DIY Guide: How to Make a 3D Printed Prosthetic Arm

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Written By Charlie Humphreys

Charlie Humphreys is a respected expert in the field of 3D-printed prosthetics. With a background in biomedical engineering and extensive experience in 3D design and printing technologies, Charlie has dedicated his career to developing innovative prosthetic solutions that are both accessible and affordable.

Creating a 3D printed prosthetic arm is an innovative and cost-effective way to provide functional prosthetics to individuals in need. By following a step-by-step process and utilizing 3D printing technology, anyone can create a customized prosthetic arm. This DIY guide will walk you through the required parts and tools, the printing process, and the necessary modifications to the servos. Start crafting your own functional prosthetic arm today.

Step 1: Required Parts and Tools

To create a 3D printed prosthetic arm, you will need a list of specific parts and tools. These include:

Parts Tools
3D filament in various colors 3D printer
SG90 servos Soldering iron
Fishing line Wire cutters
Elastic cord Tweezers
Springs Heat shrink tube
Arduino Uno Scissors
Battery Pliers
Allen wrench set

These components will be used throughout the construction process to ensure a functional and durable prosthetic arm. Having the necessary parts and tools ready ensures a smooth and efficient assembly.

Step 2: Printing

The next step in creating a 3D printed prosthetic arm is the printing process. To begin, you will need to download the Fusion 360 files for the hand and forearm. These files can then be exported as .stl files and imported into your preferred 3D printing software.

When selecting the printing material, it is recommended to use either PLA or ABS plastic, as they are widely available and offer good durability. PLA is a biodegradable and easy-to-print material, whereas ABS is known for its strength and impact resistance.

Before initiating the printing process, it is important to consider the support structure and layer height. The hand should be printed with support structure to ensure the intricate design is properly formed. This support structure can be easily removed after printing. Additionally, determining the suitable layer height is crucial for achieving the desired level of detail and resolution. A lower layer height will result in a smoother and more detailed finish, while a higher layer height will provide a faster print but with decreased resolution.

Lastly, it is worth noting that white plastic may show dirt more easily than other colors. Depending on your preference and needs, you can opt for colored filaments to enhance the aesthetics or choose a surface treatment such as painting or coating to protect the final product.

Material Advantages Disadvantages
PLA – Biodegradable
– Easy to print
– Wide range of colors
– Lower heat resistance
– Prone to warping
ABS – High strength
– Impact resistance
– Good heat resistance
– Requires a heated bed for printing
– Releases fumes during printing

Step 3: Hacking the Servos (part 1): Continuous Rotation Servo

Modifying the servos is an essential step in creating a fully functional 3D printed prosthetic arm. By hacking the servos to enable continuous rotation, you can achieve the desired range of motion for the fingers. This modification allows the fingers to contract and release properly, ensuring optimal functionality.

Continuous Rotation Servo Modification Process

  1. Start by identifying the continuous rotation servos in your prosthetic arm assembly.
  2. Using a pair of pliers or wire cutters, carefully cut off the plastic stopper on the top gear of the servo.
  3. With a small drill, create a hole through the top gear to allow for free rotation.
  4. Clean any excess plastic debris from the servo gears to ensure smooth movement.

This modification converts the servo into a fully rotational motor, allowing the fingers to move in a continuous motion. The hacked servos will be responsible for providing the necessary movement for finger flexion and extension.

Testing the Continuous Rotation Servos

After modifying the servos, it is crucial to test their continuous rotation to ensure proper functionality. To do this, utilize the provided test code specifically designed for continuous rotation servos. This code will allow you to check if the modified servos rotate in the desired direction and speed.

Test Code Description
void setup() {
servo.write(90); // Set servo to neutral position

void loop() {
servo.write(0); // Rotate servo counterclockwise
delay(1000); // Wait for 1 second
servo.write(180); // Rotate servo clockwise
delay(1000); // Wait for 1 second

A simple test code that rotates the modified continuous rotation servo counterclockwise and then clockwise, with a 1-second delay between movements.

