Screw Nut Research Articles

Design of Bending Fatigue Machine for Flexible Electronics

According to the current requirements of bending fatigue test for flexible electronics, a bending fatigue machine based on SCM (single chip Microcomputer) has been designed. using stepper motor driving screw nut body as loading mechanism, improve the accuracy of the structure effectively by gaps eliminator, and achieve the requirement of precision control by using fraction driving technology in the motor control. Photoelectric counter and electrical signals detection circuit have also been designed to achieve unattended function. This design plays an important role in the following testing process.

Establishing a cost-effective sensing system and signal processing method to diagnose preload levels of ball screws

This paper presents an embedded sensing system for precisely measuring acceleration and temperature of interest points on a ball screw structure and diagnosis of different ball-screw preloads based on processing acquired signals with further classification using the support vector machine (SVM) method. The sensing system consists of a sensing unit and a hardware signal-processing unit. The core sensors utilize a MEMS-type accelerometer and glass-type SMD PT-100, integrated into a 1cm×1cm circuit board and packaged with a metal housing sensing unit with a dimension less than 1.5cm3. The sensing unit is embedded into the screw nut of a designed preload-adjustable ball screw, installed on a computer-controlled single-axis stage for testing. Acquired signals with good noise immunity in an industrial environment are achieved through the developed hardware signal-processing unit. Measured acceleration and temperature data for different ball-screw preload levels based on time and frequency domain analysis are performed. The results demonstrate achieving diagnosis of a ball-screw preload within 20s, with a preload level classification reaching nearly 100%. The developed sensing system and analysis method can apply to monitor ball-screw health and would be very useful in industrial applications.

Design of a Hand Exoskeleton Rehabilitation Device

As stroke is one of the most morbidity disease, some rehabilitation devices has been developed to solve the problem, but there isn’t maturation in hand. This paper presents a new hand exoskeleton rehabilitation device to improve the result of rehabilitation and help doctors to perfect theory about hand rehabilitation. We set 8 DOF in this three fingers device, with 2 active DOF and 1 coupled DOF in index or middle finger, 1 active DOF and 1 passive DOF in thumb. The 5 active DOF is driven by motors. The transmission consists of screw nut and multi-link mechanism. We control the device through a typical secondary control system. As this device is designed to help patients not only regain the range of flexion/extension but also complete some typical simple grasping movements. To substantiate the feasibility, an experiment has been carried out. Finally, Suggestions for improvement are given.

볼트 홀 결함 평가용 와전류 센서 설계제작 및 특성분석

This paper introduces the special eddy current sensor and its characteristic for bolt hole defect evaluation in gas turbine rotor. In the past, Fluorescent penetration inspection method was used for qualitative defect evaluation in gas turbine rotor bolt hole. This method can defect the bolt hole defect but can not evaluate the defect size. Nowadays, eddy current method is used quantitative defect evaluation due to advanced sensor design technology. And eddy current method is more time and cost saving than the old method. We developed bolt shape eddy current sensor for the rotor bolt hole defect detection and evaluation. The eddy current sensor moves to the bolt hole guided by screw nut and detects the defect on the bolt hole. The bolt hole mock-up and artificial defects were made and used for the signal detection & resolution analysis of eddy current sensor. The results show that signal detection capability is enough to detect 0.2 mm depth defect. And the resolution capability is enough to differentiate 02, 0.5, 1.0 and 2.0 mm depth defect.

Optimal Design of Triangle Fastening Screw Thread's Turn Number

The paper firstly numerically simulates the coupled model of triangle fastening screw threads in the application of ANSYS software. Calculate stress intensity of the screw thread on the axial pressure of 200MPa. The fittest coupled turn number of the screw nut is designed to make sure the strength of coupled teeth and make every turn of the screw thread go on very well and also save material. The maximum equivalent stress of the screw thread changes linearly with the axial pressure. The stress of the thread's root is greater than that of the thread's top so that the root is easily damaged. The paper's research method can apply to the optimal design of the other patterns of screw thread's turn number.

