Manufacturing processes are categorized into:
Forming: Includes wasting and deforming.
Redistribution: Includes casting and moulding.
Addition: Includes additive processes and fabrication.
Examples:
Wasting/Deforming: Cutting, drilling, bending.
Casting/Moulding: Die casting, injection moulding, extrusion.
Additive/Fabrication: Welding, joining, 3D printing.
Material is moved around to shape it into a product.
Two methods:
Deforming: Changing shape without changing the material's state (remains solid).
Reforming: Changing the material's state (e.g., solid to liquid and back to solid).
Changing the shape of a material without altering its state (remains solid).
May involve heat and/or pressure.
Wood:
Generally not suitable for deforming due to its natural state and strength.
Exceptions: Steam bending, kerfing, laminating.
Thermoplastic Polymers:
Soften at relatively low temperatures, making them easy to deform.
Metals:
Relatively easy to deform with heat and pressure.
Typically, wood is joined rather than deformed.
Steam Bending:
Wood is bombarded with steam until flexible, then bent into shape.
Held in place while water content is slowly removed.
Traditionally used for Windsor chairs.
Kerfing:
Grooves are cut into the wood to facilitate bending.
Technically a wasting process.
Used for guitar and violin shells.
Laminating:
Thin sheets of wood (veneers) are glued together and placed in a mould.
Retains the mould's shape once the glue sets.
Used to make skateboards.
Metal is well-suited to deformation with pressure and heat.
Bending and Folding:
Can be done cold or hot.
Sheet metal can be folded like plastic but needs high-pressure machinery.
Spinning:
A disc of metal is rotated at high speed and formed into a symmetrical part.
No material removal; the metal is moulded over an existing shape.
Applications: rocket nose cones, cookware, gas cylinders, musical instrument bells, waste receptacles.
Sinking:
Flat sheet metal is formed into a non-flat object by hammering.
Stretches and thins the metal, risking failure if sunk too far.
Used in jewelry and plate armour manufacture.
Punching:
A punch press forces a tool (punch) through the workpiece to create a hole via shearing.
A scrap slug is deposited into a die.
Cost-effective for creating holes in sheet metal in medium to high production volumes.
Blanking:
A shaped punch creates multiple usable parts from a sheet of material.
Blanking and Piercing:
Shearing processes using a punch and die. Tooling and processes are the same, but terminology differs.
Blanking: punched out piece is used.
Piercing: punched out piece is scrap.
Parts manufactured with both techniques are termed 'pierce and blank'.
Piercing can also be called punching.
Forging:
Shaping metal using localized compressive forces.
Classified by temperature: cold, warm, or hot forging.
Forged parts range from less than a kilogram to 580 metric tons.
Usually requires further processing.
Drop Forging:
A hammer is raised and dropped onto the workpiece to deform it according to the die shape.
Two types: open-die and closed-die drop forging.
Drawing:
Uses tensile forces to stretch metal.
Two types: sheet metal drawing and wire, bar, and tube drawing.
Sheet metal drawing: plastic deformation over a curved axis.
Wire, bar, and tube drawing: stock is drawn through a die to reduce diameter and increase length.
Usually done at room temperature (cold working), but can be done at elevated temperatures (hot working).
Deep Drawing:
Sheet metal forming process where a sheet metal blank is radially drawn into a forming die by the mechanical action of a punch.
Sheet metal is drawn into a die.
'Deep drawing' when the depth exceeds the diameter; achieved by redrawing through a series of dies.
Used to make aluminium drink cans.
Press Forming:
Sheet metal process using a die inside a press.
High pressure (3000+ tons) is applied to form the material to match the die shape.
Used for white product cases (fridges) and car body parts.
Polymers are commonly formed due to their ease of softening and solidifying at low temperatures.
Line Bending:
A small area of plastic sheet is heated to allow folding or bending around a former.
Vacuum Forming:
A heated plastic sheet is draped over a former, and a vacuum removes air below.
Gravity forces the plastic onto the former.
Used for hollow 'shell-like' items like yoghurt pots, baths, and moulds.
