Overview#
Removing bulk material efficiently and safely is the heart of milling. Fusion provides two main 2.5D strategies for clearing regions:
- 2D Offset Roughing (previously 2D Pocket Clearing, and 2D Pocket in older guides): a roughing operation with options for a finish pass. The toolpath resembles the shape of the selected boundary and steps over by a Maximum Stepover; the tool still sees full engagement when it moves from one pass to the next.
- 2D Adaptive Roughing (previously 2D Adaptive Clearing): a roughing toolpath that "flows". It maintains the Optimal Load (the maximum engagement) by varying the stepover, so you can take deeper cuts. Autodesk states that adaptive roughing results in 40% faster material removal than traditional pocket paths.
Both can clear a cavity, an open pocket, or the area around a standing boss. The tradeoff with adaptive paths (general guidance, not Autodesk data) is longer G-code files and many direction changes, so the real speed on a light machine with weak acceleration can be lower than programmed.
Other 2D operations in the same family include Slot, Bore, Circular, Thread and Trace. This page focuses on offset and adaptive roughing.
Where to find it#
- Milling > 2D > 2D Adaptive Roughing
- Milling > 2D > 2D Offset Roughing
- Toolbar search (S): "Adaptive" or "Offset"
Selecting geometry#
Both operations share geometry selection.
- Geometry types: Closed Pocket Machining, Open Pocket Machining, and Standing Boss Machining.
- Pocket Selection: select any face, edge or sketch to define the machining boundary. Use edge selection for areas with holes or pockets inside pockets. For a standing boss, select its outer boundary and enable Stock Contours.
- Extension Method (open pockets): the selected chains extend to the stock boundary to form a closed boundary. Options are Tangent (default), Closest boundary and Parallel; if Tangent is not appropriate, Autodesk recommends Closest boundary next.
- Stock Contours: when checked, the toolpath considers the stock boundary (default, the Setup stock box) or a selected closed boundary. A boundary larger than the stock extends the cutting area. It is not a containment boundary, because the tool approaches from outside the selected area.
- Contour arrows (offset roughing): point clockwise for outer contours and counter-clockwise for inner contours to maintain a climb cut; click an arrow to change direction.
Tip: Selecting the pocket floor face lets Fusion pick heights from the geometry; edges alone may need manual heights. Prefer floor faces when the model has them.
2D Adaptive Roughing#
Step by step#
- Milling > 2D > 2D Adaptive Roughing.
- Tool: choose a flat end mill with ample flute length (for example, 10 mm tool with 22 mm flutes) and a preset with feeds suited to low engagement.
- Geometry: select the pocket floor. Check Stock Contours and the extension method for open pockets.
- Heights: top = stock top; bottom = selected floor.
- Passes: set the parameters in the table below.
- Linking: choose a Ramp Type; set the Helical Ramp Diameter and Ramp Clearance Height.
- Generate and watch the simulation. Check the cut direction and any air cutting.
Passes tab options#
| Option | What it does |
|---|---|
| Tolerance | Maximum chord distance used when linearising splines; very tight values mean large G-code files and risk data starving |
| Optimal Load | Maximum engagement the toolpath maintains; the stepover is varied to avoid overloading the tool |
| Both Ways | Uses both climb and conventional milling for open profiles (adds Optimal Load Other Way and Other Way Feedrate) |
| Minimum Cutting Radius | Smallest toolpath radius in a sharp corner; blends inside corners but leaves more material for rest machining |
| Use Slot Clearing / Slot Clearing Width | Starts pocket clearing with a slot along the middle, then spirals to the walls |
| Direction | Climb or Conventional |
| Multiple Depths, Maximum Stepdown | Depth per Z level (applied to the full depth less stock to leave and finish amounts; the final pass may be smaller) |
| Use Even Stepdowns | Equal distances between passes for steadier tool load |
| Order by Depth / Order by Area | Sequence for multiple cavities: all by Z level, or one area at a time |
| Stock to Leave | Separate Radial (wall) and Axial (floor) values |
| Smoothing | Smooths the path |
| Feed Optimization | Reduces feed in sharp corners (Maximum Directional Change, Reduced Feed Radius, Reduced Feed Distance, Reduced Feedrate, Only Inner Corners) |
| Rest Machining | Removes only material a previous tool could not; enter the previous tool's Tool Diameter, Corner Radius, Taper Angle and Shoulder Length |
Typical stock-to-leave values such as 0.2 to 0.5 mm radial and 0.1 to 0.3 mm axial are general shop practice, not Autodesk data.
