Manufacturing Process ME1107 Cutting tool and Cutting fluid

Course Overview

• Course No: MECO Manufacturing Process

• Instructor: Rubiat Mustak, Assistant Professor, Department of Mechanical Engineering, Khulna University of Engineering & Technology.

Recommended Reading

• Main Text: Machine Tool Engineering by G.R. Nagpal

Manufacturing Overview

Definition

• Manufacturing: Application of physical and chemical processes to alter geometry, properties, and appearance of materials to create parts or products.

  • Term "manufacture" comes from Latin: manus (hand) + factus (make).

Machine Tools

• Definition: Power-driven machines used for machining operations.

  • Functions:

    • Hold work parts stiffly.

    • Accurately position tools.

    • Provide power for machining processes.

  • Ensures high accuracy and repeatability.

Machining Process

Definition

• Machining: Manufacturing process to remove excess material using cutting tools.

Cutting Tools and Materials

Metal Cutting Process

• Definition: Thin layers of excess metal (chips) removed to achieve desired shape.

  • Motion: Relative motion between the workpiece and cutting tool, produced by rotary and/or translatory movements.

Relative Motion Types

1. Workpiece Rotation Against Tool: Example - Turning.

2. Tool Rotation Against Workpiece: Example - Drilling, Milling.

3. Linear Workpiece Movement Against Tool: Example - Planer.

4. Linear Tool Movement Against Workpiece: Example - Shaper.

Cutting Tools Characteristics

Essential Properties

1. Hardness: Must be harder than the workpiece.

2. Hot Hardness: Ability to retain hardness at elevated temperatures.

3. Low Friction: For better surface finish and reduced wear.

4. Wear Resistance: Achieve acceptable tool life before replacement.

5. Chemical Stability: Non-reactive with work materials.

6. Strength & Toughness: Handle shocks and vibrations.

7. High Thermal Conductivity: Dissipate heat effectively.

Metal Cutting Processes

Types

1. Chip Removal Processes: Obtain desired shapes by separating layers from the workpiece.

   • Examples: Turning, Shaping, Drilling, Milling, Honing, Grinding.

2. Non-Chip Removal Processes: Not covered in detail.

Examples of Cutting Processes

• Turning: Produces round parts using single-point cutting tools.

• Drilling: Produces cylindrical holes.

• Milling: Removes metal using a rotating cutter.

• Boring: Enlarges existing holes.

• Shaping: Reciprocates tool against a stationary workpiece.

Mechanics of Machining

• Objective: Create desired shape, size, and finish by removing excess metal.

• Compressive force exerted by cutting tool stresses work material past its yield point, causing plastic deformation and chip formation.

Shear Plane and Chip Formation

• Cutting Force: Force exerted to form chips.

• Heat generated in the cutting process contributes to tool wear.

Chip Types

1. Continuous Chips: Typically from ductile materials; ideal for smooth finishes.

2. Discontinuous Chips: Produced when cutting brittle materials; easier for disposal.

3. Continuous Chips with Built-Up Edge: Hard layer of material develops on the tool face, increasing surface roughness.

Tool Geometry

Cutting Tool Parts

1. Shank: Main body of the tool.

2. Face: Surface where the chip slides.

3. Flank: Adjacent surfaces to the cutting edge.

4. Cutting Edge: Edge removing material from workpiece.

Angles in Cutting Tools

• Back Rake Angle: Guides chip flow; variable based on material.

• Side Rake Angle: Influences chip bending and power requirements.

• End Cutting Edge Angle: Reduces vibration and chatter.

• Side Cutting Edge Angle: Controls chip flow and avoids built-up edge.

• Relief Angles: Prevent rubbing and overheating.

Chip Control

• Control in high-speed production is crucial for operator safety and tool integrity.

• Chip breakers effectively reduce the formation of long, continuous chips.

• Proper lubrication enhances chip flow and tooling life.

Cutting Conditions

Variables Affecting Conditions

1. Cutting Speed: The speed at which the tool moves over the workpiece.

2. Feed Rate: Slow lateral motion of the tool.

3. Depth of Cut: Penetration of the tool into the workpiece.

General Relationships

• Speed, feed, and depth of cut together influence the material removal rate.

Forces in Metal Cutting

Principal Forces

1. Cutting Force (Fc): Force in the direction of cutting.

2. Thrust Force (Ft): Perpendicular to the cutting force.

3. Shear Force (Fs): Causes shear deformation in the shear plane.

4. Normal forces associated with friction and shear are critical to balancing these forces.

Tool Life

Definition

• Time from when a tool begins operation until it requires reconditioning or replacement.

  • Indicators of tool life:

    1. Tool wear.

    2. Power increases during cutting.

    3. Poor surface finishes.

Factors Affecting Tool Life

• Machining variables, tool geometry, materials, temperature, type of cutting fluid, and workpiece properties.

Taylor's Tool Life Equation

• Relationship between tool life (T) and cutting speed (V).

  • Form: VTn = C; where n is the tool life exponent, C is a constant based on various factors.

Common Tool Materials

• Types:

  • High-Speed Steels (HSS)

  • Cemented Carbides

  • Coated Carbides

  • Ceramics

  • CBN (Cubic Boron Nitride)

  • PCD (Polycrystalline Diamond)

• Characteristics vary based on material use and geometry.

Cutting Fluids

Functions

• Cool cutting tools and workpieces.

• Lubricate to reduce friction and tool wear.

• Facilitate chip removal and prevent corrosion.

Properties of Cutting Fluids

• High thermal conductivity, good lubricating properties, stability, and non-corrosive.

Selection Factors for Cutting Fluids

• Based on cutting speed, material properties, tool material, fluid velocity, and cost considerations.

Summary of Self-Study Topics

• Review cutting tool requirements, comparison of cutting methods, and detailed properties of different cutting materials.