Most people think 3-axis CNC machining is enough. But when you need angled holes, complex surfaces, or better access to tricky features, 3-axis just doesn’t cut it. That’s where 3+2 CNC axis machining steps in. This method allows precise machining at fixed angles, reducing setups and boosting accuracy.
It solves many common problems — less fixturing, fewer setups, more accuracy. Now let’s see how it works.
What is 3+2 Axis CNC Machining?
3+2 machining, or positional 5-axis machining, means the part is rotated into a set position using two rotational axes. Once fixed, the tool performs the cutting using three-axis motion. The rotary axes don’t move during the actual cutting. They only move before cutting starts to position the part.
This lets the tool hit features from the right angle, avoiding awkward setups or special fixtures. It’s useful for holes on angled faces, deep pockets, and complex contours.
Rotational Axes Explained (A and B Axes)
The A axis rotates around the X-axis. The B axis rotates around the Y-axis. These movements tilt the part forward, backward, or side to side.
Combining A and B allows the machine to fix the part at almost any angle. This helps reach surfaces that would be blocked in a flat setup.
The rotary table or head adjusts the position and stays locked during cutting. This makes the setup more stable than complete 5-axis milling.
Fixed Angled Positioning vs. Continuous Movement
In 3+2 machining, the rotary axes move the part into a set angle, then stop. The machine cuts while the part stays fixed. This is called positional or indexed machining.
In full 5-axis, the rotary axes move while the tool cuts. This is continuous machining. It allows for smoother surface finishes and more complex shapes.
But fixed positioning is more stable. It also reduces vibration and tool deflection, which helps extend tool life and improves accuracy. It’s ideal when you don’t need curved surfaces but still need access to difficult angles.
How 3+2 Differs from 3-Axis and 5-Axis？
In a 3-axis machine, the tool moves in X, Y, and Z directions. It can’t reach tilted surfaces unless the part is repositioned manually. This limits access and precision.
Complete 5-axis machining uses all five axes—X, Y, Z, A, and B—simultaneously. The tool and part can move together during cutting. This creates complex shapes in one pass. However, it costs more and requires more profound programming knowledge.
3+2 is in between. It doesn’t cut with all five axes at once. It only uses the two rotary axes to set the part at an angle, then mills with three axes. This lowers cost and complexity while offering better access than 3-axis.
How 3+2 Axis CNC Machining Works?
3+2 axis CNC machining is about tilting the part, locking it in place, and then machining it like a standard 3-axis job. It gives you the reach and flexibility of five-axis setups, but with simpler programming and lower risk.
Step-by-Step Process of Machining a Part
- Design the part in CAD, including any angled or hard-to-reach features.
- Import the model into CAM software. Set the tool orientation for each surface or feature.
- Choose the angle for the rotary axes (A and B) to orient the part correctly.
- Lock the part at that fixed tilt position. The machine does this using the rotary table or head.
- Run the machining cycle using standard three-axis motion. The tool moves in X, Y, and Z directions to cut the feature.
- Reposition if needed. If multiple angled surfaces exist, the machine rotates the part again and repeats the process.
Role of CAM Software in Toolpath Generation
CAM software plays a key role. It defines the angles for the rotary axes and creates the toolpaths for the three-axis movement. The software handles the math to align the tool correctly with each surface.
Modern CAM systems support 3+2 strategies. You can set up multiple orientations in one program. Each orientation gets its toolpath. The machine runs them one after another.
This reduces programming time and improves consistency. It also helps avoid collisions by simulating the tool and part positions before cutting.
Machine Setup and Workholding Requirements
Setup for 3+2 axis CNC machining needs stable fixturing. The part must be held securely during tilting and cutting. Any movement can cause errors or damage.
Most machines use a tilting rotary table or a swiveling head. The setup must allow full access to the part without interference. Fixtures should be compact and avoid blocking the toolpath.
Use soft jaws or custom fixtures if needed. Accuracy depends on the machine and how well the part is held during rotation.
Benefits of 3+2 Axis CNC Machining
3+2 machining gives you better reach, fewer setups, and smoother results. It’s a wise choice when you need angled features but don’t want the cost or complexity of complete five-axis systems.
More Complex Parts Made Simple
3+2 machining reaches angles that 3-axis machines can’t. It cuts complex shapes in one setup. No more struggling with awkward part positions or multiple fixtures.
Better Precision, Smother Finishes
The fixed-angle approach means less vibration and more consistent cuts. Parts come out more accurately with cleaner surfaces. You’ll spend less time on secondary finishing work.
