Face milling is a process that uses a milling cutter to perform cutting operations on the surface of a workpiece. At its core, face milling involves the removal of material from a workpiece to create a flat surface, typically achieved with a face milling cutter. This technique is distinct from other milling processes due to its focus on surface quality and the ability to handle a wide range of materials. Whether shaping a massive aircraft component or fine-tuning a delicate automotive part, face milling plays a pivotal role.
This guide will take you through face milling, face milling tools, face milling operations, and how face milling differs from perimeter and end milling.
What is face milling?
Face milling is a machining operation where a cutting tool with multiple sharp teeth, known as a face milling cutter, is used to remove material from the surface of a workpiece. This cutter is typically mounted on a spindle that rotates perpendicular to the workpiece’s surface, enabling it to cut a flat, smooth surface. The primary goal of face milling is to achieve a high-quality finish and precise flatness on the workpiece, making it a widely used technique in precision engineering and manufacturing sectors.
How does the face milling process work?
The basic mechanics of the face milling process involve a rotating cutter equipped with multiple teeth that methodically remove material from the surface of a workpiece. As the face milling cutter spins, each tooth intermittently cuts into the material, shaving off layers to create a flat, uniform surface. This process is highly efficient for machining large areas, with the depth of cut, cutter geometry, and feed rate being key factors that influence the final surface finish and dimensional accuracy.
Selecting the right tool for face milling
Selecting the right tool for face milling is crucial for achieving desired outcomes in terms of surface finish, dimensional accuracy, and overall milling process efficiency.
The material of both the workpiece and the cutter is fundamental. For instance, high-speed steel cutters are suitable for softer materials, while carbide or coated carbide cutters are preferred for more complex materials due to their higher hardness and heat resistance.
- Standard Face Mill Cutters
- These are the most common, featuring multiple teeth for efficient material removal. They are ideal for general face milling applications.
- Fly Cutters
- Best for low-quantity jobs, fly cutters have a single cutting edge and are known for producing excellent surface finishes.
- Shell Mills
- Used for heavier cutting loads, shell mills have a larger diameter and multiple inserts. They are efficient in removing large amounts of material quickly.
- End Mills
- While primarily used for end milling, they can be used for face milling to produce fine, detailed work on smaller surfaces.
The lead angle in a face milling cutter refers to the angle between the cutting edge of an insert and the surface of the workpiece.
45-Degree Lead Angle
This is a commonly used angle that provides a good balance between cutting force and chip thickness. A 45-degree angle tends to produce thinner chips and requires less cutting force, leading to smoother cuts.
90-Degree Lead Angle
Cutters with a 90-degree lead angle produce thicker chips and have a more direct approach in slicing the material. This angle is often chosen for operations where material removal rate is a priority. However, it requires more cutting force and might not always provide as smooth a finish as lower angles.
Pitch of the Cutter
The pitch of a face milling cutter refers to the spacing between the inserts or teeth on the cutter’s body.
Cutters with a fine pitch have more teeth and smaller spaces between them. This configuration allows more teeth to engage with the material at any given time, distributing the load more evenly. It results in a smoother finish and is ideal for finishing operations or working with more challenging materials.
In contrast, a coarse pitch cutter has fewer teeth with larger spaces between them. This design allows for deeper cuts and higher material removal rates, as each tooth can remove more material. However, this can lead to a rougher surface finish and is generally used in roughing operations or when large amounts of material must be removed quickly.
Types of face milling operations
Face milling encompasses various operations, each tailored for specific needs and outcomes.
1. Conventional Face Milling
Also known as up milling, the cutter rotates against the feed in this operation. It is generally used for removing large amounts of material quickly. Conventional face milling is less prone to chipping the workpiece but can produce a rougher finish.
2. Climb Face Milling
Here, the cutter rotates with the feed. Climb milling provides a better surface finish and is more efficient as it exerts less force on the workpiece. However, it requires a more rigid machine setup to control backlash.
3. Heavy Duty Face Milling
This operation involves a considerable depth of cut with a high material removal rate. Heavy-duty face milling is used for roughing operations and is characterised by its aggressive cutting action.
4.Fine Face Milling
Aimed at achieving a high-quality surface finish, fine face milling uses a light depth of cut and high speeds. It’s ideal for finishing surfaces to precise dimensions and smoothness.
5.Contour Face Milling
In this operation, the cutter follows a path to create complex shapes or profiles on the workpiece. It’s often used for die and mould making.
6.High-Speed Face Milling
Utilising high rotational speeds, this technique is effective for roughing and finishing, especially in softer materials or for producing complex geometries with fine details.
Comparative analysis of various face milling techniques
|Face Milling Technique
|Best Used For
|Material Removal Rate
|Less rigid setups, where finish is not a primary concern
|Less rigid machines
|Modern setups where a smooth finish is desired
|More rigid, precise machines
|Heavy Duty Milling
|Roughing operations, large material removal
|Robust, powerful machines
|Final stages for precise dimensions and smoothness
|High precision machines
|Creating complex shapes or profiles
|Precise, CNC machines
|Both roughing and finishing, especially in softer materials or complex shapes
|High-speed, versatile machines
What are the advantages of face milling?
The advantages of face milling include:
- Enhanced Surface Coverage
- Improved Surface Finish Quality
- Precision in Flatness and Angularity
- Efficient Chip Evacuation
- Reduced Tool Wear
- Suitable for a variety of materials (e.g. plastics, composites, metals)
- High-speed cutting
When to use face milling
It is ideal for creating flat surfaces, especially on large workpieces. It’s commonly used in automotive, aerospace, and heavy machinery industries.
Face milling is suitable for a broad spectrum of materials, including metals like steel, aluminium, cast iron, plastics and composites.
Mold and Die Making
Highly effective in mass production settings, where consistent quality and high efficiency are required.