One of my favorite science fiction characters is Nomad from the original Star Trek. Nomad appeared in the episode called "The Changeling". Nomad was more than just any space probe: Nomad could levitate, had almost unlimited power and was sentient. Having just completed a class on Autodesk Inventor, I thought I'd try out my new found skills and create a 3D model of Nomad in Inventor, use 123D Make to create a sliced model, use a laser cutter to cut the slices from corrugated cardboard, and then glue them together to create a reasonable sized model.
The finished model is shown in the first photo. The second photo shows the actual Nomad in the Engineering section of the U.S.S. Enterprise. The third image is a 2D diagram of the model I created.
I made it at TechShop.
Step 1: Parts and Tools
- Eight 18" square sheets of corrugated cardboard. You can cut up corrugated cardboard boxes or you can order pre-cut sheets at office supply stores like Staples. (only four sheets are shown in the photo).
- White glue.
- One 28" 3/32" phenolic rod (available from Grainger Industrial Supply. Rods are available in 4 foot lengths - part #3HNE6). You can also use wood rods.
- Vise attached to a workbench
- Wire Cutters
Step 2: Building the 3D Model
Using plans I found on the web as a guide, I created a simplified 3D model of Nomad with Autodesk Inventor 2012. The model could also have been created with Autodesk 123D. I created a Inventor part for each section of Nomad as shown in the first diagram. Screen shots of each of the parts from Inventor are shown in the second through fifteenth images. Each part has a hole in its center that I used to align ("constrain" in Inventor terminology) the parts during assembly in Inventor. During actual construction, the center holes are used with a rod to hold the pieces together during assembly and to make the model more durable after construction. Next I assembled the parts in Inventor to create the full 3D model of Nomad as shown in the last two diagrams. I then exported the assembled model to STL format which will be used by 123D Make in the next step. The Inventor files and the STL file are attached to this step.
Step 3: Using 123D Make to Slice the Model
- I started 123D Make and used the "Import" button to load the STL file created by Inventor as shown in the first and second and third screenshots.
- The model is shown in the fourth screen. It came in upside down but that's OK - it won't effect the end result. I then used the "Select a technique" button to select "stacked slices".
- 123D Make then sliced the model and it automatically made the model 8 inches in height. See fifth screenshot.
- I used the "Manufacturing Settings" button to create an option for 18" x 18" x 0.1772" inch sheets (not shown).
- The 18" x 18" layout is shown in the sixth screenshot.
- I changed the height of the model to 48" inches to see what would be required to make a full size model. A full scale model requires 115 sheets of 18" x 18" cardboard and 271 parts! Yikes - that would take an awfully long time to cut! See seventh screenshot.
- I changed the height to 24" (half size) and the result requires a much more manageable 8 sheets and 136 parts. See eighth screenshot.
- Lastly, I used the "Get Plans" button to generate the .eps files that will be used with the laser cutter. See ninth screenshot.
Step 4: Assembling Nomad
- I imported each of the .eps files into CorelDraw in preparation for laser cutting. The CorelDraw files are attached.
- I used the laser cutter to cut each sheet. I used the color mapping settings in the print preferences for the laser cutter to only cut the blue lines (part outlines) and not engrave the red part numbers in the design files. Not engraving the part numbers dramatically reduced the time to cut the parts; however, it did require that I carefully number the parts with a pencil before removing the cut parts from the laser cutter. I used an Epilog Helix 45 watt laser cutter at TechShop to cut the parts. The vector cutting settings used were: Speed 25, Power 40, Frequency 500 Hertz.
- After cutting all the parts, I put the rod in a vise and carefully slid each part in order onto the rod with white glue in between. I found I got the best results doing about six slices at a time and waiting for the glue to hold before doing the next group of slices. Before putting any slices on the rod, I put a small amount of glue around the bottom of the rod where the lower slices would sit to ensure that the rod would be glued to the model. I also put a small amount of glue around the top of rod before adding the last slices for the antenna. The assembly and gluing of all the slices took about three hours. After the glue was dry, I carefully removed the model from the vise and cut of the part of the rod sticking out of the bottom with a pair of wire cutters.