Manufacturing and Assembly (Group 15, 2023)

The manufacturing and assembly of the machine primarily consists of two distinct parts: the mechanism's frame and the linkage assembly.

Frame

For the frame, the design was initially assembled within SolidWorks with the dimensions of the reusable plastic bag kept in mind. The frame needed to be large enough to host the bag, gear, axles, and other elements of the machine inside of it, but small enough in order for these elements to be close enough within the frame to interact with one another while also not being too costly of an investment. We decided to manufacture it out of laser cut Baltic birch plywood since the frame is large and laser cutting is significantly faster than 3D printing. The following CAD sketches for the wooden frame can be seen below:

Figure 4.1: CAD drawings of each of the four types of wooden walls for the frame, consisting of (starting from the top left, moving clockwise) the back wall, the frame base, the side wall (printed twice, one for each side), and the motor wall

Figure 4.2: In-application CAD image of how the wooden frame would be constructed

For the final prototype, the pieces of the frame were laser cut out of 1/4" Baltic birch plywood and glued together using wood glue.

Linkage Assembly

The claw link (Link 3) and one of the spacers are laser cut out of Baltic birch plywood since their geometries are completely 2D. All other parts of the linkage assembly are 3D printed with holes oversized by 0.1-0.4 mm to make up for the additional wall thickness added by 3D printers. Parts of the linkage assembly are bolted together using M3 socket screws and nuts. Bearings are press fit into the joints and shafts are kept in place using friction from the shaft collars. We used 8 in diameter shafts and linear bearings for the sliders and 6 in diameter shafts and bearings for the pin joints. The added rubber on the end of the claw and the stationary grip are super glued to the linkage assembly parts.

Figure 4.3: Complete set of construction images in order regarding the linkage assembly 

We initially had problems with machining the shafts and ultimately used a Dremel to cut them. Additionally, to reduce undesired movement which we observed upon initial testing, we added shaft end caps that are friction fit to the ends of the shafts.