Iterative Documentation
The goal of the first three protypes was to figure out how to configure our links to achieve out calculated motion profile. The following prototypes test our development of the end effector link in accomplishing our goal to open the tab of the can.
Prototype 0: MotionGen
When starting this project, our team had two ideas that could answer the problem of opening a tab of a can. Our first idea was to simplify a Janson walking linkage to am open four-bar linkage mechanism that can replicate a horizontal motion at the bottom of the loop and immediately transitions into a lifting motion.
Figure 1: Open Four-Bar Mechanism
Our next idea was to develop a crossed four-bar linkage configuration that was found to mimic the curved motion of a human finger. A patent that highlighted this mechanism and the respective motion for a finger is linked here. We based our model off of this patent and developed a curved pattern that is similar to a curved motion of a finger.
Figure 2: Finger Mechanism Patent Figure 2: Crossed Four-Bar Mechanism
After our kinematic analysis, we found that the open four-bar linkage mechanism reproduces the motion and force output that was what desired to complete the project.
Prototype 1: Cardboard
When starting our prototype, we began creating the mechanism with cardboard to map out the movement with physical pieces. We measured the the link lengths to approximately the desired lengths that were defined in Motion Gen. The goal for this prototype is to observe and understand the motion of the mechanism using physical components. However, cardboard is very flimsy and susceptible to breaking down after rep
Figure 1: Cardboard prototype of the open 4-bar mechanism
Prototype 2: Laser cut
For this prototype, we tried recreating the same prototype with the desired link lengths using laser cut wood and rods. We found that the motion is not as smooth as we desired and future iterations will have rods and bearings.
Figure 2: Laser cur prototype of our open 4-bar mechanism.
Prototype 2.1: Laser cut and Manual Motion
This prototype is similar to the previous in that we laser cut linkages; however, we replaced the rods with M6 screws and mounted it to a board to produce smooth motion. In the gif below you can see that the position profile of the end-effector models the position profile we determined in our kinematic analysis.
Figure 3: Moving laser cut prototype of our open 4-bar mechanism.
Prototype 3: Acrylic and Automation
After iterating through laser cut prototypes, we were confident in our open 4 bar mechanism's ability to achieve our desired position profile. We decided to switch to acrylic links because of the added strength and stiffness that we needed to hold our end effector so that it could open the tab of a can. In addition, the automation aspect of mechanism must be added using a 12V DC motor to create the desired cyclical pattern.
Figure 4: Acrylic automated prototype of our open 4-bar mechanism.
Prototype 3.1: End Effector
We also iterated through the potential end effectors that we could use to lift the tab of the can. We first thought of ______
End-Effector
Prototype #1
Figures 3 & 4:
Prototype #2
Figure 5:
Prototype #3
Figure 6:
Prototype 4: Final Iteration
With the previous iteration,
we found that the torque output from motor does not supply enough force to open the can. Additionally, we currently don't have linkage system at the correct height to reach the top of the can.
We addressed the torque issue by created a 49:1 gear systems from the motor shaft to the rotating link to overcome the lack of torque output. Because of the size of the gears, we elevated the system using two acrylic sheets, which addressed the height problem we were also having
[Insert Picture of the Final Iteration]