Orthogonal Cutting Process in Machining: Definition, Principles, and Applications

What is Orthogonal Cutting?

Orthogonal cutting is a basic machining process used in metal cutting operations where the cutting edge of the tool is oriented perpendicular (at a 90-degree angle) to the direction of the tool's movement or cutting velocity. It is one of the simplest types of metal removal processes and serves as an idealized model to understand the mechanics of cutting.

Key Aspects of Orthogonal Cutting

• Cutting Edge Orientation: The cutting edge is straight and oriented at 90 degrees to the cutting velocity vector.
• Tool Geometry: The tool has a narrow width relative to the chip thickness, meaning the cutting action happens in a 2D plane.
• Shear Plane Formation: A shear plane forms between the uncut material and the chip, where the material shears off to form a chip.
• Chip Flow: Chips flow perpendicular to the cutting edge along the chip-break direction.

How Orthogonal Cutting Works

During orthogonal cutting, the tool removes material by shearing it along a specific plane. The material ahead of the tool is stressed and deformed until it separates and forms a chip that slides over the tool's rake face. The angle at which the material shears off is referred to as the shear angle. Understanding this angle helps in analyzing forces, stresses, and cutting efficiency.

Parameters in Orthogonal Cutting

• Cutting Speed: Speed of the tool relative to the workpiece.
• Feed Rate: Thickness of the uncut chip (or depth of cut in a 2D sense).
• Shear Angle: Angle of the shear plane affecting chip thickness and forces.
• Rake Angle: Angle between the rake face and a plane perpendicular to the cutting direction, influencing cutting forces and chip formation.

Significance and Applications

Orthogonal cutting serves as the foundational theory for analyzing cutting mechanics. It simplifies the complex 3D cutting to 2D and helps engineers:

• Estimate cutting forces and power requirements.
• Predict chip formation and types (discontinuous, continuous, or built-up edge).
• Design cutting tools with appropriate geometry (rake angle, clearance angle).
• Improve machining performance and tool life.

Comparison to Other Cutting Types

Unlike oblique cutting, where the cutting edge is at an angle other than 90 degrees to the cutting velocity, orthogonal cutting assumes a perpendicular edge simplifying analysis. While orthogonal cutting is mostly theoretical and used in studies, practical machining often involves oblique cutting.

Summary

Orthogonal cutting is a fundamental machining concept where the cutting edge is at a right angle to the cutting direction. It involves shearing the material along a shear plane, leading to chip formation and material removal. It is crucial for understanding cutting mechanics and designing machining processes.