Metal processes

Press forming:

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How it works:

1. Metal is rolled out and straightened
2. Metal is cut to required blank size
3. The blank metal is clamped over the die and held in the correct position using the back gauge
4. A hydraulically operated punch is then pushed into the sheet metal
5. Once the desired shape is formed the punch is retracted and the sheet component is ejected

Advantages	Disadvantages
Good for high-volume production Precise and consistent results Can be used with many types of metals	Requires expensive molds Not suitable for very complex shapes Limited to thin materials

Uses: Automotive parts, appliance components

Spinning:

How it works:

1. A metal disk is mounted on a spindle and rotated at high speed
2. A tool is applied to the spinning disk to shape it into a hollow form
3. The formed piece is then removed from the spindle

Advantages	Disadvantages
Can create symmetrical shapes easily Good surface finish Suitable for producing lightweight parts	Limited to round and symmetrical shapes Not suitable for very thick materials Can be slow for large batches

Uses: Bowls, cones, cookware

Cupping:

How it works:

1. A flat sheet of metal is placed into a die
2. A punch presses down on the metal, forming it into a cup shape
3. The finished cup is removed from the die

Advantages	Disadvantages
Can form deep shapes from thin materials High precision and minimal waste	Requires specialized equipment Can be slow for large quantities

Uses: Drink cans, containers, automotive parts

Deep drawing:

How it works:

1. A metal sheet is placed in a die with a punch
2. The punch draws the sheet into the die, forming a deep, hollow part
3. The formed part is then removed and finished

Advantages	Disadvantages
Great for high-volume production of deep parts Produces parts with high dimensional accuracy	Requires expensive dies and tooling Material thinning can occur

Uses: Automotive body parts, kitchen sinks, gas tanks

Forging:

How it works:

1. Metal is heated to a high temperature and placed in a die
2. A hammer or press is used to shape the metal by applying force
3. The shaped metal is allowed to cool and is then finished

Advantages	Disadvantages
Produces strong, durable parts Suitable for high-performance applications Can create complex shapes	Requires high-energy input Limited to high-strength metals

Uses: Tooling, automotive components, industrial machinery

Drop forging:

How it works:

1. Metal is heated and placed in a die
2. A hammer is dropped onto the metal to shape it
3. The part is then cooled and removed

Advantages	Disadvantages
Produces strong, tough parts Cost-effective for large quantities	Expensive dies Limited to simple shapes

Uses: Automotive parts, hand tools, railway components

Bending:

How it works:

1. A metal sheet or bar is placed in a die or between rollers
2. A force is applied to bend the metal into the desired shape
3. The bent part is then removed and finished

Advantages	Disadvantages
Fast and cost-effective for many parts Can be used with a wide variety of materials	Limited to simpler shapes Can cause material fatigue

Uses: Brackets, structural supports, metal furniture

Rolling:

How it works:

1. Metal is passed between two rotating rolls to reduce its thickness
2. The rolls can be adjusted to create the desired thickness
3. The metal is then finished and cut into sheets, plates, or coils

Advantages	Disadvantages
Can produce large quantities of uniform products Suitable for many metals	Limited to certain thicknesses Requires specialized equipment

Uses: Steel sheets, pipes, structural beams

Sand casting:

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How it works:

1. Make a mould in the sand using two half moulds called the cope and drag and make sure the corners are rounded or tapered
2. Place the pattern and sprue in the mould and pack sand around them before removing the pattern
3. Cut gates and channels in the sand and fix the cope and drag together using nuts and bolts
4. Pour molten metal into the mould and allow it to cool before breaking the sand mould
5. Remove the casting and apply finishing processes if needed

Advantages	Disadvantages
Inexpensive Complex shapes can be produced Large components can be produced	Sand moulds can only be used once Surface finish not always good Labour intensive Slow production rate

Uses: Engine blocks, garden furniture, caterpillar tracks

Die casting:

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How it works:

1. Create and lubricate the mould
2. Once mould has been created, molten metal is shot under high pressure into the die
3. When the die is full, the pressure is maintained until the metal has solidified and cooled
4. The mould is then removed and finishes are applied

Advantages	Disadvantages
High rate of production Good surface finish Economical Precise parts can be made	High set-up costs Long lead time Limited sizes Must be large scale demand for it to be economical

Uses: Taps, model cars

Investment casting:

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How it works:

1. Cold wax mould made of desired shape
2. Wax mould attached to sprue before being dipped into liquid ceramic/stucco
3. Then heated to remove wax and set ceramic
4. Molten metal is then poured into the cermaic mould and allowed to set
5. Ceramic shell is then broken off revealing product

Advantages	Disadvantages
High quality surface finish High dimensional accuracy Very complex parts can be made Any metal can be cast No parting lines from mould	Only small castings can be made Expensive Labour intensive Time consuming to create wax mould - slow production rate

Uses: Turbine blades, gears, machine parts

Low temperature casting (pewter):

How it works:

1. Prepare a mould using sand or a permanent material
2. Heat pewter alloy to a low temperature (typically around 230°C)
3. Pour the molten pewter into the mould
4. Allow the metal to cool and solidify
5. Remove the casting and apply finishing touches