Selective thoracic fusion in the scoliosis associated with syringomyelia

To evaluate the surgical results of selective thoracic fusion (STF) for scoliosis associated with syringomyelia. From January 2001 to January 2009, 93 cases of scoliosis associated with syringomyelia were retrospectively reviewed. There were 11 cases who underwent STF and were followed up more than 2 years, which included 8 female and 3 male, the mean age was 14.9 years (9 - 21 years). Curve type, coronal and sagittal Cobb angle, apical vertebral rotation apical vertebral translation, flexibility, trunk shift were recorded and analyzed. There were 9 double curves and 2 triple curves, the Lenke type of thoracolumbar/lumbar curve included Lenke A in 2 cases, Lenke B in 7 cases and Lenke C in 2 cases. The average coronal Cobb angle of thoracic curve before and after surgery were 62.6° and 19.0° respectively, and the average correction rate was 69.6%. The average coronal Cobb angle of thoracolumbar/lumbar curve before and after surgery were 36.1° and 11.6° respectively, and the average spontaneous correction rate was 67.9%. The followed up time ranged from 24 to 48 months (mean 29.5 months), the average loss of correction rate was 6.8%. Only one trunk decompensation was noted at final follow-up. Pedicle screw nut loosening occurred in one patient and this patient underwent revision surgery, no neurological complication was noted at final follow-up. STF could be safely performed in scoliosis associated with syringomyelia. Thoracolumbar/lumbar curve in these patients has similar spontaneous correction ability compared with idiopathic scoliosis patients. The satisfactory result could be achieved according to the STF criteria for IS.

Improved Screw–Nut Interface Model for High-Performance Ball Screw Drives

Emerging applications of ball screw drives such as semiconductor inspection, fiber optic alignment, medical equipment, and miniature robotic actuators typically make use of ball screws that are compact, stiff, and precise. Existing models for the screw–nut interface stiffness of ball screw drives are however unable to accurately describe the dynamics of compact and stiff ball screws because they are derived based on the assumption that the portion of the screw within the nut is rigid. This paper proposes a new screw–nut interface stiffness model, which incorporates the elastic deformation of the screw within the nut using Timoshenko beam shape functions. The new model is shown, via simulation and experiments, to provide more accurate predictions of the natural frequencies of compact and stiff ball screw/nut assemblies compared to the existing models. It is therefore more suitable for use in the design simulation/evaluation of high-performance ball screw drives where compactness and rigidity are required.

Multiple Influencing Factors Analysis for Non-Conformal Contact Characteristics of Ball Screw

The contact between balls and screw races or nut races is a kind of typical non-conformal contact. The study of contact characteristics of ball screw will provide theoretical bases for improving transmission efficiency and working properties of ball screw. In this study, hertz contact theory was adopted to construct the solution formula of ball screw’s contact stiffness, ball screw’s contact characteristics in terms of axial load, design parameters and material properties was analyzed, and the contact deformation value of the contact between ball and screw races was got using finite element simulation method. The simulation result is close to the theoretic value, which proves the correctness of the theory analysis. The present study offers theoretical support for the design and application of high speed, heavy load and precision ball screws.

ボールねじの玉挙動とロストモーション（第２報）―ダブルナットあるいはオーバサイズ球予圧方式による荷重の影響―

It is well known that preloaded ball screws with double nut produced hysteretic motion between the rotary motion of the screw shaft and the linear motion of the nut, which is called “lost motion”, affects positioning accuracies of ball screws.Preloaded ball screws with a double nut have the characteristic that loaded balls wedge into a right angle direction to a ball rolling direction because the directions of screw shaft and nut raceways differ from the ball rolling direction. Loaded balls of preloaded ball screws with a double nut have two contact points geometrically. When the ball screw is operated under the condition of screw shaft turning and nut stationary, the balls have the velocity component perpendicular to the load line of action due to the helical raceway groove. Therefore the balls wedge into nut grooves. In the case of a ball screws with a circular-arc groove profile, “ball wedging” phenomenon is saturated when the force of resistance to ball wedging exceeds a frictional force between the ball and the raceway groove.In the present study, the authors experimentally investigated the lost motion of the X-table which is composed of a preloaded precision ball screw and a couple of linear air bearings, and the ball wedging behaviors under the condition of varied preload with double nut or over-sized balls have also measured.

