6.2 Rough-Cut Capacity Planning and MPS Validation

6.2 Rough-Cut Capacity Planning and MPS Validation

Quick Answer: Rough-cut capacity planning (RCCP) checks whether the proposed MPS overloads critical resources. It uses simplified load models—overall factors, bills of resources, or resource profiles—not the full routing detail of CRP. Fail RCCP → revise MPS or capacity; pass RCCP → release to MRP.

Section 6.1 produced a candidate master schedule that satisfied inventory and ATP logic. That is necessary but not sufficient. A schedule that books 500 units in a week when the bottleneck cell can only finish 320 is a fiction. RCCP is the bridge between master scheduling and material requirements planning: it asks, "Can the factory (and other critical resources) roughly absorb this MPS?"

Why Validate Before MRP?

MRP assumes the MPS is a valid statement of independent demand for the scheduled items. If the MPS is capacity-infeasible:

• Component orders will be released on dates the plant cannot use.
• Work-in-process and queues will explode at bottlenecks.
• Planners will thrash priorities daily.
• Customer promises based on ATP will fail even though ATP looked fine on paper.

CPIM framing: RCCP validates the MPS; CRP validates the detailed material plan / open shop orders. Mixing the two levels is a common exam trap.

RCCP Methods You Must Recognize

1. Capacity Planning Using Overall Factors (CPOF)

CPOF is the simplest approach. Historical or engineered standard hours per unit (often a single plant-wide or family factor) are multiplied by MPS quantities, then spread to key resources using historical percentage splits.

Example: Family X historically needs 1.2 standard hours per unit, of which 40% hits Work Center 10 (WC10) and 25% hits WC20.

If MPS for Week 5 = 400 units:

• Total load = 400 × 1.2 = 480 hours
• WC10 load = 480 × 0.40 = 192 hours
• WC20 load = 480 × 0.25 = 120 hours

Compare each to available capacity (shifts × hours × utilization × efficiency, or demonstrated capacity). CPOF is fast but crude: it ignores product mix changes that alter the true resource split.

2. Bill of Resources (BOR)

A bill of resources (sometimes called a bill of capacity) lists, for each MPS item, the critical resources and the capacity required per unit—usually hours at bottleneck work centers, but sometimes key machines, labor grades, or even warehouse dock slots.

Example BOR for finished good FG-200:

If the Week 6 MPS for FG-200 is 300 and for FG-300 (0.80 h on WC10, 0.25 h assembly, 0.15 h test) is 100:

WC10 load Week 6 = 300×0.50 + 100×0.80 = 150 + 80 = 230 hours
Assembly load = 300×0.35 + 100×0.25 = 105 + 25 = 130 hours
Test load = 300×0.20 + 100×0.15 = 60 + 15 = 75 hours

Suppose demonstrated weekly capacities are WC10 = 200 h, Assembly = 160 h, Test = 90 h. Then:

Validation decision: The MPS is not feasible as written. Options include moving 60 FG-200 units to Week 7, overtime on WC10, alternate routing, or reducing FG-300 in Week 6. Only after the overload is cleared should the MPS be firmed.

3. Resource Profile Approach

Resource profiles extend the bill of resources across lead-time offsets. Capacity is not all consumed in the MPS completion week; fabrication hours may load two or three weeks earlier than final assembly.

If FG-200 needs 0.50 h on WC10 two weeks before completion and 0.35 h assembly in the completion week, then an MPS receipt of 300 in Week 8 loads:

• WC10 in Week 6: 300 × 0.50 = 150 h
• Assembly in Week 8: 300 × 0.35 = 105 h

This prevents the false comfort of looking only at the finish week when the bottleneck was already overloaded upstream.

Available Capacity in RCCP

Load is meaningless without a capacity definition. CPIM-relevant capacity ideas include:

• Theoretical capacity — clocks × machines, ignoring losses
• Rated / available capacity — adjusted for utilization
• Demonstrated capacity — what the resource has actually produced recently (often preferred for RCCP realism)

A compact formula often used:

Available hours = (machines) × (shifts) × (hours/shift) × (utilization) × (efficiency)

Example: 2 machines, 2 shifts, 8 hours, utilization 0.90, efficiency 0.95:

2 × 2 × 8 × 0.90 × 0.95 = 27.36 hours per day; times 5 days ≈ 136.8 hours/week.

If MPS-driven load is 150 hours, RCCP flags overload even before detailed CRP.

Validation Workflow (MPS Gate)

1. Freeze a candidate MPS (quantities by item/period).
2. Select critical resources (Pareto: bottlenecks, constrained labor, long setups).
3. Explode MPS through CPOF, BOR, or resource profiles into load by period.
4. Compare load to available/demonstrated capacity.
5. If overloads exist: replan MPS (move mix, level load, change lot timing) or authorize capacity actions (overtime, extra shift, subcontract).
6. If balanced: approve MPS, update ATP, release to MRP.

Numeric Leveling Mini-Scenario

Weeks 5–7 MPS for a single bottleneck item (1.0 h each on WC10; capacity 200 h/week):

After moves: Week 5 = 200, Week 6 = 200, Week 7 = 140—all within capacity. Inventory and ATP must be recomputed after leveling because moving supply changes balances and promises.

What RCCP Does Not Do

• It does not explode the full BOM or create purchase requisitions.
• It does not schedule individual operations with setup matrices.
• It does not replace finite scheduling on the shop floor.
• It does not guarantee that every work center is feasible—only that selected critical resources look acceptable.

Those limitations are why CRP still exists later. For Domain IV master-scheduling questions, the scoring idea is: never release an obviously capacity-infeasible MPS to MRP.

Linking Back to ATP and Forward to MRP

After RCCP-driven MPS changes, recalculate ATP. A move of 60 units from Week 5 to Week 6 may free near-term ATP or create a promising hole. Once the MPS is capacity-validated and ATP refreshed, MRP can explode dependent demand with confidence that the independent-demand statement is operationally credible.

Master scheduling without RCCP is inventory arithmetic. Master scheduling with RCCP is operations management.