3D carve tool sizes

[dio449 (Claudio Corsi)]

I have started to do some 3D cuts with my Shapeoko 4 and am noticing that the roughing pass does not cut all the way to the edge of the shape.

This is the shape ( an example to illustrate) as it appears in the 3D preview

When I define my tool paths the rough cut stops short and does not cut all the way to the bottom of the shape.

It would appear that the center line of the tool will not travel outside the perimeter of the shape. If I use a smaller tool the cut will be closer to the edge but the shapes I am cutting are fairly large so I start with a 1/2 bull nose to remove most of the material. When I switch to a finishing pass with a 1/4 bull nose there a spots that have too much material for the bit to safely cut.

Is there an approach to get the larger tool to cut all the way to the bottom in this example?

Any insight would be greatly appreciated.

Thank You

[Tod1d (Tod (with 1 'd'))]

3D paths use a boundary with an “On” condition. As you suggested the center of the tool stops on the boundary. So use a bigger boundary? Offset the boundary by the radius of the tool. I usually add a miniscule amount to make sure. This will allow the rough path to cut to the bottom.

However, the finish path, if done with a ball mill will still have a problem. Since the tool doesn’t go below the bottom of stock it will leave a radius at the bottom.

Increase the stock height by the radius of the ball mill, and add an equal base height to the 3D model. Now the ball mill will cut the radius of the cutter below the bottom of the model.