Mechanized model to assess capsulorhexis resistance to tearing

To evaluate a model of mechanically measuring resistance to tearing of a continuous curvilinear capsulorhexis (CCC) using the entire capsular bag of fresh human cadaver eyes isolated from the eyes after complete evacuation. John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. Experimental study. After the cornea and iris were removed, a 5.0 to 5.5 mm anterior CCC was created. The nucleus was hydroexpressed and the capsular bag evacuated by irrigation/aspiration. A pair of metal shoetree-shaped fixtures, designed based on human lens geometric dimensions, were implanted separately in the capsular bag and assembled together with a screw nut. After complete zonulectomy, the fixture-capsular bag assembly was removed from the eye and loaded onto a mechanical tester. The fixtures were separated at a velocity of 7.0 mm/min in 0.15 μm intervals to stretch the CCC to its rupture point. Rupture load (N) and extension were measured and graphed. Testing of 23 donor eyes a mean of 69.04 hours ± 22.72 (SD) after death showed the following mean values: CCC diameter, 5.3 ± 0.12 mm; load, 0.39 ± 0.16 N; extension at CCC tearing, 5.85 ± 1.17 mm. There was a moderately strong negative correlation between donor age and load (P = .0018). Previous mechanized methods of assessing CCC strength used excised anterior capsules or partially phacoemulsified crystalline lenses, yielding lower tension strength values. This force-displacement method may facilitate assessment of small differences between anterior capsulotomy techniques.

Squeak noise in lead screw systems: Self-excited vibration of continuous model

The dynamic instability of a spinning lead screw in contact with a screw nut is investigated analytically. The lead screw is modeled as a circular beam vibrating in transverse and torsion direction. The contact kinematics between the lead screw and the nut is described on the contact threads in the lead screw. The onset of squeak noise is numerically predicted with a variety of system parameters. Stability analysis shows that the transverse vibration modes can generate squeak noise in the lead screw system. It is highlighted that squeak noise can be controlled by system design parameters in such a manner that the squeak propensity is dependent on rotation speed, screw radius, axial load, contact location, and so on.

20410 3点接触を考慮したボールねじにおける摩擦トルクの評価(OS8 進化を続ける転がり機械要素(1),オーガナイズドセッション)

Preloaded ball screws with a double nut have the characteristic that the loaded balls wedge into a right angle direction to a ball rolling direction because the directions of screw shaft and nut raceways differ from the ball rolling direction. Loaded balls of preloaded ball screws with a double nut have two contact points geometrically. When the ball screw is operated under the condition of screw shaft turning and nut stationary, the wedging forces of balls are produced by differences between the screw shaft and nut raceways, and then loaded balls wedge into nut grooves. When the ball wedging motion is significantly increased, loaded balls make contact with another flank of the nut groove, that is, three points contact occur. In the present study, the authors describe a theoretical analysis of the frictional torque in three point contact ball screw. In addition, the frictional torqueses of the preloaded ball screw with double nut are measured under the condition of varied preload, and the results were compared with analytical data

Development of a new type of transmission screw nut with high efficiency and heavy duty characteristics

A new approach for high efficiency and heavy-duty screw transmission was presented and studied. It is characterized by a steel base and a lining made of carbon fabric enforced polymer self-lubrication composite material lining on the thread surface. The spiral surface layer was fabricated by net-shape forming instead of traditional machining. Oil grooves were also implemented in forming. By nut contour structure optimization, the loads on every screw fillet are well distributed, decreasing the maximum loads on fillets. This type of screw nut has excellent anti-friction and wear-resisting performance as well as high burden ability. The experiments showed that the composite nuts had excellent tribology properties under heavy-duty conditions. Frictional torque on the composite nut decreased by 53.5 per cent and transmission efficiency increased by 48.65 per cent compared with bronze nuts. The development of the new type of sliding screw nut not only plays an important role for alternating current servo press development, but also has revolutionary significance for all mechanical equipment using screw transmission.

