What is 5-Axis CNC Machining and How Does it Work?

What is 5-Axis CNC Machining and How Does it Work?

Introduction:

5-axis CNC machining opens up new possibilities for producing highly complex, sculptural parts with undercuts, complex contours, and intricate features from a variety of materials. By adding two more axes of motion on top of traditional 3-axis machining, 5-axis CNC enables precise angular cutting and unrestricted part access ideal for detailed components with complex geometries.

This advanced CNC method is transforming prototyping and production across industries like aerospace, medical, automotive, and more. In this blog, we’ll break down what 5-axis CNC machining is, discuss its key components and programming methods, examine the benefits of 3-axis machining, and overview typical 5-axis applications and machine types being utilized.

What is 5-Axis CNC Machining?

5-axis machining refers to CNC milling or cutting along five different axes simultaneously. The typical five CNC machine axes include the three linear axes (X, Y, and Z) for moving the cutting tool along orthogonal directions, combined with two rotary axes (A and B) that pivot and tilt the tool or workpiece on different angular planes.

This added positioning flexibility and orientation allows the cutter to approach parts from any direction and angle. Complex 3D contours, cavities, undercuts, and intricate features no longer have inaccessible areas for the tool due to the expanded range of motion.

5-axis CNC utilizes specialized CAD/CAM software for coordinating the multi-axis movements and tool orientation strategies required to precisely machine complex geometries. The programs also incorporate advanced cutter compensation that accounts for the constantly adjusting tooltip position in space.

Key Components of 5-Axis CNC Machines

To functionally perform 5-axis machining, CNC machines require specialized mechanical designs and components that facilitate smooth, continuous 5-axis motion.

• Multi-axis machine stage: The machine base needs to allow two simultaneous rotary motions in the A and B axes on top of the three rectilinear XYZ motions. This may involve a literal tilting/pivoting platform, or separate controllable rotary axes integrated into the stage.
• Advanced CNC controller: The machine CNC unit must be capable of interpolating and coordinating the simultaneous 5-axis motions per the toolpaths generated in CAM. This requires high-performance electronics and controls.
• Precision mechanical bearings: Low-friction, backlash-free rotary bearings support the critical rotating A and B axes to enable precision multi-axis positioning. Air bearings are common in high-end 5-axis machines for maximum accuracy.
• Rigid structural design: The machine frame and moving components must offer a rigid, thermally stable construction that resists deformation under multi-axis loads without affecting tolerances.
• Tool changer: Most 5-axis CNC machines are equipped with automatic tool changers (ATCs) for fast, flexible tool swapping needed for machining complex geometries.
• Rotary axis calibration: To maintain accuracy, the rotary axes require periodic calibration via precision artifacts like reference balls to verify proper angular positions.

Common 5-Axis Configurations

There are several possible machine configurations that provide 5-axis motion by moving either the tool, workpiece, or a hybrid combination, including:

• 5-axis Table/Tilting Rotary Table: The workpiece is mounted to a tilting rotary table that pivots in the A and B axes to orient the part at different angles below a stationary 3-axis spindle.
• 5-axis Head/Tilting Spindle: The cutting tool is mounted to a tilting spindle head capable of angling the tool via the A and B rotary axes above a fixed worktable.
• 5-axis Table-Head/Tilting Rotary Table and Spindle: On hybrid machines, both the workpiece and tool can tilt in the A and B axes for enhanced positioning flexibility.

5-Axis CNC Programming Methods

Taking full advantage of multi-axis machining requires advanced CAD/CAM programming techniques. The complex tool paths involved in 5-axis CNC are generated using specialized CAM software. Here are some of the common programming methods used:

• 5-Axis Positional Programming: The toolpath is directly defined by discrete coordinate points and tool orientations sequenced along the programmed contour.
• 5-Axis Vector Programming: Instead of discrete points, tool motions are defined using vector arcs and lines interpreted by the CNC along five axes.
• 5-Axis Surface Contouring: The CAM system derives 5-axis tool paths by tracing along surface contour data from the CAD model.
• 5-Axis Swarf Milling: Toolpaths follow helical ramping motions optimized for clearing “swarf” (chips) efficiently from complex molds and dies.
• 5-Axis Machine Simulation: CAM tool paths are extensively simulated and verified on a virtual model of the CNC machine prior to any actual cutting.

