Displaying toolpaths from the tool center is the right way to do it, in my opinion. If the toolpaths were displayed from the tool tip, you would never catch it if you program with an endmill but intended to use a ballcutter, or vise versa. Also, just picture a toolpath displayed from the tooltip using a ballnose cutter and cutting an arc in the Z axis. The tool contact point changes, so the cutter path wouldn't look right. The actual contact point of the tool wouldn't be the actual tip, so the display could be deceptive. Of course the display could be calculated to display correctly, but displaying from the tool center makes this unnecessary. Check out these illustrations which hopefully illustrates the potential issue.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Actually, this appears to occurs when there is no bottom surface in the model. The logic will not consider the bottom surface of the box-region automatically generated in the same way as a "selected model surface".
In the earlier case, the toolpath will behave as descibed in the post below. When a bottom surface is selected as a model the toolpath will be correctly calculated to ensure that it does not undercut.
So, my learning is, make sure there is a bottom surface to ensure the correct generation of the toolpath.
I have noticed that the for ball-end tools, the toolpath generated will actually undercut the model by an height equal to the radius (see picture enclosed).
I am wondering if this is the expected behavior ? Or whether it would make more sense in this case to have the option to ensure that the tool tip does not go below the bottom of either the clipping plane or the bottom of the bounding box (whatever is highest).
To work around this, I have set the the lower clipping plane to be equal to z-bottom + radius of the tool. But this is quite a manual task to do...
Any thoughts there ?
Last edited by jeangui; 10-14-2013 at 11:37 AM.