Basic Manufacturing Processes - Comprehensive Notes

Basic Manufacturing Processes

Overview

  • Today's topics include:
    • Casting
    • Molding
    • Forming
    • Machining
    • Joining
    • Additive manufacturing
    • Other processes

Why Study Manufacturing?

  • It is important to understand design philosophies for efficient manufacturing and the processes comprising the manufacturing itself.
  • Studying manufacturing enables engineers to understand how best to make things and think if they can be made even better.
  • "Efficiency is doing things right. Effectiveness is doing the right things." - Peter Drucker

The Manufacturing Family Tree

  • Major categories to group manufacturing processes under:
    • Manufacturing
      • Production system
        • Finance, design, legals, etc.
      • Machine and tooling
        • Job and station process or operation

Manufacturing Process

  • An event responsible for converting an input material into a desired output.
  • Typically uses more than one machine or machine tool.

The Family Tree

  • Manufacturing Processes:
    • Casting
    • Molding
    • Forming
    • Machining
    • Joining
    • Additive Manufacturing

The Casting Family

  • Casting processes will be covered.
Casting
  • Manufacturing process using fluid properties to easily manipulate the shape of a material and let it cool to harden in a pre-made pattern.
  • Casting Considerations:
    • Mold preparation
    • Melting process
    • Pouring technique
    • Solidification process
    • Mold removal
    • Cleaning, finishing, inspection
Parts of a Mold
  • Includes:
    • Pouring cup
    • Sprue
    • Runner
    • Mold cavity
    • Riser
    • Core
    • Core print
    • Draft
    • Parting line
    • Cope
    • Drag
    • Flask
Solidification
  • A lot of things can go wrong during solidification.
Saturation in Thermodynamics
  • Energy transformations between solid, liquid, and vapor states involve melting (solid > liquid) and evaporation (liquid > vapor).
Chvorinov’s Rule
  • Developed by Nicolas Chvorinov to predict the solidification time of a casted piece of material.
  • Formula: t=B(VA)nt = B \left( \frac{V}{A} \right)^n
    • Where:
      • t = Solidification time
      • B = Mold constant
      • V = Volume of the casting
      • A = Surface area of the casting
      • n = exponent, usually 2
Gas Porosity
  • Gas porosity can be a defect in casting.
Shrinkage
  • Shrinkage can occur during the solidification process.
Casting Types of Molds
  • Expendable-mold
    • Multiple-use patterns
    • Single-use patterns
  • Multiple-use mold
Sand Casting
  • Expendable-mold, multiple-use casting using specialized sand to hold the shape of a mold and withstand high temperatures of molten metal.
  • Considerations for sand type:
    • Temperature resistance
    • Cohesion
    • Permeability
    • Collapsibility
Sand Casting in Action
  • Visual representation of the sand casting process, showing the components and setup.
Shell Mold Casting
  • Expendable-mold, multiple-use casting using sand hardened with resin to create a "shell" that makes up the mold.
Shell Mold Casting Process
  • Illustrates the steps involved in shell mold casting, including:
    • Applying sand with resin binder to a hot pattern.
    • Inverting the box.
    • Removing the dump box.
    • Ejecting the shell.
    • Clamping the matched shells.
Shell Mold Casts in Action
  • Examples of shell mold casts.
Ceramic Mold Casting
  • Expendable-mold, multiple-use casting using hardened ceramic slurries to create a "shell" that makes up the mold, providing even better precision than shell molds.
Ceramic Mold Casts in Action
  • Examples of ceramic mold casts.
Investment Casting
  • Also known as lost-wax casting.
  • Expendable-mold, single-use casting using refractory material and wax to create a one-time shell and mold.
Investment Casting Process
  • Involves:
    • Injecting wax or plastic into a die to make a pattern
    • Gating patterns to a central sprue
    • Placing a metal flask around the pattern cluster
    • Filling the flask with investment-mold slurry
    • Melting out patterns after the mold material has set and dried
    • Filling hot molds with metal by gravity, pressure, vacuum, or centrifugal force
    • Breaking away mold material from castings
    • Removing castings from sprue and grinding off gate stubs
Investment Casting in Action

Visual examples of investment casting.

Lost-Foam Casting
  • Expendable-mold, single-use casting using expandable polystyrene foam (EPS) to form the pattern.
Lost-Foam Casting Process
  • Involves:
    • Using a polystyrene pattern.
    • Dipping the pattern in refractory slurry.
    • Surrounding it with loose unbonded sand in a flask.
    • Compacting the sand by vibration.
    • Pouring molten metal onto the polystyrene pattern.
    • Removing the solidified casting and reclaiming the sand.
Lost-Foam Casting in Action
  • Visual representation of the lost-foam casting process.
Permanent Mold Casting
  • Multiple-use casting using metals like cast iron, bronze, or graphite to form the mold, which can be used for a long time.
  • Pressure may be manipulated (high-pressure clamping or low-pressure vacuums).
  • Molds may be tilted.
Die Casting
  • Multiple-use permanent mold casting using additional pressure to add detail and preserve the mold for future use.
Die Casting Configurations
  • Includes:
    • Single-cavity die
    • Multiple-cavity die
    • Combination die
    • Unit die
Centrifugal Casting
  • Multiple-use permanent mold casting using centrifuges to achieve casting without cores or risers.
Centrifugal Casting Setup
  • Includes a spinning table, flask, pouring basin, and rollers.

