I recently developed some measuring spoon models. The math and basic design were, surprisingly, the easy part. Attempting to realize an idealistic design within the constraints of the real-world was a bit more difficult and ended up being the majority of the work.
The design itself is fairly simple. Maybe you remember the volume of a sphere from geometry class, maybe not. Either way, you can confirm with Wolfram Alpha. You then chop that in half because the spoon’s scooper is only a half-sphere. That half-sphere is the hollow part of the scooper. Make a slightly larger half-sphere and fill in-between, giving the scooper thickness. Attach a rectangular handle (which is technically a geometric “prism” rather than a 2-D “rectangle”), and cap it with half of a cylinder. Then, subtract out a hole to attach it to a keyring or lanyard. That’s it. If you want to get really fancy, subtract out some text from the handle to give you a label. The result is a perfectly idealistic spoon that can be designed in OpenSCAD and rendered in Blender.
Then, you push this idealistic file to the printer and see what happens. The real-world results can be not exactly optimal. I had a number of printing errors, due to the (lack of) capabilities of my older print-head that needed several rounds of correction. The embossed label had to go. It was too detailed for the hacks I had to make to my extruder motor. The wall thickness of the scoop had to drastically increase. In printing the apex of the scoop (the spoons print face-down), I’m fighting both extruder capabilities and gravity.
After making these design concessions, I ended up with a pretty decent design — perhaps not as sleek as I’d hoped, but not as blocky as blocky as others’ designs. It is still a work-in-progress. I am trying to come up with a handle and label that prints well.
The source files are heavily commented and have clear places to insert your own parameters for scoop radius, as well as wall thickness, handle width, thickness, and length. It is an OpenSCAD file and makes a great first project for learning what OpenSCAD can do. You can easily come up with specific measures for your own spoon (e.g. if you want 2tsp or 3/4tbl or even something as bizarre as 5ml). Just convert to milliliters (e.g. by typing “2tsp to ml” into Wolfram Alpha) and plug into the following formula:
Where “v” is the volume in milliliters and your result is the radius in centimeters. Multiply your result by 10 (to convert to millimeters — OpenSCAD only deals in mm) and plug it in where the measuring spoon file asks for radius. That’s it. Many more details and pictures are at the Thingiverse project page.