5.2 Design Process

Mechanism Design

In our quest to mimic the motion of the arm of someone dealing a playing card, we went through multiple design iterations for the linkage mechanism. We were determined to find linkage mechanism that demonstrated curling and uncurling motion of the arm and a final flick that launches the playing card.  

Curling Finger Motion

For this mechanism, we liked the motion that it produced, however, to make a feasible design, we had to reduce the number of linkages. 

(Click for animation)

Flicking Motion

This mechanism was able to create more of the flicking motion that we wanted, however, it didn't produce as much velocity as we desired. 

(Click for animation)

Final Iteration

This final iteration combined the elements of our starting two iterations into a final mechanism that we liked. This final mechanism has enough torque at the end that it can project the playing card and has the correct curling motion to mimic a person's arm. 

(Click for animation)

Physical Prototype

For the physical prototype, we translated the final iteration of the mechanism design into a linkage system made up of laser cut wood and M5 nuts and bolts. 

First Prototype

Our first prototype ended up being unsuccessful. We discovered we did not have the correct linkage lengths needed to connect our mechanism together. We also needed the mechanism to be larger, so we could see the linkages moving more clearly as there was too much overlap with this smaller prototype.

Prototype

For our prototype, we ensured that we had the correct link lengths and scaled the links lengths up by two. This allowed us to clearly see the motion of all the links and smoothly show the mechanism.

Final Prototype

When attempting to make our final design, we initially lasercut our linkage system out of 1/4" acrylic and used a lower torque rated NEMA 17 stepper motor. We soon discovered that our motor was unable to drive our mechanism due to our motor not having enough torque as well as our linkage mechanism being too heavy. Knowing this was the reason our mechanism wasn't moving, we decreased the weight of our linkages by using 1/8" acrylic instead, and using a higher torque rated NEMA 17 stepper motor. 

Final Design

By reducing the weight of our acrylic linkages by cutting down its thickness by half and using a higher torque rated motor, our mechanism drove accordingly. We also opted instead of using sticky tack to hold the card to design a small part instead. This part was toleranced accordingly, so that it had enough friction to hold the card, but was smooth enough that given enough velocity the card would flick out of the mechanism. The other side was toleranced, so that it would pressfit into the link it was attached to.

Final Bill of Materials