Production Planning and Control

Learning Objectives

• Define production planning and control and explain the purpose of each component.
• Trace the PPC process from demand forecasting through dispatching and follow-up.
• Explain how Material Requirements Planning calculates material needs from a master schedule.
• Distinguish between push and pull production systems and identify when each is appropriate.
• Apply bottleneck theory to diagnose and address capacity constraints.
• Interpret key PPC metrics and explain how they interact with one another.
• Describe how demand variability undermines production plans and how managers respond.

Quick Answer

Production Planning and Control (PPC) coordinates what to produce, how much, when, where, and how — then monitors whether it is happening as planned. It connects customer demand to materials, labor, machines, and delivery commitments. Without PPC, companies face stockouts, idle equipment, missed orders, excess inventory, and poor service. PPC works in two phases: planning creates the intended schedule using forecasts, master production schedules, and MRP; control keeps the operation aligned with reality through shop floor monitoring, bottleneck management, and corrective action.

Production Planning vs. Production Control

Activity	Meaning	Example
Production planning	Deciding future production requirements and resources	Forecasting demand and preparing a monthly production plan
Production control	Monitoring actual work and correcting deviations	Rescheduling jobs when a machine breaks down

Planning creates the intended path. Control keeps the operation aligned with reality. Boeing's commercial aircraft division illustrates both: planners build multi-year production schedules by airplane type; controllers monitor daily progress and reassign workers when parts arrive late or assembly problems arise.

Objectives of PPC

PPC aims to:

• meet customer demand on time;
• use labor, machines, and materials efficiently;
• reduce idle time and bottlenecks;
• maintain optimal inventory;
• coordinate departments;
• reduce production cost;
• improve delivery reliability;
• detect deviations from plan early.

The goal is not simply maximum output. The goal is the right output at the right time, cost, quality, and quantity. General Electric's appliance plants in Louisville, Kentucky measure PPC success by on-time shipment rates and schedule adherence, not just throughput volume.

PPC Process

Typical PPC steps include:

1. Demand forecasting: estimate future demand from sales data, market trends, orders, and seasonality.
2. Aggregate planning: decide overall production level, workforce, inventory, and subcontracting.
3. Master production schedule: specify what products will be made and when.
4. Material requirements planning: calculate materials and components needed.
5. Capacity planning: check whether machines, labor, and facilities can meet the schedule.
6. Routing: decide the sequence of operations and work centers.
7. Scheduling: assign start and finish times.
8. Dispatching: release work orders and instructions.
9. Follow-up and control: track progress, delays, quality, and corrective action.

Material Requirements Planning

MRP uses the master production schedule, bill of materials, inventory records, and lead times to determine what materials are needed and when.

Example: If 500 bicycles are scheduled and each bicycle needs two tires, MRP calculates tire requirements, checks current stock, considers supplier lead time, and triggers purchase orders.

MRP works well when data is accurate. Incorrect inventory records, wrong bills of materials, or unreliable lead times can produce poor plans. At Harley-Davidson's Milwaukee facilities, MRP accuracy improved dramatically once physical inventory counts were brought in line with system records — a prerequisite for reliable planning.

Capacity Planning

Capacity planning checks whether the production plan is realistic. Capacity may be limited by machines, labor skills, space, maintenance, tools, or supplier availability.

Managers can respond to capacity gaps by:

• adding shifts;
• using overtime;
• hiring temporary workers;
• outsourcing;
• rescheduling lower-priority work;
• improving setup time;
• investing in equipment;
• smoothing demand through pricing or delivery promises.

Capacity decisions should consider cost, quality, employee fatigue, and customer commitments. During peak demand periods, US auto manufacturers routinely add third shifts to assembly plants — but only after calculating whether quality and safety standards can be maintained at higher production rates.

Scheduling and Bottlenecks

Scheduling assigns work to resources over time. A good schedule considers due dates, setup times, processing times, priority, material availability, and capacity.

A bottleneck is the step that limits total output. If one machine can process only 100 units per day, the whole line may be limited even if other machines can process 200. The Theory of Constraints suggests identifying the bottleneck, using it efficiently, subordinating other work to it, increasing its capacity, and then repeating the analysis.

