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Our team has chosen to continue with the open 4-bar design as the position profile is closely matching the continuous motion we described at the beginning. Not only is the path very similar, the distance that the end effector needs to travel when in contact with the can is more easily controlled with the open 4-bar. Furthermore, the velocity and resulting mechanical advantage from the best open 4-bar configuration provides a desirable location to apply a high force to the tab. Following this kinematic analysis is documentation of the prototype iterations we have created.
Iterative Documentation
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 repetitive use.
Figure 18: 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 will most likely use wood and rods to have more structural stability and support when developing the entire mechanism. We found that the motion is not as smooth as we desired and future iterations will have rods and bearings.
Figure 19: Laser cur prototype of our open 4-bar mechanism.
Final Prototype
The final 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 20: Moving prototype of our open 4-bar mechanism.
Bill of Materials
Our bill of materials are given within this spreadsheet . We expect to collect all the parts by 4/15.
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