The shank frame of the U-Build Bionic Knee resembles the lower leg. It connects with the thigh frame to form the knee joint and to a prosthetic foot and ankle complex. The shank frame is constructed out of durable plastic because it must support the weight of the user and withstand impulse loads at heel strike. The Shank frame also holds the motor assembly, sensors, and other electronics. This section will outline the process of printing and assembling the shank frame.
Step 0: Preview design files and print the shank frame
Please review the design and print files for the shank frame here. The shank frame can be printed with PLA material. We recommend printing with a 0.8 mm print nozzle and 0.4 mm layer height to decrease print time. The printer should be programmed to use 4 layer thick walls, ceilings, and floors and print at 50% or higher infill density. The parts should be printed horizontally such that each layer runs the length of the shank frame (see example to right). In contrast, the transmission spacers should be printed vertically.
Step 1: Prepare Shank Frame
This step outlines the process of removing support material from the shank frame. To complete this step, you will need one printed thigh frame, safety glasses, and puncture/slice resistant gloves. Tools like pliers and picks can be helpful for removing stubborn pieces of support material.
Step 2: Add Bearings and Nuts to Shank Frame
This step outlines the process of pressing the bearings and nuts into the shank frame. The larger 1.5" OD bearings form the knee joint with the thigh frame. The smaller 0.875" OD bearings support a transmission shaft. To complete this step, you will need one printed and cleaned thigh frame, two 1.5" bearings, two 0.875" bearings, and six M4 square nuts, and four M6 square nuts. You can use a hammer, clamp, or press to push the bearings and nuts into place. You may need a 10 cm (4 inch) rigid rod (i.e. extra portion of hexagonal shaft) to help transfer power from the press to the bearing (or nut).