Study on Positioning Accuracy of Aerostatic Lead Screw

Tribology ◽  
2006 ◽  
Author(s):  
Tadaatsu Satomi ◽  
Peng Zhao ◽  
Daisuke Kobayashi
Keyword(s):  
Load Capacity ◽  
Vital Role ◽  
Ball Screw ◽  
Machining Accuracy ◽  
Contact Type ◽  
Lead Screw ◽  
Guidance Theory ◽  
Static Rigidity ◽  
Semiconductor Fabrication ◽  
Air Film

The aerostatic lead screw is a non-contact type lead screw in which the contact surface of a male screw and a female screw is supported by a pressurized air film. It is characterized by the features that: (1) there is no degradation in accuracy due to friction wear; (2) no environmental pollution is caused by a leak and scattering of lubrication fluid; and (3) maintenance is easy and simple. However, drawbacks are that vibration is liable to occur and therefore the static rigidity is low. The aerostatic lead screw is useful for semiconductor fabrication and also effective in positioning a table on which a sample is placed in a biomicroscope. This study relates to a drunkenness analysis of the aerostatic lead screw. The drunkenness of a contact-type lead screw represented by the ball screw is generally transferred directly from the male screw to the female screw. In the aerostatic lead screw, the drunkenness based on machining accuracy error of each screw flank is not directly transferred onto the female screw and is instead averaged out by balancing of load capacities among each screw flank, so that the enhanced accuracy in positioning lead screws is expected. In this paper, a balance of the load capacity of each screw flank was computed using the aerostatic guidance theory, so as to carry out a drunkenness analysis. It is found that the balancing effect plays the vital role in improvement on drunkenness of an aerostatic lead screw used in this study.

Nanoparticles-Laden Gas Film in Aerostatic Thrust Bearing

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Zhiru Yang ◽  
Dongfeng Diao ◽  
Xue Fan ◽  
Hongyan Fan
Keyword(s):  
Effective Viscosity ◽  
Flow Model ◽  
Thrust Bearing ◽  
Volume Fraction ◽  
Load Capacity ◽  
Sio2 Nanoparticles ◽  
Enhancement Effect ◽  
The Novel ◽  
Two Phase ◽  
Air Film

Nanoparticles-laden gas film (NLGF) was formed by adding SiO2 nanoparticles with volume fraction in the range of 0.014–0.330% and size of 30 nm into the air gas film in a thrust bearing. An effective viscosity of the gas-solid two phase lubrication media was introduced. The pressure distribution in NLGF and the load capacity of the thrust bearing were calculated by using the gas-solid two phase flow model with the effective viscosity under the film thicknesses range of 15–60 μm condition. The results showed that the NLGF can increase the load capacity when the film thickness is larger than 30 μm. The mechanism of the enhancement effect of load capacity was attributed to the increase of the effective viscosity of the NLGF from the pure air film, and the novel lubrication media of the NLGF can be expected for the bearing industry application.

Virtual Evaluation for Machine Tool Design

2008 ◽  
Author(s):  
Masahiko Mori ◽  
Zachary I. Piner ◽  
Ke Ding ◽  
Adam Hansel
Keyword(s):  
Machine Tool ◽  
Fluid Dynamic ◽  
Dynamic Performance ◽  
Digital Simulation ◽  
Machining Accuracy ◽  
Analysis Model ◽  
Simulation Accuracy ◽  
Theoretical Simulation ◽  
Physical Experiments ◽  
Static Rigidity

This paper presents the virtual machine tool environment Mori Seiki established for the evaluation of static, dynamic, and thermal performance of Mori Seiki machine tools. In this system environment, machining accuracy and quality are the main focus for each individual analysis discipline. The structural analysis uses the Finite Element Method (FEM) to monitor and optimize the static rigidity of the machine tool. Correlation between physical experiments and digital simulation is conducted to validate and optimize the static simulation accuracy. To accurately evaluate and effectively optimize dynamic performance of the machine tool in the virtual environment, the critical modal parameters such as damping and stiffness are calibrated based on experimental procedures which results in precise setup of the frequency response models. Computational Fluid Dynamic (CFD) analysis model is built in the environment so that the thermal perspective of the machine tool is evaluated and thermal deformation is monitored. This paper demonstrates compatibility of the digital simulation with physical experiments and success in integrating theoretical simulation processes with practical Mori Seiki machine tool development.

