Manufacturing Processes- Module 1


Course Objectives

  • To introduce fundamental manufacturing processes, including casting, forming, and joining.

  • To develop skills in conventional and advanced machining, tooling, and finishing techniques.

  • To familiarize students with advanced modern manufacturing technologies such as advanced machining and additive manufacturing.

Course Outcomes

At the end of the course, the students will be able to:

  • Explain the principles and steps involved in casting and particulate processing, including powder metallurgy and ceramic techniques.

  • Describe forming and welding processes, identify common defects, and discuss basic inspection methods.

  • Apply machining principles, including tool geometry and cutting mechanics, to conventional and abrasive finishing operations.

  • Select suitable advanced machining and additive manufacturing processes based on product requirements and applications.

  • Demonstrate basic workshop skills in casting, forming, welding, machining, and finishing through hands-on practice.

Module-1: Introduction to Manufacturing & Casting Processes

Introduction to Manufacturing

  • Overview of Primary and Secondary Manufacturing processes

  • Fundamentals of casting and solidification of metals

  • Casting variations: sand casting, die casting, investment casting, centrifugal casting, and shell molding

  • Casting defects, inspection methods

  • Recent advances in casting technology

Introduction to Manufacturing (an illustrative view)

  • Prompt: Give me a list of things you use from the time you wake up to reaching the class.

  • All these products have been manufactured in a factory somewhere.

  • Manufacturing is defined as the creation of finished goods through tools, machines, labor, chemical processing, etc.; processing or transforming raw materials into finished products, driving innovation, and supporting various other industries.

Origin of Manufacturing

  • Latin roots: Manus = Hand and Facere = to make

  • Manufactus (To Make by Hand) → Facere Manus → Manufacturing

Overview of Primary and Secondary Manufacturing Processes

  • Primary: Converting raw materials into basic parts

  • Examples: Casting, Forging, Extrusion, etc.

  • Secondary: Converting basic parts into finished products

  • leads to finished products like furniture, appliances, gears, etc.

Feature (Primary vs Secondary) – Summary

  • Definition

    • Primary: Converts raw materials into basic shapes

    • Secondary: Processes that refine, modify, or assemble those shapes

  • Input Material

    • Primary: Raw materials (ore, molten metal, plastic pellets, etc.)

    • Secondary: Semi-finished products (castings, rolled sheets, etc.)

  • Purpose

    • Primary: To form the initial shape of a product

    • Secondary: To improve accuracy, appearance, function

  • Type of Change

    • Primary: Major shape change

    • Secondary: Detailing, finishing, or joining or assembling

  • Output

    • Primary: Semi-finished goods (blanks, billets, sheets, etc.)

    • Secondary: Finished goods

  • Energy & Equipment

    • Primary: Often high-energy, heavy machinery

    • Secondary: Medium to low and precision equipment

  • Material Waste

    • Primary: Typically less waste, forming-based

    • Secondary: May involve material removal (e.g., chips in machining)

  • Complexity

    • Primary: Simpler shapes, high volume

    • Secondary: More precision and accuracy

  • Examples

    • Primary: Casting, forging, rolling, extrusion, molding

    • Secondary: Machining, welding, painting, drilling, assembling

Fundamentals of Casting and Solidification of Metals

  • Casting: A primary manufacturing process where molten metal is poured into a mold cavity and allowed to solidify into a desired shape; one of the oldest and most versatile metal shaping methods.

  • Steps in Casting (overview):

    • Finishing

    • Shakeout

    • Solidification

    • Pattern making

    • Mould making

    • Melting

    • Pouring

  • Source: YouTube reference provided: https://www.youtube.com/shorts/k4vjMTg3Rq4

Basic Steps in the Casting Process

  • Pattern Making: A replica of the part (usually wood, plastic, or metal) used to create the mold cavity.

  • Mold Making: Mold prepared using sand, metal, or ceramic materials; molds can be expendable or permanent.

  • Melting: Metal melted in a furnace to reach the required temperature.

  • Pouring: Molten metal poured into the mold through a gating system.

  • Solidification: Metal cools and solidifies to the shape of the mold cavity.

  • Shakeout: Mold is broken and the solid part is removed.

  • Finishing: Removing extra metal, surface cleaning, and quality checks.

Sand Casting – Overview

  • Sand casting is the most common and versatile casting process, accounting for more than >90\% of all metal castings.

  • Materials: Granular refractory material (e.g., silica, zircon, olivine, chromite sand) mixed with clay and water; packed around a pattern to form the mold cavity.