The Molding Family

  • Different molding processes will be covered.
Molding
  • Manufacturing process using fluid properties to easily manipulate the shape of a material and let it cool to harden in a pre-made pattern.
Molding vs. Casting
  • Molding is usually reserved for plastics, while casting is for metals.
Thermoplastic
  • Polymer that can be reshaped at high temperatures.
Thermoset
  • Polymer that permanently sets once heated to a certain temperature.
Blow Molding
  • Molding process using air pressure and dies to achieve shapes in plastic parts.
  • Uses hollow tubes called parisons.
Blow Molding Process
  • Involves:
    • Preparing the parison.
    • Closing the mold over the parison.
    • Inflating the parison to fill the mold.
    • Removing and trimming the bottle.
Compression Molding
  • Molding process using pressure and heat from punches to achieve shapes in plastics.
  • Requires a heated preform.
Compression Molding Process
  • Utilizes a heated punch, flash clearance, ejector, preheated pellet, and heated die.
Transfer Molding
  • Molding process using pressure and heat from plungers to push plastic into cavities.
  • Requires raw plastic.
Transfer Molding Setup
  • Involves using granular compound or preforms to create a molded product.
Injection Molding
  • Molding process using nozzles to push (or inject) molten plastic into cavities.
  • Requires melted plastic.
Injection Molding Setup
  • Involves granular plastic, heaters, a torpedo, reactant tanks, mixing head, split mold, plunger, and ejector pins.
Thermoforming
  • Molding process using heat and low pressures to push plastic down into a given mold.
  • Requires melted plastic.
Thermoforming Process
  • Involves heat lamps, plastic sheet, die, and vacuum pump.
Extrusion (Plastics)
  • Process using heat and pressure to push plastic out continuously.
  • Produces a constant cross-section.
Plastic Extrusion Setup
  • Includes a hopper, heaters, and a conveyor system.

The Forming Family

  • Different forming processes will be covered.
Forming
  • Manufacturing process where the material (usually metal) is mechanically deformed.
  • Does not need the material to be molten.
The Family Tree
  • Manufacturing
    • Casting
    • Molding
    • Machining
    • Joining
    • Additive Manufacturing
    • Forming
Forming Subcategories
  • Forming
    • Bulk-forming
    • Shearing
    • Bending
Hot Working
  • Forming that happens above recrystallization temperature.
  • T<em>work>0.6T</em>meltT<em>{work} > 0.6T</em>{melt}
Cold Working
  • Forming that happens below recrystallization temperature.
  • T<em>work<0.3T</em>meltT<em>{work} < 0.3T</em>{melt}
  • Anything in between is called warm working.
Perks of Forming
  • Hot Working:
    • Lower deformation needed, longer deformation allowed
    • Improved ductility and grain structure
    • Lower residual stresses
  • Cold Working:
    • Better surface finish
    • Lower heat needed
    • Improved strength, fatigue, and wear
    • Higher dimensional accuracy
Working at Temperatures
  • Visual representation of material behavior at different temperatures.
Grain Structure
  • Comparison of grain structure after hot working.
Rolling
  • Manufacturing process where the material’s thickness is reduced to size via rolls that compress.
Rolling Processes
  • Rolling dominates the manufacturing industry: 90% of all metal products experience at least one rolling process.
Rolling Considerations
  • Amount of deformation
  • Friction between rollers
  • Number of rollers used
  • Starting and finishing temperature
  • Crowning
Rolling Mill Configurations
  • Includes:
    • Two-high nonreversing
    • Two-high reversing
    • Three-high
    • Four-high
    • Cluster
Law of Conservation of Mass
  • The amount of mass entering is the amount of mass going out.
  • m<em>in=m</em>outm<em>{in} = m</em>{out}
Ring Rolling
  • Rolling process where the rolls squeeze and rotate, making a ring out of the workpiece.
Thread Rolling
  • Rolling process where threads are formed, as opposed to normal threading (machining).
Crowning
  • The material is not flattened thoroughly, producing an unwanted bulge (crown) in the middle.
Forging
  • Manufacturing process where the material’s shape is greatly altered due to blows or compressive forces from dies.
Open-Die Hammer Forging
  • Forging process where the blows come from massive mechanical equipment, usually powered by gravity, hydraulics, or pneumatics.
Open-Die Hammer Forging Setup
  • Shows the top ram, die, metal/billet, and bottom anvil.
Impression-Die Hammer Forging
  • Forging process where the blows come from massive mechanical equipment with specialized dies.
Impression-Die Forging Process
  • Illustrates the dies and air pressure mechanisms used in impression-die forging.
Press Forging
  • Forging process where compression is imparted gradually through presses instead of blows from hammers and dies.
Orbital Forging
  • Forging process where a die is rotated and pressed over a workpiece to "knead" it into a given shape.
Upset Forging
  • Forging process where a bigger diameter is made via compression.
Roll-Forging
  • Forging process where cylindrical dies are rolled to create different end patterns.
Swaging
  • Forging process where a workpiece is fed and hammered radially to reduce its diameter or create tapers.
Extrusion (Forming)
  • Forging process using heat and pressure to push metal out continuously.
  • Produces a constant cross-section.
Extrusion in Action
  • Visual representation of metal extrusion.
Drawing
  • Forging process where the metal is drawn out (i.e., pulled instead of pushed).
Shearing
  • Forming process where metal is sheared.
  • Includes blanking, piercing, slitting, notching, perforating, dinking.
Bending
  • Forming process where metal is bent.
  • Includes draw bending, compression bending, press bending, roll bending.
Seaming
  • Bending process used to mechanically interlock pieces of metal with seams.
Spinning
  • Forming process used to radially deform sheet metal into rotationally symmetric shapes.
Guerin Process
  • Forming process using fluid or rubber to push down on metal, forming it into its shape using blocks underneath.
Hydroforming
  • Family of forming processes using fluid or rubber with pressure.
  • Replaces half of the die required in forging/punching.
Hydro-Forming
  • Family of forming processes using fluid or rubber with pressure to achieve forging/other complex geometries.