True 3D milling
27/05/2024
The making of this keyring in the shape of an ellipsoid gives a good example of a true 3D milling that demands at least a 4 axis CNC. The shape of an ellipsoid is anything but plane, hence the undeniable 3D characteristic of this milling. Moreover making the holes for the cord would not be possible without tilting the stock a the proper angles, hence the necessary fourth axis.
A first rough step cleans most of the wood, leaving what the tool could endure without tearing the stock from its hold.
Then it is the right time to bore the holes.
The next step is the actual milling of the ellipsoid shape itself. Here it is approximated with an horizontal 0.1 mm precision and a 0.2 vertical precision.
The previous step left a small height of wood in order to maintain the ellipsoid in place. Now the part above the middle plan of the ellipsoid is slowly removed.
The final step remove what is left on the other side. In this particular case, the shape of the ellipsoid and the small size of this object allow to let it simply fall near the end. This is seldom the case…
As for the purpose of the cord: it enables to hold the key with a simple lark's head knot.
