To achieve our design goals, there were a number of design considerations we needed to make. First, we made prototypes of both mechanisms to figure out what the optimal materials and fabrication methods would be. Through this process, we decided to laser cut links and supporting structure out of acrylic, and 3D print connecting shafts, smaller supports materials, and pieces that needed to have a complex geometry. Our idea for the final design was to build an elevated platform that would have two four-bar Chebyshev Lambda mechanisms on either side, each attached to an input shaft that runs underneath the platform and connects to our 360-degree servo motor. Attached to the motor shaft, a set of Bevel Gears was chosen to translate the input motion of the motor and cutting mechanism to the Geneva drive which rotates the platform.
To achieve our design goals, there were a number of design considerations we needed to make. First, we made prototypes of both mechanisms to figure out what the optimal materials and fabrication methods would be. These prototype mechanisms are demonstrated in the videos below.
View file name prototype lambda.mp4 height 250 View file name prototype geneva.mp4 height 250
Through this process, we decided to laser cut links and supporting structure out of acrylic, and 3D print connecting shafts, smaller support materials, gears, and other 3-dimensional pieces. Another factor that influenced our design was the size of pizza we wanted to be able to cut. Due to material, assembly, and time considerations, we decided to design our robot to be able to slice a 6-inch diameter pizza. This parameter dictated the dimensions of all our mechanism components, shafts, and housing. We were able to determine this dimension through our kinematic analysis, by . By setting the distance between the grounds flat part of our four-bar mechanism to achieve a straight line output motion of six inchesto 6 inches, we worked backwards to determine the necessary link lengths. From there, a housing structure could be designed such that the four-bar mechanisms could be grounded at the right dimension, and that the cutting stroke was lined up over the center of the upper was designed to act as the ground link for both lambda mechanisms and support the rotating pizza platform. The size of the Geneva drive components were determined by the distance between the vertical shaft attached to the platform and the motor input shaft, which correlates to the center to center distance between the Geneva wheel and the Geneva crank. With these dimensions set, we were able to begin building created a CAD model of our final design.
We also created animations of the mechanisms in motion:
View file name Assem1.mp4 height 250 View file name Geneva Animation.mp4 height 250