Motion-curve synthesis and geometric design of globoidal cam mechanism with intermittent variable speed

Abstract

A design procedure for increasing the performance of an intermittent globoidal cam mechanism is presented. The proposed procedure is based on the synthesis of roller-follower turret motions at two different speeds to lower the inertia effect caused by the start/stop behaviour of the intermittent mechanism. The motion curves in a globoidal cam mechanism with an intermittent variable speed are defined by non-parametric rational B-splines to increase the transport capability. There are four key techniques to design a cam mechanism: the first is to construct the cam profile by using the volume swept method, the second is to synthesize the motion curve of a turret by using a rational B-spline curve on velocity control, the third is to analyse the mechanical properties of cam by using the geometrical vector method, and the last is to plan an NC programme and to estimate the performance of five-axial precision machining. Four types of motion curves with similar geometric properties are used and the rational B-spline has better dynamic properties than the other three curves. The systematic design approach proposed for a globoidal cam mechanism with an intermittent variable speed is to improve its performance, to upgrade effectively the function of the indexing device, and to increase the production speed of industrial automatic conveyance.

An application of geodesics to the calculation of the rib-thickness of globoidal cam mechanisms

“…After substituting the obtained solution b into Eqs. (9) and (6), the intersection point of the contact curves with the torus can be easily derived. After the calculation results are obtained using VC programming, the simulation model of a rib of the globoidal cam used in ATC is obtained with the help of Creo Software (Fig.…”

“…Erdman [7] gave reviews of many studies on the cam mechanisms. The four applied approaches to the derivation of cam surfaces are based on the offset surface method [8][9][10], the screw theory [11][12][13], the envelope theory [14][15][16] and the conjugate theory [17][18][19][20][21]. Among them, the method based on the conjugate theory and the offset surface method are mainly applied.…”

Profile surfaces of cylindrical cams with arbitrarily-shaped followers

“…As for the concave region, the absolute value of the radius of principal curvature must be larger than that of the cutter. Otherwise, undercutting will occur [7,8].…”

“…The contact point method is a traditional, general approach that is developed based on the screw theory and the perpendicular relationship between the relative velocity and the common normal vector in a cam-follower mechanism [1][2][3][4][5][6]. The concept of the rigid body transformation approach is based on the fact that the cam surfaces can be represented as the swept surfaces of the roller of the cam-turret mechanism in motion [7,8]. Based on the theory of envelopes, the planar or spatial cam's profile is identical to the envelope of the family of curves or surfaces, which is composed of the loci of the follower contour along its movement [9][10][11].…”

Modelling concave globoidal cam with indexing turret follower: A case study

“…They represented the surface geometry of the globoidal cam as the swept surfaces of the tool paths. The globoidal cam profile was also constructed by using the volume swept method (Lin et al 2007). En-hui et al (2001) In this paper, to illustrate the cam surfaces from angular input and output displacements of the cam and the follower, some modelling methods are presented.…”