Simple Robotic Gripper




Introduction: Simple Robotic Gripper

About: Hi! I'm Aidan Leitch, a robotics, electronics, and 3D printing hobbyist.

This is a small, 3D printable, robotic gripper that works by combining soft materials with rigid materials in order to create an articulated structure that can be actuated by string connected to a servo motor. The idea was inspired by the SDM fingers found on the Soft Robotics Toolkit.


  • Ecoflex Silicone - I used Ecoflex 00-30, but I'd recommend using a more rigid one such as Ecoflex 5 or Ecoflex 00-50
  • Continuous Rotation Micro Servo
  • Nylon Thread
  • 3D printed parts
    • 1x Base.stl
    • 6x Middle.stl
    • 3x End.stl
    • 1x Mold.stl
  • Screwdriver
  • Scissors
  • Cup
  • Spoon
  • Tablespoon scooper
  • Hot glue gun with hot glue

Also, this is my entry for the 3D Printing Contest and the Move It Contest. As a maker, I feel it's important to publish my work often, so it would mean a lot if you voted for this Instructable for both contests. Thanks for taking the time to read this! This is my first instructable so I appreciate any tips or ideas!

Step 1: 3D Printed Parts

Here again are the amounts of the different parts:

  • 1x Base.stl
  • 6x Middle.stl
  • 3x End.stl
  • 1x Mold.stl

I would recommend printing all parts on .1mm layer height with decent infill. None of the parts need support.

Step 2: Mix the Silicone

Ecoflex silicone has a 1:1 ratio of parts A and B. Measure out one tablespoon of the contents of the blue bottle. Then do the same for the yellow bottle. Put both in the cup and mix it thoroughly with the spoon.

Step 3: Pour the Mold

Take the 3D printed mold and pour the mixture from the last step into this. Then let it cure for 4 hours (unless you're using Ecoflex 5, then it will be cured in ~10 minutes).

Step 4: Remove Silicone From Mold

After the correct amount of time, the silicone in the mold should have cured. Check to make sure by poking the silicone in the mold. Using your fingers, pinch the edge of the silicone pieces and pull them out. Take this slowly, but don't be afraid to use some force (the silicone is pretty tough stuff). Once you've pulled all the pieces out, you are ready to move onto the next step.

Step 5: Attach the Servo

Take the continuous rotation micro servo and position it in the printed base so the axle is positioned in the center. Then screw in the servo with the provided screws. Take out the wheel shaped attachment that came with the servo and press it onto the servo (but don't screw it in yet).

Step 6: Assemble the Fingers

Now it's time to build the fingers and attach them to the base. Start by taking one end piece and pressing one of the silicone pieces into the rectangular gap on one side of it. It is helpful to use a small, blunt object to push it in. Do not use anything sharp. Then, attach one of the middle pieces to what has been assembled thus far. Continue the process until the finger looks like the picture. Then repeat this step until you have 3 fingers. Press the ends of each of these into the parts of the base.

Step 7: Adding the Thread

Take one end of the nylon thread and feed it through the circular servo attachment and through the small holes in the base. Then continue to feed it through each segment of the finger until it reaches the end. Then glue the thread at two points: where it feeds into the servo's wheel and at the tip of the finger. Repeat this for all fingers.

Step 8: Operation

Once the previous steps have been finished, you're ready to start using your gripper! There is an included breadboard diagram for if you plan to use this with an Arduino. There is also a .ino file for controlling the gripper.



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    18 Discussions

    Wouldn't it be better to have 2 motors, arranged vertically? You would essentially attach 2 of the fingers to one motor, lined up straight, and the last one would be attached perpendicular to the other 2. While the extra motor might cost a little more money, you would have better-aligned motion (not the weird horizontal rotation that currently happens). Just a suggestion :)

    1 reply

    Not very much point to it, it probably wouldn't improve it that much. I don't know what your refering to as "weird horizontal rotation" either. The holes in which the string runs through functions as a form of a pulley, so the motion is well allinged already.

    I don't have a 3D printer, do you think there's any way I can make this? Other than that I think that this is an awesome invention

    3 replies

    Sorry for replying so late - You could mill/laser cut wooden layers to build up the parts and then drill the holes, that's the best alternative I can think of.

    Thank you! I'm going to try that method and hope for the best. also your reply wasn't that late. Thanks again!

    This is so genius! V2 should be one where you don't need the silecone (that's the only thing I dont have : ) )

    1 reply

    Unfortunately the silicone is necessary, it's not something that can simply be left out.

    It can lift a fair amount, the issue lies in keeping a hold on it. I think I'll be making some "finger tips" made of rubber for it. Thank you for voting!

    Nice, will you add that to the steps? Also i think of making this, but i don't have a 3d printer. So i will have to be creatice to make this

    Once it is done, I will add it in. I'd love to see the results of making this without 3D printing! I can't wait to see the outcome