Eccentric Cam Research Articles

Granular vibration pumping system for handling and characterizing particulate materials.

A unique setup for a granular vibration pumping system was developed to ease the installation into a wide variety of granular handling processes and provide flexible options for granular physics research. Although the granular vibration pumping system can notably lift granular materials with an oscillating pipe, the climbing mechanism and related granular physics are yet to be clarified thoroughly. The new setup employs an eccentric cam mechanism as the excitation source, a linear system with dust tolerance, and a recording system, making it simple, compact, and adaptable for extending experiments. The excitation mechanism generated a clear sinusoidal vibration in the pipe, realizing better reproducibility of the climbing motions of glass beads. Moreover, the compact design facilitates the close placement of multiple pipes vibrating individually, which affects the transport performance. In addition, various types of sample cells that store particles and the imaging system allow for the detailed observation of particle motions in the pipes and even the sample cells. This developed system provides easy and accurate tuning of the existing parameters of the granular vibration pumping system, as well as new options for a further understanding of granular physics.

Energy loss comparison between kinematically equivalent mechanisms: Slider-crank and eccentric cam

The reduction of energy consumption in industrial processes is a challenge to be confronted within the framework of the United Nations’ Sustainable Development Goals. The present study compares the energy loss per cycle of two kinematically equivalent mechanisms: a slider-crank and an eccentric cam with a translational roller follower. We use the work-energy theorem to evaluate energy losses by using a viscous friction model in a stationary regime. The innovation of this study lies in the energetic comparison to identify the best and worst alternatives by analyzing the contribution of their main geometrical parameters, such as crank length, rod-crank length ratio, roller radius and follower offset. The aim is to provide guidelines to help machinery designers to take relevant preliminary decisions that affect energy efficiency. Herein, we include analytical models, numerical simulations and experimental results using a test stand that can be adapted to other planar one degree-of-freedom mechanisms. In this context, we conclude that an eccentric cam mechanism with a big roller radius and no offset provides the best energetic efficiency among the aforementioned mechanisms.

Studies on Wear of a Milling Chuck for a Production Line of Specialized Elements Used in Lockstitch Machines.

The study aims to determine the wear intensity of selected milling chuck assembly surfaces covered with a protective DLC (Diamond Like Carbon) coating, used on the production line for elements of selected lockstitch machines, and to analyze the stress distributions in the object fixed with such a chuck for the characteristic load systems of this object during its processing. A model of the workpiece was developed using the finite element method. The boundary conditions, including the load and the method of clamping the workpiece, resulted from the parameters of the milling process and the geometric configuration of the milling chuck. Stress distributions in the workpiece for specific milling parameters and for various configurations of the milling chuck holding the workpiece are included in the article. The model experimental studies of wear were conducted in the contact zone between two surfaces covered with DLC: one on the element of the milling chuck pressing the workpiece and the other on the eccentric cams of this holder. The obtained wear values and shapes for the worn surfaces are also shown. The wear intensities for the steel plunger fins modelling swivel arm of the holder were by an order higher than those of corresponding steel shaft shoulders modelling eccentric cam of the holder. The linear wear intensities for these mating components may be expressed in terms of a function of average contact pressure and sliding speed in a corresponding contact zone. The indentation of eccentric cam into mating surface of the swivel arm of the holder increased nonlinearly with the enhancement of number of cycles of the eccentric cam.

A new low-energy nonlinear variable stiffness actuator for the knee joint

With the increase of safety requirements for human-robot interaction, variable stiffness actuators are increasingly used in joints of medical rehabilitation robots, legged mobile robots and exoskeleton-assisted robots, so the research of the variable stiffness actuator becomes more and more important. In this paper, firstly, according to the human knee joint, a low-energy nonlinear variable stiffness actuator for knee joint is proposed, it conforms to characteristics of biological joints: the actuator can be flexible when it is subjected to the small load, and the actuator can be stabilized when it is subjected to the heavy load. The realization principle of this actuator, which is combining the eccentric cam with the leaf spring, is introduced in detail, and its relatively large range of variable stiffness is accurately deduced and analyzed. Secondly, the energy cost of this actuator is reduced as much as possible by some structural designs. Finally, by experiments, the correctness and accuracy of the resistance moment and expected stiffness of the proposed nonlinear variable stiffness actuator are verified, the high bandwidth and good stability of this actuator are also verified, which meets the design principles and requirements of the actuator, and it is verified that actuator’s low energy cost.

