Design Process Group 14

The major goal of our design would be to design an infinitely looping machine where 2 cups would pour their contents back and forth.  In order to accomplish this, we needed to design a mechanism with a specific position profile throughout the motion, as well as an angular profile.  We began to brainstorm this problem with rough sketches and plots of these profiles as we predicted them to be. 

Once we had a well-documented goal for this project, we began to visualize the mechanism.  From a brief literature review, it was apparent that the desired motion would be possible with a 4-bar mechanism, and we began to experiment with different link lengths and orientations.

Using Solidworks and kinematic analysis in MATLAB, we were quickly able to determine the necessary link lengths and assembly conditions that would provide the desired motion.  This was first done within a sketch to ensure that our concept would be geometrically feasible. 

Finally, we began a rudimentary CAD design of a prototype so that we could further visualize the motion of the links.  At this point, it was apparent that links would be crossing, and we needed to ensure appropriate clearances.

Once we were confident that this design would accomplish the desired motion, we made a prototype of the essential mechanisms.  This included one 4-bar and all joints within.

From the prototyping phase, we determined that additional structural rigidity was necessary for the lower links.  This drove us to create another identical link that would be placed behind the backplate and add depth to the lifting structure.  The final CAD design is shown in the following animation.

For aesthetic purposes, the links were laser cut out of clear ¼” acrylic.  The thick acrylic was chosen to help reduce any flexing due to its relatively long length.  The middle link was cut with a slot for a t-connector in it.  This allowed us to quickly attach a variety of 3D-printed cups into the link for interaction and quick prototyping.  The back and base plate were also ¼” for strength; however, these pieces were laser cut out of plywood to reduce costs. 

Due to the symmetrical nature of our twin 4-bar mechanisms, it was clear to see that both mechanisms could be driven by a single motor with a simple gear assembly so that they would rotate in the same direction.  We decided to use the dc-motor that was provided due to simplicity.  We quickly realized that we would need to consider torque, as the links were creating long lever arms that were difficult to raise.  After a few iterations, a final gear ratio of 4.75 was established.  In order to more securely mount the motor drive gear to the motor shaft, a part was 3D printed that allowed us to secure the gear to the shaft with a set screw.