Advantages	Disadvantages
Low melting point allows for easy handling Good for small, intricate designs Low cost and fast production	Limited to low strength applications Not suitable for large-scale production Pewter can be brittle

Uses: Jewelry, small decorative items, figurines

MIG welding:

How it works:

1. Used to weld thin metals
2. MIG welding uses an electric arc to create heat
3. Carbon dioxide/argon is used to form a flux shield to protect the weld area from oxidation
4. Then an electrode wire (of the same material) is melted to fill the gap for the weld

Advantages	Disadvantages
Easier than oxy-acetylene welding Quicker than most welds Very strong joint	Poor aesthetics Can accidently melt through the metal if not careful

Uses: Cars, bike frames, metal barriers

TIG welding:

How it works:

1. Used to weld thin to medium thickness metals, often for high-precision work
2. TIG welding uses a non-consumable tungsten electrode to create heat for the weld
3. An inert gas (argon or helium) is used to protect the weld area from oxidation
4. The filler material (if needed) is manually fed into the weld pool
5. The welder controls the heat and filler material to ensure a clean and precise weld

Advantages	Disadvantages
Produces high-quality, clean, and precise welds No spatter as no filler rod is required (when welding thin metals) Can weld a wide range of materials (steel, aluminum, titanium) Great for intricate and detailed work	Slower than MIG welding Requires more skill and precision from the welder Higher equipment and operational costs Not as suitable for welding thick metals compared to MIG

Uses: Aerospace, stainless steel welding, pipe welding, artistic metalwork

Key differences between MIG and TIG welding:

• MIG welding uses a consumable electrode wire, while TIG welding uses a non-consumable tungsten electrode and manual filler addition.
• MIG welding is faster and easier for beginners, while TIG welding provides more control and precision but is slower.
• MIG welding is better suited for thicker materials and faster production, while TIG welding is ideal for thinner materials and more detailed work.
• TIG welding offers cleaner welds with no spatter, whereas MIG welding can produce more spatter, though it is quicker.

Spot welding:

How it works:

1. Spot welding uses two copper electrodes to apply pressure and heat to the material
2. The materials to be welded are placed between the electrodes, and an electric current is passed through them
3. The electrical resistance at the interface causes localized heating, forming a weld at the contact point
4. Heat and pressure are maintained for a short period, allowing the metal to fuse at the spot
5. No filler material is used, and the weld is typically small and concentrated at the point of contact

Advantages	Disadvantages
Fast and efficient for high-volume production No need for filler material Suitable for thin sheet metals Produces strong welds in less time compared to other methods	Limited to welding thin materials Can’t be used on metals with significant thickness Welds are localized and can be weak if not properly controlled Not ideal for materials that require high aesthetic quality in the weld

Uses: Automotive industries, electronics, household appliances, metal sheet fabrication

Oxy acetylene welding:

How it works:

1. Used to weld low carbon steel
2. The metal is prepared by creating a v shaped joint between to two metals
3. An oxygen and acetylene blow torch then heats the area
4. This creates a melt pool, this melt pool mixed with a steel filler rod creates the welded joint

Advantages	Disadvantages
Weld is as strong as parent metal Clean joint - no flux needed Portable equipment No electricity needed	Safety issues (gas equipment etc) Poor aesthetic joint Large heat effected zone

Uses: General engineering

Hard soldering:

How it works:

1. The two metals being joined is cleaned
2. Then the two materials are held together using a former
3. The metal is then heated up to the same temperature as the melting point of the solder
4. The solder is then applied to the joint area

Advantages	Disadvantages
Stronger than soft soldering Better aesthetics Can solder larger objects	More skill Higher melting point

Uses: Jewellery, ornaments, silverware, model engines

Soft soldering:

How it works:

1. The two metals being joined is cleaned
2. Then the two materials are held together using a former
3. The metal is then heated up to the same temperature as the melting point of the solder
4. The solder is then applied to the joint area

Advantages	Disadvantages
Low melting point Quick process Little skill	Weak joint Only suitable for small objects

Uses: Electronics

Brazing:

How it works:

1. The two materials being joined are cleaned before welding
2. Then the two materials are held together using a former
3. Flux is applied to prevent the join area from oxidation
4. A welding torch then heat the join area and a brazing rod is used to fill the joint area

Advantages	Disadvantages
A good general purpose joint Cab be undertaken with little training Low bond temperature needed Can join dissimilar materials	Needs flux (if not weak joint) Metal must be cleaned before hand (time consuming) Not as strong as other welding techniques

Uses: General engineering, bicycle frame

Riveting:

How it works:

1. Riveting involves using a rivet (a short metal pin) to join two or more materials together
2. The rivet is placed into a pre-drilled hole and the ends are deformed to hold the materials in place
3. A hammer or machine is used to flatten one end of the rivet (the “tail”) against the surface of the material, creating a strong joint
4. The process may be performed manually or with automatic riveting machines
5. Once the rivet is deformed, it holds the materials tightly together, forming a secure bond

Advantages	Disadvantages
Strong, durable joint Can be used on a variety of materials, including metals and plastics Simple, reliable method Effective for joining thick materials or materials that can’t be easily welded	Visually noticeable and may not be suitable for aesthetic purposes Can be labor-intensive for high-volume production Requires access to both sides of the workpiece for installation May not provide as high a strength-to-weight ratio as welding

Uses: Aerospace, structural steel, sheet metal work, automotive, construction

Temporary Joining Methods and Fasteners:

Self-tapping screws:

• These screws have a pointed tip that allows them to cut into the material, creating their own thread for a secure hold without the need for a pre-drilled hole.
• Used primarily in sheet metal, plastic, and wood.

