D & M Part A - Manufacturing 1. Metal Casting Casting involves melting metal , pouring it into a mould , and letting it solidify The slides cover the following processes in detail Note This PDF should summarize pretty much all of Part A of Design & Manufacture , in terms of individual manufacturing techniques and their bene fi ts / drawbacks ( which seem to be the most important things to remember ). You also will want to learn when each manufacturing method should be used , because they do like to ask " What technique should be used in this scenario ... " style questions Good luck , folks You got this ! N =) D&M Part A - Manufacturing 1 / 22 Expendable ‑ Mould Casting Sand Casting A mould made of packed sand around a pattern ; widely used and very versatile Bene fi ts Drawbacks Shell Moulding A thin resin ‑ bonded sand shell forms the mould ; higher precision than sand casting Bene fi ts Complex geometry ( internal + external ) Very large parts possible Works with nearly all alloys Low tooling cost Suitable for low – medium production volumes Poor dimensional accuracy Rough surface fi nish Labour ‑ intensive Defects common D&M Part A - Manufacturing 2 / 22 Drawbacks Expanded Polystyrene Process ( Lost Foam ) Foam pattern vaporises when molten metal is poured ; no parting line needed Bene fi ts Drawbacks Investment Casting ( Lost Wax ) Wax patterns coated with ceramic ; extremely precise and used for intricate parts Better accuracy than sand casting Good surface fi nish High production rate Higher cost Limited part size No parting line Excellent complexity Simpli fi ed moulding process Foam pattern cost Gas ‑ related defects D&M Part A - Manufacturing 3 / 22 Bene fi ts Drawbacks Permanent ‑ Mould Casting Gravity Permanent ‑ Mould Casting Molten metal fl ows into a reusable metal mould under gravity Extreme complexity and detail High dimensional accuracy Excellent surface fi nish Net ‑ shape process Suitable for high ‑ temperature alloys Expensive Slow , many processing steps Typically small parts only D&M Part A - Manufacturing 4 / 22 Bene fi ts Drawbacks Low ‑ Pressure Casting Metal is pushed upward into the mould using low pressure Good dimensional accuracy Good surface fi nish Rapid solidi fi cation → stronger parts High mould cost Limited to simple shapes Limited to low ‑ melting alloys D&M Part A - Manufacturing 5 / 22 Bene fi ts Drawbacks Die Casting ( Hot & Cold Chamber ) Molten metal is injected under high pressure into a steel die Cleaner metal → fewer defects Improved mechanical properties More complex equipment Higher cost D&M Part A - Manufacturing 6 / 22 Bene fi ts Drawbacks 2. Metal Forming Metal forming reshapes solid metal through plastic deformation using dies and high forces Bulk Deformation Processes Very high production rate Excellent dimensional accuracy Thin sections possible Good surface fi nish High equipment cost Limited to low ‑ melting alloys Geometry must allow ejection D&M Part A - Manufacturing 7 / 22 D&M Part A - Manufacturing 8 / 22 Rolling Metal is squeezed between rotating rolls to reduce thickness Bene fi ts High production rate Good dimensional control D&M Part A - Manufacturing 9 / 22 Drawbacks Forging Metal is compressed between dies to form strong parts Bene fi ts Drawbacks Extrusion ( Direct & Indirect ) Metal is forced through a die to create long parts with uniform cross ‑ section Improved grain structure High equipment cost Requires large forces Very strong parts Excellent grain fl ow Ideal for high ‑ load components High forces required Expensive dies Limited complexity D&M Part A - Manufacturing 10 / 22 Bene fi ts Drawbacks Complex uniform cross ‑ sections Good surface fi nish High material utilisation High force required Tooling cost D&M Part A - Manufacturing 11 / 22 Wire & Bar Drawing Metal is pulled through a die to reduce diameter Bene fi ts Drawbacks Limited to constant cross ‑ sections Excellent dimensional accuracy Good surface fi nish Continuous production possible Requires ductile materials High tensile forces D&M Part A - Manufacturing 12 / 22 Sheet Metalworking Bending Sheet is plastically deformed to create angles Bene fi ts Drawbacks Deep Drawing Flat sheet is stretched into a hollow shape Simple and low ‑ cost High accuracy Springback Limited complexity D&M Part A - Manufacturing 13 / 22 Bene fi ts Drawbacks Shearing Sheet is cut using a punch and die Bene fi ts Drawbacks 3. Machining Machining removes material using cutting tools to achieve fi nal geometry and fi nish Turning A single ‑ point tool cuts a rotating workpiece to form cylinders Produces hollow shapes High production rate Wrinkling Tearing Fast cutting Simple tooling Burr formation Tool wear D&M Part A - Manufacturing 14 / 22 Bene fi ts Drawbacks Drilling A rotating drill bit creates round holes Accurate cylindrical parts Flexible geometry Material waste Slower than forming processes D&M Part A - Manufacturing 15 / 22 Bene fi ts Drawbacks Milling A rotating multi ‑ edge cutter removes material as the workpiece feeds past it Simple hole creation Low cost Tool wear Chip evacuation issues D&M Part A - Manufacturing 16 / 22 Bene fi ts Drawbacks 4. Welding Welding joins metal parts by heat , pressure , or both , forming a permanent joint Fusion Welding Arc Welding ( AW ) Electric arc melts metal at joint Very versatile geometry High accuracy High machine cost Requires skilled setup D&M Part A - Manufacturing 17 / 22 Bene fi ts Drawbacks Resistance Welding ( RW ) Heat generated by electrical resistance between clamped sheets Bene fi ts Drawbacks Versatile Low equipment cost Suitable for thick materials High skill required Heat ‑ affected zone weakening Safety hazards Fast No fi ller metal required Highly automated D&M Part A - Manufacturing 18 / 22 Solid ‑ State Welding Friction Welding ( FRW ) Parts rub together to generate heat , then pressure forms the joint Bene fi ts Drawbacks Limited to sheet metal Electrode wear No melting → strong joint Low defect rate Good for dissimilar metals Limited geometries Specialised equipment D&M Part A - Manufacturing 19 / 22 5. Powder Metallurgy ( PM ) PM forms parts from metal powders through pressing and sintering Pressing & Sintering ( Conventional PM ) Powders are compacted into shape and heated below melting point to bond D&M Part A - Manufacturing 20 / 22