Investigation on Deformation of the Flex-Gear and Optimization Design of Compound Curve Cam Wave Generator with Spiral

The deformation shape and mechanical property of flex-gear greatly affect the meshing accuracy and service life of harmonic drive, and the stress wave generator plays a decisive role in the deformation shape and mechanical properties of the flexible gear. The investigation on deformation of the flex-gear around the major axis is developed with comparative analysis with three kinds of traditional and commonly used wave generators. Based on the influence of the deformation around the major axis on meshing accuracy and service life, the eccentric arc cam wave generator improved by transition curve for controlling the deformation shape and reducing the deformation stress is developed. Considering the achievable flexibility of spiral with smooth curvature change rate, the contour of the compound curve cam wave generator with arc and spiral is proposed. The deformation of the flex-gear under the influence of this compound curve cam and the standard elliptic cam is further comparative analyzed. The conclusion shows that this compound curve cam can indeed reduce the deformation stress in the meshing area by increasing the meshing width, and correct deformation shape can also be gained by shape control on the whole circumference of the flex-gear’s neutral layer.

Characteristics of the Polishing Effects for the Stainless Tubes in Magnetic Finishing with Gel Abrasive

Magnetic abrasive finishing (MAF) is a fast, high efficiency and high-precision polishing method on the surface machining of the metals. Furthermore, MAF also can be utilized to polish the stainless tubes in industrial applications; however, stainless tubes are often a non-magnetic material that makes it difficult for the magnetic field line to penetrate into the stainless tubes, thus reducing the magnetic forces in the inner tubes polishing. That is why stainless tubes are not easy to finish using traditional MAF. Therefore, magnetic finishing with gel abrasive (MFGA) applies gels mixed with steel grit and abrasives that were developed to improve the polishing efficiency and surface uniformity of the steel elements. In this study, a guar gum or silicone gel mixed with steel grit and silicon carbides are used as the magnetic abrasive gel to polish the stainless inner tubes. A DC motor was used to control the rotation speed of the chuck and an AC induction motor connected with an eccentric cam to produce the reciprocating motion of the workpiece were utilized to finish the inner surface of stainless tubes in the polishing process. The parameters of abrasive concentration, abrasive particle sizes, rotation speeds of motor and electric currents were used to investigate the surface roughness and the removal of materials from the stainless tubes. The experimental results showed that since guar gum had better fluidity than the silicone gel did, guar gum created excellent polishing efficiency in MFGA. Furthermore, the surface roughness of the stainless tube decreased from 0.646 μm Ra to below 0.056 μm Ra after processing for 30 min with the parameters of current 3A, gel abrasive with guar gum, rotational speed 1300 rpm and vibration frequency 4 Hz.

The Effect of a Flexible Blade for Load Alleviation in Wind Turbines

This article presents the analysis of the performance of a flexible wind turbine blade. The simulation analysis is based on a 3 m span blade prototype. The blade has a flexible surface and a cam mechanism that modifies the aerodynamic profile and adapts the surface to different configurations. The blade surface was built with a flexible fiberglass composite, and the internal mechanism consists of a flexible structure actuated with an eccentric cam. The cam mechanism deforms five sections of the blade, and the airfoil geometry for each section was measured from zero cam displacement to full cam displacement. The measured data were interpolated to obtain the aerodynamic profiles of the five sections to model the flexible blade in the simulation process. The simulation analysis consisted of determining the different aerodynamic coefficients for different deformed surfaces and a range of wind speeds. The aerodynamic coefficients were calculated with the BEM method (QBlade®); as a result, the data performance of the flexible blade was compared for the different deformation configurations. Finally, a decrease of up to approximately 6% in the mean bending moment suggests that the flexible turbine rotor presented in this article can be used to reduce extreme and fatigue loads on wind turbines.

