Peripheral milling, also known as cylindrical milling, is a fundamental process in computer numerical control (CNC) machining. It involves the use of a cylindrical milling cutter to remove material from a workpiece. The cutting edge of a peripheral milling tool is located on the circumference of the tool, making it suitable for specific applications where high thickness and hardness materials, particularly curved surfaces with large curvature changes, need to be machined.
Basics of Peripheral Milling
In CNC machining, peripheral milling is distinct from end milling, where the cutting edge is on the outer arc of the tool. Peripheral milling leverages the tool’s full advantage, such as maximum cutting speed, stable cutting force, and lower cutter shaft deformation. When changing the tool inclination, the working surface of the tool can better match the surface of the machined parts and adapt to its curvature changes.
Practical Example: Milling a Complex Geometry
Consider the task of milling a complex gear geometry. The process would involve several steps:
- Model Creation: Using CAD software, create a 3D model of the gear geometry. This model will be used to generate the tool paths.
- Tool Path Generation: Import the CAD model into CAM software and generate the tool paths for peripheral milling. Pay attention to detail, ensuring that the tool paths follow the contours of the gear teeth accurately.
- Machine Setup: Securely clamp the workpiece in the CNC machine and align it with the tool path. Set the spindle speeds, feed rates, and coolant application according to the material and tool selection.
- Execution: Run the CNC program, allowing the machine to execute the tool paths and mill the gear geometry. Monitor the process closely to ensure that everything proceeds as planned.
- Inspection: Once the milling is complete, inspect the workpiece for accuracy and surface finish quality. Use precision measurement tools, such as coordinate measuring machines (CMMs), to verify that the geometry meets the design specifications.
Types of Peripheral Milling
Conventional vs. Climb Milling
There are two main types of peripheral milling: conventional (Up Milling) and climb milling (Down Milling). Conventional milling involves the cutter rotating against the direction of the feed, while climb milling has the cutter moving in the same direction as the feed. Each type has its own applications and advantages depending on the specific machining requirements.
| Conventional Milling (Up Milling) | Climb Milling (Down Milling) |
|---|---|
| Cutter rotates against the feed direction | Cutter rotates in the same direction as the feed |
| Increases during the cut | Decreases during the cut |
| Generally produces a rougher surface | Typically results in a smoother finish |
| Greater tool wear due to impact forces | Less tool wear due to lower impact forces |
| Higher vibration levels can occur | Generally reduces vibration |
| Workpiece tends to lift during milling | Workpiece remains securely in place |
| Suitable for roughing operations | Ideal for finishing operations |
Detailed Peripheral Milling Methods
Peripheral Milling Methods
- Slot Milling: Produces slots and grooves.
- Plain Milling: Utilizes a flat cutter for broad surfaces.
- Side Milling: Engages the side of the cutter to create profiles.
- Profile Milling: Contours edges for complex shapes.
- Straddle Milling: Uses multiple cutters for parallel sides.
- Keyway Milling: Cuts precise keyways in shafts.
- Contour Milling: Follows specific shapes for custom parts.
Peripheral Milling Cutters
- Slab Mills: For wide surfaces.
- End Mills: Versatile for various shapes.
- Fly Cutters: Single-point tool for smooth finishes.
- Face Mills: Multi-tooth cutters for high material removal.
- T-Slot Cutters: Designed for cutting T-slots.
- Chamfer Cutters: Creates chamfered edges.
- Ball Nose End Mills: Rounded tips for 3D contouring.
Tips for Selecting the Right Tool
- Evaluate material compatibility with the cutter.
- Choose appropriate cutter diameter based on the job.
- Assess cutter geometry for task-specific requirements.
Critical Parameters in Peripheral Milling Operations
Key parameters play a significant role in optimizing the efficiency and quality of peripheral milling:
- Cutting Speed: The cutter’s rotational speed relative to the workpiece.
- Feed Rate: The distance the cutter advances per rotation.
- Depth of Cut: The thickness of material removed per pass, affecting tool life and surface finish.
Understanding Chip Thickness to Width of Cut Ratio
This ratio is crucial for optimizing tool wear and enhancing material removal efficiency. Proper management of this ratio leads to improved machining performance and longer tool life.