What adaptive does at the entry#
Adaptive paths need an entry into material. On the Linking tab, Ramp Type offers Plunge Outside Stock, Zig-Zag, Predrill, Profile, Plunge, Smooth Profile and Helix. For Helix, the Helical Ramp Diameter is the maximum helix diameter and Minimum Ramp Diameter sets the smallest allowed; Autodesk suggests a value that makes the tool overlap its centre for good chip evacuation. Ramping Angle, Ramp Taper Angle (conical helix, good for chip clearance), Maximum Ramp Stepdown and Ramp Clearance Height refine the move. With Predrill you define Predrill Positions (a drilled lead hole); Entry Positions can also be set.
Feeds for adaptive#
Adaptive roughing uses higher feed per tooth than traditional pocketing because of chip thinning. As a general-guidance example only, a 10 mm 3-flute tool in aluminum at 8 percent radial engagement might run Vc 300 m/min and fz 0.12 to 0.15 mm (about 3,400 to 4,300 mm/min at 9,500 rpm). Check the machine's acceleration, power and look-ahead.
2D Offset Roughing#
Step by step#
- Milling > 2D > 2D Offset Roughing.
- Tool: flat end mill; for a pocket with inside corner radius R, the tool radius must not exceed R.
- Geometry: select the pocket floor.
- Heights: set according to the floor.
- Passes: Sideways Compensation (Left = climb), Maximum Stepover, Multiple Depths with Maximum Stepdown, Stock to Leave, Finishing Passes.
- Linking: choose a Ramp Type and lead settings.
- Generate.
Passes tab options#
| Option | What it does |
|---|---|
| Tolerance | Maximum chord distance when linearising splines |
| Sideways Compensation | Left (climb milling) or Right (conventional milling) |
| Minimum Cutting Radius | Smallest toolpath radius in a sharp corner |
| Finishing Passes | Finish passes with the side of the tool; typically for rough and finish with the same tool |
| Number of Finishing Passes / Stepover | How many finish passes and the maximum distance between them |
| Leads on all Finishing Passes | Full lead-in/out on every finish pass (set on Linking tab) |
| Finish Feedrate | Feed for the final finishing pass |
| Repeat Finishing Pass | Repeats the final pass to remove stock left by deflection |
| Finishing Overlap | Distance the tool passes beyond the entry point before leading out |
| Preserve Order | Machine features in selection order |
| Both Ways | Climb and conventional for open profiles |
| Maximum Stepover | Maximum horizontal stepover between passes (not the same as adaptive Optimal Load) |
| Use Morphed Spiral Machining | Constant spiral move toolpath for the pocket |
| Allow Stepover Cusps | By default the stepover is overridden so a bull-nose tool leaves no cusps on flats |
| Smoothing Deviation | Maximum smoothing applied to roughing passes |
| Multiple Depths, Maximum Stepdown, Finishing Stepdowns, Use Even Stepdowns | Depth control |
| Wall Taper Angle | Tapered walls |
| Order by Depth / Order by Step | Sequence for multiple cavities |
| Stock to Leave | Radial (wall) and Axial (floor) |
| Feed Optimization | Reduces feed in sharp corners |
| Rest Machining | Uses the previous tool's Tool Diameter and Corner Radius |
A roughing stepover of 50 to 70 percent of diameter is a common general-practice value (not Autodesk data).
Adaptive or pocket: how to choose#
| Situation | Better choice |
|---|---|
| Large rigid machine, hard materials, deep pockets | Adaptive (general guidance) |
| Small desktop machine with low rigidity and slow acceleration | Offset roughing (or adaptive with conservative settings) |
| Narrow slot | Slot operation or offset roughing |
| Shallow cut, large area, wood or plastic | Offset roughing |
| Need smooth finish wall without extra passes | Offset roughing with finishing passes |
| Long G-code size is a problem (old controller) | Offset roughing, or raise adaptive Tolerance |
Finishing the pocket#
Roughing leaves stock. A finishing sequence is:
- Adaptive or pocket roughing with 0.2 to 0.4 mm radial and 0.1 to 0.2 mm axial stock to leave.
