Robotics - unit-2 - End effector

Types of End effector

1. Robotics UNIT-2 End Effectors

2. ROBOT DRIVE SYSTEMS AND END EFFECTORS Pneumatic Drives-Hydraulic Drives-Mechanical Drives-Electrical Drives-D.C. Servo Motors, Stepper Motors , A.C. Servo Motors-Salient Features, Applications and Comparison of all these Drives , End Effectors-Grippers-Mechanical Grippers, Pneumatic and Hydraulic- Grippers, Magnetic Grippers, Vacuum Grippers; Two Fingered and Three Fingered Grippers; Internal Grippers and External Grippers ; Selection and Design Considerations.

3. End Effectors Robot end effector is a device attached to the wrist of a manipulator for the purpose of holding materials, parts, tools to perform a specific task. Examples Grippers Tools End of arm tooling Welding equipment

4. Classification of End of arm tooling According to method used to hold part in the gripper According to special purpose process tools incorporated in final gripper design According to multiple function capability of gripper

5. According to method used to hold part in the gripper Mechanical pressure gripper- Friction (or) physical configuration of the gripper retains the object Vacuum Gripper - This gripper are used for flat object Magnetic devices - These devices are used for ferrous object

6. According to special purpose process tools incorporated in final gripper design Drills Grinders Polisher Paint sprayers Welding guns and torches

7. According to multiple function capability of gripper Special purpose grippers These grippers may be specialized device like remote centre compliance (RCC) to insert an external mating component into internal member, viz inserting a plug into hole.

8. Gripper Grippers are the end effectors used for grasping the object during work cycle. A gripper is a device which enables the holding of an object to be manipulated. Gripper just like a hand. It enables holding, tightening, handling, releasing of an object. Examples Vacuum grippers Magnetized gripper Adhesive grippers

9. Requirements of an effective gripper Parts (or) items must be grasped and held without damage Parts must be positioned firmly (or) rigidly while being operated on Hands (or) grippers must accommodate parts of differing sizes (or) even of varying sizes Self aligning jaws are required to ensure that the load stays centred in the jaws Gripping (or) end effectors must not damage the part being handed Jaws (or) Grippers must make contact at a minimum of two pints to ensure that the part does not rotate while being positioned

10. Application of grippers Material handling Palletizing and depalletizing Arranging parts on to pallets Machine loading and unloading Picking and placing of parts on conveyor

11. Mechanical Grippers Mechanical gripper is used as an end effector in a robot for grasping the objects with its mechanically operated fingers. In industries two fingers are enough for holding purpose. Mechanical grippers act as a robot hand. A basic robot hand will have only two (or) three fingers.

12. Features of Mechanical Grippers Simple to use Grip using pivoting, linear (or) translation movement Pneumatic control is cost effective and simple to maintain Servo controls can be used where precise controlled gripper movement is required

13. Advantages of Mechanical Grippers Palletizing Rotating objects Moving small objects Moving non uniformly shaped objects No need for compressed air (or) other supplementary materials

14. Gripper Jaw

15. Two (or) Dual jaw gripper Two jaw gripper consists of two gripping jaws that apply pressure externally (or) internally of the object. It depending on the jaw defines. Examples Angular gripper Parallel gripper Toggle gripper

16. Three jaw Gripper The three jaw gripper consists with three gripping jaw and apply pressure like two jaw grippers. Flexible Grippers Flexible grippers consist with several linkage on each finger and two (or) several fingers Multiple jaw Grippers If more than three jaws are used to hold the object, which is called as multiple jaw grippers

17. Three jaw Gripper

18. Finger Grippers As like as a jaw the fingers are used to hold (or) grasping the object is called finger grippers.

19. Single finger gripper Only one gripping fingers is mounted on the wrist for holding the objects is called single finger gripper. Two (or) dual finger gripper Two fingers are mounted on the wrist for holding the objects are called two finger (or) dual fingers Types of two finger gripper Parallel gripper Angular gripper Toggle gripper

20. Single finger gripper

21. Two (or) dual finger gripper

22. 1. Parallel gripper

23. 2. Angular gripper

24. 3. Toggle gripper

25. Three finger gripper If three fingers are attached on wrist for holding the object is called three finger gripper.

26. Multiple finger gripper If two (or) three fingers are not enough for holding work, more than three finger grippers are designed for reliable and precise palletizing (or) depalletizing and positioning of work pieces in assembly and production process.

27. Based on Hold the object

28. Internal gripper In internal gripper, the finger pads are mounted on the inside of the fingers. This mounting allows the pads to fit into the inside diameter of the part it must lift. The pads are pressed against the inside wall of the part

29. Internal gripper

30. External Gripper An external gripper is designed so that the finger pads press against the outside of the component. Grips the exterior surface of the object with closed finger.

31. External Gripper

32. Single mechanical device 1.Hook Grippers 2. Scoop Grippers

33. 1.Hook Grippers 2. Scoop Grippers

34. Mechanical gripper based on contact 1. Unilateral gripper Only one point (or) surface is touching (or) contact the object to be handled is called unilateral gripper. Example i ) Vacuum pad gripper ii) Electro magnetic gripper 2. Multilateral Gripper More than two points (or) surfaces touching (or) contact the components to be handled is called as multilateral gripper

35. Multilateral Gripper

36. Vacuum Grippers Vacuum grippers are used in the robots for grasping the non ferrous objects. It uses vacuum cups as the gripping device. Vacuum gripper is also commonly known as suction cups. Vacuum grippers are those which are suction cups for handling certain types of objects. This type of grippers will provide good handling if the objects are smooth flat and clean. It has only one surface for gripping the object.