scholarly journals Developing a Novel Miniature 3D-Printed TLBS with High Mechanical Efficiency and Better Controllability

Micromachines ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 662
Author(s):  
Chung-Wei Lee ◽  
Jung-Hua Chou
Keyword(s):  
Mechanical Efficiency ◽  
Ball Screw ◽  
Maximum Efficiency ◽  
Design Parameters ◽  
Affecting Factors ◽  
Lead Screw ◽  
Torque Loss ◽  
3D Printed ◽  
Novel Model ◽  
Better Than

This paper focuses on the development of a 3D-printed threadless ball screw (TLBS) for the applications that require miniaturization, customization, and accuracy controllability. To enhance the efficiency of the TLBS, a novel model of the TLBS for analyzing the mechanical efficiency is presented to obtain the key affecting factors. From these factors, the design parameters for fabrication are determined. For miniaturization, a novel 3D-printed one-piece preloaded structure of light weight of 0.9 g is implemented as the TLBS nut part. Experimental results show that the measured mechanical efficiency of TLBS is close to that predicted by the theoretical model with a normalized root mean square error of 3.16%. In addition, the mechanical efficiency of the present TLBS (maximum efficiency close to 90%) is better than that of the lead screw and close to the ball screw. The unique characteristic of the present TLBS is that its total torque loss is a weak function of the load, a phenomenon not observed in either the ball screw or the lead screw. This characteristic is advantageous in enhancing the controllability of accuracy at different loads.

Design of a Compact, Lightweight, Electromechanical Linear Series Elastic Actuator

2014 ◽  
Author(s):  
Coleman Knabe ◽  
Bryce Lee ◽  
Viktor Orekhov ◽  
Dennis Hong
Keyword(s):  
Elastic Element ◽  
Load Capacity ◽  
Ball Screw ◽  
Leaf Spring ◽  
Load Range ◽  
Compression Load ◽  
Design Changes ◽  
Series Elastic Actuators ◽  
Future Work ◽  
Series Elastic

Series Elastic Actuators (SEAs) have several benefits for force controlled robotic applications. Typical SEAs place an elastic element between the motor and the load, increasing shock tolerance, allowing for more accurate and stable force control, and creating the potential for energy storage. This paper presents the design of a compact, lightweight, low-friction, electromechanical linear SEA used in the lower body of the Tactical Hazardous Operations Robot (THOR). The THOR SEA is an evolutionary improvement upon the SAFFiR SEA [1]. Design changes focused on reducing the size and fixed length of the actuator while increasing its load capacity. This SEA pairs a ball screw-driven linear actuator with a configurable elastic member. The elastic element is a titanium leaf spring with a removable pivot, setting the compliance to either 650 or 372 [kN/m]. The compliant beam is positioned parallel to the actuator, reducing overall packaging size by relocating the space required for spring deflection. Unlike typical SEAs which measure force through spring deflection, the force applied to the titanium beam is measured through a tension/compression load cell located in line with each actuator, resulting in a measurable load range of +/−2225 [N] at a tolerance of +/−1 [N]. A pair of universal joints connects the actuator to the compliant beam and to the robot frame. As the size of each universal joint is greatly dependent upon its required range of motion, each joint design is tailored to fit a particular angle range to further reduce packaging size. Potential research topics involving the actuator are proposed for future work.

scholarly journals Improvement of Reverse Motion of an NC Moving Table Based on Vector Control Method by Friction Force Compensation

2019 ◽  
Vol 13 (5) ◽  
pp. 610-618
Author(s):  
Akio Hayashi ◽  
◽  
Tatsuya Mukai ◽  
Yusuke Inomata ◽  
Yoshitaka Morimoto
Keyword(s):  
Vector Control ◽  
Control Method ◽  
Numerical Control ◽  
Ball Screw ◽  
Machining Accuracy ◽  
Nonlinear Friction ◽  
Drive Current ◽  
Reverse Motion ◽  
Force Components ◽  
Motion Characteristics

