New Ball-nose Drill Bits for 3D Milling on the CNC Router
As some of you will know the CNC router can do 2D profile cutting from .DXF files and 3D reliefs from.STL files, (if you want to see some examples of both types, have a look through the blog or come to the workshop and see what’s been cut recently).
3D reliefs are cut by the drill bit going backwards and forwards up and down from one end to the other.
Bingyangs model from last year is a good example of this; https://lsaworkshop.wordpress.com/2014/05/27/bingyangs-1100-and-150-routed-model-and-former/#jp-carousel-118).
There are lots of factors to consider when 3D milling, the most important is understanding the limitations of each drill bit. When we cut a 3D job we will normally always use a ‘ball-nose’ bit shown in the photo, these drill bits have a round end and give a smooth finish.
The rule is; the deeper you want to cut the larger the diameter of drill bit. It’s also important to remember that the round end means that internal angles on the model will be curved to the radius of the bit, for example; if you want to cut a site model with buildings from one piece of material and the maximum cut depth is 70mm, we will have to use the 12mm drill bit, this means that where the building meet the floor it will be curved by 6mm.
The 4 drill bit we have are;
12mm, this has a cut depth of 100mm and can cut foam and wood, (wood roughly 2 times slower than foam).
8mm, this can cut 60mm and can cut foam and wood, (wood roughly 2-3 times slower than foam)
6mm, this can cut 60mm and can cut foam and wood, (wood roughly 3 times slower than foam)
3mm, this can cut 40mm and can cut only foam.