Ensure that the test code is uploaded to your Arduino Uno and that the modified servos respond appropriately to the commands. This step confirms that the continuous rotation servos are in proper working condition and ready for integration into the prosthetic arm structure.

Step 4: Hacking the Servos (part 2): 2-in-1 Compact DC Motors

Creating a compact and functional design for the 3D printed prosthetic arm requires modifying the servos to fit within the limited space of the hand. This step involves a series of modifications that allow for a more streamlined and realistic design.

Adapting the Servos

To begin, the potentiometer and chip of the servos need to be removed. This can be done by carefully cutting off the potentiometer and chip from the servo using a soldering iron. Take care to avoid damaging the motor during this process.

Once the potentiometer and chip have been removed, you will need to reassemble the servo case with the modified parts. Ensure that all components are securely fastened together to maintain stability.

Soldering Extension Wires

In order to properly fit the modified servos into the hand, extension wires need to be soldered to the motor. This will allow for greater flexibility in placing the motor within the limited space of the hand.

Using a soldering iron, carefully solder the extension wires to the motor terminals. Take care to ensure a secure connection and minimize any risk of loose wiring.

Gluing the Servos

Once the servos have been modified and wired, they can be glued together using epoxy glue. This glue provides a strong and durable bond, ensuring that the servos remain securely in place within the hand.

Apply the epoxy glue to the necessary areas of the modified servos, following the manufacturer’s instructions for proper application. Allow the glue to fully cure before proceeding to the next step.

Motor Testing

To ensure the functionality of the modified servos, thorough testing is essential.

Connect the modified servos to a power source and run a series of tests to ensure they operate smoothly and efficiently. This testing phase will identify any potential issues or areas for improvement before final assembly.

Testing Criteria Expected Outcome Result
Motor speed Smooth and consistent rotation
Motor torque Ability to move fingers and grip objects
Noise level Quiet operation

Step 5: Hacking the Servos (part 3): the Remaining Servos

Not all the servos in the 3D printed prosthetic arm require modification. Some servos, such as the thumb rotation and the wrist motion servos, can be used as is. These servos provide the necessary movement for the thumb and the up/down and left/right motion of the wrist.

Thumb Rotation Servo

The thumb rotation servo allows for the movement of the thumb, enabling grasping and gripping actions. It comes pre-programmed to provide the desired rotation range. No modifications are necessary for this servo, making it a simple and convenient component of the prosthetic arm.

Wrist Motion Servo

The wrist motion servo controls the up/down and left/right motion of the wrist, adding flexibility and movement to the prosthetic arm. Like the thumb rotation servo, it doesn’t require any modifications and can be used as is. However, it is important to note that the SG90 servos may have insufficient torque for the wrist rotation. In later versions of the arm, more powerful servos can be used as alternatives to ensure smooth and reliable wrist motion.

Servo Modification Required
Thumb Rotation Servo No
Wrist Motion Servo No

Step 6: Assemble the Fingers and Step 7: Build the Hand

Now that all the necessary modifications have been made, it’s time to assemble the fingers of the 3D printed prosthetic arm. Begin by gluing the individual segments of each finger together. Ensure a secure bond between the segments for a sturdy construction.

Once the fingers are assembled, thread elastic and fishing line through the appropriate holes to create the mechanism that will allow the fingers to flex and extend. This will provide the necessary movement and functionality for the prosthetic hand.

Step 7: Build the Hand

With the fingers in place, it’s time to build the hand of the 3D printed prosthetic arm. Attach the fingers to the 3D printed palm using a strong adhesive for a reliable connection. Make sure the fingers are positioned correctly for optimal grip and dexterity.

Next, wire the potentiometers through the palm according to the provided instructions. This wiring will enable the control of the finger movement, allowing for precise and coordinated actions.

Finally, equip the modified servos with pulleys and attach them to the hand as directed. Proper motor attachment is crucial for the seamless operation of the prosthetic arm. Once the hand is fully assembled, it’s important to thoroughly test it to ensure proper functionality and make any necessary adjustments.