Shape forming of ceramics with controllable microstructure by drying-free colloidal casting

A new drying-free colloidal casting method was developed for shape forming of ceramics with controllable microstructure. A polymerizable solvent such as furfuryl alcohol (FA) was employed to disperse ceramic particles to form a colloidal ceramic suspension with good fluidity. After casting, the solvent was polymerized into a polymer, resulting in solidification of the colloidal suspension. For the purpose of demonstrating this casting method, three types of ceramic powders (NiO/YSZ, Al2O3 and YSZ) were used to fabricate a NiO/YSZ ceramic tube, an Al2O3 ceramic part with a hexagonal screw nut shape, and a YSZ thin film. Our study shows that the microstructure (pore size and porosity) of ceramics can be readily tuned by adjusting the amount of FA, and the drying-free casting method offers better controllability over the shape forming of a wide variety of ceramic materials.

Mechatronic Design of the 2 DOF PRRRP Parallel Robot

AbstractMechatronics consists in integration of three fields in engineering: mechanics, electronics and information technology. The paradigm of mechatronics is the integration concept, being the first step in the design of complex mechatronic systems. The need for an integrated approach to the design of complex engineering system involving electronic engineering, mechanical engineering and computing has led to the growth of the concept of mechatronics. The paper presents details regarding the integration process for the kinematic axis in mechatronic. The example of the positioning system based on dc motor and screw–nut transmission is analysed. This actuator is further used for driving a 2 DOF PRRRP parallel robot. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Stainless steel screws coated with bisphosphonates gave stronger fixation and more surrounding bone. Histomorphometry in rats

Coating of stainless steel screws with bisphosphonate in a fibrinogen matrix leads to an enhancement of the pullout strength 2 weeks after insertion in rat tibiae. This effect then increases over time until at least 8 weeks. The pullout force reflects the mechanical properties of the bone within the threads, which acts as a screw nut. The aim of the present study was to find descriptive and morphometric histological correlates to the increased pullout strength. Because the bisphosphonates are applied via the implant surface, we also measured bone to implant contact and how far away from the surface any effects could be seen. Stainless steel screws underwent one of three treatments: uncoated control, controls coated with a layer of cross-linked fibrinogen, or screws further modified with bisphosphonates covalently linked and physically adsorbed to the fibrinogen layer. At 1 ( n = 33) and 8 ( n = 27) weeks, bone to implant contact and bone area density in the threads were measured, as well as bone area density at 250 and 500 μm from the outer edge of the threads. Additionally, removal torque for each screw treatment was measured at 2 weeks ( n = 28). At 8 weeks, the part of the bisphosphonate screw that was located in the marrow cavity had become surrounded with bone, whereas there was almost no bone surrounding the controls. The bone area density in the threads along the entire bisphosphonate screw was increased by 40% compared with uncoated controls, and at 250 μm distance it was more than doubled. At 1 week, coated screws had less implant–bone contact, but at 8 weeks there was no difference between uncoated and bisphosphonate-coated screws. The bisphosphonate screws had 50% increased removal torque at 2 weeks compared to uncoated screws. Howship's lacunae and osteoclasts were found near the screws with bisphosphonates at 8 weeks, suggesting that some bone remodeling took place near the implant, in spite of the presence of bisphosphonates.

Comparison of 1-Stage Versus 2-Stage Anterior and Posterior Spinal Fusion for Severe and Rigid Idiopathic Scoliosis–A Randomized Prospective Study

A randomized prospective study. To compare safety, efficacy, and cost between 1-stage and 2-stage anterior and posterior spinal fusion in treating rigid thoracic adolescent idiopathic scoliosis (AIS). Retrospective study issued different outcomes comparing 1-stage with 2-stage surgical procedures in treating neuromuscular and congenital scoliosis. A randomized prospective study in AIS has rarely been reported. METHODS.: Twenty-four patients were randomly divided into 2 groups. Group A underwent a 2-stage procedure, group B a 1-stage procedure. Inclusion criteria were: (1) AIS; (2) rigid single thoracic curve, > or =90 degrees on anteroposterior and > or =60 degrees on side bending view; and (3) pulmonary function tests, vital capacity > or =500 mL or FEV1 > or =50%. Exclusion criteria were: (1) curves either <90 degrees on anteroposterior or <60 degrees on bending view; and (2) pulmonary function tests, both vital capacity <500 mL and FEV1 <50%. The mean follow up was 3.3 years (range 2-5.1). Clinical outcomes between the 2 groups were analyzed. A statistical t test demonstrated no significant difference in age (P = 0.299), curves on anteroposterior (P = 0.908), on bending (P = 0.905), after surgery (P = 0.699), and at last follow-up (P = 0.946). No significant difference in blood loss (P = 0.089), transfusion (P = 0.334), operation time (P = 0.172), fusion segments anterior (P = 0.161), posterior (P = 0.546), wound drainage (P = 0.557), thoraco drainage (P = 0.948), and loss of correction at follow-up (P = 0.596). However, significant differences were found in length of stay (P < 0.001), patient cost of hospitalization (P < 0.001) between 2 groups, and curve correction (P < 0.001) in each group. Perioperative complications included 1 patient each with pneumonia, pneumothorax (group A), and ileus (group B). Screw nut loosing was found in 1 patient in group B, but no curve deteriorated. No neurologic deficit occurred in either group. A comparison of 1-stage versus 2-stage fusion in treating rigid thoracic curves in AIS did not show significant differences in safety or efficacy but did demonstrate significant difference in length of stay and patient cost.

