Milling: Techniques and Machines

• Milling is a machining process that uses rotary cutters to remove material from a workpiece by advancing (or feeding) the workpiece past the cutter.

Operational techniques

• Climb milling (also called down milling) is a milling process where the direction of the cutter's rotation is the same as the feed direction.
• Conventional milling (also called up milling) is a milling process where the direction of the cutter's rotation is opposite to the feed direction.
• Face milling is a milling process where the cutter axis is perpendicular to the surface being milled.
• Peripheral milling is a milling process where the cutter axis is parallel to the surface being milled

Types of milling machines

• Knee-type milling machine: Characterized by a vertically adjustable worktable resting on a saddle, which in turn is supported by a knee.
  • The knee is a casting that slides vertically on the machine column, allowing adjustments for different workpiece heights.
• Bed-type milling machine: Features a worktable directly mounted on the bed, offering higher rigidity and accuracy compared to knee-type machines.
  • Suited for heavier cuts and production runs where consistent precision is required
• Ram-type milling machine: Employs a ram, a sliding member that carries the spindle head, allowing it to be positioned closer to the workpiece for improved stability.
  • Offers flexibility in positioning the cutting tool.
• Planer-type milling machine: Designed for machining large, heavy workpieces, resembling a planer but equipped with milling spindles.
  • Multiple cutting heads enable simultaneous machining operations on different surfaces of the workpiece.
• Special-purpose milling machine: Includes machines designed for specific tasks, such as thread milling, gear cutting, and profile milling.
  • These machines are optimized for efficiency and precision in their respective applications.

Machine components

• Base: Provides a stable foundation for the machine, typically made of cast iron to absorb vibrations and ensure rigidity.
• Column: Vertical support structure that houses the spindle drive mechanism and provides a mounting surface for the knee or table.
• Knee: Adjustable support that carries the saddle and worktable in knee-type milling machines, allowing for vertical positioning of the workpiece.
• Saddle: Slides horizontally on the knee, providing one axis of movement for positioning the workpiece relative to the cutting tool.
• Worktable: The surface on which the workpiece is mounted and secured, providing the X and Y axes of movement for positioning during machining.
• Spindle: Rotating shaft that holds and drives the cutting tool, with bearings and drive mechanisms to ensure smooth and accurate rotation.
• Arbor: A shaft or axle that supports rotating cutting tools, such as milling cutters or saws, especially in horizontal milling machines.
• Overarm: An adjustable support that extends from the column to provide additional support to the arbor, reducing vibration and deflection during cutting.
• Head: The assembly that houses the spindle, drive motor, and related components, often capable of swiveling or tilting to allow for angled machining.
• Feed mechanisms: Systems that control the movement of the worktable and cutting tool, including lead screws, gears, and motors, to achieve precise feed rates and depths of cut.