Screw Pair Research Articles

Experimental Analysis of Axial Load Internal Circulation Ball Screw Pair of Friction Torque and the Impact

According to the working principle of the ball in and out of the race in inner circulation and external loop, analyzed under the action of axial force of the ball in and out of the influence of the raceway for the ball screw friction resistance, due to ball in rail friction drag is small, that the inner loop no loss as external loop ball friction energy in the circulation pipe, friction torque variation of the ball in and out is small. Experimental results show that the inner loop of the ball screw's friction torque increases with the increase of rotational speed, but the amount of friction torque fluctuation is small, under the screw speed, the axial force has certain influence for inner loop ball screw's friction torque fluctuation and ball impact, but under the relatively high speed is not obvious of on the two.

Research on Contact Strength between Roller Screw Pair on Hoisting Mechanism Applied in Deep Sea Crane

Roller screw pair is the major part of the rope guiding device that used in deep-sea hoisting mechanism. This paper focuses on the contact problems of the roller screw pair. The hoisting mechanism used in the deep sea engineering has the rope with large diameter, sustaining the great rope tension force. So its important to research the contact stress of the roller screw, This paper study the impact of surface hardness of the roller on the performance of the roller screw, sums up the effect of hardness on the bearing capacity of the roller, and provides the theoretical support and references for the designing and application of this new type of roller screw in marine engineering.

The Simulation Analysis of Ball Screw Pair Contact Characteristics Based on ADAMS

In the mechanical motion ,wear always exists. Different contact stress will lead to different wear characteristics. This paper proposes a method for contact force analysis. According to the Hertz contact theory and in impact function model the dynamic simulation mold is set up. Taking the recognition system with binocular visual angle ball screw pair for example, based on ADAMS and virtual prototype technology, establishment of ball screw ADAMS model and theoretically analyse the impact of ball screw pair contact force causes . In view of the main factor, get the ball contact force distribution. Analysis shows that reasonable selection of ball screw parameters can reduce the ball contact force extreme and inhibit ball screw wear ,which has the reference significance. At the same time, the research of virtual prototyping technology application provides an effective method in new product development.

THE DYNAMICS OF A SINGLE ALGEBRAIC SCREW PAIR

The algebraic screw pair, or A-pair, represents a new class of kinematic constraint that exploits the self-motions inherent to a specific configuration of Griffis-Duffy platform. Using the A-pair as a joint in a hybrid parallel-serial kinematic chain results in a sinusoidal coupling of rotation and translation between adjacent links. The resulting linkage is termed an A-chain. This paper reveals the dynamic equations of motion of a single A-pair and examines the impact of the inertial properties of the legs of the A-pair on the dynamics. A numerical example illustrates the impact of the leg effects from different perspectives and shows that while the gravity effects of the legs are significant, it may be possible to neglect the leg kinetic energy from the dynamics model.

Kinematic and Singularity Analysis of 3 PRR Parallel Manipulator

Three degrees of freedom (DOF) parallel manipulator is used in the applications such as base for various machining operations, drilling inclined holes, airplane and automobile simulators, walking machines, pointing devices, contour milling and machining etc. The 3 DOF parallel manipulator consists of a fixed platform and a movable platform, which are connected by means of three identical links. Pin joints are used to connect the one end of the link and the lead screw pair. This 3 DOF 1R2T parallel manipulator is having one orientation freedom and two translational freedom, which is actuated by means of screw pair, which in turn operated by a stepper motor. The inverse kinematics and velocity equations of this mechanism have been derived mathematically. Based on this inverse kinematics and velocity equations singularity analysis is completed. Two kinds of singularities are compared with ADAMS simulation results and a prototype of the manipulator is developed for further study.

