Chapter End Effectors 9

Objectives Discuss the types of movements an end effector can perform. Describe the types of end effector grippers and end effector tools. Identify the benefits of changeable end effectors. List important factors and desirable characteristics to be considered in the design of end effectors.

End Effector Movement Prehensile movements use thumb and fingers Nonprehensile movements do not require dexterity or use of thumb

Prehensile Movements Five basic prehensile, or gripping, movements Goodheart-Willcox Publisher

Nonprehensile Movements Do not require finger dexterity or use of opposable thumb Goodheart-Willcox Publisher

Types of End Effectors Grippers Tools Prehensile; grasp and move objects Tools Nonprehensile

Grippers

Grippers Mechanical finger grippers Move in parallel or angular motion Goodheart-Willcox Publisher

Grippers Two-finger grippers Human thumb and index finger SCHUNK Intec Inc.

Grippers Two-finger with rotating joint Goodheart-Willcox Publisher

Grippers V-shaped fingers with two points of contact on each finger Schunk-USA

Grippers Three-finger grippers Human thumb, index finger, and third finger SCHUNK GmbH & Co. KG

Grippers Four-finger grippers Collet grippers Square and rectangular parts Collet grippers Pick and place uniform cylindrical parts 360° of clamping contact Round, square, or hexagonal shapes

Grippers Vacuum grippers Use suction One or more suction cups Exact positioning not as critical

Grippers Multi-cup vacuum grippers increase contact surface area Pacific Robotics, Inc.

Grippers Electromechanical grippers Magnetic field created by permanent magnet or electromagnet Electromagnetic gripper uses dc power source Only handle materials containing iron Custom designed for specific applications

Tools Various types perform specific tasks Automatic tool changer Welding Material application Machining and assembly Automatic tool changer More than one end effector Change when needed

Tools Typical automatic tool changer applications Schunk-USA

Tools Welding tools vary according to operation Arc welding torch attached to robot arm Tool changers attach spot weld device to arm Laser and gun welding systems with proper tool changers

Tools Material application for palletizing, packaging, and handling operations Rapid tool changing automates and improves process Robots for machining and assembly require different tools Rapid tool changing critical to productivity

Changeable End Effectors Required by manufacturing robots Increases effectiveness and flexibility Quick-change tooling Interface adapters must be standardized Change end effectors with minimum downtime

End Effector Design Evaluate operation, workpiece(s), and environment Inertia Gripping force Part orientation Gripper sensing capabilities

Desirable Characteristics Strength to carry out tasks Withstand rigorous use Guard against strain damage Breakaway devices Overload sensor detects obstructions or overload conditions Signals controller to shut down

Desirable Characteristics Compliance is ability to tolerate misalignment of parts Remote center compliance (RCC) device Compensates for workpiece misalignment or irregularities

Custom-Designed End Effectors Can be designed for a particular application Broaden range of tasks that can be performed Can be designed to handle fragile or oddly shaped parts

Custom-Designed End Effectors Dual end effector has internal and external gripping capabilities Schunk-USA

Custom-Designed End Effectors Vision guidance system allows robot to find objects not placed symmetrically De-STA-Co

Custom-Designed End Effectors Expandable grippers clamp irregularly shaped workpieces Hollow rubber envelopes enlarge when pressurized Even distribution of surface pressure Grip outside or inside surface