I don't know about you but I have a certain preference for grounded coffee prepared with a moka. Now, filling the funnel or basket with grounded coffee it's a problem that troubled Humanity since the Stone Age*: using ancient tools such as spoons will lead inevitably to spill precious product all around.

After years of research in secret government laboratories* the first coffee doser emerged. This device is now available everywhere and it basically a can with a lid on one side and an adapter on the other side. The adapter will nicely fit your moka pot funnel and rotating a knob will let the grounded coffee fill it without any mess or spillage and in a consistent way.

What I wanted was an adapter for the coffee cans I usually buy. So first thing first I measured the can with a vernier, then started the design.

*ok, ok... I'm definitely making things up here. It's so difficult to glorify a coffee doser! :)

Supplies

You will need:

3D printer
STL files (see below)
an Illy Caffè can (or anything else if you design your own reducer)
glue

Should you need to modify any of the parts please get the STEP files here.

Step 1: Design

The design is modular so you can adapt it to any can or moka. It includes the following parts:

cup
handle
pivot
housing
reducer

The surfaces highlighted in red are the surfaces that are meant to be glued. Be careful particularly when you glue pin and knob to avoid locking the mechanism: the pivot must be glued to the casing only and the handle must glued to the cup only.

The cup is probably the trickiest part because of the curvature. In the commercial models it is hemispheric but I designed it as a truncated hemisphere to 3D print it easily without supports.

Some of the part will be fitted together, some other will need to move relatively to each other. Because of this I allowed for a tolerance of 0.5 mm on the diameter (eg between cup and housing).

While this is reasonable enough, it is also printer-dependent so I suggest you to print a test design (see this instructable) and adjust the dimensions if needed.

Step 2: Print and Assembly

The 3D printing process could take a lot, it depends on the printing parameters. The software I used is Ultimaker Cura 4.5. I printed everything with a layer thickness of 0.15 mm because I wanted a nice finish and 100% infill except the casing, where I used a 30% infill. The material I used is PLA+ from Sunlu, with build plate temperature of 85 °C and nozzle temperature of 205°C.

Another parameter I modified to avoid a joint along the cylindrical surfaces is the "Z seam alignment" (basically the starting point of each layer): I set this value to "random". In this way there will not be aesthetically unpleasant vertical scars on the surfaces.

Eventually, after 20 hours or so my 3D printed parts are ready to be assembled:

fit the cup into the casing
put some glue on the pivot where indicated in the previous step (red zone). The pivot will be glued to the casing but NOT to the cup, even if it will fit into it. The cup is meant to be free to rotate around the pivot.
put some glue on the handle and carefully insert it in the hole opposite to the pivot. The handle is meant to be glued to the cup but NOT to the casing.
glue the casing to the reducer
screw the reducer on the coffee can...

...and you are ready to enjoy your coffee!

Step 3: Use!

To fill your moka (can you smell the coffee yet?) simply turn the can upside down and fit it on your moka pot, turn the handle 360 degrees (one full turn) lift the can and you are ready to go!

A couple of notes:

the doser is designed to fit the coffee can and the moka I have, a plain vanilla Bialetti (2 cups). As I mentioned before the design can be adapted to other models as well.
remember to turn the handle one full turn. If you turn it just half turn the cup fill be facing downward, spilling coffee as soon as you lift the can. To remember it I colored one face of the handle with a permanent marker.

While you enjoy your coffee why not voting for me in the contest?

Thanks! :)