1. Assembly components: Grippers, bowl feeders, and part handling components
October 3, 2012
Lance Astle

2. Handling components Where can you learn about handling components?
Material handling involves moving, selecting or packing products. Material handling robots are used to automate moving, feeding or disengaging parts or tools to or from a location, or for transferring parts from one machine to another.
Where can you learn about handling components?

4. Bowl Feeders

5. Types of Bowl Feeder Tracks
Multiple Track
Multiple Track bowls have two or more tracks. Each track carries parts from the bottom of the vibratory bowl to its discharge. The discharge of stock bowls can have up to ten tracks. Advantages include higher production rates and the simultaneous delivery of fixed numbers of parts to the bowl's discharge.
Positive Tracks
Positive Tracks have a less than 90° included angle between the track and the side wall of the vibratory bowl. Track angle is expressed in degrees of slope above the horizontal plane - usually 7°, 8°, 15°, or 60°.

6. Radius-Form Tracks V-Form Tracks
Radius-Form Tracks generally have a groove for the entire length of the track, but some just for the last quadrant. They are designed to feed a cylindrical part whose length is equal to or greater than its diameter. The track's radius should match the profile of the part being fed.
V-Form Tracks
V-Form Tracks contain grooves of 60°, 90°, 120°, or 150° as the included angle. Some run the entire track length, others only the latter part of the track. These tracks are designed to feed cylindrical parts.

7. Part Orientation

9. The ups and downs Ups Downs
Takes high quantity of parts and feeds them out one at a time
Can have multiple ramps to feed several different lines simultaneously
Ramps can be made to custom fit the geometry of the part to determine orientations upon line entry
Can feed parts as thin as inches at a rate of up to 24 linear feet per minute
Some parts are difficult to orient properly
Can be costly to try to tool your own
Must be accompanied by appropriate vibratory control unit that may or may not be interchangeable with other bowls
Can damage more sensitive and fragile components
Limitations on part size and geometry

10. PROBLEMS OCCURING IN VIBRATORY FEEDERS
Declining feed rate due to low amplitude. Usually this will occur gradually over a period of time. A dead spot in the bowl. Parts will not feed past a certain point in the bowl, even though they are moving elsewhere in the bowl. Intermittent operation. The feeder will spontaneously run at excessive amplitude or possibly no amplitude without apparent cause. Included in this category is for a feeder not to work at all. Noise in vibratory feeders.

11. Causes of Declining Feed Rate
Cracked spring -creates dead spots
Change in durometer -rubber feet can cure with age
Cut/slice in rubber foot -foot is part of the spring system. Must be in good working order
Loose feet -part of spring system
Coil gap -affects amplitude
Weld seam -can break on the coil when hit repeatedly by the armarture
Rust and oxidation -can negatively affect amplitude when present between springs and spacers
Operation without shell -amplitude is negatively affected when run without the shell/lid

12. Gripper:
A component of a robot that grasps an object, generally through the use of suction cups, magnets, or articulated mechanisms.

13. Types of grippers Adhesive Double Expanding Mechanical Vacuum Hook
Magnetic
Hook
Inflatable
Ladle

14. Where are they used?
Industrial robots –handling and manipulation Hard automation –assembling, micro assembling, machining and packaging NC machines –tool changers (see PML or CTB 101 on campus) Lifting tools –load carrying equipment

15. Vacuum Grippers
Simple models operating off of syringes cost $ holds 3.5 ounces for ½ hr Larger models can move entire pallets of parts. Can cost thousands, but prices are generally given out to prospective customers only, as number of fittings depends on load.

16. Where are they used?
Vacuum grippers are used in the robots for grasping the non – ferrous objects. It uses vacuum cups as the gripping device, which is also commonly known as suction cups. This type of grippers will provide good handling if the objects are smooth, flat, and clean. It has only one surface for gripping the objects. Most importantly, it is not best suitable for handling objects with holes.

19. What types are there? Ball joint Lever compensator
These help to balance the material when it has multiple levels and also absorbs some shock.

