Water Pumping Piston

The final project for my manufacturing processes class was to build a piston that would pump five gallons of water from one bucket to another. It was a collaborative project with the entire class and a competition between class sections to build the pump that completed the job in the least amount of time with the fewest leaks or other damages to the system. The class was split into groups, each group given a part to design, which they would then swap for the building phase. This was to simulate working in the real world, where groups have to collaborate, and build based off designs made by others. Knowing we wouldn’t be the ones to build our own part helped emphasize the importance of listing machining steps and other important information for those not involved in the design process.

My group was in charge of designing the cam shaft and I took the lead in much of the design and building phase. This part connects the rotary motion of the engine to the connecting rod in order to drive the piston in and out of its housing. Later on we would be assigned the building the connecting rod, which the another group had designed.

Because the design of the cam shaft is so depend on other parts, my group needed to gather specs from the other groups before we could start the design of our own part. This mainly included things such as the distances the piston would need to travel, how long the connecting arm was, the RPM and torque of the motor, and so on. We then took this information and designed our cam shaft. I factored in its center of mass and balanced it so that it wouldn’t vibrate during spinning. I minimized the surface area in contact with the connecting arm and with the table it would be set on to minimize friction and wear on the part (it was aluminum, and the table was steel). Additionally, we designed the locking key so that it met the fit standards of the part and would slip into place, but not slip out during operation.

After all this was finished, our group reviewed the design. We determined that while it was well thought out, its complexity would require more time than we had available to machine in the lab during our collective free time and class times. So, we had to simplify the design in order to minimize the time it would take to machine. This revised design would be impacted by wear more than the original design, something we had tried to carefully avoid, but it would regardless be fully functional. Thus served as an important lesson in balancing design complexity against machining time and cost.

After all part designs were finalized, we swapped and began working on manufacturing them. Unfortunately, the group we were assigned to work with wanted to leave for break early and decided to machine their own part, forcing us to machine our own part (the cam shaft) as well. This required milling a rectangular block to size, first with rough cut speeds and then precision cut speeds. Then we drilled a hole where it would connect to the engine and slowly reamed it out until it met the dimensions specified for a tight fit. After that, we went to the pneumatic press and broached a key cut. Finally, we drilled a partial hole for the connection pin to attach to the connecting arm. Final surface sanding was done to remove burrs and sharp edges.

I also had to modify another group’s part, the connecting arm. Because it was made of steel, compared to the aluminum of our part, its rough burrs would cut into, damage, and possibly lead to function failure as the operating time increased. They needed to be sanded and removed much like we had done on our own part.

https://video.wixstatic.com/video/79f2b3_13ce68b81ee74cfa9451d6c448bda102/1080p/mp4/file.mp4

In testing, the assembled piston moved all five gallons of water with no leaks or breakages. Our part worked perfectly as intended and as a bonus, I got to keep it after the class was over. I keep it on my desk as a trophy and reminder of all the design and work that went into our successful project.