Design and CAD

Our device meets Javier's requirements through two mechanisms.

The first mechanism is based off of a scissor lift, and allows the grabbing head to articulate forward. It's comprised of 8 links which are 3D printed out of ABS plastic. Rather than using laser cut acrylic links, these 3D printed links allowed us to tune the fit of the bearings, providing a precise press fit. The ABS plastic is also relatively light weight and stiff. Each link has 3 inexpensive RC car bearings, which provide for low friction actuation. In order to prevent the links from rubbing together, they are separated by a 1mm thick ABS spacer. The links are joined together with 5mm stainless steel pins, which were manufactured in the machine shop.

The scissor mechanism is supported by a 3D printed brace. The brace straps to the users arm and allows the scissor mechanism to open and close via a rail and slider. The scissor mechanism has a special drive link that allows the mechanism to be joined to a high torque RC servo. When the drive link is rotated the mechanism can open and close.

The controls for the device are attached via industrial Velcro at the back of the brace. The Velcro allows for the controls to be moved around and replaced if need be. The controls feature a toggle switch for each mechanism, which allows closed and open movement. An on/off switch on top stops all movement of the device. Excluding the connections to the Arduino, all of the connections are soldered for reliability.

The gripper mechanism attaches at the end of the scissor mechanism via a rail and slider, just like the base. The gripper features two 4-Bar parallelogram linkages which move the gripper claws together and apart. The linkages are joined together via two injection molded gears. One of the gears is screwed into a servo arm, which allows the servo to move the gripper claws. Like the brace, the base of the gripper mechanism is 3D printed to allow for an easy to manufacture, lightweight and strong design.