276 Industrial Robotics Fundamentals Copyright Goodheart-Willcox Co., Inc. transfer. They are also used for grinding and deburring operations. Collet grippers are typ- ically controlled by a solenoid and have excel- lent repeatability. They are available in round, square, or hexagonal shapes. Vacuum Grippers Vacuum grippers are end effectors that use suction (vacuum) to pick up an object. They consist of one or more suction cups made of natural or synthetic rubber. They are extremely lightweight and simple in construc- tion. The number, size, and type of suction cups used depends on the weight, size, shape, and type of material being handled. Multi-cup vacuum grippers increase the contact surface area, which allows workpieces of increased size and weight to be handled, Figure 9-9. Vacuum grippers can be used on curved and contoured surfaces as well as on fl at surfaces. fl The fl exibility of the suction cups provides fl the robot with a certain amount of adaptabil- ity. Therefore, exact positioning is not as criti- cal as with some other types of grippers. To Contact point 1 Contact point 1 Contact point 2 Contact point 2 Schunk-USA Figure 9-7. This two-fi nger gripper has two points of contact per finger, fi which allows it to fi grasp large cylindrical objects securely. SCHUNK GmbH & Co. KG Figure 9-8. Three-fi grippers can grasp and handle objects of finger various shapes.