5. Lessons Learned

Lessons Learned

1. Tolerances: Dealing with the tolerances of the 3D printers and laser cutters proved to be a considerable challenge, requiring extensive trial and error to create parts that fit our bearings and links as they did in the CAD. Through trial and error, we gained familiarity with the tolerances associated with various manufacturing methods such as laser cutting and 3D printing.  

2. Material selection: Material selection played a pivotal role in the prototyping phase. Laser-cut plywood and 3D-printed PLA/PETG proved beneficial for their adaptability to filing and drilling. We gravitated towards these because of their availability and versatility. However, issues arose as the project progressed. The wood introduced friction and also deteriorated, prompting the realization that better materials, such as smoother acrylic gears and metal shafts, could have enhanced the overall performance of later prototypes. We also learned that our ordered aluminum shafts were much softer than steel shaft, which caused our aluminum shafts to chip and the material to shave off as we tried to fit our bearings onto our shaft. In the end, we had to use steel shafts to avoid this damage to the shafts from the bearing fit.

3. Detriment of cantilevered shafts: Even though these shafts didn’t necessarily contribute to the mechanism’s functionality, they affected the project’s rigidity. If there is not adequate support, then the mechanism will not execute its goal properly.  

4. Accounting for material interaction: When the mechanism was designed in SolidWorks it was flush and perfect. However, when we made the components, we realized that there was friction we didn’t account for and spacing conflicts that made the mechanism collide with itself. If we had known about this, earlier we would’ve incorporated small shims into the linkage stack as well as spacers. 

5. Strain relief: The importance of strain relief became evident as wires consistently detached from the motor, leaving the team without a means of reattachment when TIW was closed. We had to resolder our wires to our motor 6 times before demonstration day due to this.

6. Interference fit: When we originally ordered our bearings and aluminum shafts, we tried to press-fit our shaft into our bearings with our hands. We soon realized that this did not work and believed it was because our bore diameter was too small or our shaft diameter was too large. We came to find out that our bearings and shafts were made with such small tolerances that we had to press-fit them using the vises in the machine shop.

7. Simplification and alteration of linkage shapes: A valuable realization was that the linkages themselves could take on various shapes, provided the joints were appropriately positioned. This flexibility allowed for customization of the shovel link to better suit the specific requirements of the project. Initially, we made a 6-bar linkage that was used in our prototype. We were told that we could treat our 6-bar linkage as a 4-bar linkage and create the links to be whatever shape we wanted to meet the needs of the robot. By following this advice from the judges on prototype demonstration day, we were able to create the maze within our linkages for the seed to drop out, as well as a better way to incorporate our shovel head without spacers. 

Image of our prototype as six linkages on the left. Image of our final prototype as a four-bar linkage with our red maze in between the links.

Tips for Future Groups

Starting early is essential for the project. Your first idea might not be adequate when executed, so go to the TAs as many times necessary to have a solid and precisely defined idea to launch. The time for the completion of this project will be at least twice what is expected. Additionally, make sure to take advantage of operational hours in TIW and ask anyone for help when needed.

Acknowledgments

To Ashwin: Thank you for teaching us about press-fitting for our bearings and shafts. Also, a huge thank you for allowing us more time in TIW the night before the project was due so that we could continue to make parts for our prototype. We could not have completed this project without you. And thank you for resoldering our wires to the motor at 1am. 

To Victor: Thank you for answering all of the questions we had about ordering parts. And a huge thank you for resoldering our wires to the motor right before demonstration day.

To Professor Rohit: Thank you for being encouraging. You made us feel like we had a lot to be proud of, even when we didn't feel that way.  

To Sid: Thank you for pushing us to think critically about the 'why' of every aspect of our project. 

Thank you to all of our TA's and Professor Rohit: We have learned so much from you this semester and will be better engineers from your help.