Intel applies bottleneck management in semiconductor fabrication: the most expensive and constrained equipment — photolithography steppers — drives the entire production schedule. All other steps are subordinated to maximize stepper utilization.

Push and Pull Systems

In a push system, production is based on forecasts and planned schedules. Goods are pushed through the system in anticipation of demand.

In a pull system, production is triggered by actual demand or downstream signals. Just-in-time and kanban systems are pull-based.

Push systems can build inventory when forecasts are wrong. Pull systems reduce inventory but require reliable suppliers, stable processes, and quick response. Most US manufacturers use hybrid systems: push planning for capacity and materials procurement, pull signals for daily production authorization.

Forecasting and Demand Variability

PPC begins with demand information, but demand is rarely perfectly stable. Forecasts may use historical sales, confirmed orders, market trends, seasonality, promotions, and sales team input.

Common demand problems include:

• seasonal peaks;
• sudden promotional spikes;
• customer order changes;
• inaccurate sales forecasts;
• new product uncertainty;
• supplier or logistics delays;
• demand shifted by competitors.

Managers should not treat a forecast as a guarantee. They need buffers, flexible capacity, and regular forecast review. Amazon's US fulfillment network uses rolling demand forecasts that are revised daily, with automatic safety stock adjustments based on forecast error.

Shop Floor Control

Shop floor control tracks what is actually happening in production. It monitors work orders, machine status, labor availability, quality issues, material shortages, and completion times.

Useful control questions include:

• Which orders are late or at risk?
• Which work center is overloaded?
• Are materials available before jobs are released?
• Are defects causing rework?
• Is actual output matching the schedule?
• What corrective action is needed today?

This makes PPC dynamic. A plan created at the start of the week may need revision after a machine breakdown or urgent customer order.

Practical Example: Bakery Production Planning

A bakery supplies bread to supermarkets every morning. PPC decisions include:

• forecasting demand by day of week;
• planning flour, yeast, packaging, and labor;
• scheduling mixing, proofing, baking, cooling, slicing, and packing;
• ensuring ovens are not overbooked;
• dispatching delivery vehicles by route;
• adjusting production during festivals or holidays.

If demand is underestimated, shelves go empty. If demand is overestimated, unsold bread becomes waste. The bakery must balance freshness, capacity, and forecast accuracy. Flowers Foods, which supplies bread to Walmart and other US retailers, uses PPC systems that adjust daily production quantities based on point-of-sale data from store partners.

PPC Metrics

Useful metrics include:

• on-time delivery;
• schedule adherence;
• capacity utilization;
• machine downtime;
• work-in-process inventory;
• throughput time;
• defect rate;
• overtime cost;
• forecast accuracy;
• order backlog.

Metrics should be interpreted together. High utilization may look efficient but can create long queues and delays if there is no buffer.

Key Terms

Term	Definition	Related Concept
Master Production Schedule (MPS)	A plan specifying what products will be produced and in what quantities over time	MRP, aggregate planning
Material Requirements Planning (MRP)	A system that calculates material and component needs based on the MPS, BOM, and inventory records	Bill of materials, lead time
Bill of Materials (BOM)	A structured list of components and sub-assemblies required to build a product	MRP
Routing	The defined sequence of operations and work centers a job must pass through	Scheduling
Dispatching	The release of work orders and production instructions to the shop floor	Shop floor control
Bottleneck	The resource or process step that limits total system output	Theory of Constraints
Theory of Constraints	A management approach focused on identifying and improving bottlenecks to increase system throughput	Scheduling, capacity
Push system	A production system that manufactures based on planned forecasts rather than actual demand signals	MPS, MRP
Pull system	A production system triggered by actual downstream demand using signals like kanban	JIT, kanban
Capacity utilization	The percentage of available capacity being used in production	Capacity planning
Schedule adherence	A measure of how closely actual production follows the planned schedule	PPC control
Aggregate planning	A medium-term plan setting overall production levels, workforce size, and inventory targets	MPS

Common Mistakes

Misconception: A production plan only needs to be set once per planning period and then followed strictly. Why it's wrong: Demand changes, machines break down, suppliers are late, and quality issues create rework. A plan that cannot adapt to these realities quickly becomes irrelevant and causes cascading delays. Correct understanding: Production plans require active monitoring and regular revision. Shop floor control, feedback loops, and re-scheduling are essential parts of PPC — not signs of planning failure.