Vacuum Forming Mould Characteristics:
Sides should slope outwards (draft angle) for easy removal.
No sharp edges (radius edge) to prevent thinning.
Air holes to avoid trapped air.
Sufficient space between peaks to avoid webbing.
Thermoforming:
Similar to vacuum forming but uses an outer mould for greater detail, lettering, and sharp edges.
Blow Moulding:
Forms hollow plastic parts.
Plastic is melted and formed into a parison (tube-like piece with a hole).
The parison is clamped into a mould, and air is blown into it.
The plastic expands to match the mould, cools, hardens, and is ejected.
Changing the shape of a material by changing its state (solid to liquid to solid).
Wood isn't typically reformed, but:
In a pulped state, it can be mixed with resin to make MDF.
Paper and board are sourced from wood and can be shaped when reformed into egg boxes.
Commonly formed due to the ease of transitioning between liquid and solid states at low temperatures.
Commonly reformed as they are originally processed in a liquid state.
Sand Casting:
Uses sand as the mould material.
Over 70% of metal castings are produced this way.
Sand is mixed with a bonding agent (clay) and moistened.
The mixture is compacted around models to create mould cavities.
A slow process because the sand mould must be broken up to remove the cooled metal object.
Die Casting:
Molten metal is forced under high pressure into a mould cavity.
Mould cavity is created using hardened tool steel dies.
Most die castings are made from non-ferrous metals (Zinc, Copper, Aluminium, Magnesium, Lead, Pewter, and Tin-based alloys).
Uses hot- or cold-chamber machines depending on the metal.
High capital costs limit the process to high-volume production.
Simple, four-step manufacturing process keeps incremental cost per item low.
Suited for large quantities of small to medium-sized castings.
Characterized by good surface finish and dimensional consistency.
Gravity Die Casting:
Uses gravity to force molten material into the mould.
Pressure Die Casting:
A ram forces molten metal into the former using a hot or cold chamber.
The additional pressure ensures greater accuracy and detail.
Industrial Die Casting:
Uses multi-slide die castings; traditional die casting only uses two halves, limiting shape complexity.
Four or more slides enable complex 3D shapes.
Lost Wax Casting:
A metal object (often Pewter, Silver, Gold, Brass, or Bronze) is cast from an original wax sculpture.
Intricate works can be achieved.
The mould is destroyed to remove the cast item.
In modern industrial use, the process is called investment casting.
Extrusion:
Creates objects of a fixed cross-sectional profile.
Material is pushed or drawn through a die of the desired cross-section (hot or cold).
Commonly extruded materials include metals, polymers, ceramics, concrete, play dough, and foodstuffs.
Commonly reformed due to their ease of transitioning between liquid and solid states at relatively low temperatures.
Injection Moulding:
Material is injected into a mould cavity, where it cools and hardens.
Can be performed with metals, glasses, elastomers, confectionary, and most commonly thermoplastic polymers.
Moulds are made from steel or aluminium and precision-machined.
Widely used for manufacturing parts, from small components to car body panels.
Rotational Moulding:
A heated hollow mould is filled with a charge of material and slowly rotated.
The softened material disperses and sticks to the walls.
Continuous rotation during heating and cooling maintains even thickness and avoids deformation.
Shapes can be hollow with thick walls.
Compression Moulding:
A preheated moulding material (thermosetting polymer such as Urea Formaldehyde) is placed in an open, heated mould cavity.
The mould is closed with a top force, and pressure is applied.
Heat and pressure are maintained until the material has cured.
Used for complex, high-strength fiberglass reinforcements.
One of the lowest cost moulding methods with relatively little material waste.
Resin and GRP Moulding:
Not strictly a reforming process, but involves using a liquid polymer (Resin) that cures and sets hard.
Combined with glass strips (GRP) to reinforce the resin.
3D Printing:
An additive process that builds a 3D shape by adding layers of plastic.
The molten plastic makes it essentially a reformation process, but it's considered additive.
Can print metal, food, and body parts.
Redistribution involves moving material to shape it, either by deforming or reforming.
Reforming is mainly used with metal and plastics.