  • Mold types: Expendable (used once) or permanent (reused).

Sand Casting – Key Features

  • Simple and scalable process

  • Low tooling costs

  • Wide material compatibility

  • Versatile for complex shapes

  • Flexible size range

  • Rough surface finish

  • Slow production rate and quantity

  • Environmentally friendly

Sand Casting – Advantages and Disadvantages

  • Advantages:

    • Relatively inexpensive in production costs, especially in low-volume production

    • Fabrication of large components

    • Casts both ferrous and non-ferrous alloys

    • Recycling ability, and short lead time

    • Processing of metals with high melting temperatures, such as steel and titanium

  • Disadvantages:

    • Lower degree of accuracy compared to alternative methods

    • Difficult to meet fixed size/weight specifications

    • Surface finish is rough; requires post-processing

    • Slow production rate

Sand Casting – Applications

  • Engine blocks and cylinder heads

  • Pump and valve bodies

  • Large industrial machine components

  • Pipes and pipe fittings

  • Railway components

  • Agricultural equipment parts

  • Wind and hydro power equipment

  • Manhole covers and drain grates

  • Construction machinery parts

  • Artistic and decorative items

  • Sand Casting process video: https://www.youtube.com/watch?v=2ClcvB72dmk&t=203s

Die Casting

  • Process: Melts non-ferrous metal alloys and forces them into a mold cavity under high pressure and high speed to produce complex metal parts rapidly with high dimensional accuracy, smooth surface finish, and excellent mechanical properties.

  • Key Features:

    • Uses non-ferrous metals like aluminum, zinc, and magnesium

    • High-pressure injection of molten metal (typically 10–150 MPa10\text{--}150\ \mathrm{MPa})

    • Dies are reusable and made of hardened steel

    • Ideal for mass production of complex shapes with thin walls

    • Produces components with tight tolerances and good surface finish

Die Casting – Advantages

  • High precision and dimensional accuracy

  • High production efficiency and speed

  • Cost-effectiveness for high-volume production

  • Ability to create complex geometries

  • Excellent surface finish and detail

  • Material versatility (many non-ferrous metals)

  • Enhanced mechanical properties

  • Reduced post production operations

  • Suitable for varied production volumes

  • Minimal material waste due to process efficiency

Die Casting – Disadvantages

  • High initial costs

  • Limitations on size and weight

  • Prone to porosity

  • Material limitations (primarily non-ferrous metals like Al, Zn, Mg)

  • Design constraints

  • Prone to defects

  • Labour intensive

Die Casting – Applications

  • Automotive parts (engine blocks, gearboxes, transmission housings)

  • Consumer electronics (laptop frames, phone bodies, camera housings)

  • Home appliances (fan blades, washing machine parts, microwave/AC components)

  • LED and electrical fittings (lamp housings, heat sinks, switchgear enclosures)

  • Aerospace components (interior parts, actuator housings, seat belt anchors)

  • Medical equipment (surgical tools, device enclosures, lightweight frames)

  • Industrial machinery (valve bodies, pump housings, motors, gearboxes)

  • Office equipment (metal casings for printers/copiers)

  • Decorative items (nameplates, trophies, emblems)

  • Telecommunication hardware (housings for routers, antennas, junction boxes)

  • Die Casting video: https://www.youtube.com/watch?v=0l nY45Fwlo

Investment Casting

  • Definition: A wax pattern is coated with refractory ceramic material to form a mold; wax is melted out, and molten metal is poured into the cavity to form the final component.

  • Key Features:

    • Produces highly accurate, complex shapes

    • Excellent surface finish (Ra = 1.5!–3.0 μm1.5!\text{--}3.0\ \mu\text{m})

    • Capable of casting thin walls (as low as 0.5 mm0.5\ \mathrm{mm})

    • Suitable for small-to-medium sized parts

    • Allows high dimensional precision (±0.1%0.1\% of length)

    • Minimal or no machining required

    • Can cast high-melting-point alloys like titanium or Inconel

Investment Casting – Advantages

  • Excellent surface finish

  • High dimensional accuracy

  • Complex geometry

  • Material versatility

  • No flash or parting lines

  • Near-net-shape production

  • Small batch compatibility

Investment Casting – Disadvantages

  • High cost

  • Long lead time

  • Limited size

  • Fragile shells

  • Not suited for high-volume production

Applications of Investment Casting

  • Turbine blades (gas turbines, jet engines)

  • Biomedical implants (knee/hip replacements)

  • Precision military components

  • Industrial valves and pump parts

  • Art and jewelry

  • Investment Casting video: https://www.dailymotion.com/video/xstua8

Centrifugal Casting

  • Definition: Molten metal poured into a rotating mold; centrifugal force distributes the metal against the inner surface, yielding dense, high-integrity castings—especially suited for cylindrical or tubular shapes.