Misconception: High capacity utilization always indicates efficient production planning. Why it's wrong: Running at 100% utilization means no buffer for unexpected demand, machine breakdowns, or quality rework. High utilization leads to long queues, late deliveries, and stressed employees. Manufacturing research consistently shows that utilization above 80–85% increases lead time exponentially. Correct understanding: Optimal utilization depends on demand variability and required responsiveness. A buffer of unused capacity is not waste — it is the system's ability to respond to the unexpected.

Misconception: MRP is sufficient on its own to ensure reliable production output. Why it's wrong: MRP calculates material requirements mathematically, but its output is only as good as its inputs. If inventory records are inaccurate, lead times are outdated, or the BOM is wrong, MRP generates plans that cannot be executed. Garbage in, garbage out. Correct understanding: MRP is a powerful planning tool that requires rigorous data maintenance — accurate inventory counts, validated BOMs, and realistic lead times — to produce actionable schedules.

Comparison and Connections

Feature	Push Production System	Pull Production System
Trigger for production	Forecast-based schedule	Actual downstream demand signal
Inventory level	Typically higher	Typically lower
Responsiveness to demand change	Slower (relies on forecast revision)	Faster (responds directly to demand)
Risk	Overproduction when forecasts are wrong	Stockouts if demand spikes suddenly
Best suited for	Stable, predictable demand; long lead-time materials	Variable demand; reliable suppliers; stable processes
US example	Chemical plant batch scheduling	Toyota Georgetown kanban system

Practice Questions

Recall

1. List the nine steps in the PPC process in correct order. Guidance: Start with demand forecasting. Progress through aggregate planning, MPS, MRP, capacity planning, routing, scheduling, dispatching, and finish with follow-up and control.

2. What three inputs does MRP require to calculate material needs? Guidance: Master production schedule, bill of materials, and current inventory records (plus lead times).

Understanding

3. Explain why the Theory of Constraints says you should not try to improve the efficiency of a non-bottleneck step. Guidance: If a non-bottleneck step produces faster, it only creates more work-in-process inventory piling up at the bottleneck. Total output does not increase. Improvement effort should target the constraint.

4. How does demand variability create problems for a push production system? Guidance: Push systems produce based on forecasts. When actual demand differs from the forecast, the system either overproduces (excess inventory) or underproduces (stockouts). The larger the variability, the larger the mismatch.

Application

5. A US auto parts manufacturer produces 2,000 steering assemblies per week. Each assembly requires 4 bolts. Current bolt inventory is 1,200 units and supplier lead time is 3 days. The production run is scheduled for 5 days from now. Using MRP logic, determine when the bolt order must be placed and for how many bolts. Guidance: Gross requirement = 2,000 x 4 = 8,000 bolts. Net requirement = 8,000 - 1,200 = 6,800 bolts. Order must be placed 3 days before the production start, so in 2 days.

6. A food manufacturer has an oven that can bake 500 units per hour and a packaging line that can pack 400 units per hour. The sales target is 450 units per hour. Where is the bottleneck, and what should the manager do? Guidance: Packaging is the bottleneck at 400 units/hour, which is below the 450 target. The manager should focus on improving packaging throughput — not the oven. Options: add a second packaging shift, improve changeover, reduce downtime.

Analysis

7. Boeing has faced persistent production delays on its aircraft programs despite detailed production plans. Using PPC concepts, analyze what structural factors make aircraft production planning especially difficult. Guidance: Extremely long lead times, enormous BOM complexity (millions of parts per aircraft), thousands of suppliers, regulatory approvals, and highly skilled labor constraints. Any single supplier delay becomes a bottleneck. The system has very low slack.

8. A US retailer is considering switching from a push replenishment system to a pull system for its stores. Analyze the conditions that would make this switch beneficial versus risky. Guidance: Beneficial: stable store-level demand patterns, reliable distribution centers, short replenishment lead times, good POS data. Risky: high demand variability (seasonal fashion), long supplier lead times, system unreliability, poor forecast capability at store level.

