- [Instructor] CNC is a category of manufacturing
that stands for Computer Numeric Control.
A high speed carving head removes material
following a computer generated path
in incremental layers.
Since CNC is a subtractive method,
your starting material must exceed
the volume of your final part's bounding box.
You can carve away your block to reveal
both stand-alone volumes and cavities.
CNC is also incredibly handy for carving
single-layer designs out of sheet material,
like plywood or acrylic.
CNC can carve away most materials,
from hardened steel to the softest foams.
The tool bits are made of special hardened material
designed to cut in every direction.
The best materials to be used are ones
that have consistent densities.
Materials that melt easily
or have inconsistent densities are not recommended.
There a couple of different levels and types of CNC.
I'll use these planes to demonstrate.
2-axis will only cut along the x and y axis,
with very limited up and down, z axis adjustment.
3-axis, adds another layer of movement,
and can move along all three axes, x, y and z,
more freely, but within certain height limits.
3-axis is one of the most common types of CNC,
and is a great choice for large sheet carving operations.
5-axis combines the technology of 3-axis,
but also moves the work piece in concert
with the carving head, enabling more complex
geometric volumes.
Another type of CNC is CNC lathing.
The work piece rotates along a central axis,
while the carving head creates revolved volumes.
Once you've modeled a project in the computer,
you can use specialized software packages
to generate tool paths.
These are the paths the cutting tool will take
to make your design a reality.
I'll use the Section View Tool to demonstrate
what these layers could look like.
Depending on your layer height,
you could do a rough cut, resulting in aggressive
stair stepping, as shown, or take longer
to shave much more incremental layers,
and remove smaller amounts.
So while your computer model may look
smooth and undulating, you'll still have layer marks.
Finally, CNC has some limitations.
For example, the size of the carving tool
can only be so small.
And even with the thinnest spindle head,
it can only carve so deep.
Your manufacturer will have specific information
on how deep they can drill and how thin features can get.
Knowing these limits will help save time
in the production process, in combination
with the consideration of the plastic's ability
to flow through the mold.
It's considerably harder to get super fine interior sharps.
This is another reason
why interior fillets are so important.
There are some specialized carving bits
than can get close to a true sharp.
But as you may know, the more difficult it is to make,
the more expensive it'll be.