4-Axis and 5-Axis Milling

Overview#

Standard 3-axis milling moves a vertical tool in X, Y and Z. Adding rotary axes lets the part or the tool tilt, which gives you:

• Access: reach features on several sides in one clamping (fewer setups, better positional accuracy between sides).
• Better cutting conditions: tilt a ball mill away from its dead-center tip, shorten tool stick-out, and keep an optimal engagement on steep walls.
• Complex shapes: impellers, blades, turbine components, helical flutes, and undercuts.

The vocabulary matters:

Much valuable "5-axis" work is actually 3+2, which is simpler, safer and often available on cheaper machines and licenses. Fusion supports 3+2 by using multiple Setups or tool orientations, and simultaneous multi-axis strategies through the Multi-Axis panel; many of these need the Manufacturing Extension.

Autodesk's multi-axis overview splits the capabilities as follows.

Check Autodesk's current licence comparison for your account; Personal-use limits are covered on the manufacturing extensions page.

Where to find it#

• Milling > Multi-Axis panel: Swarf, Advanced Swarf, Rotary Contour, Rotary Parallel, Rotary Roughing, Multi-Axis Contour, Multi-Axis Roughing, Multi-Axis Finishing and related strategies. 3+2 Roughing is under Milling > 3D.
• Setup dialog > Machine to attach a machine definition with rotary axes.
• Operation dialog > Tool Orientation group (to override the WCS Z) and the Multi-Axis tab (machining type, tool axis limits, collision avoidance).
• Most 3D toolpaths can be used with 4-axis machining (a Manufacturing Extension feature); the Multi-Axis tab offers 3-axis, Polar, 4-axis and 5-axis Machining Type on strategies such as Drill.

Machine definitions#

Multi-axis toolpaths depend on kinematics. In Fusion:

1. In the Setup dialog click Machine > Select and pick a machine from the library. You can edit a machine with the Machine Definition dialog (Edit next to Machine) or build one with the Machine Builder (see the Machine Library and Machine Builder topics).
2. A machine definition holds kinematics (axis configuration, pivots and limits), an optional linked post processor, and optionally a machine model used for collision checks (Check Machine Spindle / Table options on some operations).
3. The post configuration is often tied to the machine, though you still select a post at post time. The post must match the machine's controller and axis arrangement.

Without a machine definition, multi-axis strategies cannot plan with real limits. Autodesk notes you can also enter your machine's minimum and maximum tilt range in Tool Axis Limits (a Manufacturing Extension feature).

Tip: Create a custom machine for your actual hardware. Even a simplified model with correct pivot distances and travel limits prevents most surprises when you move from simulation to the controller.

3+2 positional machining#

The most approachable multi-axis approach. For each tilted face:

1. Create a new Setup (or duplicate) and set the Work Coordinate System so Z points along the tool direction (normal to the face), or override it with the operation's Tool Orientation group. See the WCS page.
2. Attach the multi-axis machine so Fusion can compute the rotary angles that place the tool along that Z.
3. Add normal 2D or 3D operations. They see the tilted face as if it were the top.
4. Post. The post outputs the rotary positioning move (for example G0 B30 C90) and, depending on the post and controller, may use work plane commands (general guidance: G68.2, TRAORI, CYCLE800).

Benefits: all the 2D and 3D strategies are available; the part is machined without releasing the clamp; positional accuracy depends on the rotary axis calibration, not on the operator.

Setup logic for multiple faces#

For a cube-like part needing machining on five sides, you may structure it as:

• Setup 1: top (Z up)
• Setup 2: front face (WCS Z along -Y)
• Setup 3: right face, and so on

All Setups can share the same Work Offset (G54) if the physical part does not move, with orientation handled by the rotation commands. The shared origin must be placed at a point that does not move when the rotary axes turn (usually the rotary center) or must be defined consistently with the post's expectations. This is where machine and post configuration matter most.

4-axis operations#

A fourth axis (typically A, a rotary table or indexer rotating about X) lets you wrap geometry around a cylinder or machine multiple sides of a bar.

4th axis wrap and rotary strategies#

The 4th axis wrap toolpath (included with Fusion) wraps a toolpath around a cylindrical part. The Manufacturing Extension adds dedicated rotary strategies:

• Rotary Parallel: a finishing operation using continuous rotary motion on revolved parts or any part with a centerline axis; it generally creates 360-degree motion, though you can specify an angle range. Toolpath style (Circular, Spiral or Line) depends on the model, for example a Line style handles a large step better.
• Rotary Contour: finishing of steep walls on rotary parts, including spiralled walls such as extruder screws; Minimum Final Cutting Radius controls the final stepdown.
• Rotary Roughing (previously Rotary Pocket): clears large quantities on rotary parts; Automatic Stepdown aligns stepdowns with cylindrical surfaces, and Tool Offset avoids cutting with a ball tool's centre.

Define the rotary axis orientation correctly, and verify fidelity at small diameters.

Multi-axis contour and swarf with 4 axes#

4-axis machining (Manufacturing Extension) machines features on a cylindrical part; you can set the Clearance Geometry to a cylinder, sphere or inclined plane for rapid links in 4- and 5-axis motion.