37. Vacuum gripper specification 1. Size of suction cups 2. Supporting requirements 3. pressures requires 4. Gripping force

38. Suction Cups Different devices are used in the suction cups for creating the vacuum. 1. Venturi 2. Vacuum Pump

39. 1. Universal suction cups The universal suction cups are used for flat (or) slightly arched surfaces

40. 2. Flat suction cups With bars are suitable for flat (or) flexible items that need assistance when lifted.

41. 3. Suction cups with bellows Suction cups with bellows are usually used for curved surfaces. It is used for example when separation is needed (or) when a smaller item is being gripped and needs a shorter movement.

42. 4. Depth suction cups The depth suction cup can be used for surfaces that are very irregular and curved (or) when an item needs to be lifted over an edge.

43. Working of Vacuum Gripper (or) Suction Gripper

44. Vacuum Cup

45. Venturi type Vacuum gripper Venturi principles are used in the suction cups for creating vacuum It consist of 1. Nozzle 2. Venture jet 3. Compressor

46. Magnetic Gripper Making use of the principle of magnetism these grippers are used for holding ferrous work part. A gripper in which work piece is held by magnetic force. Magnetic has developed a magnetic gripper (or) robot end of arm tooling. A magnetic gripper is one which uses a permanent magnet for handling ferrous materials.

47. Magnetic Gripper

48. Electro magnetic Grippers In electro magnetic grippers require any sort of external power for handling the material. Gripper using electro magnets are generally powered by dc power for handling materials.

49. Electro magnetic Grippers

50. Permanent magnetic Grippers In permanent magnetic grippers do not require any sort of external powered by DC power for handling the materials. The holding grippers permanently possess high magnetic properties. They do not lose their magnetic force.

51. Permanent magnetic Grippers

52. Adhesive Gripper Grippers in which an adhesive substance performs the grasping action for handling fabrics and other light weight materials are called adhesive gripper.

53. Hydraulic gripper A gripper in which the work piece is hold by hydraulic force. A hydraulic gripper is used as end effector in a robot for grasping the object with its hydraulically actuated fingers. Elements of the hydraulic gripper 1. Reservoir 2.pump 3. Prime mover 4. Actuator 5. hydraulic piping Force = pressure x surface 6. Valves

54. Hydraulic gripper

55. Hydraulic gripper

56. Pneumatic Gripper A gripper in which the work piece is hold by pneumatic force. A pneumatic gripper is used as end effector in a robot for grasping the object with its pneumatically operated fingers. Elements of the pneumatic system 1. Air filter 2. compressor 3. Air cooler 4. Drier 5. Control Valve 6. Air Actuator 7. Electric motor 8. Receiver tank

57. Pneumatic Gripper

58. Gripper Mechanism Gripper mechanism consists of finger (or) hand plates, membrane, roller suction, Vacuum, magnetism, adhesive, scoops and hooks, linkages, screws, cam, spring, string, hydraulics , rope and pulley

59. Linkage actuation gripper mechanism Linkage actuation gripper mechanism is no cam, screw and gear. There is movement only because of links attached to input and output. There must be perfect design of mechanism such that input actuator motion is transformed into the gripping action at the output.

60. CAM actuated gripper mechanism A cam actuated gripper with spring loaded follower can be used to provide open and close actions of fingers. The spring function is to force the gripper to close if the cam is moved in open direction, while the movement of cam on the other direction causes the gripper to open

61. Screw driven (or) actuated gripper mechanism The screw type actuated gripper consists of a screw connected with a threaded block. Screw driven grippers operated by turning screw. In turn giving motion to connecting links output.

62. Rope and Pulley driven gripper mechanism Rope and pulley gripper mechanism consists of a rope connected with pulley. If the pulley is rotated on revolving motion, the rope is transfer along with the direction the motion

63. Gear and Rack actuation system It consist of gear, rack and guide rail. Gear and rack mechanisms are used to convert rotation motion into linear motion.

64. Gripper with a rotary actuator

65. Translation Gripper Mechanisms Translational mechanisms are widely used in grippers of industrial robots. The finger motion corresponds to the piston movement without any connecting mechanisms between them.

66. Types of tools 1. Machine tool 2. Measuring instrument 3. Welding torches 4. Spray painting gun 5. Assembly tool

67. Wrist interface Wrist interface refers to those connections of one system that are matched to another system that is distinctly different because of the basic nature of each system

68. Wrist Assembly A wrist consisting of two (or) three compact joints attached to the wrist is a gripper to grasp a work part (or) a tool to perform process

69. Gripper force analysis Gripping force is the maximum effort applicable by the end effector.

70. Design of Gripper When designing a gripper there are a number of factors that may need consideration. Gripping Force Weight Supply of service Environmental capabilities Sensor capabilities Others

71. Selection of gripper