Wood can be reformed into MDF, Chipboard and Maplex but can be deformed by steam bending or laminating.
Most complex plastic components are made by moulding.
Plastic bottles are commonly made by deforming.
Terms are not rigid; 3D printing is additive but involves melting the polymer filament, potentially considered reforming.
Joining like or unlike materials (additive process, opposite of wasting).
Wood and metal are often fabricated; plastic is more commonly formed or moulded.
Two main types:
Temporary (T): can be dismantled.
Permanent (P): fuses materials together.
Commonly used method.
Typically permanent if nails or glue are used, otherwise, they can be dismantled.
Many types of wood joints; can combine different types for reinforcement.
Wood joints fall into two categories: frame joints and box joints.
Frame Joints
Corner halving
Cross halving
Dowel joint
Mitred bridle
Dovetail halving
Bridle joint
Tee Halving
Box Joints
Dovetail nailing
Dovetail Plywood
Housing Joints
Veneer keys
Mitre joint
Butt joint
Wood (porous) joins with resin, polymer, and water-based adhesives.
PVA (Polyvinyl Acetate): Most common; requires clamping while setting (hours).
Cascamite: Resin-based powder (mix with water); ideal for laminating/veneering.
Gorilla Glue: Strong adhesive; requires wetting surfaces before clamping; expands like foam for a strong joint.
Versatile material (hot or cold); fabrication is common.
No common metal joints; fused/welded or joined using screws, rivets, and bolts.
Crimping (P):
Joins thin sheets using folded edges pressed together by rollers.
Can be reinforced by welding.
Soldering (P):
Joins metal items by melting solder (Tin and Lead alloy) into the joint.
The solder has a lower melting point (180^{\circ}C) than the adjoining metal.
Suitable for intricate work (circuit boards).
Silver Soldering (P):
Joins precious metals (Gold, Silver, Brass, and Copper).
Solder is classified as easy, medium, or hard, based on melting temperature (not strength).
Extra - easy solder
56% Silver, Meltsat1, 618 degrees C
Extra - hard solder
80% Silver, Meltsat1, 740 degrees C
Small pieces of solder wire are placed onto the metal before heating.
Flux is used to keep the metal and solder clean.
The joint is stronger than the base metal, requiring perfectly flush pieces because silver solder cannot fill gaps.
Brazing (P):
Joins metal by heating a filler metal above its melting point and distributing it between close-fitting parts.
Protected by a flux; used for decorative work as the soft (Brass) brazing rod is easier to file to shape.
Welding (P):
Joins materials (metals) by melting the workpieces and adding a filler material to form a weld pool for a strong joint.
Several types are used, depending on the job and material.
Gas Welding (P):
Uses Oxygen and Acetylene gases; filler material is like brazing but at a higher temperature.
The metal is heated until white hot, then welding rod is added.
Slower but yields a neater finish; inexpensive equipment without an electrical supply.
Arc Welding (P):
Uses an electric arc between an electrode and the base material.
The welding region is protected by shielding gas, vapor, or slag.
Important for steel structures and vehicles.
MIG Welding (P):
Metal Inert Gas (MIG) or Metal Active Gas (MAG) welding.
Uses a consumable wire electrode and shielding gas (usually Carbon Dioxide) to weld steel.
TIG Welding (P):
Tungsten Inert Gas (TIG) welding.
Uses a non-consumable tungsten electrode. Shielding by an inert gas such as Argon, and a filler metal is normally used.
Typically used to weld thin sections of Stainless Steel and non-ferrous metals (Aluminium, Magnesium, and Copper alloys).
Greater control over the weld; stronger, higher quality welds. This is a skilled process which is difficult to master, and furthermore, it is significantly slower than most other welding techniques.
Spot Welding (P):
Joins contacting metal surfaces using heat from resistance to electric current.
Shaped copper alloy electrodes concentrate welding current into a small ‘spot’, simultaneously clamping the metal sheet together.
Metal must be meticulously cleaned since its non-porous and difficult to manage using adhesives, however, Epoxy Resin may be used.
This adhesive is stronger than a welded joint.