FAQ

What is the difference between aggregate planning and a master production schedule? Aggregate planning sets the overall production strategy — how much to produce in total, at what workforce level, and with what inventory strategy — usually over a 3-to-18-month horizon. It answers the question "roughly how much?" at a product family level. The master production schedule translates aggregate plans into specific product quantities and timing, usually for the next few weeks or months. The MPS is the input to MRP. Think of aggregate planning as the budget and the MPS as the detailed spending plan.

Why do companies often have inaccurate inventory records, and how does this affect MRP? Inventory records become inaccurate for many reasons: unreported scrap, picking errors, incorrect receiving counts, theft, unprocessed returns, and data entry mistakes. When records show 500 units in stock but only 350 physically exist, MRP calculates a lower order quantity than needed and triggers a shortage during production. Cycle counting — regularly auditing a portion of inventory rather than one annual count — is the main tool for maintaining record accuracy. Without accurate records, MRP outputs are unreliable regardless of how sophisticated the software is.

How does scheduling differ from sequencing, and why does it matter? Scheduling assigns work orders to specific time slots and resources. Sequencing determines the order in which jobs are processed at a work center. Multiple sequencing rules exist: first-come-first-served, shortest processing time, earliest due date, and critical ratio. The choice of rule affects average waiting time, late orders, and customer satisfaction. Shortest processing time minimizes average wait but may starve long jobs. Earliest due date minimizes lateness but not total waiting time. In practice, schedulers combine rules with judgment about customer priority and bottleneck management.

What happens when a sales team makes delivery commitments that operations cannot support? This is one of the most common and damaging PPC failures in US companies. Sales teams, incentivized to close deals, promise delivery dates without checking production capacity, material availability, or current order backlogs. When operations cannot meet the promise, customers receive late shipments and lose trust. The fix requires a formal process — often called Available to Promise — where the production system verifies remaining capacity and inventory before a delivery date is committed. ERP systems like SAP and Oracle have ATP modules that support this in real time.

Is PPC still relevant with modern AI-driven demand forecasting and automated scheduling tools? The principles of PPC are more relevant than ever, even as the tools evolve. AI improves forecast accuracy but does not eliminate uncertainty or the need to manage capacity, materials, and schedules. Automated scheduling tools optimize within constraints but still require humans to define those constraints and review outputs. Modern PPC is faster and more data-driven, but it still requires managers to understand the logic of MRP, the impact of bottlenecks, and the difference between planning and control. Tools are only useful to people who understand the underlying problems they are solving.

Quick Revision

• PPC coordinates what to produce, how much, when, and with what resources — then monitors execution.
• Planning creates the schedule; control detects deviations and triggers corrective action.
• The nine PPC steps run from demand forecasting through dispatching to follow-up.
• MRP uses the MPS, bill of materials, and inventory records to calculate material needs and timing.
• Capacity planning checks whether the schedule is achievable with available resources.
• A bottleneck limits total system output — improving non-bottlenecks does not increase throughput.
• The Theory of Constraints says: identify the bottleneck, exploit it, subordinate everything else to it.
• Push systems produce based on forecasts; pull systems respond to actual demand signals.
• High capacity utilization is not always efficient — it removes the buffer needed to absorb variability.
• MRP accuracy depends entirely on the quality of inventory records and BOM data.
• Demand variability is the main enemy of production planning — buffers and flexibility are the response.
• PPC metrics include on-time delivery, schedule adherence, utilization, work-in-process, and forecast accuracy.

Related Topics

Prerequisites: Introduction to Operations Management (transformation process, bottlenecks, capacity), Basic Statistics (forecasting, averages, variability)

Related Topics: Inventory Management (safety stock, reorder points, EOQ), Supply Chain Optimization (supplier lead times, demand sharing), Quality Management (defect rates affect rework and scheduling), Lean Manufacturing (pull systems, kanban, flow)

Next Topics: Quality Management (ensuring output meets standards), Inventory Management (balancing stock levels with service targets)