Chapter 9 End Effectors ff ff 273 Copyright Goodheart-Willcox Co., Inc. • Lateral grip. Grasping fl at objects from the sides with the fingers fl and thumb fi rather than around the object. Holding a quarter by the edges is an example of using a lateral grip. • Oppositional grip. Using the tip of the index fi nger and the thumb to hold fi an object, such as a key. 9.1.2 Nonprehensile Movements Nonprehensile movements do not require fi nger dexterity or use of the opposable fi thumb. These movements include pushing, poking, punching, and hooking. Two specifi types of nonprehensile movements are hook and spread, fic Figure 9-2. The hook movement involves curling the tips of the fingers t to pull or lift objects. To fi perform the spread movement, the fingers t and thumb are extended outward until fi they make contact with the interior walls of a hollow object. The force of the fin- fi gers against the walls of the object allows it to be picked up and carried. 9.2 Types of End Effectors End effectors can be classifi as grippers or tools. fied Grippers are end effectors that perform prehensile movements by grasping objects and moving them. Tools are end effectors that execute nonprehensile movements to perform specific tasks, fi such as welding or painting. 9.2.1 Grippers Robots use a variety of grippers to grasp, handle, and transport parts, Figure 9-3. Some common types of grippers are presented in the sections that follow. Hook Spread Goodheart-Willcox Publisher Figure 9-2. Nonprehensile movements, such as hook and spread, do not depend on movement of the thumb.