Design and Analysis of Cam Wave Generator Based on Free Deformation in Non-Working Area of the Flexspline

Deformation stress of a flexspline under the action of a wave generator directly affects the service life of the flexspline and meshing quality of meshing pair. This study proposed a new deformation model for a flexspline, which incorporates forced deformation in the working area and free deformation in the non-working area, keeping the deformation shape unchanged during rotating. Based on this assumption of a deformation model, the mathematical model is further established, and the design approach of a cam wave generator is developed with the deflection curve of the ring structure. Then, a sample design with a double eccentric arc cam wave generator based on this deformation model is developed and analyzed in FEM. The results show that the deformation stress of the flexspline can be improved by relaxing the forced deformation in the non-working area, and the selected deformation shape can also remain unchanged during rotating. Moreover, the stress distribution and the maximum stress value could be improved with the variation of the combination coefficient, especially for the wrap angle.

Investigation for synchronization characteristics of double cam vibrating screen

Aiming at the shortcomings of traditional vibrating screens with large vibration mass, a double eccentric cam self-synchronous vibrating screen is proposed. The motion differential equation of the vibrating screen system is derived by using Lagrange equation and the steady state solution is obtained. According to Hamilton principle, the synchronization condition of the vibration system is deduced, and the stability condition of the self-synchronization motion is obtained. The influencing factors of synchronization and stability are investigated by using numerical calculation and simulation analysis methods. The results show that stable self-synchronous motion of the vibration system is implemented when the synchronization and stability conditions are satisfied; the value of the stable phase difference of two cams varies in the range of (–1.5 rad, 0), and compared with the residual torque difference, the eccentricity of eccentric cams has a greater impact on the stable phase difference; additionally, a linear motion track of the vibrating screen is achieved.

Stresses and deformations of an eccentric cylindrical cam during hydro-joining

The stresses and deformations of an eccentric cylindrical cam during the process of hydro-joining have been calculated in orthogonal curvilinear coordinates according to the mechanical model of the cam and governing equations in terms of appropriate complex potentials with suitable boundary conditions. The radial and shearing stress coefficients determined for an example cam are far less than that of the tangential stress during hydro-joining. The tangential stress coefficient of the outer surface of the cam is greater than that of the internal surface when the polar angle exceeds a particular value. The position of the maximum value of the radial stress coefficient is located on the internal surface of the cam, and the maximum shear stress coefficient is located between the inside and outside surfaces of the cam. The cam deformations on the internal and external surfaces under internal pressure respectively attain maximum values at particular angles. The maximum values of the radial and y-directional deformations are located at the position of the minimum wall thickness. The radial deformations determined for an example cam are far larger that the tangential deformations during hydro-joining. The errors between the theoretical and numerical solutions for the tangential stress and the y-directional deformation are both very small.

Development of a Robot Hand with an Eccentric Cam for Lifting Stacked Loose paper

Development of a Robot Hand with an Eccentric Cam for Lifting Stacked Loose paper

Contact Force Measurements in Cam and Follower Lubricated Contacts

Cam-follower contacts are characterized by continuous changes of operating parameters such as speed, load and geometry, so that both numerical simulations and experimental measurements are very complex. An experimental apparatus has been specifically designed and realized to perform tests with cam–follower pairs. The apparatus allows measurements of contact forces with a custom-made dynamometer and of lubricant film thickness and shape with optical interferometry. After an introductory review of experimental works on cam-follower pairs mainly related to force measurements, the test rig used for the experimental work reported in the paper is briefly described. Some trends of all components of the contact forces measured during the rotation of a circular eccentric cam and an engine spline cam are presented. Tests have been performed at different rotational speeds and preloads. The friction trends can be associated to mixed and boundary lubrication regimes. Some unattended friction peaks are found in tests with the spline cam and possible explanations are given.

