IV. Manufacturing & Assembly

To begin the manufacturing and assemblage of our prototype, we first inspect the full CAD model.

Figure 8: Top view of the avocado assembly

Figure 9: Close up of the sliding joint

For the sliding joint, only the wooden plate (1) and the acrylic plate (2) were laser cut. The wooden plate (1) was fastened to the base board by four quarter inch screws (shown). To ensure the sliding of the acrylic (2), nuts and washers were used to raise the the wooden plate (1) above the base board. Eight quarter inch nuts and eight flat washers (not shown), two per screw, were twisted around the screws after the wooden plate (1) and before the base plate. An additional four quarter inch nuts fastened the screws to the base board (not shown). The acrylic (2) had a hole that fastened to the wooden dowel (5) as a press fit. The end effector (3) was 3D printed with enough tolerance that it could rotate well about the wooden dowel (5). The blue effector (4) was 3D printed with enough clearance between the hole and the wooden dowel (6) so that it could rotate freely about it but remain fitted to the knife by the other wooden dowel (7). Both dowels (6) and (7) were cut from the same wooden dowel while (5) was a reused dowel. Both the holes through the steel knife and its black plastic handle had to be machined.

Figure 10: Close up of the other side of the knife

The knife is connected to the link (2) by the wooden dowel (1). Link (2) was 3D printed in a manner that would keep it fixed to the knife by the dowel (1) but freely rotating about the other dowel (3). Both the wooden dowels (1) and (3) were cut from the same dowel as in the above Figure 9 (dowels (6) and (7) above) while dowel (6) was reused. The link (4) was 3D printed, with the same tolerance as mentioned in Figure 9, in a manner that allowed free rotation about the dowel (3) but remain fixed to the screw (5). The hole in the wooden dowel (6) had to be machined.

Figure 11: Top portion of the actuator

The base of the actuator (2) shows two separately laser cut pieces of baltic birch wood glued together which was then glued to the base board. The extruding wall of base (2) had three laser cut hole that were cut in a manner that the wooden dowel (1) and the steel shafts (3) rotate freely within. The wooden dowel was fastened as a press fit into the 3D printed flange (4). This flange was glued onto the servo horn (5). The the servo horn was threaded to fit onto the servo. The servo was fitted into the white 3D printed servo holder (6). This holder was 3D printed to the same tolerance as stated before so that it could slide freely on the steel rods (3). 

Figure 12: Bottom portion of the actuator

A 5 mm bore ball bearing was fastened by press fit into the laser cut link (1) as well as glued. This ball bearing would be press fit around what would later become a wooden dowel at (2) instead of the 3D printed extrusion. An additional ball bearing with the same dimensions was press fit into the other hole in link (1) (not visible). Links (1) and (5) were connected by a cut wooden dowel of the same dowel mentioned for Figures 9 and 10. Link (5) would later be connected to the servo (6) by a steel servo horn (not shown), not by our original idea of a threading press fit. A small screw fastened link (5) to the servo horn (not shown). The base board and the wooden base of the linear actuator had a rectangular hole laser cut to allow the servo to be pressed almost all the way through the board.

Figure 13: Avocado grip and holder

Not shown in Figure 8, this holder consists of five pieces of laser cut wood, with the fifth piece not shown in Figure 13. This last piece not shown was glued not only to the base board, but also to the edges of the walls and base of the grip.