Lexan Spindle

Charged with the objective of creating an innovative digi-tile that places its emphasis on exploring digital ornament using the operations dictated by the lathe production process, we worked at creating a column-shaped prototype that exploited the 2, 2.5, and 3.0 dimensional milling processes.

Before meeting with our contacts in the engineering college at UNL, we prepared two distinct prototypes. Our first prototype was what we understood to be an easily achievable iteration out of lexan (Figure 1.0). However, in an attempt to utilize our abilities using grasshopper, we created another option (figure 2) that exploited both our understanding of the parameters of the tooling process and our understanding of creating a grasshopper definition file (Figure 3). However, after meeting with our contact, Jim McManis, at the mechanical engineering lab at UNL, our understanding of what was possible and what was achievable changed drastically. From our meeting with Jim, we were able to grasp a better understanding about how the fabrication process worked and what exactly our outcomes would be. Our first attempts, (figure 1 and figure 2), came in at a cost estimate of $1000.00 to $1500.00. The majority of this cost was a reaction to the labor invested in programming the g-code for transference to their CNC machine.

In an attempt to lower cost, we discussed several variations with Jim. Each of these variations fed directly to our final design process (figure 3). One variation concerned increasing the diameter of the initial stock to a point where the cost of material and the cost of fabrication leveled out. Through discussion with Mr. McManis, we learned that the cost of fabrication could be lowered if we increased the diameter of the rod from two inches to three inches. A production threshold exists where the cost of the material and the hourly production rate of the g-code equal out. Simply, the smaller the object the larger the production cost. However, in this scenario, the material cost is lowered. The larger the object, the lower the production cost and the greater the material cost.
Another large indicator of costs deals with the amount of material extracted from the original stock. In our first two iterations, figures one and two, we started with an original diameter of 2 inches and resulted in a minimum diameter of ½ inch. In our third iteration (figure 4), we tried to address this by allowing for only a 3/8 inch differential.
Another large factor in the fabrication process is the amount of operations included in the file prep time. For example, the voronoi etch pattern costs extra due to it being a second file preparation operation. In our final iteration, to simplify the file preparation of this operation, we created an etching pattern that consists of horizontal banding. This pattern is considerably simpler to program than the voronoi pattern, thus taking less time to produce and lowering cost.
Our third, and final, fully explored iteration, (figure 4), is our current CAD/CAM solution to the digi-tile problem provided to us. Feb. 08, 2010. To be continued…