Kayla Lynne Wolfe

04/29/2021

CARTESIAN MOTION SYSTEM

Teammates

Will Armstrong, Edward Luka, Gabrielle Chan, ShuLan

Goal

“The goal of the assignment is to apply the concepts and methods that we have reviewed in class to the design of a complete 2.5-axis motion system. Your primary task is to design and build the mechanical sub-system.”

Constraints

• The working envelope of the end effector is 2.5 x 2.5 x 2.5

• Materials provided include: 8020 aluminum extrusion, two stepper motors, and the required belts and pulley for 2 linear stages.

• All other required parts will be 3D printed or laser cut according to the design

• All teams will submit a complete simulation model

Initial Design

During our first group meeting we started by deciding how we would extrude the frosting with the end effector. We came up with two initial designs. First, the end effector would work by pushing an archimedes screw down to extrude the frosting. After discussing the challenges of the 3D printed archimedes screw we decided that the best approach would be to use a predetermined syringe attached to a lead screw that would push the plunger down to extrude the frosting onto the cupcake. Below are initial design sketches showing our end effector concepts as well as our first idea of how we would use pulleys to move in the x and y direction.

Concept Sketches by Will Armstrong

Design Process

During our continued design iteration, we decided as a team to use an H-bot pulley system instead of separate pulleys to move each motor. In this new version of our pulley system each motor will need to be turned in the same or opposite direction in order to move in the x and y directions. Below is our initial motion study showing how our belt will be used to move the stepper motors.

Motion Simulation Model

Below is the final simulation model of our design. As you can see in this motion study the belt is moved using two stepper motors, while the end effector is powered by a stepper motor that pushes down on a lead screw that extrudes the frosting to output text. We went through many design iterations to get each piece connected to the belt to allow the belt to be all on one plane so that the motion moves smoothly.

Final Design and Next Steps

Our final prototype used a program of G-code to extrude the frosting in the shape of an “o.” It was very clear during the coding process, that unlike some robots, our designs code really depended on the mechanical system. For example, it was very difficult to get the G-code to move the motors at the right speed in order to get the frosting to extrude at an even rate as the x and y motions moved in the shape of an “o.”

If we were able to redo this project and make certain changes it would be key to consider the type of frosting we would use from the beginning of the project. The challenges of using frosting as an extrusion substance is the amount of pressure required in order to extrude the frosting is highly dependent on the viscosity of the frosting. For example, when testing our motion system we tried two different types of frosting. The first frosting was extremely liquid and would puddle, making it hard to see the letter or number we had printed. The second type of frosting was too thick for the end effector to handle. Due to the pressure, one of our parts on the end effector ended up snapping because the stepper motor could not handle the pressure that the frosting was causing.

During discussions post presentation, Will and I discussed possible solutions to this issue. As the frosting easily hardens and clumps together causing blockage and increased pressure for the end effector, it becomes difficult to expect a consistent result for the output of our motion system. One way we think this issue could be resolved is by including a heater in the end effector to keep the frosting at room temperature and ensure it is liquid enough to extrude through the plunger.