Manufacturing Processes and Engineering Materials
Manufacturing Processes and Engineering Materials tests process selection, material behaviour, and producibility. Expect casting yield and shrinkage, welding heat-affected zones, machining time and tool life, bulk forming loads, heat-treatment sequences, and corrosion or failure modes.
Core rules
- Casting: riser must feed shrinkage; yield = casting weight/charge weight.
- Welding: preheat and controlled cooling reduce cracking in high-carbon or thick sections; HAZ properties differ from parent metal.
- Machining: N = 1000V/(πD) with V in m/min and D in mm; feed rate = fN; time = L/(fN).
- Taylor tool life: VTⁿ = C; increasing speed sharply reduces tool life.
- Heat treatment: annealing softens and relieves stress; normalising refines grain; quenching hardens; tempering restores toughness.
- Materials: carbon equivalent helps assess weldability; composites are anisotropic, so design allowables depend on fibre direction.
Worked example
Turn a 50 mm diameter, 200 mm long bar at cutting speed 100 m/min and feed 0.2 mm/rev. Find spindle speed and machining time. N = 1000 × 100/(π × 50) = 636.6 rpm. Feed rate = 0.2 × 636.6 = 127.3 mm/min. Time = 200/127.3 = 1.57 min, before adding approach and retract allowance. A higher speed would reduce time but accelerate flank wear according to Taylor's equation.
Traps
- Entering spindle speed directly as cutting speed.
- Forgetting approach/retract length in machining time.
- Confusing feed per revolution with feed per tooth.
- Treating quenched steel as finished without tempering.
- Assuming weld strength equals parent-metal strength without checking filler and HAZ.