Domestic version is commonly sold in hardware stores and is known by the brand name Araldite. 2-part glue with resin and hardener is needed.
Polymers can be welded (P) using a heat gun or plastic welding or glued together with Tensol Cement or Polystyrene Cement (lightly melts surfaces).
Nails (P)
Reinforce joints or quickly join wood.
Not for metal; likely to crack plastic.
Different shapes/sizes.
Screws (T)
Pass through one material, screw into another; act as a clamp.
Wood screws vs. self-tapping screws (metal/plastic).
Countersunk, dome, and pan heads;
Nuts and Bolts (T)
Join materials by passing through holes, clamping them.
Washers protect surfaces.
Different lengths/gauges/styles (glass/concrete).
Rivets (P)
Clamp materials like nuts/bolts; require drilling/boring for removal classified as permanent.
Traditionally Iron (heated red hot).
Now Aluminium pop rivets.
Hinges (T&P)
Allow parts to hinge or swing.
Attach through gluing/welding (permanent) or screws/bolts (temporary).
Knock Down (KD) Fittings (T)
Modern invention for flat pack furniture (temporary fixing).
Other Adhesives (P)
Araldite for gluing unlike materials.
Contact adhesive for laminates to wood.
Multi-Purpose Adhesives (T)
Araldite, Gorilla Glue, Bostick and UHU, Superglues, Copydex (fabrics/paper).
A chart to match adhesives to material combinations including paper, plastic, and wood.
A table summarizing: Wood, Metal, Plastic, Paper, Glass, Fabric.
Material vs process/techie
Wasting, Redistribution, Fabrication.
Fabrication joins materials permanently or temporarily.
Methods vary for like or unlike materials.
Fabrication joins parts unless moulded/cut into shape.
Wood and metal use fabrication; plastic easily moulded.
Furniture uses flat pack fittings (KD fittings).
Welding and brazing permanently join metal.
The object or component is shaped by material removal (subtractive).
Can be wasteful; some materials (metals, polymers) are recyclable, but wood waste isn't always usable.
Processes presented in the order of waste produced (guideline only).
Used for wood, metal, polymers, styrofoam.
Wood lathe (wood) or centre lathe (metal/polymers): the material rotates.
A cutting tool shapes the material by moving left to right and towards the centre.
CNC versions allow greater speed and accuracy.
Only suitable for wood (cold chisel on sheet metal).
Flat chisels - used to remove wood for making joints.
Gouging chisels can be used for carving.
For metal and plastic.
Uses rotary cutters to remove material.
Traditional milling moved in three axes manually; CNC machining is now computer controlled.
For paper and board.
Products like fold-flat cardboard packaging are made from a flat sheet and are cut and creased with a die.
For wood and plastic.
Rotary cutters remove material but for softer materials such as wood, foam, and some metals.
CNC-operated or handheld form:
Plunge router (profile on the edge or cut shapes).
Table-mounted (user feeds the material into the cutter).
For wood.
Shaving away at the wood with a sharp blade mounted into the plane's body.
Wood saws (hand saws).
Metal saws.
For wood, metal, and plastic.
Holes in materials generally made by using a drill and a dril bit.
Different materials call for different types of drill bits and different speeds.
Metal should be slow and wood fast with plastic somewhere in between.
Used to apply a final shape to a product or to remove imperfections.
Products that affect the surface finish of a material.
On wood use glass/sandpaper to remove the rough surface and leave the wood smooth.
Wood, particularly after varnish or lacquer has been applied, receive a final smooth finish by using wire wool.
On metal you use emery cloth and/or silicon carbide (wet and dry) paper.
Many polymers used, such as Acrylic, are self finishing so do not need abrasives other than for cut edges.
File to shape, sand to finish= affect the surface finish and feel of the material rather than shaping it.
Wasting is a subtractive process.
Because of the nature of wood, it is commonly shaped through wasting techniques.
Metal and plastic can exist in a molten state.
Wasting techniques are often the least environmentally friendly due to the amount of waste material.
There are a range of tools and processes that can be used to shape an object by removing material.
There are various abrasives used to affect the surface finish of materials.