Radial Cam Research Articles

Nomograms for maximum pressure angles in radial cams with follower eccentricity for cycloidal and harmonic motion curves

For an adequate design of radial cams with translating roller followers, it is necessary to maintain the constraint that maximum pressure angle cannot exceed the empirically accepted value of 30°. The direct calculation of this parameter is difficult and it is usually sought to reduce it by trial and error. Nomograms that exist so far only calculated this angle for cams with no eccentricity between follower and cam. This research presents two nomograms with this additional parameter, which allows for greater design freedom using all available variables. The charts are for cycloidal and harmonic motion curves, and can be used for their full and half curves. The study discusses the advantages of using nomograms and the methods to obtain low values of maximum pressure angle by satisfactorily combining available parameters. Although nomograms are no longer a widely used tool in the industry, they still have didactic functions in textbooks and could be useful for preliminary analysis in engineering projects.

Analytical solutions and computational nomograms for maximum pressure angle for cam mechanisms for full and half cycloidal and harmonic motion curves

High pressure angles in cams with roller followers still pose as a problem in cam projects. The main objective of this work is to deduce the maximum pressure angle equations for full and half cycloidal and harmonic motion curves for translating roller followers in radial cams and create nomograms that can calculate this parameter by simply connecting two points by a straight line in a chart. The nomograms were made for the mentioned curves via an open source software and it is discussed the limitations of the given charts and the advantages of using the current method. Additionally, the paper reinforces the need for authors to make it clear that another well known and frequently used nomogram cannot be used as is for half curves. Although use of nomograms has fallen into disuse, it still has applications in textbooks and quick preliminary analysis in real life projects.

Comparison of geometrical accuracy and surface finish of cam profile generated by wire-EDM and CNC milling machine

CAM is a machining element that has a curved groove or curved outline used for converting rotary motion into the form of linear motion or vice versa. The radial cam is a type of cam which having rotating plate or disc with an outer circumference shaped for producing a linear movement to a follower which is held against it. The quality of the final machined component surface depends on the accuracy and surface finish, position, orientation and run-out. The main aim of this paper is to machine a CAM profiles with CNC milling and wire cut EDM process and comparing the surface finish and accuracy of the machined surface with surface roughness tester and coordinate measuring machine (CMM).

Circular-Arc Radial Cams with One Connection Arc

This paper deals with the geometric and kinematic analysis of the circular-arc profile cams with one connection arc. If the maximum lift of the follower is required, it is shown that it is possible to connect two circular-arcs – that are defined by center of curvature and radius – through a single circular-arc, and the connection points result. But, if the connection points of two given circular-arcs of the cam profile are required, at least two circular-arcs are needed to connect them. The specific equations for the geometric analysis for one circular-arc profile are described. Also, for two mechanisms, one with straight-line profile and another with one circular-arc connection profile, the geometric and kinematic analysis and simulations of the movements using SolidWorks and ADAMS programs are presented

Acetabular and spino-pelvic morphologies are different in subjects with symptomatic cam femoro-acetabular impingement.

Acetabular and spino-pelvic (SP) morphological parameters are important determinants of hip joint dynamics. This prospective study aimed to determine whether acetabular and SP morphological differences exist between hips with and without cam morphology and between symptomatic and asymptomatic hips with cam morphology. A cohort of 67 patients/hips was studied. Hips were either asymptomatic with no cam (Controls, n = 18), symptomatic with cam (n = 26) or asymptomatic with cam (n = 23). CT-based quantitative assessments of femoral, acetabular, pelvic, and spino-pelvic parameters were performed. Measurements were compared between controls and those with a cam deformity, as well as between the three groups. Morphological parameters that were independent predictors of a symptomatic cam were determined using a regression analysis. Hips with cam deformity had slightly smaller subtended angles superior-anteriorly (87° vs. 84°, p = 0.04) and greater pelvic incidence (53° vs. 48°, p = 0.003) compared to controls. Symptomatic cams had greater acetabular version (p < 0.01), greater subtended angles superiorly and superior-posteriorly (p = 0.01), higher pelvic incidence (p = 0.02), greater alpha angles and lower femoral neck-shaft angles compared to asymptomatic cams (p < 0.01) and controls (p < 0.01). The four predictors of symptomatic cam included antero-superior alpha angle, femoral neck-shaft angle, acetabular depth, and pelvic incidence. In conclusion, this study illustrates that symptomatic hips had a greater amount of supero-posterior coverage; which would be the contact area between a radial cam and the acetabulum, when the hip is flexed to 90°. Furthermore, individuals with symptomatic cam morphology had greater PI. Acetabular- and SP parameters should be part of the radiological assessment of femoro-acetabular impingement. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1840-1848, 2018.

