Trammel of Archimedes - 3D Print

This is a more advanced version of the Trammel of Archimedes I posted last week. Since this is above my woodworking skills, I took the easy road and 3D printed the design. All STP and STL files are included in the last step for you to download. Also, I bet there are woodworkers and machinists that can produce a much nicer version out of “real” materials. If anyone tries, please post pictures in the comments.

The CAD animation which is quite mesmerizing is shown here:

See the actual print version in motion here:

Step 1: Tools/Materials

Tools:

• 3D Printer
• Screw Driver
• Wood file or sandpaper (depends on the quality of your printer)

Materials:

• Screws: Pan Head, #6, ¾” Long

Step 2: Base

The base is a six sided shape (hexagon) which you might recall from school has a total of internal angles equal to 720 degrees. The 3 passes on the trammel are centered on the vertices of the hexagon. For the paths, a chose a dovetail groove. This groove was based off a lesson learned on my previous print (T-Slot) where I had to remove the supporting structure above the slot. I added rounds to the center edges which help keep the slides on track if they enter to the middle section at an angle. The pockets around the parameter are mostly cosmetic even though they do add a nice place to grab the trammel from underneath as you are spinning it. I mainly added them to reduce the weight since my printer (local library) charges $.25/gram. For reference, the entire trammel cost ~ $22.

Step 3: Slides

The slides were designed to match the grooves with a 1/32” clearance. I added chamfers and rounds on the slides to allow for cleaner movement. Note that when looking at the drawing you will see more than 1/32" of an inch clearance. The final dimensions are after the rounds. For each slide piece, the hole is centered on the top and is sized for a #6 screw.

Step 4: Handle

This took a little geometry to figure out the correct spacing of the holes. I've included my attempt to explain the the dimensions.

Step 5: Knob

Arbitrary design for the handle knob. You could also purchase one from a hardware store for the same price as a 3D print.

Step 6: Assemble

Place the three slides in the grooves. Screw the handle to the slides as shown. Attach the knob to the handle from the backside.

Step 7: Final Product

Twirl away.

Step 8: Files

All files are included to build your own. You will need to purchase screws. I've also included STP files in case you would like to modify the design.