Machine screws:

• Machine screws are typically used with nuts or threaded holes to fasten components together.
• They are versatile and available in different sizes, providing a strong, secure connection.

Nuts and bolts:

• Consist of a bolt (a threaded fastener) and a nut (a threaded component) that are used together to clamp materials securely.
• This method allows for easy disassembly and reassembly, making it ideal for temporary or adjustable connections.

Uses: Furniture assembly, machinery, automotive repairs, electronics, construction

Vertical milling:

How it works:

1. Material is clamped into place
2. Cutter is selected and RPM is chosen
3. The material always remains stationary while the machines cutting tool rotates
4. As the cutting moves, it presses against the workpiece and shapes the material

Advantages	Disadvantages
Visibility - can see machine work Can be CNC controlled and so automated Ease of use Very precise	Uses electricity/needs to be plugged in Expensive to buy machines

Uses: Cutting gears, produce slots, drilling

Horizontal milling:

How it works:

1. Material is clamped into place
2. Cutter is selected and RPM is chosen
3. The material always remains stationary while the machines cutting tool rotates
4. As the cutting moves, it presses against the workpiece and shapes the material

Advantages	Disadvantages
Runs faster than vertical milling Very precise Can run at a higher capacity than vertical milling Durable machine - can do many runs No parting lines from mould	Not good at doing radial cuts Machinery takes up lots of space compared to handheld version Uses electrcity/needs to be plugged in More expensive machinery than vertical milling

Uses: Cuttings gears, produce slots, drilling

Turning:

How it works:

1. Begin by placing a circular, square or rectangular shaped peice of metal/wood into the lathes drive area
2. The metal/wood piece is typically secured using a pressure pad
3. Once in place, the lathe is activated to rotate and press the mould against the metal/wood piece
4. The rotational force of the lathe then deforms the metal/wood piece to achieve the same shape as the mould
5. When metal/wood spinning is performed by hand, a worker manually presses the mould against metal/wood piece

Advantages	Disadvantages
Complex designs/shapes can be made Energy efficient Good surface finish Can be computer controlled	Dangerous pieces can be ejected from machine potentially causing harm Some materials are very hard to turn

Uses: Table legs, table lamp, engine parts, handles

Note: Turning machines are different depending on the material being used.

Flame Cutting:

How it works:

1. Oxygen and fuel gas (acetylene or propane) are used to heat and melt the material.
2. A stream of oxygen is directed at the molten material to blow it away, creating a cut.
3. This process is typically used for cutting thicker materials, especially steel.

Advantages	Disadvantages
Economical for thicker materials Good for cutting ferrous metals Simple and portable equipment	Not suitable for precision cutting Produces rough edges Requires post-cut cleanup

Uses: Cutting steel, pipes, and plates

Plasma Cutting:

How it works:

1. Plasma cutting uses a high-temperature plasma jet to cut through electrically conductive materials.
2. Compressed air or other gases are ionized by the electric arc, turning them into plasma which melts and blows away the material.
3. Commonly used for cutting metals like steel, aluminum, and brass.

Advantages	Disadvantages
Fast and efficient cutting process Can cut a variety of metals with thicknesses up to 100mm Provides a cleaner cut compared to flame cutting	Higher initial equipment costs Produces slag and requires post-cut clean up Not ideal for cutting reflective materials like copper and brass

Uses: Sheet metal, heavy machinery, automotive parts

Laser Cutting:

How it works:

1. A high-powered laser beam is directed at the material to melt, burn, or vaporize it.
2. The laser beam is highly focused and can cut with extreme precision.
3. Laser cutting is often used for thin materials and is ideal for intricate and detailed cuts.

Advantages	Disadvantages
Extremely precise cuts No tool wear, reducing maintenance costs Can cut complex shapes with high accuracy	High initial setup cost Not suitable for thick metals or materials with high reflectivity Can cause material warping from heat generation

Uses: Cutting thin sheet metal, precision components, aerospace parts

Stamping/Punching:

How it works:

1. Process is usually done via a CNC
2. The CNC program moves the platen carrying the sheet metal
3. Once the sheet metal is under the stamp the die is punched against the sheet metal
4. The waste material is then recycled and the stamped metal is collected

Advantages	Disadvantages
Economical Can be done many times very quickly Highly automated	Residual cracks appear along the edges Hardening along the edges Burrs can be created if clearance is excessive

Uses: Shape sheet metal into shapes with holes, washers, cogs, tin can pull tabs

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