2. Design Process - ES

The design process required making multiple decisions in regards to the materials. First of all, the the links were all made out of 1/8 inch acrylic because acrylic has a lower coefficient of kinetic friction than plywood. Acrylic has a coefficient of kinetic friction of .15, and the coefficient of kinetic friction of plywood is between .25-.55. In addition, acrylic can be laser cut quicker than plywood. Plywood requires multiple passes to laser cut properly, while acrylic only requires one pass.

The grounding platform where the links are assembled on is the only piece that is 1/4 inch thick. The thickness of the grounding platform was made to be higher than the thickness of the other pieces to increase the contact area that was going to be used as support to maintain the vertical alignment of the assembly. In addition, all vertical grounded links that were glued to the board had a support structure to keep them in place. Glue was used to fix all the grounded links into the grounding platform.

The size of the assembly was determined from the transportation needs of the mechanism. Since I was planning on moving my prototype back and forth from my home to Texas InventionWorks, I decided to minimize the prototype's dimensions. The prototype's dimensions are 4 inches wide, 8.50 inches long, and a maximum height of 12.35 inches. The sizing of the holes required two iterations. I bought 1/4 inch diameter flange bearings to apply to each joint, however, the bearings did not fit because it is the inside diameter which was 1/4 inches but the outside diameter was actually 5/16 inches. Subsequently, I increase the diameter of the hole by 1/16 inches, and the bearings fit perfectly. The bearings were added to decrease friction during rotation, and they are made out of nylon due to its low coefficient of kinetic friction. The coefficient of kinetic friction of nylon against acrylic is .06, significantly lower than using acrylic against acrylic (.15). A total of 3 bearings were used in the final design, one for each rotating joint. Bolts and nuts were placed with each bearing to hold together the links.

The sliding joints were initially made using a bearing, nuts and bolts. However, after submitting the initial joint assembly and receiving feedback from Aldo, I changed the sliding joints to be composed of pins instead. 1/4 inch diameter pins were used at each sliding joint, for a total of 2 pins. In order to hold the pins in place, a 1/2 inch diameter cap was laser cut and glued at each end of the pin.