Transitioning to Autodesk Fusion from traditional 2D CAM software like Alphacam or AutoCAD can feel daunting, especially when trying to translate standard woodworking operations into CNC toolpaths. For cabinet makers and woodworkers, programming clean dados and rabbets is a foundational task. A common hurdle for beginners is figuring out how to make the router bit clear the edge of the wood completely, ensuring a sharp, straight joint without leaving an uncut radius at the corners.
By understanding how Fusion processes 2D geometry and stock boundaries, you can easily automate your toolpath extensions. Whether you are cutting a single cabinet gable or nesting multiple parts on a full $4 times 8$ sheet of plywood, implementing the right software settings will significantly speed up your manufacturing workflow and prevent ruined workpieces.
Mastering Toolpath Extensions for Clean Joints
When machining a dado (a groove cut into a board across the grain) or a rabbet (a recess cut into the edge of a piece of wood), a standard toolpath will stop precisely at the boundary of your 2D geometry. Because router bits are cylindrical, this leaves an unwanted radius equal to the radius of the bit at the end of the cut. To achieve a clean, square-edged joint, the tool must extend past the physical edge of the material.
The 2D Contour and 2D Pocket Strategies
For most woodworking applications on a CNC router, you will rely on the 2D Contour or 2D Pocket strategies. When dealing with open contours—where the cut intersects the edge of the board—you have two primary methods to push the tool beyond the material boundary:
- Start/End Extension: Found within the Geometry tab of your toolpath setup, this feature allows you to input a specific linear value (e.g., matching or slightly exceeding your tool radius) to stretch the tool path at the entry and exit points.
- Stock Contours: By enabling this option, Fusion automatically recognizes the raw material boundaries defined in your Setup. It will dynamically scoot the tool out past the material to ensure the geometry is fully cleared.
Strategy Adjustment for Full-Sheet Plywood Nesting
While using automatic Stock Contours works beautifully for isolated components, nesting multiple parts across a full sheet of plywood requires a different approach. If you apply global stock boundaries to nested parts, the software can become confused about where individual part edges end and where the outer sheet boundary begins, leading to unpredictable tool movements or unnecessary air-cutting.
Tangential Fragment Extensions
When programming nested cabinet parts on a full sheet of plywood, it is best practice to avoid global Stock Contours. Instead, utilize Start/End Extensions or Tangential Fragment Extensions directly on your selected geometry chains.
This manual extension ensures that the router bit plunges safely outside the specific part boundary, cuts straight through the joint line, and exits cleanly before retracting. This method maintains tight control over your nesting nests, preventing the tool from colliding with adjacent nested parts on the sheet.
Managing Complex Intersections and Cutting Order
Cabinet bottoms often require multiple dados and rabbets that run into or intersect each other to accommodate vertical uprights and dividers. To program these efficiently, it is highly recommended to design with solid models within Fusion rather than relying strictly on imported 2D DXF files. Solid models provide explicit depth and volume data, allowing the CAM workspace to calculate toolpaths more reliably than flat lines.
[Import DXF/DWG] ➔ [Extrude to 3D Solid Body] ➔ [Select Faces/Edges in CAM]
Controlling the Cut Sequencing
When machining multiple intersecting joints, the order of execution is critical to prevent wood tear-out or part shifting. You can manually dictate the order in which your CNC router executes cuts within a single toolpath definition:
- Open your toolpath strategy (e.g., 2D Contour) and navigate to the Passes tab.
- Look for the Preserve Order or selection-ordering check box.
- When enabled, Fusion will execute the cuts precisely in the order you selected the geometry on your screen, giving you total control over the machining sequence.
Transitioning from Mill-Centric to Router-Centric CAM
A common point of frustration for woodworkers entering the Autodesk ecosystem is that many default tutorials focus heavily on metal milling operations. Metal milling relies on precise stepovers, high-speed adaptive clearing, and coolant control. Router-centric CAM, however, prioritizes flat sheet nesting, chip load management in various wood species, and specialized aggregate heads.
Note on Multi-Drill Boring Heads: If your CNC router features a multi-drill line boring block (such as an 8-spindle head for 32mm system holes), this hardware cannot be directly simulated or configured on the standard design side of Fusion. In the CAM workspace, you will program the holes using a single drill toolpath. Splitting that data across multiple physical spindles is handled entirely by your machine’s Post-Processor.
If you are running specialized industrial machinery like an SCM Morbidelli router and find that the generic post-processors included in the software do not output the correct G-code for your drilling blocks, you should connect with an authorized reseller or post-processor specialist to customize the script for your controller.
References
- Autodesk Fusion Manufacture Forum. Topic: “how to make dados and rabbits”.
- Autodesk Partner Marketplace: Post-Processor Solutions for Fusion.
Related Knowledge Base
What is the difference between a dado and a groove?
In woodworking, a dado is cut across the wood grain, while a groove runs parallel to the wood grain. Both are handled similarly in CAM software using open 2D contours or pocketing strategies.
How do I calculate the extension distance for a router bit?
To ensure a clean edge, the toolpath extension distance should be at least equal to the radius of the router bit plus an extra 1-2mm clearance. For a 12mm diameter bit, a minimum extension of 7-8mm is recommended.
Can I use 3D Pocket clearing for simple woodworking joints?
While 3D strategies work, they generate larger file sizes and longer processing times. For flat cabinet work, 2D toolpaths with manual extensions are cleaner, faster, and more efficient for CNC controllers to interpret.