MPEN 414 and MPEN 518 semester one notes

1. MACHINE TOOL TECHNOLOGY Introduction to Machine Tool Technology A machine tool is a power-driven device designed to remove material from a workpiece, usually in the form of chips, to produce a desired shape, size, and surface finish. These machines achieve this by holding both the workpiece and a cutting tool in controlled relative motion. Common examples include lathes, milling machines, drilling machines, grinders, and CNC machining centers. Machine tool technology is the branch of engineering that studies the design, operation, capabilities, and applications of these machines, along with the cutting tools, workholding methods, and process parameters required for efficient manufacturing.

2. Why It Is Necessary for an Engineering Student Foundation of Manufacturing – Most mechanical components in industries (gears, shafts, housings, molds) are produced using machine tools. Understanding them is essential for any engineer working in design, production, or maintenance. Bridging Design and Production – An engineer must design components that can be manufactured economically and accurately. Knowledge of machine tools ensures designs are practical and compatible with available manufacturing processes. Quality and Precision – Machine tools enable high accuracy and surface finish, which are critical in fields like aerospace, automotive, robotics, and medical devices. Technological Adaptation – Modern industry relies on CNC and automated machine tools, which integrate mechanical systems with electronics and software. Understanding them prepares students for Industry 4.0 and smart manufacturing environments. Problem-Solving and Innovation – Knowledge of machining principles helps engineers troubleshoot production issues, optimize processes, and develop innovative solutions for manufacturing challenges.

3. Types of Machine Tools Turning machines (lathes, CNC lathes) Milling machines (horizontal, vertical, CNC mills) Drilling machines Shaping and slotting machines Grinding machines Broaching machines Sawing machines Special purpose machine tools Cutting Tool Technology Tool materials (HSS, carbides, ceramics, CBN, diamond) Tool geometry, coatings, and life Chip formation and cutting mechanics

4. Machining Processes and Parameters Cutting speed, feed rate, depth of cut Material removal rate (MRR) Surface finish and tolerance control Workholding & Fixturing Chucks, collets, vises, clamps, jigs, fixtures Automation in Machine Tools CNC (Computer Numerical Control) principles DNC (Direct Numerical Control) systems Tool changers, probes, and adaptive control Maintenance & Troubleshooting Preventive, predictive, and corrective maintenance Alignment, lubrication, and calibration Safety and Standards OSHA/ISO machine tool safety Proper guarding, PPE, and operator training

5. SHARP CUTTING TOOL Classification of material removal processes. hard, abrasive particles VARIOUS FORMS OF ENERGY

6. Machining Machining is a manufacturing process in which a sharp cutting tool is used to cut away material to leave the desired part shape. The predominant cutting action in machining involves shear deformation of the work material to form a chip; as the chip is removed, a new surface is exposed. Machining is not just one process; it is a group of processes. The common feature is the use of a cutting tool to form a chip that is removed from the workpart. To perform the operation, relative motion is required between the tool and work. This relative motion is achieved in most machining operations by means of a primary motion, called the cutting speed, and a secondary motion, called the feed.

7. Machining is important commercially and technologically for several reasons:

8. On the other hand, certain disadvantages are associated with machining and other material removal processes:

9. Types of Machining Operations The three most common types: turning, drilling, and milling. In turning, a cutting tool with a single cutting edge is used to remove material from a rotating workpiece to generate a cylindrical shape. The speed motion in turning is provided by the rotating workpart, and the feedmotion is achieved by the cutting tool moving slowly in a direction parallel to the axis of rotation of the workpiece. Drilling is used to create a round hole. It is accomplished by a rotating tool that typically has two cutting edges. The tool is fed in a direction parallel to its axis of rotation into the workpart to form the round hole. In milling, a rotating tool with multiple cutting edges is fed slowly across the work material to generate a plane or straight surface. The direction of the feedmotion is perpendicular to the tool’s axis of rotation. The speedmotion is provided by the rotating milling cutter. The two basic forms of milling are peripheral milling and face milling.

10. Other conventional machining operations include shaping, planing, broaching, and sawing. Also, grinding and similar abrasive operations are often included within the category of machining.

11. Cutting Tool Definition:A cutting tool is a device with one or more sharp edges, made from material harder than the workpiece, used to remove material in the form of chips. Key Surfaces & Angles: • Rake Face: Directs chip flow; set at a rake angle (α) – positive or negative. • Flank: Provides clearance to avoid abrasion; set at a relief angle. Types of Cutting Tools: • Single-Point Tool • One cutting edge (e.g., turning). • Has a nose radius for strength and finish. • Multiple-Cutting-Edge Tool • Several cutting edges (e.g., drilling, milling). • Usually rotates during operation. Function:Separates a chip from the parent material, shaping the workpiece with precision.

