offsets

[kclayton]

Is there any tutorial on boundary offsets.
Using the material boundary.
On 3d roughing work I am using a 0.24 offset with a 6mm end mill and a 0.03machine allowance.
On the finish a 2mm round nose bit with a boundary offset at 0.08
I am trying to get the roughing and finishing the same size.
At the moment I get a step between the roughing and finishing.
Any help appreciated.
Kevin Clayton

[SteveNelson46]

Make the boundary offsets in the roughing toolpath the same as the finish toolpath. The program will compensate for the difference in bit diameters.

[kclayton]

Hi Steve
I made both boundary offsets 0.12 but still get the finish short of the roughing.
The distance is about 4mm. On the other hand it does look like a mount in a picture.
Just finished this - next time I will raster oak at 0.0 instead of 90

[SteveNelson46]

Can you post your file?

[gregk]

Hi Steve
I made both boundary offsets 0.12 but still get the finish short of the roughing.
The distance is about 4mm. On the other hand it does look like a mount in a picture.
Just finished this - next time I will raster oak at 0.0 instead of 90

Hi Kevin,

The reason why roughing removes more material even if the same boundary vector is used, is that if it didn't do that, in some instances it would leave more material near the boundary. The smaller finish tool could then break there.
Thus roughing overcuts by a half of the large tool diameter.

In your example it looks like the 3D model sits in the pocket with flat bottom. Could you just run a quick profile toolpath at a correct depth to clean it out?

Greg K

[kclayton]

I can see that a 2mm tool might break if it touched the roughing edge.
I think it looks fine with the border almost as if it was intended.
I would have attach the file Steve but it is 7MB.