Weight activated mechanical knee prostheric

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Hi Everybody!
This project comes as a remix of Incept 3D's Leg prosthetic.

Disclaimer: This prosthetic leg design is an experimental prototype and is provided as-is for educational and developmental purposes only. It is not certified, approved, or tested for clinical, medical, or long-term use.

Here are main improvements of the new model compared to the original:

1. New hole sizes for Metric system heat threaded Inserts.
2. Main leg component is now a more avaliable M12 Screw and Nut.
3. Spring mechanism to lock the M12 Screw in place.
4. Many TPU parts to get around wide tolerances due to printing imperfections and to dampen the movement and provide a more comfortable experience.
5. Thicker and more robust foot.
6. Flexible foot on the fingers' level.
7. Different shaft lengths for different heights.

Single axis Weight activated linkage:

 

Description:
This mechanism is a 3D printed version of the weight activated linkage (Weight-activated knee with the brake shaft and band (Ossur® Balance OFM2, Karlsson et al., 2015), reproduced with permission from copyright 2017 by Ossur®). It implements the flexion of the part when subjected to the user’s weight to grip on the shaft and stop the knee’s rotation. The weight activation acts as a locking mechanism. It can be fitted with a tension relief spring so that the plastic deformation doesn’t become permanent

 

Advantages:

The mechanism is compact and stable as the possibility of disengaging it doesn’t occur when loading it with weight.

 

Disadvantages:

The friction coefficient between the plastic printed part and metal shaft is low around 0.4, therefore an aluminium open cylinder will be more suitable for the mechanism around 1 ([2] J. Li et al., "Tribo-Mechanical Properties of Carbon Fiber-Reinforced Cyanate Ester Composites Filled with Multifunctional Fillers," Polymers, vol. 12, no. 8, p. 1725, Jul. 2020, doi: 10.3390/polym12081725). It relies on friction therefore a significant wear and tear over time.
 

IMPORTANT NOTES:
ONLY BUY 2x70mm SHOULDER SCREWS  and 4 bearings for this model

PAUSE THE PRINT for the leg's inner shaft TO INSERT THE TPU DAMPERS AND M12 NUT

 

Bill Of Materials:

 

Important parts Images:

 

1-Shoulder screws

2- Micro Steel Deep Groove Ball Bearings 688ZZ (4PCS) - EA026

 

 

Please refer to the original Incept 3D model for the build instructions!
There are only some minor changes as the TPU parts to be glued as shown in the pictures (blue parts are out of TPU and are to be glued)
 

Build Photos: