UC Berkeley ME130 Class Project
CAD and Manufacturing Contributor
August 2013 - December 2013
Introduction
This was a class project for Design of Planar Machinery (ME130), in which we had to design and fabricate a machine that included mechanisms and interworking systems.
I was part of a 5 person team and my role included concept generation, CAD drawing, and machining the final product.
Concept Generation
We wanted our machine to have environmentally friendly implications so we chose to create a machine that automatically planted seeds into a window box planter. The machine had to plow the soil, deposit the seeds at a regularly spaced interval, and cover the seeds with the plowed soil.
After many concept iterations, we landed on a design that would simplify the process and conduct all three actions using a single motor as the power source.
Final CAD drawing of the machine. It surrounds the window planter box and contains a 4-bar mechanism
Analysis
We used a number of analytical techniques to validate the mechanism design. We had to account for linkage lengths, torque required, motor speed, gear ratios, and the frequency that seeds would be dispensed at.
The Mechanism
To control the deposition of seeds, we created a seed dispenser, hooked it up to the motor via 4-bar mechanism, and surrounded the dispenser with a sheath that would moderate the seed dispensing.
The 4-bar mechanism was a crank-rocker mechanism, which meant that based on the lengths of the linkages, a single driving source (the motor) would rotate a full 360 degrees while the opposite link (the seed hopper) would rotate only a fraction of a revolution. Using the speed of the motor, we could fix the frequency that seeds would fall from the hopper into the soil bed.
A close up of the seed dispenser. The outer sheath is transparent for clarity in seeing how the seeds are moderated through the hopper.
A detailed view at how the motor powers the 4-bar mechanism along with moving the entire mechanism along the track.
Manufacturing
All the parts in the machine were custom machined except for the gears, motor, rack, pinion, screws, and power source. Here is a look at some of the parts I worked on:
A photo of the frame being milled to fit the screws
The frame put together with the mechanism housing on the tracks. Trying to get the spacing down for the motor mount and gear mounts.
The 3D printed ABS plastic seed dispenser. The grooves that allow the seeds to fall can be easily seen here.
To move the mechanism back after the seeds were planted, we created a gear that could be disengaged from the track in order to move the entire system to the beginning of the track.
The Final Product
The end machine with the planter box inside. It worked fairly well but the motor drained the AA batteries in a matter of minutes.
Key Takeaway
Keep design simple and design for manufacturability:
Though I became thoroughly experienced with machining, we could have saved a huge amount of time if we produced our parts using a water jet instead of manually machining them. We could have done this if we drew the CAD model with the intention of water jetting as much as we could.