Analytic Analysis of a Cam Mechanism

Cam mechanisms are integral parts of many products. They are used in many applications from combustion engines through milling machines to fitness machines. As suggested by their range of applications, it is an important issue. In this article the configuration of a mechanism, comprising a flat faced follower, which is pressed to the surface of a radial cam by the coil spring, is studied. On the basis of the known lifting function (the results of previous work) a new cam profile will be proposed. Lifting functions are of a polynomial character. Particularly, a cubic polynomial, the fifth degree polynomial and the seventh degree polynomial will be studied. Subsequently, there will be proposed a methodology for the calculation of torque according to the desired angular velocity of the cam. This methodology will be used for choosing a suitable electric motor and for a proper selection of coil springs. The spring preload will be determined with intention to avoid the rebound of the follower from the cam surface. Based on the analytical analysis a new measuring stand will be proposed. In future, the analytical results will be complemented by experiment.

A compact stepper motor actuated disposable microgripper

This paper describes the design, modeling and experimental testing of a disposable microgripper for manipulation of micro particles and objects. We utilize a CO2 laser cutter to fabricate acrylic microgripper capable of handling objects less than 300 μm in size. The microgripper forms a flexure-based compliant mechanism which is actuated with a radial cam driven by a miniature stepper motor. Finite element analysis is used to optimize the selected design for optimal stress distribution and tip displacement in response to the applied force on the legs of the mechanism. The gripper fits on an ergonomically designed holder that contains the stepper motor and a microstepping driver to control the motor. A push of a button on the holder opens and closes the microgripper, thus, making it very easy to operate. We demonstrate the utility of the microgripper through various pick and place experiments. The experimental results exhibit a high level of integrity in the design of the microgripper to manipulate a variety of microparticles.

Optimization of Radial Cams with Translating Roller Follower through Genetic Algorithms

In this work, the optimization problem is studied for a planar cam which rotates around its axis and moves a centered translating roller follower. The proposed optimization method is a genetic algorithm. The paper deals with different design problems: the minimization of the pressure angle, the maximization of the radius of curvature and the minimization of the contact pressure. Different types of motion laws are tested to found the most suitable for the computational optimization process.

The Synthesis of a Hook Drive Cam Mechanism

Cam mechanisms are very important mechanical objects which are used in the design of various machinery. Their application can be found, for example, in machine tools, textile, printing, sewing machines, etc. This mechanical object was used in the design of a sewing machine hook drive. The hook drive is composed by a four-bar linkage and a cam mechanism with radial conjugate cams and an oscillating roller follower. The main aim of the kinematic synthesis was to determine the optimal characteristic parameters of the cam mechanism hook drive. As the criterion for the determining of the most appropriate dimensions, it was chosen the pressure angle course in the proposed mechanical system. Another goal of the computational analysis was the determining of the cam mechanism dynamic behavior and properties, which are expressed in the Hertzian pressure course and estimated rating life of curve roller bearings.

Tools for Automated Design of Intermittent Mechanisms with Radial Parallel Cams

The paper deals with the kinematics and automated calculation of intermittent mechanisms with radial cams. Currently, electronic cams are increasingly applied in the drives of working link mechanisms. Despite a huge advantage of electronic cams in their re-programmability or instantaneous change of displacement diagrams, conventional cam mechanisms have an irreplaceable role in production and handling machines. With high frequency of working cycle periods, the dynamic load of the proper servomotor rotor increases and efficiency of electronic cams strongly decreases. Though conventional intermittent mechanisms with radial cams are representatives of fixed automation, they have distinct advantages in their high speed (high dynamics), positional accuracy and relatively easy manufacture. We try to remove the disadvantage of firm displacement diagram by reducing costs for simple design and automated calculation that leads reliably to high-quality and inexpensive manufacture.

Active Chaos Control of a Cam-Follower Impacting System using FPIC Technique

In this paper, we apply a novel active control scheme to suppress chaotic behavior in a cam-follower impacting system using Fixed-Point Inducting Control or FPIC Technique. Namely, the input speed of the cam-follower system is actively controlled in order to reach a single-impact periodic motion. A cam-follower system characterized by a radial cam and a flat-faced follower is used as a representative example. High-order periodic-impact and chaotic motions are controlled varying the input speed of the cam-follower system. Stroboscopic and impact maps are used to select the suitable control parameters under which stable single-impact periodic responses are reached.

Experimental and numerical verification of bifurcations and chaos in cam-follower impacting systems

In this paper, we present the design, modelling and experimental validation of a novel experimental cam-follower rig for the analysis of bifurcations and chaos in piecewise-smooth dynamical systems with impacts. Experimental results are presented for a cam-follower system characterized by a radial cam and a flat-faced follower. Under variation of the cam rotational speed, the follower is observed to detach from the cam and then show the emergence of periodic impacting behaviour characterized by many impacts and chattering. Further variations of the cam speed cause the sudden transition to seemingly aperiodic behaviour. These results are compared with the numerical simulation of a mathematical model of the system which shows the same qualitative behaviour. Excellent quantitative agreement is found between the numerical and experimental results.