Workpiece Entry Techniques: Advantages of Rolling Into the Cut
The method of workpiece entry is vital for performance. Rolling into the cut minimizes shock and wear on tools, promoting smoother operations and extending tool longevity.
Cutting Force Modeling for Effective Cutter Entry
A robust cutting force model aids in predicting performance outcomes, facilitating optimal selections for feed rates and cutting depths. This modeling is essential for maintaining consistent machining quality.
Benefits of the Rolling-In Entry Technique
Rolling-in entry reduces vibration and enhances tool life, allowing for a gradual engagement with the workpiece that optimizes overall cutting performance.
Peripheral Milling vs. Face Milling: Key Differences
While both techniques are used for surface finishing, face milling employs a cutter that rotates perpendicular to the workpiece, ideal for flat surfaces. In contrast, peripheral milling uses cutting edges aligned parallel to the workpiece surface, making it effective for detailed and complex features.
| Peripheral Milling | Face Milling |
|---|---|
| Cutter rotates parallel to the workpiece surface | Cutter rotates perpendicular to the workpiece surface |
| Ideal for detailed profiles and intricate features | Best for flat surfaces and surface finishing |
| Engages the side of the cutter | Engages the face of the cutter |
| Generally produces thicker chips | Produces thinner chips due to higher cutting speeds |
| Slab mills, end mills, fly cutters | Face mills, end mills, shell mills |
| Can operate in both conventional and climb milling | Typically climb milling for better surface finish |
| Slots, grooves, complex contours | Flat surfaces, large area machining |
| Can vary; may require additional finishing processes | Generally achieves a better surface finish |
| Can handle deeper cuts effectively | Typically shallower cuts for finish |
Comparison with Other Milling Methods
Peripheral milling differs from other milling methods, such as end milling and face milling, in several key ways:
- Cutting Edge Location: In end milling, the cutting edge is located on the outer arc of the tool, making it ideal for smaller and more intricate cuts. In contrast, the cutting edge of a peripheral milling cutter is on the circumference, allowing for faster material removal.
- Application Scope: Face milling is typically used for flat surfaces, while peripheral milling is better suited for curved surfaces and complex geometries.
- Tool Wear and Life: Due to the differences in cutting forces and temperatures, the tool wear patterns and life expectancy can vary significantly between these methods.
Advantages and Applications
Peripheral milling offers several advantages over other machining methods:
- Efficiency: The large cutting edge of the cylindrical milling cutter allows for faster material removal rates, reducing overall machining time.
- Precision: The CNC machine’s ability to follow precise tool paths ensures high dimensional accuracy and surface finish.
- Versatility: Peripheral milling can be applied to a wide range of materials, including metals, plastics, and composites.
- Adaptability: The process can be easily adapted to complex geometries and intricate patterns through the use of advanced CAM software.
Due to these advantages, peripheral milling is commonly used in a variety of industries, including aerospace, automotive, and medical device manufacturing. It is particularly suited for applications requiring high precision and complex shapes, such as the production of gears, turbines, and implants.
Challenges and Considerations
Despite its advantages, peripheral milling also presents some challenges:
- Tool Wear: The high cutting forces and temperatures generated during the process can lead to rapid tool wear and deformation. Regular tool inspection and replacement are essential to maintain process stability and part quality.
- Vibration: The large cutting edge of the milling cutter can increase the risk of vibration, which can affect surface finish and dimensional accuracy. Proper fixture design and machine stiffness are critical to minimize vibration.
- Programming Complexity: Achieving the desired tool path and cutting parameters requires advanced programming skills and a thorough understanding of the machining process.
To overcome these challenges, manufacturers often invest in high-quality tooling, advanced fixture designs, and state-of-the-art CAM software. Additionally, regular machine maintenance and operator training are essential to ensure optimal process performance.
Conclusion
Peripheral milling is a versatile and powerful technique in CNC machining. By understanding its principles, advantages, and challenges, manufacturers can harness its full potential to produce high-quality components efficiently. With the right tool selection and optimization, peripheral milling can be a key driver of productivity and innovation in modern manufacturing.
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This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