13. Cutting Conditions 1. Definition Cutting conditions are the set of parameters that define how the tool and workpiece move relative to each other during machining. They determine productivity, surface finish, and tool life. Main Parameters: • Cutting Speed (v): Primary motion speed between tool and workpiece (m/s or ft/min). • Feed (f): Lateral movement per revolution or stroke (mm/rev or in/rev). • Depth of Cut (d): Penetration of the cutting tool into the workpiece (mm or in). Material Removal Rate (MRR):

14. 2. Interpretation in Different Operations • Turning: • Feed in mm/rev • Depth in mm from surface to cut bottom • Drilling: • Depth refers to the drilled hole depth • 3. Categories of Machining Operations • a) Roughing Cuts • Purpose: Remove large material volume quickly • Feeds: 0.4 – 1.25 mm/rev • Depths: 2.5 – 20 mm • Speed: Lower than finishing • Result: Near-net shape, leaves allowance for finishing • b) Finishing Cuts • Purpose: Achieve final dimensions, tolerance, and surface finish • Feeds: 0.125 – 0.4 mm/rev • Depths: 0.75 – 2.0 mm • Speed: Higher than roughing

15. 4. Cutting Fluid Use • Purpose: Cool and lubricate tool, improve tool life and finish • Considerations: Material type, tool type, and operation specifics • 5. Importance • Directly affects machining time, quality, cost, and tool wear • Selection depends on work material, tooling, and desired outcome

16. CHIP FORMATION IN METAL MACHINING Chip formation is the process by which material is removed from a workpiece in the form of chips during a machining operation. It occurs when a cutting tool shears the material ahead of it, separating it from the parent body. How It Happens (Mechanics of Cutting) The cutting tool is harder than the workpiece. As it moves forward, the tool edge applies shear stress to the work material. The material ahead of the tool reaches its shear strength and shears along a narrow shear plane, separating as a chip. The rake face of the tool guides the chip away from the cutting zone.

17. Surfaces in Chip Formation • Rake Face: Top surface of the tool where the chip flows. • Flank Face: Clears the newly formed surface to prevent rubbing. • Shear Plane: Imaginary plane where the material deformation and separation occur. • Types of Chips • Continuous Chips • Formed in ductile materials at high cutting speeds and small feeds and depths. • Smooth surface finish, but can tangle because they are long and continous. • Reduced friction with cutting fluid or chip breakers on the turning tool to enhance their disposal. • Discontinuous (Segmented) Chips • Produced in brittle materials or under low cutting speeds/high feeds. • Appear as small segments that break off. • Poor surface finish(tends to impart an irregular texture to the machined surface) but easy chip disposal. • High tool–chip friction and large feed and depth of cut promote the formation of this chip type.

18. Continuous Chips with Built-Up Edge (BUE) • A small piece of work material welds to the tool tip due to pressure and heat. • Periodically breaks off, affecting surface finish and tool life. • Occurs when machining ductile materials at low-to-medium cutting speeds. • Cause: High friction between tool and chip causes work material to adhere to the rake face near the cutting edge. • Process: BUE forms, grows, becomes unstable, and breaks off in cycles. • Effects: • Detached BUE may carry away portions of tool rake face → reduces tool life. • BUE fragments may embed in work surface → poor surface finish. • Nature: Cyclical and undesirable in precision machining.

19. Serrated Chips (Shear-Localized Chips) Appearance: Saw-tooth or segmented shape. • Formation: Caused by cyclical chip formation with alternating high and low shear strain. • Common in: • Difficult-to-machine metals (titanium alloys, nickel-based superalloys, austenitic stainless steels) at high cutting speeds. • Also occurs in steels at high speeds. • Nature: Semi-continuous — between continuous and discontinuous chip types.

20. The orthogonal cutting model • Definition • Orthogonal cutting is a machining model where the cutting edge of the tool is straight, perpendicular (90°) to the direction of tool travel, and the cutting process happens in two dimensions only. • It is mainly used for theoretical and experimental studies because it simplifies analysis of forces, chip formation, and temperature. • Main Characteristics • Cutting edge orientation: Perpendicular to cutting direction (no inclination). • Chip flow: Chips move in a direction normal to the cutting edge. • Tool geometry: Usually a single-point tool with a defined rake angle. • Deformation zone: Material shears along a single shear plane.

21. Forces measured: • Cutting force (Fc): Parallel to cutting direction. • Thrust force (Ft): Perpendicular to cutting direction. • Key Parameters in Orthogonal Cutting • Rake Angle (α): Angle between rake face and normal to cutting direction. • Shear Plane Angle (φ): Angle between shear plane and cutting direction. • Chip Thickness Ratio (r):

22. Forces measured: • Cutting force (Fc): Parallel to cutting direction. • Thrust force (Ft): Perpendicular to cutting direction. • Key Parameters in Orthogonal Cutting • Rake Angle (α): Angle between rake face and normal to cutting direction. • Shear Plane Angle (φ): Angle between shear plane and cutting direction. • Chip Thickness Ratio (r):

23. Applications • Understanding chip formation mechanics. • Calculating cutting forces and power requirements. • Studying tool wear and temperature rise in cutting. • Serves as a foundation for more complex 3D cutting models (like oblique cutting). • Limitations • Real machining is often oblique, not purely orthogonal. • Doesn’t capture side-flow of chips or multi-directional stresses.