Grippers: Components, Types, Actuation, History, and Usage

1. Assembly Components-Gripper Ming Jin 10/6/2004

2. Basics Grippers are end effectors used to grasp and manipulate objects during the work cycle. The easier way to describe a gripper is to think of the human hand. Just like a hand, a gripper enables holding, tightening, handling and releasing of an object. A gripper is just one component of an automated system. A gripper can be attached to a robot or it can be part of a fixed automation system.

3. Basics Types of Grippers: Mechanical grippers-two or more fingers actuated by the robot controller Vacuum grippers-suction cups used to hold flat objects Magnetized grippers-for holding ferrous parts Adhesive devices-adhesive substance used to hold flexible material Single mechanical devices-hooks and scoops

4. Basics Gripper Style: Angular: The gripper jaws are opened and closed around a central pivot point, moving in a sweeping or arcing motion. Angular grippers are often used when limited space is available or when the jaws need to move up and out of the way. Parallel: The gripper jaws move in a parallel motion in relation to the gripper body.  Used in a majority of applications, parallel grippers are typically more accurate than other style grippers.

5. Basics Gripper Actuation: Manual: Actuated by hand crank, wheel, levers, or other manual or mechanical means.   Electric: Grippers fingers or jaws actuated by electric motor, solenoid, etc. Pneumatic: Gripper is actuated by compressed air acting on a cylinder or vanes.   Hydraulic: Gripper is actuated by hydraulic fluid acting on a cylinder or vanes.

6. History of the Gripper The first gripper, or artificial hand, was probably a hook replacing a lost human hand. An artificial hand is first recorded in 1509---an iron hand made for a German knight.

7. Current State Great variety of grippers available. Used widely in many different fields: nuclear science, aeronautics and medical robotics. With the development of technology, microgrippers(better 1nm resolution) appear.

8. Where used? Machine loading/unloading Assembly lines Material transfer Manufacturing processes

9. Who uses it? What used for? When used? Workers in nuclear science use grippers to move things remotely when the things dealt with are dangerous for body health. Astronauts can manipulate remote-controlled grippers in space from within the safety of the spacecraft when they are building the space station.

10. Costs Based on what you need: - the object - material - robot Almost no listed prices, only quotes

11. Supporting Technology Sensors Power supply Drive system Control system

12. Reference http://www.grippers.com/ http://www.nanomotor.de/n_nmg_grippers.htm http://www.arobotics.com/products/grippers/ http://www.arobotics.com/resources/tutorials/index.cfm James L. Fuller, “Robotics” D. T. Pham and W. B. Heginbotham, “Robot Grippers”

13. Application Rules Things to be considered in choosing what type of gripper a robot should use: The weight of the part The gripping distance from the center of gravity of the part The coefficient of friction between the part and the gripper The gravitation force (G) involved in moving the part The angle of the gripper’s fingers to each other The necessary safety factor The part’s characteristics

14. Application Rules Parallel grippers have their own set of specifications. These include gripping force, stroke and gripping size.  Angular grippers have a specific set of specifications. These include gripping torque, angular stroke, 180 degrees open, and gripping size.

15. Limitations Limited availability of compatible devices Highly Customized / Not Flexible Errors in the process of grasping

16. Primary Vendors Barry Wright Corporation ISI Manufacturing Inc. ZAYTRAN, Inc. Applied Robotics, Inc. AGI - American Grippers Inc. Robotic Accessories - Tipp City,

17. Standards Each is customized and works in a narrow range of variation, so specifications are important and useful. No Real Standards.

18. Application Examples AUTOMATED ASSEMBLY AND QUALITY CONTROL CNC GRINDER LOADER/UNLOADER

19. Videos

20. Videos

21. Technical Paper “Development of the 6-axis force/moment sensor for an intelligent robot's gripper” Sensors and Actuators A: Physical, In Press, Corrected Proof, Available online 27 September 2004, Joong-Jo Park and Gab-Soon Kim “Aspects of controlling a multifingered gripper” Engineering Applications of Artificial Intelligence, Volume 11, Issue 1, February 1998, Pages 87-96, T. Doersam and T. Fischer

22. Integration Gripper can be equipped with sensors for monitoring the grasping function. The integration of sensors leads to more intelligent gripper system. Sensor-integrated grippers can provide the robot system with flexibility needed to cope with uncertainties. The gripper must be adapted mechanically with flanges to the robot.

23. Class Application In the Lab 513-Robotic Assembly, the robot will pick up a vacuum gripper to finish task.

24. Summary Grippers are used widely in many industries. Grippers are usually custom designed. When looking for a gripper, know what you want it to do. Many modern grippers are sensor-integrated.