2. Design Process - SV

To begin the design process, I started by modeling the mechanism in the PMKS software, which gave me coordinates, link lengths, and other useful information. Figure 2 shows the result of the PMKS software. Based on these coordinates, I was able to create Solid works sketches of each of the parts. 

Figure 2. PMKS Analysis

I based my design on the available materials and processes in Texas Invention works. Since we had a large supply of  1/4" acrylic sheets wood, nuts/bolts, and washers, I decided to incorporate these materials. I had the choice of using either wood or acrylic for my project. Due to the better aesthetics and smoother finish of acrylic, I chose that over wood. For the hole sizes, I found an abundance of M3 bolts and screws, so I created holes of size 3.5 mm in all of the links.

Next, I had to figure out how to mount the mechanism. The two main options that I was considering were flat and upright. A flat design means that I had to screw in the bars to a flat sheet of acrylic or other material while laying flat. While this is certainly the easier option, there can be problems with how gravity interacts with the mechanism’s bars. The second option, which is a standing mechanism, was also a viable solution, but needed design work to ensure that the mechanism stands upright and stable. I made the decision of going with the flat approach, because I was more confident I could overcome gravity. 

I had to make a design decision about the size of all of the components. If I were to laser cut acrylic with the exact dimensions as shown by PMKS, I would have an incredibly long slider, making the mechanism difficult to operate. Hence, I chose to shrink the entire mechanism in half, including the lengths of the links, sliders, and distances. 

Since the 3 bars rotate across each other, they will inevitably bump into one another, leading to the need of spacers. Spacers help create gaps between the bars so they can freely rotate and not interfere with each other. I chose to make my spacers with the associated nuts that come with the M3 bolts that I used. In hindsight, this was not a great idea, as nuts do not work that well as spacers due to their grooved fit.