Industrial Engineering
Industrial Engineering
This domain tests work study, inventory control, project management, quality control, and plant layout. The exam expects formula recognition and correct units.
Core rules
- Economic order quantity: EOQ = √(2DS/H), where D is annual demand, S is ordering cost per order, and H is holding cost per unit per year. Reorder point = demand during lead time + safety stock.
- Work measurement: standard time = observed time × rating factor × (1 + allowance). Allowances cover personal needs, fatigue, and delay; do not add them to the rating.
- Project management: CPM is deterministic; PERT uses t_e = (a + 4m + b)/6. Total float = LS − ES = LF − EF; the critical path has zero total float. Crash cost slope = (crash cost − normal cost)/(normal time − crash time).
- Quality: C_p = (USL − LSL)/(6σ); C_pk = min[(USL − μ), (μ − LSL)]/(3σ). C_pk accounts for centering.
Worked example
Annual demand is 10,000 units, ordering cost is ₹200 per order, and holding cost is ₹10 per unit per year. EOQ = √(2 × 10,000 × 200/10) = √400,000 = 632.5 units. Ordering and holding costs are equal at EOQ: at 632.5 units, the annual ordering cost is about ₹3,163 and the annual holding cost is about ₹3,163, confirming the balance.
Traps
Using monthly demand with an annual holding cost; treating safety stock as cycle stock; confusing free float with total float; adding allowances before applying the rating; and using C_p as if it measured centering.