Robotica (1989) volume 8, pp 223-230 Optimum design of gripper jaws for tapered components D.T. Pham* and MJ. Nateghf (Received: August 3,1989) SUMMARY For ease of manufacture, axisymmetric components produced by processes such as forging, casting and moulding are often designed with a taper angle. This paper presents a family of devices for handling such components by their tapered portion. The devices are essentially finger tips, or jaws, to be fitted to standard scissor-type robot grippers. The jaws possess a three-dimensional profile constructed as a stack of v-shaped planar curves. The special jaw profile enables components of different diameters and taper angles to be gripped concentrically without calling for complex movements to reposition the gripper. The equations describing two categories of profile are derived and the optimum selection of profile parameters to yield compact jaws to grip components of a wide range of dimensions is discussed in the paper. KEYWORDS: Gripper; End effector; Tooling; Jaw profiles; Tapered components; Design. 1. INTRODUCTION As part of a project aimed at producing robot grippers to handle groups of geometrically similar components, 1 " 3 specially-profiled gripper jaws were developed for concentrically gripping tapered components of small taper angles and different diameters. 4 This work has been extended, and other jaws with profiles in the same family have been generated which can deal with components of a larger range of taper angles. The design of the new jaws is reported in the present paper. The basic equations for the jaws as derived in ref. 4 apply for the whole family. They are: = r(d,L) (1) (2) where r is the radius of the component to be gripped, 6 is the angle between the central axis of the gripper and the line joining the centre of a component gripped by the jaw and the pivot of the latter, L is the jaw thickness, and F and G are arbitrary functions of 6. Other * Intelligent Systems Research Group, School of Electrical, Electronic and Systems Engineering, University of Wales, Cardiff (U.K.). t Plan and Program Department, Ministry of Heavy Industries, Tehran (Iran). applicable equations are: 3r(0, L)I3L = tan 0 (3) (4) (5) where 2)3 is the taper angle of the component to be gripped, xp is the open angle of the jaw, and 0 max is the maximum value of 0. In the following, the general features of the new jaws are outlined, the equations describing the jaw profiles derived, and the selection of optimum profile parameters discussed. 2. DIFFERENT CATEGORIES OF JAW PROFILES Different jaw profiles can be defined according to equation (2). These can be classified into three categories, one of which has already been reported. 4 Within that category 0 max remains constant and the maximum radius (r max ) that the jaw could grip changes along the jaw. A jaw of the second category is shown in Figure 1. The maximum radius that this jaw can grip is constant and the value of 0 max varies along the jaw. The general equation for this category is obtained by assigning the following values to F(0) and G(0) of equation (2): F(0) = 0, G(0) = C (constant) As r max for a given L is obtained when 0 = 0, it can be concluded from equation (2) that: The values of 0 max along the jaw can be found from: (6) If F(6) or G(0) are non-linear functions of 0, there would be more than one solution for 0 max at each section of the component with a specific value for L. From equation (6) it can be seen that 0 max is a non-linear function of L. Only when F(d) = k x and G(0) is linear, would 0 max and f(L) be linear. In this case equation (2) reduces to: where Jfci, k 2 , and k 3 are constants. A jaw of the third category is shown in Figure 2. Here,