In my projects i talk about 2D contours, 2,5D V-carve, and full 3D...
But a got some questions about that... So lets explain...

2D milling / routing / carving...

In the above picture we see a typical 2D design (for more detail see picture below). The cnc machines we are using have at least 3 axis, the X, Y and Z axis.
In the picture X goes from left to right, Y from bottom to top and Z is the depth of the cut.

When i talk about a 2D design there is only 1 depth per toolpath. So in this case the '2' and the box around the 'D' are carved out to 3mm with a flat endmill.
The endmill  will do a raster of moves and cleans the edges, but stay's cutting at the same 3mm depth. If the '2' was at 3mm depth and the box at 4mm depth it would of course still be 2D, but it would be 2 toolpaths.

2D toolpaths take some time, if you don't want a big radius in each corner you will have to use a very small bit. This way the tool have to do a lot of passes to take the material away.

2,5D... does it even exist? Well no i don't think so.... But it's no 2D and no 3D so it must be somewhere around 2,5D 🙂

There are 2 toolpaths in this category that i use, V-carve and bevel-carving. The one that is used most is the V-carving, its a real great technique to use.
In this example i used the V-carve on the text 'carve', see the picture below.

In V-carving the V-bit is not at the same depth the complete toolpaths.
In stead it is constantly checking the width of the character, and adjusts is Z axis depending on it.
So if the width is big the bit goes deeper, if it is small the bit goes up again.

In the picture below with the 'V-' i have used bevel-carving.
It is really similar to the V-carve, but is is the other way around.
This way the text seems to be on top of the material.
This is a lot more work then V-carve since you will have to use a 2D toolpath to take away the rest of the material.

Last but not least the full 3D carving.

With 3D carving you can really make anything you want,  but it takes a lot of time...
In a 3D design the bit that is used is most of the time a ball-nose endmill, to get the best result.
The downside of this ball-nose is that the step over should be very low, therefore this takes a long time to do.

With 3D you can make reliefs, surfaces, text, you just name it...

Excellent explanations.