How does the Moulding Toolpath work in VCarve Pro & Aspire for cutting swept moulding profiles along a drive rail?

Overview

The Moulding Toolpath extrudes a 2D cross-section profile along a drive rail vector to create a 2.5D machining path. It's classified as 2.5D because it doesn't use a 3D component model: the tool movement is generated from the profile and rail. This makes it fast to calculate and efficient for architectural mouldings, picture frames, arched sign borders, and any shape with a constant cross-section. It is available in both VCarve Pro and Aspire.

The Two Inputs

Drive Rail: A vector defining the path the profile follows. For a picture frame, this would be the rectangular frame outline. For a straight moulding, a single line. You may select multiple rails.

Cross Section Profile: An open vector representing the profile shape. This is what the tool traces. Imagine slicing the finished moulding perpendicular to its length and viewing the outline. On a closed rail, the cross section always hangs on the outside of the shape.

Workflow

1. Draw the drive rail vector (closed rectangle, arc, or open curve)
2. Draw the cross section profile vector, an open shape representing the moulding's side profile
3. Open Moulding Toolpath from the Toolpaths tab
4. Select the drive rail in the 2D view. It turns orange and shows a green square (start point) and directional arrows
5. Hold Ctrl and click the cross section profile. It turns orange. The last vector selected is the profile that is extruded. Red lines appear on the rail showing which side the profile sweeps along
6. If the red lines are on the wrong side, right-click the rail vector and choose Reverse Rail (this also changes the direction, and the start point on an open vector)
7. The start point of the cross section attaches to the start point of the drive rail. If the profile hangs the wrong way, right-click the profile vector and choose Reverse Profile
8. Select the finish tool (typically a ball nose or tapered ball nose)
9. Set Boundary Offset if needed (see below)
10. Calculate

The Clear Rail button empties your current selection without leaving the form.

Key Settings

Toolpath Position (Z height): The Z height of the toolpath is determined by the height of the cross section vector. Drag the slider or enter exact values to position the moulding within the material block. If the cross section is taller than the material, edit the cross section vector height or change the material thickness in Material Setup.

Vary Step Over: Normally the stepover is a horizontal distance projected down. This option adjusts the stepover based on the shape of the cross section instead. Where edges are steeply curved, angled or near vertical, the passes are closer together. This usually improves finish quality, and it can increase machining time.

Use Larger Area Clearance Tool: Uses two tools. The larger tool works like a 3D Z Level roughing toolpath and is cut first, making multiple-depth 2D pockets along the rail to clear excess material. The software calculates two toolpaths, and the one with [Clear] in its name should be run first. Use it when the material is too deep or hard to cut directly with the finishing tool. A Machining Allowance and Ramp Plunge Moves are available for the larger tool.

Machine Flat Regions: With the larger tool selected, the software looks for flat or horizontal areas of the cross section that the larger tool can fit into and machines them as part of the roughing. With a flat tool this gives a better finish and shorter cutting time. This option overrides the Machining Allowance in the flat areas.

Skip Flat Regions: Available when Machine Flat Regions is checked. The finish tool then avoids re-machining the flat areas.

Create Sharp Corners: For rails with sharp corners, forces mitre-style corners instead of the toolpath rolling around the corner.

Boundary Offset: Forces the toolpath to cut past the ends of the profile that run parallel to the drive curve. By default the center of the tool goes to the edge of the profile ends. To make sure a vertical or steep end edge is machined, enter at least the tool radius plus a small extra amount (the documentation suggests about 10% of the radius). For a 0.25" (6mm) ball nose, that is at least about 0.15" (3.6mm). If you want the roughing to reach these areas too, base the value on the larger area clearance tool size. There is also a Use automatic boundary offset option.

Drive Rail Direction and Start Node

The direction arrows on the rail vector determine how the profile is oriented as it sweeps. If the moulding appears mirrored or flipped, right-click the rail and choose Reverse Rail to flip the direction.

On an open vector the generated toolpath lifts at the end by at least the stepover distance, steps over, comes down and returns along the vector in the opposite direction. On a closed vector it lifts, steps over and continues in the same direction, which Reverse Rail can change.

Use Cases

• Picture frame mouldings (closed rectangular drive rail + ogee/cove profile)
• Arched sign borders (arc drive rail + decorative profile)
• Architectural baseboards, crown moulding, chair rails (straight open rail + a profile from a moulding catalog)
• Cabinet door edge profiles
• Column capitals and base mouldings (circular closed rail + classical profile)

Moulding vs Two Rail Sweep

Two Rail Sweep is an Aspire-only modeling tool.