Benefits of 5-Axis CNC Machining

The expanded capabilities of 5-axis CNC provide a number of significant advantages over conventional 3-axis machining:

• Complex geometries: 5-axis motion facilitates machining highly complex contours and cavities with undercuts, curved surfaces, and organic shapes that cannot physically be reached with a straight 3-axis tool.
• Multi-sided access: The tool can approach parts from any direction (front, back, side, top, bottom) rather than just a perpendicular Z-axis in 3-axis machining. This is key for detailed 3D features.
• Improved surface finish: By continually adjusting the tool’s angle of attack to match the changing contours of curved parts, 5-axis machining maintains optimal perpendicular engagement for precision cutting.
• Reduced process time: The free tool motion allows completing intricate parts in fewer operations and setups compared to multi-step 3-axis machining. The non-stop rotary movement also eliminates time wasted retracting and repositioning the cutter.
• Minimal fixturing: Workpieces often only need basic 5-axis fixturing to expose all areas to the rotating, tilting tool motions rather than complex multi-sided fixtures.
• No special tooling requirements: The same end mills, drills, and inserts used for 3-axis CNC work for 5-axis machining. Although 5-axis optimized tool designs are available.
• Improved tool life: The constantly adjusting tool orientation maintains perpendicular engagement, allowing the use of a smaller portion of the tool’s cutting edge and reducing wear.

Typical 5-Axis Machining Applications

Here are some examples of where 5-axis CNC’s capabilities are being applied across industries:

Aerospace: Machining intricate aerodynamic components with sculpted, organic surface contours for planes, turbines, and rockets. Allows machining deep cavity propeller blades from solid billets.

Medical: Manufacturing plastic and metal orthopedic knee/hip implants featuring complex curved joint surfaces. Also used for dental drill guides, crowns, and implants.

Automotive: Producing automotive wheel and tire molds with complex curved spokes, as well as engine components with organic shapes.

Mold & Die: Efficient machining of plastic injection molds and die-cast mold tooling with conformal cooling channels and complex part geometries.

Consumer products: Machining parts for items like golf clubs, power tools, bicycles, and sporting goods requiring organic, sculpted contours.

Prototyping: Enables rapid prototyping of highly detailed scale models, mockups, patterns, and castings. Allows verifying complex geometries before final production.

Common 5-Axis CNC Machine Types

5-axis CNC capability is available across a range of machine tools. Here are some of the most common:

• 5-axis CNC machining centers with trunnion tables or tilting spindle heads from brands like Haas, Hurco, Makino, Okuma, and DMG Mori.
• 5-axis vertical milling machines with additional rotary axes for aerospace and mold tooling applications.
• Precision 5-axis CNC mills optimized for titanium or composite aerospace components.
• 5-axis routers designed for high-speed machining of plastic, foam, and non-ferrous metals. Used for mold tooling and prototyping applications.
• 5-axis bridge mills with large, rigid moving column designs capable of precision, dynamic machining.
• 5-axis horizontal machining centers for heavy-duty cutting of large parts like castings and plates.
• Gantry-style 5-axis CNC mills that utilize overhead traveling columns rather than moving worktables.

Conclusion:

The capabilities opened up by adding 5-axis rotational movement to CNC machining centers and mills have allowed the creating of previously impossible geometries. Tilting and pivoting both the workpiece and cutting tool radically improves access for machining highly complex, organic 3D contours quickly and accurately. 5-axis CNC has become indispensable for industries that require precise, detailed components with complex curvatures or internal features. Continued improvements in multi-axis machines, CAM programming, and cutting tools will further expand 5-axis CNC applications.