- A 2D Contour on the pocket walls with a finishing tool, zero stock, perhaps with a spring pass.
- A floor finish: a Pocket with only floor passes, or a Face-like pass. Or use the Pocket's built-in floor finishing.
Use a smaller tool for corner cleanup. Both operations offer Rest Machining, which limits the toolpath to material the previous tool could not remove; enter the previous tool's diameter and corner radius (adaptive also takes taper angle and shoulder length).
Options reference: Linking tab#
| Option | What it does | Operation |
|---|---|---|
| Retraction Policy | How the tool retracts between passes | Adaptive |
| High Feedrate Mode / High Feedrate | Feed used for fast non-cutting moves | Both |
| Allow Rapid Retract | Rapid instead of feed retract | Both |
| Safe Distance | Clearance distance for retracts | Offset roughing |
| Keep Tool Down / Maximum Stay-Down Distance | Stay at depth between nearby passes instead of retracting | Both (Minimum Stay-Down Distance and Stay-Down Level on adaptive) |
| Lift Height | Height of lift for stay-down moves | Both |
| No-Engagement Feedrate | Feed when the tool is not engaged | Adaptive |
| Lead-In / Lead-Out | Horizontal and vertical radii, sweep angle, linear distance, perpendicular option | Both |
| Ramp Type, Ramping Angle, Ramp Taper Angle, Maximum Ramp Stepdown, Ramp Clearance Height, Helical Ramp Diameter, Minimum Ramp Diameter | Entry moves | Both |
| Predrill Positions / Entry Positions | Pre-drilled entry holes or chosen entry points | Both |
Tips and pitfalls#
Tip: For adaptive roughing, use the full flute length when your machine and tool allow it. This spreads wear along the flutes instead of burning out the tip. But do not exceed the flute length: the shank cannot cut.
Tip: Run Simulate and look at the stock result for leftover material; check the engagement visually in the playback.
Tip: Use Predrill entries when the pocket is deep and narrow, so the endmill does not need to ramp into a tight space.
Warning: Adaptive clearing creates very large G-code files and many small moves. Machines with limited memory or slow serial links can starve. If the machine stutters (data starving), loosen the operation Tolerance; Autodesk notes that very tight tolerances create large files and very short moves.
Warning: A pocket with a corner radius smaller than the tool radius cannot be cleared to the corner. The strategy will leave material. Plan a smaller tool pass in advance.
Warning: Narrow stepdowns with large radial engagements in pockets produce chatter in thin-walled parts. Reduce engagement or stay at consistent chip load.
Note: 2D Pocket is now 2D Offset Roughing and 2D Adaptive Clearing is now 2D Adaptive Roughing; older tutorials use the old names.
Practice exercise#
Model a 90 x 60 x 25 mm aluminum block with a 70 x 40 mm pocket, 18 mm deep, with 6 mm internal corner radii, and an 8 mm cylindrical island in its center.
- Create a Setup with a 2 mm top offset.
- Add a 2D Adaptive Roughing with a 10 mm, 3-flute tool, Optimal Load 1.0 mm, Maximum Stepdown 15 mm, stock to leave 0.3 mm radial and 0.1 mm axial.
- Add a 2D Contour on the pocket walls with a 6 mm tool for finishing, zero stock to leave.
- Add a 2D Offset Roughing operation for the floor, with radial stock to leave and axial stock to leave of zero.
- Generate and compare the cycle time of adaptive vs. a pocket-only approach using a duplicate with 2D Offset Roughing at 50 percent Maximum Stepover.
Expected result: the adaptive toolpath shows smooth, curving passes with small stepover; the simulation leaves a thin radial skin on the walls; the finishing contour cleans it. Cycle times will depend on feed and machine limits, but adaptive should show a shorter time at equivalent tool-life safe parameters on most machines.
Related#
- Face and 2D Contour
- Feeds and speeds
- 3D milling (3D adaptive and rest machining)
- Toolpath simulation