Modeling and experimental investigation of drilling force for low-frequency axial vibration-assisted BTA deep hole drilling

The ability to form regular chips and evacuate them smoothly is crucial for deep hole drilling. In this work, an eccentric cam mechanism is used to apply low-frequency axial vibration at the end of the drill tube for boring and trepanning association (BTA) deep hole machining, and the instantaneous cutting thickness equation of low-frequency axial vibration assisted drilling is derived, which can actively control the length of the chip and achieve a good chip removal effect. Considering the variable geometric parameters and the scale effect of teeth cutting, a new analytical model is established to obtain the instantaneous drilling force of staggered teeth BTA deep hole drill assisted by low-frequency axial vibration. The relevant parameters in drilling force model are identified, and the distribution laws of the normal friction angle, normal shear angle, and shear stress with instantaneous cutting layer thickness and drilling radius values are achieved. The influence of the vibration drilling process parameters, including feed, speed, amplitude, and frequency ratio, on the drilling force is investigated experimentally, and the validity of the drilling force model is verified. These results show that the drilling force model is reliable, and the thrust and torque of the low-frequency axial vibration assisted drilling relative to ordinary drilling are reduced by 21.63% and 13.74%, respectively.

Analysis on Static Performance of Flexible Bearing in Harmonic Reducer

The harmonic reducer has been widely used in military, industrial and agricultural fields because of its large transmission ratio, high precision, small backlash, stable transmission and small volume and weight. Flexible bearing is a key component of harmonic reducer, and its static mechanical properties are one of the main factors influencing the fatigue life and load carrying capacity of harmonic reducer. Mathematical model of contact force between rolling element and outer ring is established basing on three bending moment equations. This paper takes the CSF-40-80 flexible bearing with double eccentric arc cam as the research object, the finite element methods (FEM) analysis is used to study the deformation and stress of the flexible bearing under no-load and load. The effect of the double eccentric arc cam eccentricity on the stress is also presented, which provides theoretical support for the optimization of harmonic reducers and the manufacture of high-performance harmonic drive systems.

Design & Development of Four Way Hack Saw

Cutting of material is one of the important machining parameters for development of different fabricated model like shaft, bolts and screws etc. for a mass production the material need to cut in a multiple way or manner at a same time and this is to be perform on a power hack saw or multiple way hack saw machine which consume less time. This paper propose the design considerations and development of four way hacksaw machine which is able to cut four pieces of same or different material simultaneously with a very less time consumption. The motor is used as a source of power generation. Conversion of rotary motion of motor shaft into reciprocating motion is obtained by using eccentric cam. This machine can perform cutting operation on four different components by four ways at a time on different material simultaneously and therefore this machine becomes very useful in industry because of its efficiency, reliability and compatibility. This machine overcomes traditional hack saw machine which cuts material single work piece at particular time interval and also fulfills today’s need of mass production

Qualitative effect of velocity ratio on the behaviour of a circular synthetic jet flush mounted on a torpedo model in quiescent and cross-flow conditions

A synthetic jet on a curved surface and at high velocity ratios is of immense interest for its possible usage in a torpedo or other naval applications. However, despite exhaustive research on synthetic jets on a flat surface in cross-flow, very few studies have been conducted on synthetic jets on a torpedo-like surface. This study experimentally explores a synthetic jet mounted on a torpedo shaped model in quiescent and cross-flow conditions. The synthetic jet actuation mechanism consists of a motor driven eccentric cam, which oscillates the diaphragm and generates synthetic jet. Initially, the synthetic jet is characterized for two different diaphragm displacements and at four distinct actuation frequencies in the range of 1 Hz – 6 Hz in a quiescent flow environment. Subsequently, similar study is carried out in cross-flow for three different cross-flow velocities ranging from 7.2 – 32 cm/s, at a fixed amplitude of diaphragm oscillations. The flow visualization results qualitatively indicate that the vortex rings in synthetic jet can be classified into two major groups: stretched vortex rings and distorted tilted vortex rings. The flow structures primarily depend on the velocity ratio, which is function of actuation frequency and cross-flow velocity. At a low velocity ratio, the leading vortex is followed by a strong trailing jet. Two distinctly different trajectories are observed for the leading and trailing vortices at higher velocity ratios. At a low cross-flow velocity and higher actuation frequency, synthetic jet leads to increase in the velocity within the boundary layer on the upstream side of the orifice.

