4) Manufacturing and Assembly [ATD]

To create our device, we decided to use laser-cut wood as the main material for our device mainly because the design required a large number of parts and 3D printing would not be feasible due to time constraints. Laser cutting allows for quick iteration on design, and this became very important as we had to change an important part of the design halfway through the building phase of the project. We mainly used 0.25” wood for our laser-cut parts as it is stronger, but we also used some 0.125” wood in places where the thinner material would help save space and strength was not imperative. 

We 3D printed several key components in the design, such as the track for the follower to roll along or small mounting components, as their geometry was difficult to create out of flat sheets of material. For hardware, we used a variety of M4 and M5 bolts and nuts to secure each component. We designed certain fasteners in compact locations so we used smaller sized bolts there, and we used long bolts to secure multiple components together such as the Lazy Susan and gear assemblies. To simplify our design and manufacturing process, we utilized prebuilt shaft mounts and linear bearing mount blocks; the SOLIDWORKS models we used are shown below in Figures 4.1 and 4.2. Using these meant we did not have to design and manufacture our own versions and could simply design using the existing, robust part.

Figure 4.1: CAD of metal linear bearing

Figure 4.2: CAD of metal shaft mounting piece

We began manufacturing by cutting out the main drive gears and food turntable. We 3D printed the track profiles that the follower would run on and bolted them to the turntable. We assembled these initial gears on a small, temporary main platform to validate that the gears would mesh well with low friction, and they did, so no redesign was necessary for the gear dimensions. The gears are highlighted in green and the track is highlighted in blue.

Figure 4.3: Top view of initial assembly (gears and cam)

Figure 4.4: Side view of initial assembly 

Figure 4.5: 3D view of initial assembly 

After the turntable, we assembled the initial assembly designed to constrain the topping container and oscillate it on the upper rail system as the crank slider mechanism moved. This rail system, shown in the video below, did not work as intended. Ideally, the follower would have been able to create an upward force on the rail system and raise the food dispenser as it slid on the crank slider shafts. We assembled the parts and tested the rails and saw that the follower created a large rotational moment on the linear bearings which caused them to seize whenever the follower shafts pushed up into the rail system. 

This forced us to reconsider our design for the follower rail system and find another method to raise the food dispenser. We could not add another follower on the track to remove the moment without making the design considerably more complex. Our solution was to drastically reduce this moment by moving the food dispenser closer to the follower, and to reduce the mass the follower pushed by simplifying the way the food dispenser was held. This simplification reduced part count overall and allowed the follower to function well without making the linear bearings seize due to a large moment pulling them off-axis. 

We inserted pictures of the final CAD for this device below. The three output motions are highlighted in different colors: the turntable is green, the crank-slider is orange, and the follower is blue. Structural parts are transparent or gray. There is also a video showing the assembled final device not in motion. Videos of the device in motion are in the Final Prototype section.

Figure 4.6: 3D view of full assembly 

Figure 4.7: Top view of full assembly 

Figure 4.8: Side view of full assembly