Our stamp mechanism is made up of a 4-bar mechanism and two 5-bar mechanisms starting with the 4-bar as the input followed by the 5 bars.
The 4-bar is driven by a two gear system powered by a motor to create circular, 360॰ motion from the input link. We used the two gear system in a 2:1 gear reduction to maximize our torque output for the mechanism, and this 4-bar drives the motion throughout the rest of the mechanism.
Our design considerations for this stamping-inking mechanism are as follows:
- Minimal friction
- Minimal non-planar motion
- Compact assembly
- Minimal use of adhesives
- No play in the joints
We wanted to minimize the friction present in the mechanism in order to maximize the efficiency of the mechanism itself, reducing the amount of power the motor would need to operate at the same angular velocity. Minimizing non-planar motion was also critical, as any linkages bending or sliding in the vertical plane could compromise the entire motion of the system. A compact assembly would allow us to easily transport the mechanism around and allow for a more structurally robust system. We aimed to make this mechanism as modular as possible, so we avoided using adhesives in favor of M3 fasteners anywhere we could. Finally, we felt that minimizing the play in each of the joints was also critical in allowing us to achieve the full desired range of motion from our mechanism.
For the assembly of the design, we used quarter inch acrylic to reduce any bending of the links during motion. We attached the links together using press-fit flanged bearings and 6mm steel shafts to allow for smooth rotations, and we 3D-printed clamps control the planar motion between the links. The gears were laser cut from wood and mounted using 3D printed parts as well. We wanted to keep the electronic component simple for users, so we only used one DC motor to drive the entire mechanism and we programmed the motor to run at a constant angular velocity at all times.