5-axis strategies#

Multi-Axis Contour#

Machines along 3D curves, which can be model edges or curves projected onto a face. By default the tool orientation stays perpendicular to the underlying surface; the Multi-Axis tab has further controls for the tilting motion. It is a Manufacturing Extension strategy. Useful for edge finishing, chamfers on 3D edges and trimming.

Swarf#

Swarf machines with the side of the tool and suits chamfered or beveled edges and tapered walls, as long as the side of the tool can sit flat on a face. Tool Offset (Passes tab) controls how far the tool extends so you can use sharper parts of the flute. Drive Mode chooses whether contours or surfaces drive the path; with contours, the first selection determines the direction the tool tip faces. Advanced Swarf extends this. It is a Manufacturing Extension strategy.

Multi-Axis Roughing and Finishing#

Multi-Axis Finishing (Manufacturing Extension) finishes curved walls or pocket floors and can use circle segment (barrel) tools for larger stepovers; when machining only walls you must also select floor surfaces, whose normal sets the entry direction. A contact point range can be set manually. 3+2 Roughing removes stock from several fixed orientations in one toolpath, with Offset Roughing, Parallel or Adaptive Roughing styles; tool orientations can be Automatic, Semi-automatic or Selection, the machining type 5-axis (default), Polar or 3-axis, and a Virtual Fixture on the Heights tab limits orientations that would go beneath the part.

Flow and surface-driven operations#

The Flow strategy machines a face by driving the tool across the U or V direction of the selected face and suits curved surfaces; it aligns the selected surfaces automatically.

Multi-axis drilling#

The Drill operation's Multi-Axis tab offers Machining Type 3-axis, Polar, 4-axis (holes perpendicular to a defined rotary axis, with options such as holes intersecting the axis, shifting axes and a tilt angle) and 5-axis (full 5-axis movement with axis limits and tilt angles). Some of these options need the Manufacturing Extension.

Tool axis control#

Tool orientation can be set per operation in the Tool Orientation group: by default the setup WCS Z sets it, and you can override it with orientation options such as Turn, Tilt, Align to View and Surface normal, or set it from model geometry. For 5-axis strategies, Tool Axis Limits (Manufacturing Extension) restrict the tilting range and Limit the tilting angle helps avoid axis limits. As general machining guidance, keep ball-end tools a few degrees off the surface normal so cutting is not done at the zero-velocity tip.

Collision and limits#

Multi-axis motion creates many collision opportunities:

• Holder and shaft vs. part: 5-axis and collision-avoidance settings (Manufacturing Extension) adjust the tool orientation to avoid them; define the holder accurately.
• Machine components vs. part/fixture: checked in Simulate with a machine that has a kinematic model.
• Axis limits: the rotary axes have travel limits; reorient or choose a different tilt solution if a limit is hit. Read all messages in the Simulate dialog.
• Singularities: near the poles of the tilting axis the rotary axis can spin quickly (general machining behaviour); limiting the tilt angle helps.

Post processing for multi-axis#

The post decides how rotary data are output:

• Either as machine axis angles with tool-centre-point control enabled or not, or as tilted work planes for 3+2.

The controller codes involved (general guidance, not Autodesk data) include G43.4/G43.5, TRAORI and M128 for TCP, and G68.2, CYCLE800 and PLANE SPATIAL for tilted planes.

A post written for a 3-axis machine will not produce correct multi-axis output. You need a post that matches your machine kinematics and controller. See the post processing page.

Step by step: a 3+2 example#

1. Model a block with a 30-degree sloped face with three holes.
2. Create Setup 1 (top) with a 3-axis 2D Adaptive Roughing on the top.
3. Create Setup 2: attach a 5-axis machine. Set Orientation to Select Z axis/plane & X axis and click the sloped face for Z. Set the origin at a point on that face.
4. Add a 2D Offset Roughing operation and a Drill for the holes. They treat the sloped face as horizontal.
5. Simulate with the machine: watch the rotary axes position before the cuts.
6. Post with a 5-axis post; inspect the rotary moves.

Options reference#

Tips and pitfalls#

Tip: Start with 3+2. It needs less post and machine trust and is easy to verify visually (general guidance).

Tip: Model the true pivot position of your machine and test with a simple part and air-cutting before trusting the program.

Warning: Do not assume a 3-axis post works on a 5-axis machine. Verify rotary output and TCP handling with your post provider or controller manual.

Warning: Read all messages in the Simulate dialog; axis limit problems can show up there rather than in the toolpath.

Practice exercise#

Using a generic 5-axis trunnion machine from the library (A and C axes), create a 3+2 job on a hexagonal prism, machining a 6 mm deep pocket on each of three adjacent side faces and the top. Use duplicates of one Setup, changing only the Z axis face selection.

Expected result: Simulate shows the table indexing to a new orientation for each Setup, with identical pocket toolpaths in each tilted frame, and no axis-limit warnings.

Related#

• WCS and orientation
• 3D milling strategies
• Toolpath simulation (machine simulation)
• Post processing (multi-axis output)