Spiral Flow Capability Research in the Rotary Cylinder

In order to obtain the lubricating capabilityof screw rotary cylinder, its structural design and operation principle were introduced. Seven screw pairs with different radial clearance were designed. The models were built by Pro/E. Structure mesh was generated by using Gambit. Based on laminar flow model and SIMPLE algorithm, the interior flow field in different radial clearances and the same radial clearance at different inlet pressure were numerically simulated and analyzed with Fluent. The relationship of loading force, stiffness, maximum temperature, flow rate and radial clearance were obtained. Simulation results show that the performance of oil lubricated screw pair is the best at the radial clearance of 0.10 mm. At the same radial clearance, when back pressure is constant, with inlet pressure increasing, loading force, stiffness, flow rate and maximum temperature increase completely.

Optimal Design and Contact Analysis for Planetary Roller Screw

Based on the meshing principle of Planetary Roller Screw (PRS), the meshing clearance of screw pair is minimized by taking the half of thread angle, and the pitch diameter tooth thickness, e, as the optimization variables. Optimal structural parameters are obtained by using optimization module of the software Matlab. The 3D model of PRS structures are established with Solidworks and the finite element contact analysis is carried out with Ansys. The contact deformation and stress distribution are calculated among screw, rollers and nut. The results can be used for PRS design.

Grinding Wheel Carriage Mode Analysis of Vertical Glass Edging Machine

The finite element model of grinding wheel carriage on glass edging machine was established, some key mechanical joints such as ball lead screw pair, linear rolling guide pair and lead screw bearing were simulated by combin14 spring-damp unit. The mode analysis was finished by ANSYS software, the frontal 4 modes and natural frequencies indicated that the weak part of grinding wheel carriage vibration was lead screw and assembly board of sliding block. The natural frequency and dynamic behavior of grinding wheel carriage will be improved by increasing diameter of lead screw and thickness of assembly board of sliding block, preloading lead screw bearing and ball lead screw pair, using middle or heavy preload linear rolling guide. The research result is very important for the design of large scale vertical glass edging machine.

A thermal model of a ball screw feed drive system for a machine tool

The feed drive system is a major heat source of machine tools, which results in considerable thermal drift at the tool. Therefore, there is a need to establish a scientific and systematic model that can be used to predict the temperature distribution of the feed drive system. In this research, considering the thermal contact resistance between the bearing and its housing, an integrated thermal model has been developed by the aid of the finite-element method to analyse the temperature distribution of a ball screw feed drive system, in particular the theoretical determination of power losses caused by the friction in ball screw pair, rolling bearings, and guide ways. Thermal boundary conditions including the convective heat transfer coefficients and heat flux have been obtained using the Fourier's law. Results reveal that the ball screw shaft surface has a uniform temperature rise of 4.2 °C under a given condition. The temperature rise agrees with the data obtained by an infrared thermometer.

Study on Screw Pairs Life Prediction Based on Hidden Markov Model and Neural Networks

In order to estimate and predict the screw performance in the process of machining, a screw life monitoring system was built. Current signal was processed and features sensitive to cutting force were selected, a virtual force sensor was constructed to model the relation between cutting force and current by BPNN. Cutting force was indirectly calculated by the model, so the rating life of screw in different condition could be known and residual life also be reckoned by historical database. A three-way vibration sensor was installed on screw pair base; screw condition could be induced by HMM which input was 15 vibration signal features. As machining condition changed, corresponding new HMM would be built by adaptive method. Finally, the residual life of screw could be gotten by multi-HMM and BPNN. The experimental results show the model proposed in the paper is effective and high precision.