An Underactuated PASA Finger Capable of Perfectly Linear Motion With Compensatory Displacement

This paper presents a novel design for a robotic end effector. In particular, the design features a multifingered underactuated gripper capable of performing parallel and self-adaptive (PASA) grasping. The unique use of an eccentric cam fixed to a modified four-bar linkage mechanism allows the finger to compensate for the typical gap distance found during parallel pinching, improving the ability to grasp objects against surfaces and in tight spaces. A static analysis is performed on the design to determine the equilibrium conditions necessary for a successful grasp using this design in both the PASA modes. The mechanics of a four-bar mechanism are used to determine the grasp velocity and positioning of the hand in both grasp modes. Experimental results with a finger prototype confirm the desired closing trajectory.

Design of a novel coaxial eccentric indexing cam mechanism

A novel coaxial eccentric indexing cam mechanism (CEC) is proposed for high-speed automatic machineries. In comparison with the conventional indexing cam mechanisms such as parallel, globoidal, cylindrical cam mechanisms as well as the Geneva mechanism, the merits of this novel mechanism are: (1) more compact structure and (2) higher indexing rate. The structure and transmission principle of the mechanism are introduced and the cam profiles are formulated with an emphasis to derive two design criteria. The influences of the geometric parameters on the kinematic performance of the mechanism are also discussed through significant numerical analyses. Finally, the dynamic performance of a virtual prototype is analyzed with the aid of SolidWorks, and the physical prototype is manufactured to verify the validity of this design.

Influence of the wave generator type on the stress distribution in the flexible wheel of double harmonic transmissions

The main factor that influences the lifecycle of the double harmonic transmission is the durability of the flexible toothed wheel, which is the most strongly stressed element of the transmission. The complexity of the stress distribution in the flexible toothed wheel depends on many factors, such as: the type of wave generator, the flexible wheel construction shape, the coupling mode of the flexible wheel and the transmission load. In the paper it was studied the stress distribution in the flexible wheel body, as well as the variation of the displacements of the nodes located on certain generatrix of the flexible wheel, by considering three types of mechanical generators with two deformation waves, materialized by: 2 rolls, 2 eccentric discs or cam. The numerical simulation of the flexible wheel was made in the elastic domain using a Finite Element Method with SolidWorks software.

Design and Development of Plane Bending Fatigue Testing Machine for Composite Material

Fiber reinforced composite materials are finding increasing applications in aerospace structures, naval industry, military and automotive industry, because of their high specific stiffness and strength. Although the fatigue behavior of fiber reinforced composites has been studied for a long time, the fatigue of composite materials is not completely understood as the fatigue in composites is quite different from metal fatigue. From the literature review it is revealed that less number of fatigue life prediction models are available for composite materials and majority of the research work is related to the tension-tension fatigue and tension-compression fatigue but less work is reported in bending fatigue life estimation.In this paper the development of a plane bending fatigue testing machine for composite material is presented. The work is undertaken considering the high cost of the presently available fatigue testing machines. Copan shaped work pieces are used for the testing. Specimens are subjected to repeated fluctuating stresses and the number of cycles is counted till the breakage of the specimen and the results are plotted. The proposed machine is simple in design and economical. An eccentric cam and connecting rod arrangement is done for the fully reserve bending motion of the work piece. The machine is equipped with speed measurement, speed control, force measurement, displacement measurement and fatigue life measurement and data acquisition system.For the validation of the machine, the fatigue testing of some samples is carried out and the results are presented to show the efficiency of the system. The results show that the machine is capable of satisfying the requirements of ASTM standard.