Let's Make Robots!

Precise gripper

holds objects

I equipped my robot with gripper for moving the objests. Based on questions I will try to explain the construction and operation.

This gripper is intended to hold and move objects from one place to another. For this purpose it is enough to lift the object several milimeters from the floor. This simplifies the construction.

Maximum width of the object is 60mm at fully open jaws. Jaws are parallel at any position. It is done using 2 pairs of arms. The distance between arms in pair is 4 mm which allows to move them by 45° .  Servo is connected using screwing sticks and ball joints. It is possible to use only 90° of the servo movement.

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 On the internal side of jaws there is thin neoprene to hold objects safely without excessive force.

 

Bottom view. 

IMG_5776.jpg

Both parts are attached to aluminium plate. This plate is mointed to robot chasis on two plastic hinges (black pieces. Up/down motion is driven by microservo without fix connection to the plate. Servojust pulls the plate forward and this lifts the tips of jaws 1 cm up. Down it goes by gravity when the servo turns away.

 

The material used for all parts is aluminium. This you can cut and drill using simple tools even on kitchen table. Pieces are glued with metalic epoxy and screwed.

It is possible to use different materials and profiles.

I used squared 10x10 mm profiles and 12x10 U-shape profiles

I took advantage of these specific shapes. square profile fits inside the U profile which makes the construction robust.

 

.... will be ammended based on questions

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Maybe I can do something similar for my robotic arm. Which reminds me, I know my local hobby shop has most of the metal type material, but where do you guys get these nice screws, hobby shop screws are like five bucks for four screws in a little bag. Home improvement stores don't seem to have the really small screws.

Can anyone clue me in on a place to get good screws, bolts, nuts, and all the other neat little parts he has on here like the bars that attach the servo to the gripper?

I buy my metric nuts and bolts from ebay.

Very nice example of fine mechanical engineering!

 I really like it! Great job dude!
could you make some sort of file, drawing, cad thing, anything I could print out and use to mark aluminum? As a WT, it may be helpful, although this is spectacular of its own accord. Just what I needed!

Hi Benbo,

 

I do not have any drawing. Everithing was done using try/error method. I can help you when you get stuck at some point.

For the beginning some tips:

 

  • Expect to do everything at least twice (buy enough material)
  • Drill the holes 1mm wider than is bolts diameter  (otherwise it will not move)
  • Glued parts must be also screwed together - epoxy does not like vibrations
  • Make two complete jaws before fixing it to common plate - then decide how far away they should be (it is not needet to hold objects 1 mm wide)
  • servo joints must be 3D movable - ball joints are recommended

Feel free to ask for any details. I can make more detailed pictures if you wish.

 

Richard

Nice and clear explications! Thank you!

Maybe you could add some sort of pressure sensor in the internal side of the jaws, to have  a return on the force applied to the object...

Hi dnl82,

 

I already ordered pressure sensor, It is on its way to my home.

 

I do not know where to place it.

Jaws are parallel. Sqeezing force is limited.

 

Where to place them?    Tip, middle, back ?

 

I will inform you about the results.