What is 4-axis CNC machining?

Want to complete multi-sided machining of complex parts in a single setup? If you're an engineer or industry professional looking to balance cost and performance, you should know what to choose-4-axis CNC machining. This article will guide you through understanding 4-axis CNC machining from different perspectives.

We can understand 4-axis machining by using 3-axis machining as an analogy. You can think of a 3-axis machine tool as a camera fixed on a tripod, which can only move in three linear directions: X (left/right), Y (forward/backward), and Z (up/down) to photograph (cut) the object. To photograph the side or back of the object, you must manually remove the object, rotate it, and then refix it-this is called "re-clamping" in machining.

Now, imagine adding an electric rotating platform to this tripod, with the object (workpiece) fixed on this platform. In addition to the X, Y, and Z axis movements, it now has an added rotational axis-usually called the A-axis. This axis allows the workpiece to rotate around the X-axis. This is 4-axis CNC machining.

Working Modes
 

3+1 Axis
The workpiece is rotated to a specific angle (e.g., 90 degrees) and fixed, and then the cutting tool performs the machining. After one side is machined, the workpiece is rotated again to the next angle. This is ideal for machining holes or grooves on the sides of parts.

4-Axis Simultaneous Machining
While the X, Y, and Z axes are moving, the A-axis is also continuously rotating. The cutting tool maintains continuous relative motion with the workpiece. This is suitable for machining cams, helical blades, or complex cylindrical surfaces.

Different projects require different machining methods, from 3-axis to 4-axis machining. Based on our practical experience in CNC projects, Hansheng Automation provides you with five reasons why you should choose 4-axis CNC machining services.

Increased Efficiency and Reduced Costs
Unlike 3-axis CNC machining, 4-axis CNC machining eliminates the need for multiple workpiece setups, which means reduced machine downtime and lower labor costs.

Higher Machining Accuracy
Manual re-clamping is one of the main sources of machining errors. Each time the workpiece is moved, it's difficult to guarantee that its position is exactly the same as the previous one (datum loss). 4-axis machining eliminates cumulative errors through a single setup, ensuring consistent tolerances across all machined surfaces.

Ability to Machine More Complex Geometries
The addition of a rotational axis in 4-axis machining makes it ideal for machining complex geometries such as continuous arcs, gear teeth surfaces, or oil grooves around cylindrical parts.

Improved Surface Quality
When machining cylindrical parts, 3-axis machining uses very small step sizes to approximate the curved surface, which leaves noticeable tool marks. 4-axis machining allows the workpiece to rotate in conjunction with the tool movement, generating a smooth and uniform surface texture.

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Increased Production Flexibility

For small-batch precision machining orders requiring rapid iteration, 4-axis machine tools offer great flexibility, allowing for quick adaptation to different part designs without the need for complex dedicated fixtures.

Vertical 4-Axis Machining Center (VMC)

A standard 3-axis vertical milling machine is equipped with a CNC rotary table. The workpiece is clamped on the rotary table and rotates around the X-axis.

Horizontal 4-Axis Machining Center (HMC)

The machine spindle is horizontal, and the worktable has a built-in rotation function (usually called the B-axis, rotating around the Y-axis).

Turning and Milling Machining Center

Although primarily classified as a lathe, a turning center equipped with a powered tool turret and C-axis functionality can also achieve efficient 4-axis machining.

As a professional manufacturing partner, we can clearly explain the advantages and limitations of 4-axis machining.

Advantages

Multi-sided machining capability: Allows access to four sides of a part without manual intervention.

High rigidity: Compared to 5-axis machines, 4-axis machines typically have a simpler structure and better cutting rigidity, making them suitable for heavy cutting.

Cost-effectiveness: Compared to expensive 5-axis machining, 4-axis machining offers similar capabilities for complex parts at a lower hourly rate.

Limitations

Processing blind spots still exist: It cannot machine angled holes at arbitrary angles between the top and side surfaces like a 5-axis machine (unless a special angled head is used).

Programming complexity: Compared to 3-axis machining, 4-axis simultaneous machining requires more advanced CAM software and more skilled programmers, which increases costs to some extent.

Interference risk: When the workpiece rotates with the rotary table, special attention must be paid to whether the fixture and workpiece will collide with the machine spindle.

Aerospace: Used for machining complex engine mounts, fuel system components, and wing rib structures.

Automotive Industry: Camshafts, high-performance crankshafts, gearbox components, and steering system parts.

Medical Devices: Orthopedic implants, surgical instruments with complex helical features, and endoscope parts.

General Machinery and Automation: Worm gears, spur gears, indexing plates, and rotating shaft components in non-standard automation equipment.

Creative and Consumer Goods: High-end flashlight casings, musical instrument parts (such as flute bodies), and artistic metal decorations with complex curved surfaces.

Can 4-axis machining process all materials?

The choice of material primarily depends on the cutting tools and machining parameters, not the number of axes. 4-axis machining can be used to process all materials, whether metals such as aluminum alloys, stainless steel, and titanium alloys, or engineering plastics such as PEEK and nylon.

What documents do I need to provide to get a quote for 4-axis machining?

To get the most accurate quote, you need to provide a 3D CAD model (STEP or IGES format) and a 2D drawing (PDF format) with tolerances, threads, and surface finish requirements clearly marked.

How should I choose between 4-axis and 5-axis machining?

If you only need to machine side features of a part or continuous features around a cylinder, 4-axis machining is the best choice. If the part has complex undercuts, angled surfaces, or requires extremely short tools to ensure rigidity, 5-axis machining may be more suitable.

Oberg, E. et al. Machinery's Handbook. 31st Ed. Industrial Press, 2020.

Zelinski, P. "The value of 4-Axis Machining." Modern Machine Shop, mmsonline.com.

ISO 2806:1994. "Industrial automation systems - Numerical control of machines - Vocabulary."