Common Manufacturing Processes in Detail
From Type to Technique
The specification requires you to know the specific named processes within each type — their tools, the steps involved, and the safety measures that must be followed. OCR exam questions regularly ask you to name a specific process, describe the steps, and justify why it suits a particular material or product.
Wasting Processes
Nine wasting processes are specified. Sawing uses a toothed blade to cut stock to length; workpieces must be clamped and PPE worn. Shearing (manual guillotine or tin snips only) cuts sheet metal with opposing blades — fast, no heat, but fingers must stay clear. Drilling uses a twist bit in a pillar drill; work is clamped, speed matched to the material, and swarf cleared regularly. Filing removes small amounts of material to refine surfaces; the workpiece is held in a vice and the file must have a handle fitted to prevent the tang injuring the hand.
Threading is restricted to manually cutting internal threads with a tap and external threads with a die; cutting paste is applied and the tool reversed every half turn to break swarf. Routing uses a rotating cutter for profiles and slots; dust extraction and guards are required. Laser cutting vaporises material along a programmed path with a high-energy beam — highly precise, minimal kerf, but requires interlocked enclosures and fume extraction. Turning on a centre lathe rotates the workpiece against a fixed cutting tool to reduce diameter; loose clothing must be secured. Milling uses a rotating multi-tooth cutter on flat or contoured surfaces; CNC milling achieves complex shapes accurately and repeatedly.
The nine wasting processes in the specification are: sawing, shearing (manual guillotine/tin snips only), drilling, filing, threading (tap and die only), routing, laser cutting, turning, and milling. Each generates waste swarf or offcuts and requires appropriate PPE and clamping.
Shaping Processes
Sand casting packs sand around a split pattern in a two-part mould, pours molten metal into the cavity, then breaks away the sand to reveal the casting — suits large, complex shapes at low-to-medium volume. Die casting forces molten metal under pressure into a permanent hardened steel die, giving high dimensional accuracy and surface finish at high volume. Key difference: sand casting = single-use expendable mould; die casting = permanent reusable die. Injection moulding melts thermoplastic granules and injects the melt into a cooled steel mould; on solidification the mould opens and ejects the part — suits very high volumes of complex plastic components. Powder metallurgy for ceramic products compacts ceramic powder at very high pressure, then sinters it without fully melting to bond the particles.
Sand casting uses an expendable (single-use) sand mould — once the metal solidifies, the mould is broken apart, so a new mould is needed for every part. This suits one-off and batch production of large, complex parts such as engine blocks. Die casting uses a permanent hardened steel die reused thousands of times; cycle times are very short, making it cost-effective at high volume, with far superior dimensional accuracy and surface finish. Remember: sand = expendable/single-use; die = permanent/reusable.
Forming Processes
Forging compresses hot metal between shaped dies, aligning the grain structure to produce a strong, tough component — spanners, crankshafts, aerospace fittings. Press forming blanks and bends sheet metal between punch and die — car body panels, casings and brackets. Strip heating softens a thermoplastic sheet along a line using a resistance heater (line bender) so it can be folded to a precise angle. Vacuum forming clamps a thermoplastic sheet over a mould, heats it until pliable, then draws it onto the mould by removing air; moulds need 3–5° draft angles for release, and surface detail reproduces on the mould-contact face only. Moulding of composite materials lays reinforcing fibres (glass or carbon cloth) in a mould, saturates them with liquid resin, and cures the assembly — used for boat hulls, sports equipment and aerospace panels.
Vacuum forming moulds must have draft angles (typically 3–5°) to allow the formed polymer sheet to be released. Deep draws with vertical walls cannot be vacuum formed because the sheet would lock onto the mould.
Additive Manufacturing
Fused deposition modelling (FDM) melts a thermoplastic filament (PLA or ABS) in a heated nozzle and deposits it layer by layer; the platform lowers by one layer after each pass. Slicing software converts the digital model into cross-sections and adds support structures automatically; supports are removed after printing. Tools: FDM printer, slicing software, filament spool. Safety: nozzle temperature 200–260 °C — avoid contact; ventilate to remove fumes.
Joining and Finishing Processes
Brazing melts a filler metal between closely fitting parts using a gas torch, WITHOUT melting the base metals themselves (only the filler melts — unlike welding); the filler flows by capillary action and solidifies on cooling — used for pipework, cycle frames and tool tips. PPE: face shield, heat-resistant gloves, ventilation. MIG/MAG welding feeds consumable wire electrode with a shielding gas (argon for MIG; CO₂/mix for MAG) to fuse steel; PPE: welding helmet, gloves, leather apron, ventilation. Riveting: hammered rivets are set with a hammer and dolly; pop rivets are installed from one side only using a rivet gun, suited to hollow sections. Mechanical fastening: nuts and bolts pass through clearance holes (removable); self-tapping screws cut their own thread in a pilot hole. Painting applies pigmented liquid by brush or spray to a clean, primed substrate. Powder coating electrostatically charges dry polymer powder onto an earthed component and cures it at 160–200 °C, giving a tough corrosion-resistant film without solvents.
Ask four questions to choose the right joining method. Are both parts metal? Brazing and MIG welding suit metals; nuts and bolts suit mixed materials. Must the joint be permanent? Welding and brazing are permanent; bolts and self-tapping screws allow disassembly. Is only one side accessible? Pop rivets are the answer. How heavy is the load? MIG welding gives the strongest bond; a self-tapping screw suits light-duty assembly only. Apply this checklist to every OCR scenario question on joining.