CPM MRP & Production Control 3 — Questions and Answers
Question 1: A Rough-Cut Capacity Plan (RCCP) differs from Capacity Requirements Planning (CRP) in that RCCP:
- Uses actual shop-floor queue data and routing details
- Checks capacity at only key or critical resources against the MPS, before MRP is run (Correct answer)
- Plans capacity all the way to the supplier level
- Replaces the need for a Master Production Schedule
Correct answer: Checks capacity at only key or critical resources against the MPS, before MRP is run
RCCP is a quick check of critical resources against the MPS to validate feasibility before the detailed MRP explosion is performed.
Question 2: Which production scheduling approach sequences jobs to minimize the total time all jobs spend waiting and being processed (makespan)?
- First-Come, First-Served (FCFS)
- Shortest Processing Time (SPT)
- Johnson's Rule (Correct answer)
- Critical Ratio
Correct answer: Johnson's Rule
Johnson's Rule is a scheduling algorithm that minimizes makespan for n jobs processed through two machines in sequence.
Question 3: In MRP II, what does the 'resource planning' module address that basic MRP does not?
- Short-term daily scheduling on the shop floor
- Long-range capacity planning including capital equipment and workforce needs (Correct answer)
- Vendor lead time negotiation and purchase order management
- Real-time inventory transaction processing
Correct answer: Long-range capacity planning including capital equipment and workforce needs
Resource planning in MRP II provides long-range aggregate capacity planning covering equipment, facilities, and workforce over a multi-year horizon.
Question 4: What is the primary purpose of safety stock in an MRP environment?
- To buffer against demand variability and supply uncertainty so that net requirements are met even when inputs are unpredictable (Correct answer)
- To reduce the frequency of purchase orders by ordering extra each time
- To satisfy seasonal demand peaks identified in the sales forecast
- To account for scrap and yield losses during production
Correct answer: To buffer against demand variability and supply uncertainty so that net requirements are met even when inputs are unpredictable
Safety stock protects service levels against variability in demand or replenishment lead times, acting as a buffer in the MRP inventory record.
Question 5: A planned order release in MRP becomes a 'firm planned order' when a planner:
- Manually freezes the order so the system will not automatically change it during re-planning (Correct answer)
- Converts it to a purchase order and sends it to a supplier
- Sets the order quantity to the economic order quantity
- Attaches it to a specific machine work center
Correct answer: Manually freezes the order so the system will not automatically change it during re-planning
A firm planned order is manually protected from automatic rescheduling, giving the planner control over a specific order during the re-planning process.
Question 6: Which dispatch rule prioritizes the job with the smallest ratio of time remaining to work remaining?
- Shortest Processing Time (SPT)
- Earliest Due Date (EDD)
- Critical Ratio (CR) (Correct answer)
- Least Slack (LS)
Correct answer: Critical Ratio (CR)
Critical Ratio = (Due date − Today) / (Remaining lead time); a ratio below 1.0 indicates the job is behind schedule and should be expedited.
Question 7: In production control, 'input/output control' is used primarily to:
- Manage raw material receipts at the receiving dock
- Monitor and regulate the flow of work into and out of work centers to control queue lengths (Correct answer)
- Track finished goods inventory movements in the warehouse
- Schedule preventive maintenance windows on production equipment
Correct answer: Monitor and regulate the flow of work into and out of work centers to control queue lengths
Input/output control compares planned versus actual input and output at work centers so managers can adjust releases or capacity to maintain target queues.
CPM MRP & Production Control 3
A Rough-Cut Capacity Plan (RCCP) differs from Capacity Requirements Planning (CRP) in that RCCP: