Fabrication
The following sections include instructions for fabrication for both gripper designs. The step-by-step instructions are provided on the subsequent pages.
Electronic Gripper:
A detailed Bill of Materials is included in the Downloads page listing specific part numbers, quantity, suppliers and cost. Please note: some materials can be substituted for cheaper or more widely available version at your own discretion. Some of the materials are also called for in the SDM finger activity and can be reused used for this activity.
The Downloads link below also includes templates to build the angled cardboard stands for the fingers and the code file that will be uploaded to the Arduino microcontroller to control the circuit.
Manual Gripper:
This version of the gripper is also significantly cheaper per unit than the electronic gripper requiring only household materials such as a hollow tube (cardboard or plastic), crafts string and zip-ties.
The Bill of Materials for this version of the gripper is also located within the Downloads page.
Bill of Materials
This section will give a list of items that are used in this project with selected links to suppliers. You can download a more detailed Bill of Materials sheet here.
Note: Many of the items listed are just examples and you can use your own discretion to substitute parts which are easier or cheaper to obtain.
Materials for Electronic Gripper
Electronics
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Other Materials
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Materials for Manual Gripper
Required Materials
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 | bom_gripper_for_sdm_fingers.xlsx | 1.55 MB |
Electronic Gripper
Gather the materials labeled for the electronic gripper from the Bill of Materials page and a downloadable file located in the Downloads tab. Fabrication the electronic gripper involves the following steps:
1. Making repositionable cardboard bases for each finger (below)
2. Connecting motor and pulley to the fingers
3. Attaching electronic components to the pegboard
4. Placing and connecting fingers to integrate the mechanical and electronics
Step 1: Making repositionable cardboard bases for each finger
Print the 'FingerBaseTemplate.pdf' on letter size paper and using the paste glue, adhere the paper to cardboard.
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Students have the option of choosing one of two varying angles for the finger base. Once this is chosen, cut out the corresponding template using scissors or a craft knife. The holes within the template can be hole punched using the punch purchased for the SDM finger activity.
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Note: If the provided templates do not have the angle that is required for a specific design, these can be customized to increase or decrease the angles of the base.
Cut the cardboard according to the template using craft knife.
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Fold the card board into a triangle as shown with the tabs folding out and down from the sides, as shown to make a prism. Apply glue from a gun liberally to make the base firm. Be careful not to hot glue the base to the surface you are gluing on.
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Insert one of the SDM fingers as shown within the base. Secure the finger through the punched holes using two zip ties. Place a screw through the bottom of the base sticking outward to allow for attachment from the bases to the pegboard.
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Once the bases are attached the finger is now ready to be placed anywhere on the pegboard with the help of the screw at the bottom. This process can be repeated for as many fingers as students would like to test.
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Connecting motor and pulley to the fingers
Step 2: Connecting motor and pulley
Cut about 2 feet of string to thread into the pulley. Loop around the pulley once and tie a knot that will allow the string to be secured to the internal channel of the pulley.
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Lace one end of the thread through the two adjacent holes in the pulley and tie a knot there as shown. This will prevent thread from slipping around the center channel of the pulley and ensure that the pulley winds as it pulls. Double knot is necessary.
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Connect the pulley on the mounting hub using the screws and nuts provided with the motor and pulley.
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Attach the aluminum bracket, the motor and the mounting hub using the screws provided. Your motor is ready to be attached to the gripper board.
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Attaching electronic components to the pegboard
Step 3: Attaching electronic components on board
Cut the pegboard to the recommended size 12x12 inches using a craft knife or similar. This may need to be cut before beginning the activity to reduce time to complete. Attach one of each of the spacers to all four corners of the pegboard.
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Using an eye hook, divide the board into roughly two halves. On one side, the electronics and the motor will be placed and on the other side, there will be space to place the fingers in various configurations.
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Using two of the M2 screws provided, fix the motor to the peg board so that the pulley is aligned with the eye nut. This will create a routing point for the string to make sure that it correctly routes to the pulley.
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Gather the battery, motor, Arduino and breadboard together. Using your jumper cables, resistors and push buttons create the following circuit.
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To upload the code that programs the microcontroller, connect your Arduino to a computer. Open 'Master.ino' file in Arduino IDE. Upload 'Master.ino' to your board.
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When upload is complete the entire circuit can be disconnected from the computer and adhere to the pegboard as shown using double sided tape.
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Placing and connecting fingers to integrate the mechanical and electronics
Step 4: Placing and connecting fingers
Using the screws on the finger bases, attach the finger using the pegboard. The fingers can be placed anywhere on the board. Using a nut on the underside of the pegboard to adhere the screw, fasten the finger and base tightly into place. Insert eye screws within the finger configuration to channel the string back to the motor pulley.
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When adding another finger do the same for the base screw and eye screw, making sure to secure both with nuts on the underside of the pegboard. Tie the threads of all fingers to the thread coming from pulley, making sure to keep this connection tight.
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Manual Gripper
The following materials are the only supplies needed to create the manual gripper:
- A hollow tube (cardboard or plastic)
- Crafts string
- and zip ties (2)
- Download the detailed bill of material here.
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To create different grippers to test, the following variables can be altered:
- Number of fingers
- Orientation of fingers towards each other
- Distance between the fingers (depending on availability of tubes of different diameter)
To assemble, place the laced fingers on either side of the hollow tube as shown, if using three or more fingers, you may need to pretension the zip ties before wiggling in a third and fourth finger inside the zip ties. Situate the fingers so that the natural position of the fingers is slightly angled outward, by pulling the bottom of the finger down slightly until the last segment intersects with the handle, as shown. Using the two cable ties to secure the fingers, pull taught and cut the excess zip ties.
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Your gripper is ready!
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