Treatment of femoral intercondylar comminuted fracture with retrograde intramedullary supracondylar nail and stable screw nut

目的 探讨股骨髁上交锁髓内钉加稳定螺母治疗股骨髁间粉碎骨折的优势.方法本组18例股骨髁间粉碎骨折的病例,按AO分类,C1型2例,C2型10例,C3型6例,均采用股骨髁上交锁髓内钉加稳定螺母进行治疗.结果随访6～29个月,18例骨折全部愈合,平均愈合时间3.5个月,按Noves的评分标准评定膝关节功能,优6例,良10例,可2例,优良率达88.89%.结论股骨髁上交锁髓内钉加稳定螺母是目前治疗股骨髁间粉碎骨折的有效选择之一,但术中应注意解剖复位,牢固固定、钉长合适及术后早期功能锻炼等以避免膝内外翻畸形、下肢短缩旋转畸形、膝关节僵硬、骨性关节炎、撞击综合征及骨不连或骨延迟愈合的发生。

Autonomous form measurement on machining centers for free-form surfaces

This research aims at developing a measurement technique on machining centers for 3D free-form contours. An autonomous measuring principle is proposed and a prototype measuring device applicable to a machining center has been produced. In the measuring device, a laser displacement detector in a narrow range, which directly detects the distance from a point on the measured surface to the reference position of the detector output, is put together with the movable part of a linear encoder on the nut of a ball screw. A stepping motor controls the laser detector position to keep the output at the central value of the detector measuring range by driving the ball screw. Both the motor and the fixed part of the linear encoder are placed on the device base. The linear encoder detects the moving displacement of the screw nut, i.e. the position change of the laser detector. By installing the base on the spindle of a machining center and moving the table along a plane perpendicular to the spindle, the laser detector can automatically follow the contour of a work piece set on the table and measure its form along a scanning line, simultaneously. The displacement of a measured point relative to the reference position of the linear encoder output on the spindle side is just equal to the sum of the outputs of the two sensors, i.e. the laser detector and the linear encoder. Moreover, a simple experimental approach to identifying the sensing direction errors for an assembled measuring device is developed. The results of some experiments are also shown, which sufficiently demonstrate the effectiveness of the proposed inspection method and error identification approach.

LEAN ENGINEERING FOR MASS HOUSING — DESIGN, MANUFACTURE AND SITE ERECTION

There is a tremendous housing shortage in the world that can only be overcome by innovative designs and enlightened production management, such as lean construction. This paper presents a method for fast and low-cost erection of apartment housing units that have architectural flexibility, manufacturing flexibility, and erection flexibility. Flexibility is one of the fundamental aspects of lean manufacturing. The paper describes an innovative design using cam and nut jointing methods for large panel erection, and presents characteristics of an appropriate structural system to correspond to the mechanical jointing and quick erection needs. Current precast plants can quickly acquire capabilities to manufacture large panels as per the stated design using cam and nut. The cam screw and cam nut scheme is conducive to quick erection, besides being capable of withstanding all structural and natural loads. Erection speeds using this method are estimated to be about ten times as fast as conventional methods, thereby facilitating lean production. This paper presents an overall lean approach to the design, manufacture, and construction of this innovative housing system. It is believed that only through innovative systems can future technology needs of the world be met.