  • Key Features:

    • Utilizes centrifugal force for uniform distribution

    • Produces defect-free, dense castings

    • No cores required for hollow cylindrical parts

    • Inside diameter machined; outside conforms to mold

    • Ideal for rotationally symmetric parts (pipes, rings)

    • Can be used for casting ferrous and non-ferrous metals

Centrifugal Casting – Advantages

  • High density and strength (impurities forced to center and machinable)

  • No core required for tubular shapes

  • Fine grain structure due to rapid solidification at mold wall

  • Improved mechanical properties and reduced porosity

  • Good surface finish on outer surface

  • Material efficiency (waste minimized)

Centrifugal Casting – Disadvantages

  • Limited to symmetrical shapes (best for round/cylindrical)

  • High equipment cost (heavy-duty rotating equipment)

  • Internal surface roughness may require machining

  • Center inclusions; lighter impurities gather at axis and must be machined

  • Skilled operation required for rotation speed and temperature control

Centrifugal Casting – Applications

  • Pipes and tubes (steel, bronze, cast iron)

  • Bushings and bearings

  • Cylinder liners for engines

  • Gun barrels

  • Flywheels

  • Gear blanks

  • Brake drums

  • Hydraulic cylinders

  • Water meter bodies

  • Large rings and sleeves

  • Centrifugal Casting video: https://www.youtube.com/watch?v=TpAMreTdk9s

Shell Moulding

  • Definition: A metal casting process where a resin-coated sand is formed into a shell around a heated pattern; the shell becomes the mold for precision parts.

  • Key Features:

    • Uses fine resin-coated sand

    • Produces thin, rigid, high-precision shell molds

    • Excellent surface finish and dimensional control

    • Pattern is reusable; mold is disposable

    • Ideal for small-to-medium castings in mass production

Shell Moulding – Applications

  • Gear housings

  • Cylinder heads and manifolds

  • Connecting rods

  • Valve bodies

  • Camshafts and crankshafts

  • Impellers and rotors

  • Small and medium automotive components

  • Machine tool parts

  • Pump housings

  • Pipe fittings

Shell Moulding – Advantages

  • Superior surface finish (Ra ≈ 1.5!\text{--}3\ \mu\text{m}})

  • High accuracy and repeatability

  • Reduced machining requirement

  • Suitable for automation and batch production

  • Less material waste compared to full sand molds

Shell Moulding – Disadvantages

  • Higher tooling cost due to metal patterns

  • Not suitable for very large parts

  • Resin-coated sand is costly

  • Shells are thin and may crack during handling

Shell Moulding – Applications

  • Gear housings

  • Cylinder heads and manifolds

  • Connecting rods

  • Valve and pump bodies

  • Camshafts and crankshafts

  • Impellers and turbine blades

  • Automotive engine components

  • Machine tool parts

  • Pipe fittings

  • Defense and aerospace castings

Shell Moulding – Process (sequence)

1) Heat the metal pattern to 175!–370∘C175!\text{--}370^{\circ}\mathrm{C}
2) Pour resin-coated sand over the pattern
3) Resin sets to form a thin shell (thickness 5\–10\ \mathrm{mm})
4) Remove the shell from the pattern
5) Join shell halves and provide support
6) Pour molten metal into the shell mold
7) Allow cooling, break shell, and retrieve casting

  • Shell moulding process diagram and animated examples are provided in the course videos linked in the slides

  • Shell moulding videos: https://www.youtube.com/watch?v=SU48T8Jt31 and https://www.youtube.com/watch?v=OtG-ox3i0ko

Casting Defects – Overview

  • Any undesirable feature adversely affecting quality and function

  • Categories:

    • Gaseous defects: blow holes, open blows, air inclusions, pinhole porosity (due to reduced permeability or venting)

    • Shrinkage cavities: due to volumetric contraction during solidification

    • Defects due to poor molding material: cuts, washes, swells, drops, fusion and penetration

    • Poor molten metal quality: cold shut, misrun, slag inclusions

    • Metallurgical defects: hot tearing, hard spot

Defect Types (overview)

  • Porosity: small cavities or pinholes due to trapped gases

  • Cracks: fractures or fissures

  • Shrinkage defects: voids due to contraction during solidification

  • Inclusions: non-metallic materials within the casting

  • Surface defects: roughness, misruns, cold shuts

  • Additional listed defects: pinholes, shifts, hot tears, hot spots, penetration, slag inclusions, drops, warpage, swell

