7.2 Design Process

Iteration Documentation

Our team initially wanted to use a quick return slider mechanism but was advised against that because prismatic joints are hard to get working in real mechanisms. Instead, we decided to use a Peaucellier-Lipkin linkage to help achieve the up-and-down shaking motion. The initial design was made in motion gen to get a feel for how the links would interact. Then the CAD model was made to map out link lengths that we wanted to use. Then we created a prototype out of popsicle sticks to get a real-life view of the motion before moving on to our final prototype. 

After multiple prototypes, our team discussed how to create the angle change in the shaking motion. Initially, we thought of laying the linkage flat and adding something underneath to lift the entire plate up and down. Ultimately we decided to turn the linkage so that the shaker would sit horizontally above the ground and add a cam below the plate to help change the angle of the linear motion. We created a stand that would allow the linkage plate to stand upright and allow for space to hold the cam underneath the plate. We also designed a simple shaker holder that features a shelf to keep the shaker level.

Initial Design

Below is a Peaucellier-Lipkin linkage which can transform rotational motion into a perfectly linear motion and the CAD model with final dimensions.

Rough Prototype

We made our rough prototype using popsicle sticks, screws, and nuts. We mounted it by holding the grounded joints to a table with clamps. We did not incorporate the crank in this iteration, and therefore ran it backward by actuating the output joint. 

The path of motion of the output joint was a straight line, which is what we wanted, meaning we could move on to the next iteration.

Physical Prototype

Our final prototype we made out of laser-cut wood, screws, and nuts. We scaled it down to save resources. This prototype allows for a full rotation of the crank and follows a straight path at the output joint. 

There was some slight sticking in this prototype and this was due to screw heads and nuts needing a lot of extra space. The final system will be smoother because we will use axles and bearings.

Linkage Plate Design

We designed the plate to have bearing connection points to help decrease the friction between the shaker holder and the linkage plate. This will make the linear motion of the shaker run smoother. 

Shaker Holder Design

For this mechanism, we chose to go with a plastic toy cocktail shaker because it was smaller and lighter. We also decided to use a press fit to decrease 3D printing material and time. In the second design, we thickened the arms to increase the structural integrity.

Initial Design	Second Design

Second Design

Our second iteration of the mechanism has a crank or cam mechanism to rotate the entire linkage plate. A pivot point is needed on the edge of the linkage plate to rotate about. This is how we incorporated an angle change.

Stand Design

The stand design features two plates connected through a shaft which is the pivot point of the plate. The linkage motor is attached directly to the linkage plate to help add weight and keep the plate in contact with the cam. The cam motor is then mounted to the back plate of the base.

Cam Design

Our team decided on a cam to move the linkage plate. Initially, we had a 14 cm diameter (~5.5 in) with a groove that would keep the bearing in line with the Cam and prevent misalignment. The cam was 3D printed and we found that it was too big, so we decided to create a 1.25 in diameter Cam that was laser cut due to time constraints. 

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