Manufacturing Processes
Covers casting, forming, machining, joining, molding, and additive processes, plus the process-selection logic that ties them together.
Casting and forming
Casting families: sand, die, investment, and their trade-offs in finish, tolerance, and volume. Shrinkage allowances require riser design; typical defects are porosity, cold shut, misrun, and hot tearing. Forging, rolling, extrusion, and drawing are classified by whether the work is hot or cold, which governs strength, finish, and dimensional control. In sheet metal, distinguish blanking from piercing, and account for bend allowance and springback.
Machining
Turning speed: N = 12V/(πD), with V in surface feet per minute and D in inches - the factor 12 converts feet to inches. Material removal rate in turning is MRR = v·f·d (speed, feed, depth). In milling, MRR = width × depth × feed rate. In drilling, thrust and torque grow with diameter. Taylor tool life, VT^n = C, shows that a modest speed increase sharply shortens tool life. Cutting temperature, not cutting force, usually limits speed.
Joining and molding
Know fillet versus groove welds, arc versus resistance welding, and the heat-affected zone. Injection molding: clamp tonnage, shrinkage, and draft angle; cooling dominates cycle time; defects include short shots, flash, sink marks, and warpage.
Traps
Reporting rpm when surface speed is required; dropping the factor 12; confusing climb and conventional milling; assuming tighter tolerance always costs more.
Worked example
V = 300 sfpm on a 2-in diameter workpiece: N = 12(300)/(π × 2) ≈ 573 rpm. With feed 0.010 in/rev and depth 0.100 in, MRR = 3600 × 0.010 × 0.100 ≈ 3.6 in³/min.