Numerical and experimental analyses of radial cams with circular-arc profiles

Cam profiles with circular arcs can be useful for low-cost transmissions and for applications in micromachines. They are usually designed by means of graphical techniques. Recently, at Laboratory of Robotics and Mechatronics (LARM) in Cassino, a research line addressed the problems of modern design and characterization of cams with circular-arc profiles by looking at computer-oriented formulations and by investigating experimentally the operation characteristics. In this article, we have given an overview of the results achieved for radial cams and also attempted to extend to a general case that is useful for studying and validating any planar cam profile. The approach is algebraic, because it is based on the geometry of the mechanical design of circular-arc profiles. The experimental analysis has been conceived for a low-cost easy-operation performance of the circular-arc profiles, using a suitable test-bed that has been designed at LARM in Cassino. The results of the experimental tests are useful to validate both the numerical design procedure and the designed cam profiles. Examples are reported to illustrate the practical engineering feasibility of the proposed analysis procedures for radial cams with circular-arc profiles.

Cam Design and Manufacturing Handbook

Written by a professional with extensive practical and teaching experience in Mechanical Engineering. Cam Design and Manufacturing Handbook brings together up-to-date cam design technology, correct design and manufacturing procedures, and recent cam research results in one volume that is indispensable to the design and manufacturing of cam-follower systems. Beginning at an introductory level and progressing to more advanced topics, this comprehensive handbook includes complete coverage of: Proper Cam Design Techniques, Single- and Multi-Dwell Cams, Classical Cam Functions, Polynomial Cams, Spline Functions for Cams, Pressure Angle & Radius of Curvature, Radial and Barrel Cams, Translating & Oscillating Followers, Roller & Flat-Faced Followers, Forward & Inverse Dynamic Analyses, Residual Vibrations, Polydyne & Splinedyne Cams, Cam Profile Definition, Cutter Compensation, Conjugate Cams, Cam Materials & Manufacturing Techniques, Stress Analysis of the Cam Follower Joint, Lubrication of the Cam Follower Joint, Measurement of Cam Follower Dynamics, Extensive Bibliography. What's more, this unique book is accompanied by a 90-day trial demonstration copy of the Professional Version of Dynacam for Windows V. 7.0. Written by the author and used worldwide, this program solves the equations described in the book and allows in its fully licensed version the design, dynamic modeling, analysis, and generation of follower center, cam surface, and cutter coordinate data for any cam. It also defines conjugate cams for any cam design.

板カム輪郭フライス切削における工作物熱変形の適応制御

This paper deals with the real-time cutter path modification in radial cam profile milling, by which the shape error due to the workpiece thermal deformation could be reduced. A cam profile is determined by the computer using the parameters indicated by a designer. And then, the temperature rise and the thermal deformation of the workpiece, during the cutting process, are roughly predicted by the finite element method previously. During actual machining process, the workpiece temperature rise, which is concerned with the variance of cutting conditions, is monitored by the minicomputer. By comparing the measured workpiece temperature with the previously predicted value, the actual thermal deformation of the workpiece is estimated. Since the minicomputer is directly connected to the numerical control unit, it generates the modified cutter path instructions and sends these instructions to the NC unit. These instructions are based on the original cam profile and the thermal deformation. It is certified through some experiments that this method improves the machining accuracy without some cooling systems. Furthermore, the minicomputer is connected to the large scale time sharing system via telephone line. Using this two level hierarchical system, computational load is shared effectively between the large scale computer and the minicomputer.

Discussion: “Determination of Radius of Curvature for Radial and Swinging-Follower Cam Systems” and “Determination of Pressure Angles for Swinging-Follower Cam Systems” (Kloomok, Martin, and Muffley, R. V., 1956, Trans. ASME, 78, pp. 795–800 and 803–806)

Discussion: “Determination of Radius of Curvature for Radial and Swinging-Follower Cam Systems” and “Determination of Pressure Angles for Swinging-Follower Cam Systems” (Kloomok, Martin, and Muffley, R. V., 1956, Trans. ASME, 78, pp. 795–800 and 803–806)

Determination of Radius of Curvature for Radial and Swinging-Follower Cam Systems

Abstract An exact expression is derived for the radius of curvature of disk cams with either radial or swinging followers. Several charts are included which illustrate a quick method for arriving at a solution for a particular cam contour, such as the harmonic.

Closure to “Discussion of ‘Determination of Radius of Curvature for Radial and Swinging-Follower Cam Systems’ and ‘Determination of Pressure Angles for Swinging-Follower Cam Systems’” (1956, Trans. ASME, 78, pp. 801–802)

Closure to “Discussion of ‘Determination of Radius of Curvature for Radial and Swinging-Follower Cam Systems’ and ‘Determination of Pressure Angles for Swinging-Follower Cam Systems’” (1956, Trans. ASME, 78, pp. 801–802)