Faster Production with Fewer Setups
Forget constantly repositioning parts. 3+2 machines handle multi-angle features in a single setup. This cuts your production time significantly compared to 3-axis machining.
Budget-Friendly Alternative to 5-Axis
Get 5-axis capabilities without the high price tag. 3+2 machines cost less to buy and operate. They’re perfect when you need angled cuts but don’t require simultaneous 5-axis movement.
Limitations and Challenges
While 3+2 machining offers many advantages, it’s not the perfect fit for every job. Some parts or features still require full five-axis motion. The tool, machine, or setup may limit others.
Not Ideal for Continuous Contour Machining
3+2 machining uses fixed positioning. The rotary axes tilt the part, then lock it in place. The toolpath stays in standard three-axis motion. This works well for flat surfaces or simple angles. But it can’t continuously follow smooth curves or complex contours that change direction.
Tool Reach and Collision Risk
Tilting the part to reach an angled face may require a longer tool. Longer tools can bend or vibrate, which affects accuracy and surface finish. Also, some angles create awkward tool paths. The risk of hitting clamps, fixtures, or the table goes up.
Machine Calibration and Maintenance Complexity
3+2 machines use rotary tables or swiveling heads. These need regular calibration to keep them aligned with the principal axes. If the rotary axes lose accuracy, it affects the whole setup. Even a small error in tilt angle can ruin the cut.
Common Applications
3+2 axis machining fits industries where precision and angled features matter. It works well for jobs requiring complex geometry but not full five-axis motion. Here are some key use cases.
Aerospace Components
3+2 machining creates complex brackets, mounts, and enclosures for aerospace. It handles the exact angles needed for wing components and engine parts. The process ensures tight tolerances for critical flight hardware.
Medical Device Machining
Medical manufacturers use 3+2 for precise bone screws, implant guides, and diagnostic tools. The angled machining capabilities produce the clean edges and sterile surfaces required for medical devices.
Automotive Prototypes
Automotive engineers rely on 3+2 for prototype transmission cases and suspension components. It quickly produces functional prototypes with properly angled features for testing.
Precision Tooling and Molds
Mold makers benefit from 3+2’s ability to machine deep cavities and complex draft angles. It creates injection molds and die-cast tools with precision, reducing polishing time.
Design for 3+2 Axis CNC Machining
Good part design makes machining faster, easier, and more accurate. When designing for 3+2 axis setups, you must consider how the part will be tilted, how tools will reach the surfaces, and how to avoid risky features.
Key Design Guidelines for Engineers
Start by identifying which features will need angled access. Group them so they can be machined from the same tilted position.
Keep critical surfaces within reachable angles. Design flat surfaces that can be easily aligned to a rotary tilt. Avoid designs that require constant angle changes.
Plan around standard tool lengths. Don’t place key features too deep inside the part, or far from the fixture base.
Minimize sharp internal corners. Use radii that match standard end mill sizes to reduce tool wear and machining time.
Avoiding Undercuts and Tool Interference
Avoid features behind walls or under surfaces unless you have special tools. Standard end mills can’t reach undercuts unless you plan to tilt the part.
When tilted, check for possible collisions between the tool, spindle, and part. Use CAM software to simulate tool paths from each angle.
Design fixtures to stay clear of the cutting zone. Slim, compact clamps and custom soft jaws help reduce interference when tilting the part.
Tolerancing and Dimensional Planning
Know which features will be machined in the same orientation. Group these features under the same tolerance zone.
Avoid applying tight tolerances across different angled faces. Changes in part tilt can introduce alignment shifts. It’s harder to hold close tolerances across multiple positions.
Use GD&T (Geometric Dimensioning and Tolerancing) to control how the part should be measured. Make sure your tolerances match what’s realistic in 3+2 setups.
Conclusion
3+2 axis CNC machining combines the simplicity of 3-axis cutting with the added flexibility of two fixed-angle rotary axes. It allows parts to be tilted and machined from multiple angles in a single setup. It is a cost-effective and practical solution for complex jobs that don’t require full five-axis motion.
Need parts with angled holes, chamfers, or multi-face features? Contact us now for fast, accurate machining solutions tailored to your project needs.
Hey, I'm Kevin Lee
For the past 10 years, I’ve been immersed in various forms of sheet metal fabrication, sharing cool insights here from my experiences across diverse workshops.
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Kevin Lee
I have over ten years of professional experience in sheet metal fabrication, specializing in laser cutting, bending, welding, and surface treatment techniques. As the Technical Director at Shengen, I am committed to solving complex manufacturing challenges and driving innovation and quality in each project.
