Stella Parks has an awesome cookbook (Bravetart) with a recipe for making Oreo cookies at home. I made them and they were delicious.
Stamping A Design
But I wanted to stamp a design onto the cookies, like real Oreos. I first tried milling aluminum stamps, then cutting the stamped cookie dough from a big sheet of dough. This sort of worked but was time consuming and labor intensive. Nevertheless, I now felt certain that stamping the cookies would work.
Stella recommends using a rolling pin to imprint the dough before baking, and my research found that the Oreo factory uses rollers to stamp their dough. Unfortunately, I had no way to precisely carve my design onto a wooden cylinder to make a rolling pin, let alone onto an aluminum one that I would be able to wash after use. A little more research and I concluded that in fact I could machine an aluminum rolling pin IF I had a fourth axis for my CNC mill.
A Fourth Axis
My CNC mill has a cutting tool that moves up and down (z-axis) and left and right (x-axis). It has a table that holds the material to be milled, and this table moves forward and backward (y-axis). My task was to convert the linear y-axis movement into rotational movement. I did this by designing (in Rhino) then 3d-printing a rack to attach to the left side of the table, and a gear that spins as the rack moves. The rest was housing the gear and the rack to keep milling debris from fouling the mechanism, and providing a structure that minimizes motion of the jig in all axes without requiring modifications (such as bolt holes) to the mill itself. The first complete fourth axis worked when I tested it by carving a greenman into a branch from a tree that came down in the storms this spring.
Several refinements later yielded the current version (shown below), for which I have carved a sort of “hood ornament” or logo for the front cross brace of the jig. (The logo came after the photo on the left was taken.) The photo of the logo shows its four axes (surrounding a gear) being milled.
This is all very recent work, and I have not yet milled the rolling pin for the Oreos that led me down this particular rabbit hole.