Parallel Finish [to edge] not recognizing surface edge

[MS1640987267]

I'm having trouble with a parallel finishing operation.

I am trying to parallel finish a surface that has a vertical feature. I always use "Surface Extent Condition" = TO, because otherwise the tool path always gouges into the vertical feature. The gouge in the part is mirrored in the simulation, so there is a problem in the parallel tool path. Using surface extent condition solves the problem.

Today I have a file that won't cooperate. The part is a scaled version of parts I have programmed like this in the past. What is happening is that when I select just the perimeter serface and select condition "to", it ignores the inner boundary and machines over the entire vertical feature and raised surface.

The bad tool path I am getting.

2024-03-31 15_07_44-2024-03-31 (Medium) Silicone Bottom Mold.3dm (45 MB) - Rhino 7 Commercial - [Per.jpg (221.91 KiB) Viewed 185 times

It should look like this:

How the parallel finish tool path should look.

2024-03-31 15_06_13-test 2023-11-16 (Small) Silicone Top Mold CAM.3dm (7 MB) - Rhino 7 Commercial - .jpg (116.47 KiB) Viewed 185 times

I've done a few experiments while troubleshooting. I deleted the vertical feature leaving a single surface with a hole in the middle. It went past the inner edge. Then I started over, creating a new file, re-importing the part. No change. I analyzed the surface, but I didn't find any issues. I duplicated edges and analyzed with curvegraph, and no self-intersecting edges or other oddities detected.

I have re-installed Rhino and RhinoCAM (v2021). No change. I opened another version of the exact same part to test, and it behaved normally (screen shot).

Here I used a larger step-over to show a simulation of what is happening. The parallel pass is running over the entire part, and then it makes a second pass over the raised feature.

It runs a parallel pass over the entire part, then comes back and does another parallel pass over the vertical feature

2024-03-31 15_41_37-Rhino 7 Commercial - [Perspective].jpg (225.28 KiB) Viewed 185 times

[MS1640987267]

Here's a screen shot of the control geometry selection.

2024-03-31 15_46_02-Rhino 7 Commercial - [Perspective].jpg (308.66 KiB) Viewed 184 times

Example of eliminating the raised feature:

2024-03-31 15_23_29-2024-03-31 (Medium) Silicone Bottom Mold.3dm (45 MB) - Rhino 7 Commercial - [Per.jpg (138.3 KiB) Viewed 183 times

[MS1640987267]

Problem avoided, not solved!

I offset the surface edge by 1/2 the cutter diameter, creating a curve that I could use as a boundary. Then I selected the region between the edges and the new curve.

I'd still like to know what went off the rails on this one!