Manufacturing Processes and Materials
Manufacturing Processes and Materials tests casting, forming, machining, joining, additive manufacturing, heat treatment, and material selection.
Core rules and concepts
- Casting: shrinkage allowance is added to pattern dimensions; risers feed solidification shrinkage; chills promote directional solidification.
- Forming: rolling, forging, extrusion, and drawing depend on flow stress, friction, and temperature. Cold work increases strength and reduces ductility.
- Machining: cutting speed V=pi D N/1000; feed f is in mm/rev; material removal rate MRR is approximately V f d for turning.
- Welding: heat input and cooling rate control microstructure and defects such as porosity, lack of fusion, and cracking.
- Heat treatment of steel: annealing softens, normalizing refines, quenching hardens, and tempering restores toughness. The Fe-C diagram and TTT curves guide treatment.
Worked example
A turning operation has length 200 mm, feed 0.2 mm/rev, and spindle speed 800 rev/min. Feed rate is fN=0.2 x 800=160 mm/min. Machining time for one pass is L/(fN)=200/160=1.25 min. If cutting speed is specified instead, first convert V to N using N=1000V/(pi D); do not use cutting speed directly as a feed rate.
Traps
Confusing feed per revolution with feed per minute, omitting approach and exit allowances, treating cast and wrought properties as identical, and ignoring residual stress from welding or machining are frequent errors.