Specific Defect Descriptions (highlights)

  • Blowholes: larger gas bubbles; caused by air in melt, moisture, or gases from mold; often located in the cope part of the mold in poorly vented pockets

  • Open blows: moisture boils to steam; due to poor venting/permeability

  • Air inclusion and pin hole porosity: due to low gas-permeability in mold

  • Shrinkage cavities: significant structural issue; central large crevices

  • Cuts and washes: mold erosion by liquid metal; surface bulges toward flow direction

  • Swells and drops: mold strength issues; rammed mold must withstand liquid metal pressure

  • Fusion and penetration: rough surface; large sand grains allow metal to fuse with sand

  • Cold shut: two streams solidify before fusing; prevent with sufficient superheat and adequate wall thickness

  • Misrun: incomplete mold fill; due to low pouring temperature or poor fluidity

  • Slag inclusions: non-metallic pockets within casting; slag interacts with melt

  • Hot tearing (hot cracking): occurs during cooling due to residual stresses; proper mold design helps

  • Hot spot / Hard spot: localized rapid cooling causing hardness difference

Inspection Methods – NDT vs Destructive Testing

  • Non-Destructive Testing (NDT) methods:

    • Visual Inspection (VT)

    • Dimensional Inspection

    • Radiographic Testing (RT)

    • Ultrasonic Testing (UT)

    • Magnetic Particle Inspection (MPI)

    • Liquid Penetrant Inspection (LPI/DPT)

    • Eddy Current Testing

    • Pressure Testing

    • Thermal/Infrared Testing (IR)

    • Acoustic Emission Testing (AE)

    • Computed Tomography (CT) Scanning

    • Metallurgical Analysis (microstructure inspection, non-destructive context)

  • Destructive Testing methods:

    • Mechanical Testing (tensile, hardness, impact, etc.)

    • Chemical Analysis (composition)

    • Metallurgical Analysis (microstructure, often destructive)

Non-Destructive Testing (NDT) – Details

  • Visual Inspection (VT): surface defects, cracks, porosity, warpage

  • Dimensional Inspection: calipers, micrometers, CMM for tolerances

  • Radiographic Testing (RT): X-ray or gamma image of internal defects (voids, porosity, cracks, inclusions, shrinkage)

  • Ultrasonic Testing (UT): high-frequency waves detect internal defects via reflections

  • Magnetic Particle Inspection (MPI): for ferromagnetic materials; magnetic flux leakage highlights defects

  • Liquid Penetrant Inspection (LPI): dye penetrant reveals surface-breaking defects; developer makes them visible

  • Eddy Current Testing: detects surface and near-surface defects via induced currents

  • Pressure Testing: checks leaks in pressure vessels

  • Thermal/Infrared Testing: infrared thermography detects variations in thermal conductivity indicating flaws

  • Acoustic Emission Testing (AE): sensors capture stress waves from defects

  • Computed Tomography (CT) Scanning: 3D internal imaging for complex defects

  • Metallurgical Analysis: microstructural examination to identify grain structure and inclusions

Destructive Testing

  • Mechanical Testing: tensile, hardness, impact tests; measures strength, ductility, and toughness

  • Chemical Analysis: composition verification

  • Metallurgical Analysis: microstructure and phase assessment (often destructive)

Recent Advances in Casting Technology

  • Additive Manufacturing (3D Printing) Integration:

    • Complex geometries, internal structures

    • Rapid prototyping and tooling

    • Reduced waste due to layer-by-layer build

  • Advanced Alloys and Materials:

    • Magnesium and aluminum-lithium alloys for high strength-to-weight ratio

    • Improved aluminum alloys with better strength, corrosion resistance, thermal conductivity

    • Sustainable materials: recycled aluminum and eco-friendly alloys

  • Simulation and Digitalization:

    • Casting simulation software to predict defects and optimize design

    • Digital Twin technology for process optimization and real-time control

    • Industry 4.0 integration with IoT and data analytics for quality control

  • Automation and Robotics:

    • Robotic extraction, inspection, finishing for consistency and speed

    • Improved worker safety by removing dangerous tasks

    • Flexibility to reprogram for different designs and volumes

  • Sustainable Practices:

    • Energy-efficient furnaces and process optimization

    • Recycling and material reuse to minimize waste

    • Green casting: holistic approach to reduce environmental impact

End of Module

  • End of Module -1