C Ch a ap ter t 9 E En d d Effecto Eff Eff e t or s s ff 283 Copyright Goodheart-Willcox Co., Inc. Copyright Goodheart-Willcox Co., Inc. Summary • End effectors are devices attached to the wrist of a robot manipulator. They are used to grasp, lift, transport, maneuver, or perform operations on a workpiece. • End effectors for robots perform many of the same movements as a human hand. • Prehensile movements require the use of the thumb to grasp objects and include palmar grip, cylindrical grip, spherical grip, lateral grip, and oppositional grip. • Nonprehensile movements do not require the movement of a thumb and include pushing, poking, punching, hooking, and spread movements. • End effectors are classifi as grippers or tools. Grippers perform prehensile fied movements, and tools execute nonprehensile movements. • Types of grippers include mechanical fi nger grippers (two-, three- or four- fi fi nger), collet grippers, vacuum grippers, and electromechanical grippers. fi • Tools attached to a robot arm are used for welding, material application (palletizing, packaging, or handling operations), and machining and assembly operations. • Robots used in manufacturing require either multipurpose or changeable tooling. An automatic tool changer can change end effectors when needed to execute operations. • End effector design must include study of the type of operation to be performed, the workpieces, and the work environment. • End effectors should be designed with the appropriate desirable characteristics, such as strength, durability, strain and overload protection, and compliance. • Custom-designed end effectors can be made for specific operations, such as fi handling fragile objects or grasping parts that vary greatly in size. Review Questions Answer the following questions using the information provided in this chapter. 1. Distinguish between prehensile and nonprehensile movements that robot end effectors can make. 2. Describe fi ve types of gripping movements an end effector can make. fi 3. Describe the hook movement and the spread movement that can be performed by an end effector. 4. Describe the two major classifications for end effectors. fi 5. What are four types of grippers? 6. For what tasks are mechanical fi nger grippers typically used? fi 7. Explain how a vacuum gripper operates. 8. What is a major disadvantage of an electromechanical gripper? 9. What are three categories of tools used for robotic applications? 10. How does changeable tooling impact the operation of a robotic system? 11. What are the advantages of using automatic tool changers? 12. What are three factors that should be considered when determining the type of end effector needed to do a job? 13. What are some desirable characteristics that should be part of the design for an end effector?