Maxillary Fragment Stabilization After Le Fort I Fracture With 1 Screw Pair per Plate

The aim of the present study was to determine whether plates with only 1 screw pair can be used for Le Fort I fracture management. Good postoperative results motivated the direct application of mandible fixation principles to the fractured midface region without additional experimental research. However, the amount and distribution of the forces in the midface region is different from those on the mandible. Testing was conducted on plastic anatomic models. The validity of the experimental model was tested before the fixation techniques were compared. Standard miniplates and miniscrews were used for fixation of the maxilla. The model surface strain analysis was conducted using the noncontact object grating method, which enabled the surface strain measurement without direct influence on the measured model. In 2 screw pair fixation, the outer screw pair has little effect on the local strain distribution, but it lowers the contact forces along the crack. One screw pair fixation is stable enough for fixation, but it has a greater strain peak at the crack edges. Our results showed that 1 screw pair per plate was enough for stable fixation, and 2 or more screw pairs should only be used when the bone fragment at the fracture site cannot sufficiently transmit forces along the crack.

Dynamic Characteristic Parameters of Linear Guideway Joint with Ball Screw

A dynamic model of linear guideway joint with ball screw is built by means of the linear stiffness of linear rolling guideway and the axial stiffness of ball screw and angular contact ball bearing,which can be calculated by using the Hertz Contact Theory of elastic mechanics,and related computer program for calculating the contact stiffness is developed. A vertical machining centre is selected as an example,the effect of cutting load on the dynamic stiffness of joint part is analyzed,and the dynamic characteristics of the entire machine tool with the joint stiffness considered are also discussed on the basis of finite element method. The analytical results show that it can not only overcome the shortcoming of the conventional method in without considering the effect of ball screw pair,but also appear clarity in physical concept and simplification in computation.

A rotationless formulation of multibody dynamics: Modeling of screw joints and incorporation of control constraints

In the present work, a new energy-momentum conserving time-stepping scheme for multibody systems comprising screw joints is developed. In particular, it is shown that the underlying rotationless formulation of multibody dynamics along with a specific coordinate augmentation technique makes possible the energy-momentum discretization of the screw pair. In addition to that, control (or servo) constraints are treated within the rotationless framework of multibody dynamics. The control constraints are used to partially prescribe the motion of a multibody system. In particular, control constraints, in conjunction with the coordinate augmentation technique, make possible to solve inverse dynamics problems by applying the present simulation approach.

Rapping experiment of rolling mill pressure screw-pairs and plastic bulge of nut teeth analysis

A 1/8 mill screw pair experiment model of heavy and medium plate mill is made to analyse the rapping mechanism and the forming reason of plastic bulge quantitatively. Based on the experiment model, a series of experiments are done like rapping distance testing, vibration experiment and FEM nu- merical simulation of the copper nut tooth plastic bulge. The mill screw pair is oriented on medium radius, which is force constraint and is unreliable. There is time difference betweenthe mill screw and balance mechanism when bite and toss of steel, which is the main reason for the forming of rapping and plastic bulge. Compound nut is provided, which can take place of force constraint with geometric constraint which depends on the rear of nut tooth. In the compound nut, the back side of slave nut tooth is the working face. The results of 1/8 model experiment show that it can control screw-pair dynamic gap, realize self-balance of screw, reduce the effect of mill screw-pairs rapping and prevent the emergence of a plastic bulge of copper nut tooth with compound nut. At the same time, adopting compound nut can reduce the abrasion of copper nut effectively and elongate the nut lifetime.

Residence time distributions in extrusion-cooking. Part 6: Viscous dissipation in a drossel element in the feed zone of a counter-rotating, twin-screw extruder

The effects of hold-up, die diameter, rotational velocity of the screws and moisture content on the viscous dissipation in a counter-rotating, twinscrew extruder processing maize grits were studied by means of stepwise regression. The screw pair studied has a drossel element in the feed zone which acts as a high shear throttle valve. Two hypotheses could be formed from the stepwise regression equations found: the axial mixing action in the feed zone determines the viscous dissipation; and the axial mixing in the feed zone is affected by backmixed steam from the transport and compression zone. These hypotheses were confirmed by experiments in which sunflower oil or water was pumped in halfway along the screws. Up to 13% (w/w) oil could be mixed uniformly with the maize grits without instabilities in the extruder. Brabender amylographs showed that maize grits which had passed through the drossel element became extensively depolymerised.