20. Things to consider for vacuum grippers
Theoretical force
Shear force
Holding force
Weight of workpiece
Work conditions
Suction area
Difference in ambient pressure and system pressure
Coefficient of friction
Workpeice material and geometry

21. Suction Force Theoretical Force: Force perpendicular to the surface
Shear Force: Force adjacent to the surface

22. Holding Force
F=∆P*A
F = Holding force (without safety factor, purely static)
∆P = Difference between ambient pressure and pressure of the system
A = Effective suction area (the effective area of a suction cup under vacuum)

23. Diameter and suction force
Horizontal
Vertical
D=1.12√(MS/PN) M = mass of the workpiece in kilograms S = safety factor P = vacuum in bar N = number of suction cups
D=1.12√(MS/PNµ) M = mass of the workpiece in kilograms S = safety factor P = vacuum in bar N = number of suction cups µ=coefficient of friction

24. Hey kids, it’s problem time
A certain line has glass, stone and plastic table tops that must be sorted into separate lines. They scratch easy so vacuum grippers must be used. The stone platters can sometimes come out a little moist. They will be lifted in a vertical direction The manufacturer wants to know how many suction cups he will have to use to be safe in all circumstances. The diameter of available vacuum grippers is 95mm or 150mm. The 95mm device costs $160 and the 150mm device costs $190. The masses are as follows Glass-40kg, stone-32kg, plastic-5kg
Workpiece surface Friction coefficient approx. μ Glass, stone, approx. 0.5 plastic (dry) Moist or oily surface Vacuum pressure is -0.4 bar Calculate all diameters in cm. Which device is the better choice financially while still achieving a factor of safety of at least 2 in all scenarios?

25. What is the limiting factor?
which table tops will require the most vacuum grippers?
When the factor is found, which will cost more?
compare pricing for both sizes

26. D=1.12√(MS/PNµ)
N = MS/(Pµ(D/1.12)^2) Evalute both at 95mm N(glass) = (40*2)/(.4*.5*(9.5/1.12)^2) = N(wet stone) = (32*2)/(.4*.1*(9.5/1.12)^2) = Wet stone table is limiting factor Evaluate wet stone at 150mm N(wet stone) = (32*2)/(.4*.1*(10.5/1.12)^2) =

27. What costs more? 95 mm: 15o mm: 23 x $160.00 = $3680.00

28. Problems with grippers
Contact with grippers can cause static electricity
Multiple contacts with sensitive surfaces can cause scratches rendering defective products
Contact on food surfaces can increase the spread of bacteria

29. Current solutions Pneumatic Non-Contact Grippers
“Uses air flow as the medium to apply a lifting force to pick up and grip a work piece, because air flow is free from magnetism and generates little heat.”

30. Disadvantages
Losses when converting electric energy to compressed air:
When air is compressed and transported it experiences “mechanical energy loss in the compressor, thermal energy loss due to heat transfers when air (is) being compressed, energy loss due to viscous friction and turbulence in the transmission and depressurization” -Kagawa
Must be taken into careful consideration whether or not implementing such a device can be justified financially

31. Robotics and Computer-Integrated Manufacturing Volume 29, Issue 1, February 2013, Pages 63–70
Development of a new noncontact gripper using swirl vanes
Xin LiCorresponding author contact information, the corresponding author
Toshiharu Kagawa
Precision and Intelligence Laboratory, Tokyo Institute of Technology, R2-14, 4259 Nagatsuta-chou, Midori-ku, Yokohama, , Japan
How to Cite or Link Using DOI

32. Swirl Vane

37. Pneumatic non-contact gripper
Energy required to produce a 0.2N lifting force:
Required air flow:
1.17×10−3 m3/s (ANR)
Compressor pressure:
200 kPa (abs.)
Air power formula:
PaQln(Ps/Pa) (Q=volume flowrate, Pa=abs atm, Ps=abs calculated positon)
At 90% efficiency the energy required to produce 0.2N lifting force is:
90 watts

38. Swirl vane non-contact gripper
At 24 Volts and 0.08A the swirl vane produces a lifting force of 0.2N using only:
2 Watts

39. Link to article for Swirl vane

40. Questions?

41. References Grippers Vacuum grippers Bowl feeders
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Vacuum grippers
Bowl feeders
Swirl vane non-contact gripper
Material handling