Christina Holman | Design Blog

We finally made it to the end! After the preliminary design report, it was time to finalize our actual design (since we were given enough materials to make one truss to test). After doing a few more draft sketches and analysis, I was able to pick up on patterns on which types of designs produced the maximum strength (all within the parameters we were given). Finally, I came up with the sketch at the bottom-right, and the MATLAB analysis produced the highest load we were able to reach. We theorized that: two members would buckle first instead of just one (Members 3 and 4); the maximum load is 11.62 ± 0.063N; and the total cost of the truss is $290 (under the budget limit). From there, we moved to prototyping: we cut the straws as close as possible to the lengths specified in our final design. To create uniform gusset plates, our "joints," we used the circular cap of an individual Tropicana Orange Juice bottle. It met the area requirements and acted as a stamp...

Planetary Carrier Somehow I was able to use Creo to create all of the components of the gearbox in one day (not recommended). After destructing the B&D Li2000, opening up the gearbox (which took a bit of strength), and calculating the measurements of each component, I was finally able to re-create all of the parts. Ring Gear Then, with each individual design, attach the components to one another in assembly (left) so that the kinematics or the motion of the CAD-assembled gear train resembled that in the gearbox. Planet Gear Additionally, I was able to use the motion analysis feature in Creo to model the pitch diameters and gear ratios for the cylinders representing each gear. (We did not go into depth on how to actually create the teeth on the gear since it requires manufacturing details we did not have.) Sun Gear Below is a video demonstrating the mechanism analysis for a multi-stage epicyclic gear train like the one used in the B&D Li2000 Screwdri...

Motor and Case So, in the most recent lectures, we've talked a lot about what is called " Design for Manufacturing and  Assembly (DFMA) " -- or the combination of designing for the ease of manufacture and designing for the ease of assembly. Even the best assembly process in the world can fail under human errors like fatigue, time pressure, and plain carelessness. (We've all accidentally dived into an Ikea furniture assembly without fulling reading the instructions beforehand.) Hence, wisely, product designers tend to use 'mistake-proofing' features in order to make those kinds of careless mistakes obvious within seconds. Like a puzzle, either a piece fits or it doesn't. Otherwise, you'll end up with a deformed piece and an unclear final product. Honestly, those small DFMA pieces like a raised section of plastic can make or break how well-connected a handle is -- or even how easy it is to replicate the same level of quality that the company is promi...

So ME359 has been great but it has been an exercise in stamina . For a 2-credit class, where weekly homework is 70% of your grade, this is a lot of time and energy -- but, still, exciting. Like I said before, I do really well when it comes to project-based learning and real-world applications. And this course's final project has really been wonderful for that. The final project is to reverse engineer the Black and Decker Li2000 Screwdriver and then use the computer-aided design (CAD) software Creo to re-create the gearbox. This is an interesting task since the B&D Li2000 uses a planetary gearbox, which consists of three types of a gears that all lie on the same horizontal axis. My task is to create the ring gear (the outermost gear), the three pinion gears that rotate around that inner radius of that ring, the sun ring around which the pinion gears rotate, and, then, the planetary gear connected to the central axis of the screwdriver. Ultimately, I need to create all of ...