Kazemzadeh, H.A. Rothan, R. Yusof, M. Madou, Reversible thermo-pneumatic valves on centrifugal microfluidic platforms, Lab Chip. 15 (2015) 3358–3369. doi:10.1039/C5LC00634A. [2] M.M. Aeinehvand, P. Magaña, M.S. Aeinehvand, O. Aguilar, M.J. Madou, S.O. Martinez-Chapa, Ultra-rapid and low-cost fabrication of centrifugal microfluidic platforms with active mechanical valves, RSC Adv. 7 (2017) 55400–55407. doi:10.1039/C7RA11532F. [3] J.L. Prieto, H.-W. Su, H.W. Hou, M.P. Vera, B.D. Levy, R.M. Baron, J. Han, J. Voldman, Monitoring sepsis using electrical cell profiling, Lab Chip. 16 (2016) 4333–4340. doi:10.1039/C6LC00940A.

Developing a new energy performance indicator for the spindle system based on power flow analysis

The evaluation of the energy performance of spindle systems with a proper metric is extremely important for energy-efficient machine tools. However, there is a lack of appropriate index to achieve this evaluation. To close this gap, the additional power requirement, which is defined as the discrepancy between the material removal power and the power gap of the spindle system from air-cutting state to cutting state, was proposed as a new indicator based on a detailed power flow analysis. The additional power requirement universally exists in machining and results from the efficiency and power losses of the system, which makes it a good energy performance indicator candidate. A theoretical model for the additional power requirement of spindle systems was built and verified in a lathe machine, through which two causes of additional power requirement were pointed: less than 100% efficiency throughout the system and efficiency change of the spindle motor under a dynamic load and a variable speed. The first cause has a positive effect on the additional power requirement, whereas the second one generally plays a negative role. Furthermore, the additional power requirement can be negative because of the negative effect, which is different from previous studies. The close relation between the additional power requirement and the energy performance of the spindle is demonstrated by an in-depth analysis. This work is an important building block for energy-efficient machine tools.

Vibration transmission mechanical model between the shaft and housing of a high speed motor spindle

Vibration transmission mechanical model between the shaft and housing of a high speed motor spindle

Sensor Selection Method to Accurately Model the Thermal Error in a Spindle Motor

Thermal error in machine tools arises from error in positioning the tool due to thermal distortion of the machine structure. Thermal error can be effectively reduced by implementing a compensation algorithm into the machine control loop. The compensation algorithm is derived from a disturbance model or mathematical representation of the thermal error. In this paper, thermal error in a spindle motor assembly is predicted from temperature measurement through the disturbance model. Model reduction technique is applied to eliminate the temperature sensor, which has least effect on the model output (thermal error). Applying the sensor selection method resulted in a reduced number of temperature sensors (10 to 4) required to achieve the same model prediction accuracy. In the final experiment, the spindle motor is subjected to a 5-h cyclical heat load and the maximum prediction accuracy achieved using the reduced set sensors is 1.5 $\mu$ m (time averaged accuracy of 0.77 $\mu$ m).

Spectroanalytical method for evaluating the technological elements composition of magnets from computer hard disks

In this study, inductively coupled plasma optical emission spectrometry (ICP OES) was used for the development of an analytical procedure for elemental analysis of hard disks (HDs). More than 50 samples were acquired and separated according to the manufacturers. Both magnets were used, namely, the actuator (a) and the spindle (s) motor. The samples were heated to remove magnetism, ground in a knife mill and sieved. Different digestion procedures were performed with a block digester and microwave, and three acid concentrations were employed. Due to the lack of certified materials or references from HDs, tests of standard addition and recovery were performed to verify the accuracy of the proposed method. Hyperspectral image and principal component analysis were also used to assist in the data treatment related to the Ni layer. For both magnets, the best analytical procedure was 100 mg of sample, 7 mol L−1 nitric acid and a digester block. The elements observed in the highest concentrations were Fe followed by Nd and Pr. This procedure was simpler than others were and prioritized the principles of green chemistry.

Investigation of Mechanical and Metallurgical Properties of Friction Stir Corner Welded Dissimilar Thickness AA5086-AA6061 Aluminium Alloys

In this investigation, an attempt has been made to fabricate dissimilar thickness corner joint using non-heat treatable (AA5086) and heat treatable (AA6061) dissimilar aluminium alloys by friction stir welding process with plate thicknesses of 6mm and 4mm. Three parameters and three levels were considered to conduct the experiments such as welding and rotational speeds of 100, 150 and 190 mm/min and 900, 1000 and 1100 rpm and plunge depth of 0.1, 0.2 and 0.3 mm. The mechanical properties were evaluated using hardness and tensile tests. Taguchi grey relational analysis was carried out to determine the optimum process parameters. The higher value of tensile strength was obtained 192 MPa at rotational and welding speeds of 1000 rpm and 150 mm/min which was 76.80% of parent material and maximum hardness was 157 HV at thermomechanically affected zone for the rotational speed of 1100 rpm and hardness at stir zone was maximum because of refined grain formation. The microstructures of various regions were observed and analyzed by optical and scanning electron microscopes. The tensile samples fractured at the heat affected zone. The spindle motor current consumption, work material temperature distribution, and force generation during friction stir welding were estimated and analyzed.