Lost motion is a phenomenon that often occurs during the motion of a moving table, which is used for machine tools to ensure their precise positioning. Lost motion occurs when the direction of the table’s motion reverses as a result of nonlinear friction characteristics between the feed drive mechanisms such as the ball screw and linear guide. Lost motion directly influences the machining accuracy of a machine tool, because the accuracy of machining depends on the relative motion between the tool and the workpiece. A number of studies have dealt with suppressing the occurrence of lost motion using model-based control. However, nonlinear friction has not been addressed to the same extent, as it is difficult to determine the motion characteristics of and therefore develop a model for the nonlinear friction. Thus, to address these problems, we propose a compensation method for revers motion based on vector control, which is used to control the torque and velocity of the alternating current (AC) servomotor in the moving table. In this study, the current applied to the AC servomotor for a vector with force components in the rotational direction (torque component) and in the direction perpendicular to the axis of rotation (field component) was measured to clarify and establish the relationship between the motion and the control current. The compensation current was then derived as a functional value based on the results of the measured torque at the occurrence of lost motion. Further, tests were carried out using the proposed method, which directly applies the drive current of the AC servomotor by using a field-programmable gate array controller to improve the reverse motion of the table. The results reveal that the motion characteristics of a numerical control (NC) table can be determined by measuring the drive current of the AC servomotor. In addition, it is verified that the proposed method can compensate for the torque command smoothly at the time of velocity reversal, resulting in suppression of the lost motion and reduction of reverse motion of the moving table.

Design of the Ball Screw Mechanism for Optimal Efficiency

1989 ◽  
Author(s):  
M.-C. Lin ◽  
S. A. Velinsky ◽  
B. Ravani
Keyword(s):  
Closed Form ◽  
Static Analysis ◽  
Load Capacity ◽  
Equations Of Motion ◽  
Closed Form Solution ◽  
Form Solution ◽  
Ball Screw ◽  
Exact Theory ◽  
Screw Mechanism ◽  
Extensive Computation

Abstract This paper develops theories for evaluating the efficiency of the ball screw mechanism and additionally, for designing this mechanism. Initially, a quasi-static analysis, which is similar to that of the early work in this area, is employed to evaluate efficiency. Dynamic forces, which are neglected by the quasi-static analysis, will have an effect on efficiency. Thus, an exact theory based on the simultaneous solution of both the Newton-Euler equations of motion and the relevant kinematic equations is employed to determine mechanism efficiency, as well as the steady-state motion of all components within the ball screw. However, the development of design methods based on this exact theory is difficult due to the extensive computation necessary and thus, an approximate closed-form representation, that still accounts for the ball screw dynamics, is derived. The validity of this closed-form solution is proven and it is then used in developing an optimum design methodology for the ball screw mechanism based on efficiency. Additionally, the self-braking condition is examined, as are load capacity considerations.

scholarly journals Reliability analysis of hanger shot blast KAZO machine in foundry plant

2018 ◽  
Vol 204 ◽  
pp. 03007
Author(s):  
Rinaldi Sam Prabowo ◽  
Priyo Agus Setiawan ◽  
Anda Iviana Juniani ◽  
Wiediartini ◽  
Ika Erawati
Keyword(s):  
Risk Assessment ◽  
Reliability Analysis ◽  
Load Capacity ◽  
Vital Role ◽  
Metal Casting ◽  
Analysis Method ◽  
Risk Priority Number ◽  
Effect Analysis ◽  
A Value ◽  
Casting Industry

In a metal casting industry, Hanger Shot Blast KAZO machine plays a very vital role for blasting. The downtime equipment data for the last five years, 2013 to 2017, shows that the hanger shot blast KAZO is the machine which frequently encounters downtime with the number of 503,75 hours. As the only blasting machine with 2 (two) tons of load capacity, the issues of hanger shot blast KAZO affect to the targeted production process of company. Moreover, it increases risk of safety for the workers surround the machine. The purpose of this current research is to find out the reliability value of the item/ component of hover shot blast KAZO machine using Reliability Analysis method. The malfunction of its component is reviewed by FMEA (Failure Mode and Effect Analysis). While the risk assessment is obtained from RPN (Risk Priority Number) calculation - MTTF value and reliability value R(t). The result of this current study found that there are 21 malfunctions on hanger shot blast KAZO machine. MTTF analysis shows the highest MTTF value is 9195,324 hours for bearing impeller component and the lowest is 3498,997 hours for motor components. Meanwhile, reliability analysis shows that the largest reliability value with 0.999915 is encountered by motor contactor of crane, while with a value of 0.26385, hanger rotator motor contactor component encountered the lowest reliability value.

