Why does my Moulding toolpath cut the wrong direction, and when should I use it instead of 3D finishing?

The direction "problem" (it's a rule, not a bug)

The Moulding toolpath always cuts PARALLEL to the drive rail you select. It sweeps your cross-section profile along that rail. So if you select a short rail with a wide cross-section, the tool travels the short direction, by design. To change the cutting direction, you would have to make the other edge the drive rail (with a matching cross-section). If the geometry can't be expressed that way, model the shape as a 3D component instead and machine it with 3D toolpaths.

The underused superpower

For frames, rounded edges, and swept profiles along curves, meaning anywhere the shape is "a cross-section traveling along a path", the Moulding toolpath can beat 3D Rough plus Finish:

• Smoother: it machines ALONG the profile continuously, with no raster scallops across the curve, so the finish can come off the machine nearly polished.
• Faster: often several times quicker than 3D-finishing the same geometry, because it isn't rastering a whole field.
• Classic uses: picture-frame profiles, rounded sign borders, steering-wheel-style rounded rings, chair-rail style trim, plinth edges.

The "Vary Step Over" option adjusts the step over based on the shape of the cross-section profile, which helps keep quality on steep sections (see the 3D-ridges entry).

When NOT to use it

Geometry that isn't a constant cross-section along a rail (varying profiles, organic reliefs) is 3D modeling plus 3D toolpaths territory.

Pro tips

• Rounding the border of a 3D relief: pocket or finish the field, then use Moulding for the border profile. The combo is often faster and cleaner than one giant 3D finish.
• The cross-section vector's scale relative to the rail matters. Preview before cutting, because a mis-scaled profile shows immediately.