A theoretical and experimental study of spindle imbalance induced forced vibration and its effect on surface generation in diamond turning

Abstract In diamond turning, spindle error motions exhibit dynamic characteristics under spindle imbalance, which significantly deteriorate form accuracy and surface roughness. However, in the spindle error motion community dynamic characteristics of spindle imbalance induced forced vibration have not attracted much attention, involving unbalanced magnetic forces induced forced spindle vibration, unbalanced air bearing pressure induced forced spindle vibration, and spindle whirling and spindle tilting under bearing hydrodynamics along with inertial effect. In this study, a theoretical and experimental investigation has been conducted to discuss dynamic characteristics of spindle imbalance induced forced vibration and its effect on surface generation in diamond turning. Firstly, an analysis model of magnetic forces for a spindle motor was built up to study dynamic characteristics of unbalanced magnetic forces induced forced spindle vibration. Secondly, a mathematical model of Reynolds equations for air bearings was established with a five-DOF dynamic model for spindle motion to discuss dynamic characteristics of unbalanced air bearing pressure induced forced spindle vibration, spindle whirling and spindle tilting. Finally, it has been verified by two kinds of designed face-turning tests for comparison carried out in diamond turning. The theoretical and experimental results revealed that bearing hydrodynamics coupled with inertial effect would jointly induce synchronous quasi-elliptical spindle whirling/tilting, accordingly producing a quasi-elliptical concave/convex surface in diamond turning, whose cyclic frequency is 2 rev.−1. Under spindle imbalance, unbalanced magnetic forces induced forced spindle vibration with the fundamental cyclic frequency of 2p rev.−1 (the spindle motor pole number) would occur as well as unbalanced air bearing pressure induced forced spindle vibration with the cyclic frequency of α rev.−1 (the air bearing orifice number) further to produce the corresponding straight radial patterns at the machined surface. This research work gives a deep insight into dynamic characteristics of spindle imbalance induced forced vibration and its effect on surface generation in diamond turning.

High-power density switched reluctance machine development for high-speed spindle applications

In this study, a high-speed switched reluctance machine (HS-SRM) with cobalt-iron lamination material is proposed for spindle motors, which are used in computer numerical control machines. Wide torque-speed range, high power density, high efficiency, and low cost are the crucial issues in spindle applications. Three types of electric machine candidates, the permanent magnet synchronous machine (PMSM), induction machine (IM), and switched reluctance machine (SRM), are compared with their outstanding features. The SRM spindle motor will offer a more robust, reliable, compact, and cost-effective solution compared to the IM or PMSM spindle applications. Moreover, advancement on cobalt-iron laminations gives a chance to the SRM for competing with the PMSM and IM in terms of power density and efficiency. In this study, a high-speed SRM is designed, optimized, and analyzed. Its performance metrics are obtained based on torque-speed range and efficiency over a wide speed range. The proposed SRM is compared with existing industrial products in terms of power densities. Then the design is verified via experimental study. The results show that the HS-SRM with cobalt-iron lamination material offers ultimate power density and efficiency in wide operating conditions.

Energy modeling and a method for reducing energy loss due to cutting load during machining operations

In a typical part manufacturing system, machining operations represent a major proportion of the total energy consumption. The energy consumption (in the form of electricity power) of a machining operation can be divided into four types, that is, standby power, operational power, cutting power and power loss due to cutting load. Power loss due to cutting load includes the power loss caused by the friction of mechanical transmission and the power lost in the motor when the cutting load is applied to the spindle system. While the first three types of power consumption have been studied intensively by previous researchers, the power loss due to cutting load, which accounts for up to 20% of the cutting power consumption during machining operations, has received relatively less attention. This article proposes a novel model to characterize power loss due to cutting load, in which the power lost in the mechanical transmission and in the spindle motor are analyzed and modeled separately. Cutting tests have been carried out to validate the proposed model using two numerical control lathe machines. And a method has been developed for reducing energy loss caused by cutting load, which includes cutting force prediction, power loss due to cutting load prediction and decision making. The method was evaluated through its application in the process design for a shaft part, and the results show a significant saving of up to 70.8% of energy loss caused by cutting load.

Modeling and optimization of thermal characteristics for roll grinders

The thermal deformation has a significant effect on the processing precision of the machine tool. In this paper, a simulation model and an experimental method of the thermal performance were proposed for a roll grinder. The calculation methods of thermal boundary conditions including the heat power caused by the spindle motor with water cooling, headstock motor with air cooling and hydrodynamic bearings, the convective heat transfer coefficients of the rotating surface at different spindle speeds, and machine tool contact resistance were provided to establish a high-precision FEM model. Based on the achieved key temperature points in the simulation, thermal characteristic experiments were carried out at different spindle speeds with 18 temperature sensors and three displacement sensors. The experimental results of the temperature field and thermal displacement were then compared with the simulation results to verify the effectiveness of the constructed finite element model. Finally, three kinds of optimization schemes of the roll grinder structure were discussed to further improve the thermal performance. The simulation results indicated that the thermal deformation of the spindle decreased in the X- and Y-axis directions.