What is Milling?

Milling is a type of machining process that has generally been used to make different mechanical components made of such materials as plastic and metal. Its final products are very accurate due to the accuracy of the tools involved in their manufacture.

In this article, we look at some of the types of machines used in milling, some of the various kinds of tools employed, and the range of shapes obtainable from the process.

What is Milling?
Milling is a machining process in which some cutting tools, commonly referred to as milling cutters, rotate at very high speeds to enable the cutting of a workpiece that is affixed to a worktable. By simply changing these cutting tools, milling can perform a variety of shapes such as flat and curved surfaces, drilled holes, and grooves.
Because it can move in three dimensions, this process can produce complex shapes. On most of its types, the milling cutters move up and down while the worktable holding the workpiece slides sideways horizontally. Howsoever, all will depend on the choice of the right machine which fixes what shape can be machined.
Milling machines come in two major classes, namely: Vertical Milling Machine The spindle is perpendicular to the worktable. It is the most common milling machine found in machine shops. Horizontal Milling Machine The spindle is parallel to the surface of the worktable.

Key Milling Machines

1. Universal Milling Machine
This machine features a manually operated milling table where cutting tools are attached and controlled by hand. The quality of the output heavily relies on the operator’s skill and experience. With a skilled operator, it can deliver precise and high-quality results, making it suitable for complex shapes, prototypes, and high-precision tasks.

2. Numerical Control (NC) Milling Machine
An NC milling machine is computer-controlled, enabling operators to set precise processing conditions. Unlike manual universal machines, NC machines minimize variations in output quality, improving both efficiency and consistency in manufacturing.

3. Machining Center
A machining center combines NC capabilities with automatic tool-changing functions, holding multiple tools simultaneously for seamless operations. This feature greatly enhances work efficiency and supports complex, high-precision machining. At meviy, machining centers are the primary tools used to ensure top-quality milled parts for customers.

4. Numerical Control Gear Cutting Machine
This specialized machine is designed for gear manufacturing. It uses a cutting tool called a “hob” to precisely machine gears, allowing for easy adjustments to the number of teeth and automatic hobbing. These features make NC gear-cutting machines ideal for efficient, high-precision gear production.

Types of Milling Tools

The precision of milled parts depends heavily on the tools employed. Here are four common milling tools and their features:

1. Face Milling Cutter

• Features multiple blades around a circular edge.
• Rotates parallel to the workpiece to machine flat surfaces efficiently.
• Ideal for machining large, flat areas with high precision.
• Commonly used with vertical milling machines.

2. End Mill

• A versatile, drill-like tool used for flat, stepped, and groove machining.
• Includes various types, such as:
  • Square End Mills: Flat-tipped for sharp-edged machining.
  • Ball End Mills: Spherical tips for machining curved surfaces.
• Suitable for intricate shapes and reduces frequent tool changes. Typically features two to four blades, depending on the application.

3. Groove Milling Cutter

• Designed for machining grooves by rotating circular blades parallel to the workpiece.
• The width and depth of grooves depend on the blade's dimensions.
• Offers faster cutting speeds and higher precision for long, deep grooves.

4. Plain Milling Cutter

• Cylindrical with blades on its outer surface, used with horizontal milling machines.
• Efficient for material removal during flat surface machining.
• Ideal for rough machining, though less precise than face milling cutters.

Types of Milling Operations

Below are some common milling operations, each suited for specific tasks and outcomes:

Flat Surface Machining

Flat surface machining involves cutting a workpiece to create a flat surface. The workpiece is mounted on a table that moves back and forth or side to side during cutting.

• Tools & Machines: Typically performed with a face milling machine (vertical type) or a flat milling machine (horizontal type).
• Considerations: End mills can be used but are better suited for machining smaller flat areas rather than large surfaces.

Side Milling

Side milling cuts the sides of a workpiece by moving the tool up and down, often using face mills, end mills, or side cutters attached to a horizontal mill.

• Primary Use: This operation is primarily used for roughing.

Step Milling

Step milling creates steps by simultaneously machining the face and sides of a workpiece.

• Tools: Face milling is ideal for wide surfaces or small steps, while end milling is more effective for narrow surfaces and high steps.

Grooving

Grooving machines a groove into the workpiece using tools like end mills or slotting machines.

• Process:
  • End mills cut the groove to the required depth.
  • For wider grooves, T-groove cutters can shape grooves with broader bottoms, such as those used in bolt fittings.

Hole Machining

Hole machining drills precise holes into a workpiece.

• Tools:
  • A center hole drill creates a guide hole, followed by a drill bit for deeper cuts.
  • End mills are often used for holes requiring high positional accuracy, as they can machine both the surface and hole without tool changes.

3D Machining

3D machining uses simultaneous control of the tool and table via numerical control (NC) to create complex 3D shapes.

• Operation: Known as simultaneous 3-axis machining, this process offers unmatched precision for intricate designs.

Conclusion

Milling is a foundational technique for manufacturing custom mechanical components, providing versatility, precision, and efficiency. From traditional manual mills to advanced NC machining centers, the choice of machine and tool is crucial for achieving optimal results. Milling processes allow for the creation of intricate designs, ensuring custom components meet exacting quality and functionality standards. As technology continues to evolve, milling remains at the forefront of precision manufacturing, enabling innovation across industries.