scholarly journals Study of the Dynamic Characteristics of Ball Screw with a Load Disturbance

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Zhe Du ◽  
Xiao-Lan Zhang ◽  
Tao Tao
Keyword(s):  
Machine Tool ◽  
Dynamic Characteristics ◽  
Numerical Control ◽  
Hertzian Contact ◽  
Ball Screw ◽  
Machining Accuracy ◽  
Contact Deformation ◽  
Nc Machine Tool ◽  
Load Disturbance ◽  
Nc Machine

The dynamic character of ball screw is the key factor that influences the machining accuracy of numerical control (NC) machine tool. To improve the dynamic characteristics of the NC machine tool, it is necessary to study the dynamic characteristics of a ball screw. In this paper, the kinematics of a ball screw mechanism (BSM) are studied to expound the dynamic process of the drive, and the load disturbance is considered to analyze the contact deformation based on the Hertzian contact theory. The velocity relationships among the ball, screw, and nut are analyzed, and the influence of the contact deformation on the dynamic characteristics is simulated and investigated experimentally. The results show that the relationships between the contact deformation, which is affected by the material characteristics, the contact angle, and the load of nut are nonlinear. The contact deformation is a factor that cannot be ignored when considering the dynamic machining error of high-speed and high-precision machine tools.

The Dynamics of Lead-Screw Drives: Low-Order Modeling and Experiments

2004 ◽  
Vol 126 (2) ◽  
pp. 388-396 ◽  
Author(s):  
Kripa K. Varanasi ◽  
Samir A. Nayfeh
Keyword(s):  
Transfer Functions ◽  
Ball Screw ◽  
Distributed Parameter ◽  
Viscoelastic Damper ◽  
Thrust Bearings ◽  
Screw Drive ◽  
Lead Screw ◽  
Distributed Parameter Model ◽  
Modeling And Experiments ◽  
Low Order

The closed-loop performance of a lead-screw drive is usually limited by a resonance in which the carriage oscillates in the direction of motion as the screw undergoes longitudinal and torsional deformation. In this paper, we develop a model of lead-screw system dynamics that accounts for the distributed inertia of the screw and the compliance and damping of the thrust bearings, nut, and coupling. The distributed-parameter model of the lead-screw drive system is reduced to a low-order model using a Galerkin procedure and verified by experiments performed on a pair of ball-screw systems. The model is found to accurately predict the presence of a finite right-half plane zero in the transfer function from motor torque to carriage position. A viscoelastic damper incorporated into one of the lead-screw support bearings is shown to give rise to significant, deterministic damping in the system transfer functions.

The Static Characteristics of Bump Foil Thrust Bearing Considering Tilting Condition

2009 ◽  
Author(s):  
Tae-Young Kim ◽  
Dong-Jin Park ◽  
Yong-Bok Lee
Keyword(s):  
High Efficiency ◽  
Thrust Bearing ◽  
Numerical Models ◽  
Load Capacity ◽  
Static Characteristics ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Foil Thrust Bearing ◽  
Thrust Pad ◽  
Air Film

Air foil thrust bearings are the critical component available on high-efficiency turbomachinery which needs ability to endure the large axial force. Previous investigations about the static characteristics were obtained over the region of the thin air film using finite-difference method and the characteristics of the corrugated bump foil using finite-element method. Moreover, a recent study demonstrated that bearing performance is sensitive to tilting thrust pad condition. In this study, experimentally measured bearing static characteristics are compared with the numerical model of the foil thrust bearing considering tilting pad condition. Three geometrically different type foil bearings were tested to measure their load capacity under tilting conditions that have continuous angles from zero to 0.0002 rad. These data are presented for use i1n the development of more accurate foil thrust bearing numerical models.

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