UNIT 3: Production Planning and Control (ME-802(D))

I. Production Systems and Overview

Job Production vs. Batch Production

[!TIP] Exam Focus: Be prepared to cite specific Indian industry examples (e.g., Job: Specialized turbine manufacturing; Batch: Textile dyeing, FMCG production).

Need for Production Planning and Control (PPC) in Developing Economies (India-specific)

Significance & Drivers:

1. Resource Optimization: Maximizes output from scarce capital, skilled labor, and raw materials.

2. Meeting Global Competition: Essential for Indian industries to compete on cost, quality, and delivery in a liberalized market.

3. Reducing Waste: Controls overproduction, waiting times, and inventory costs (Muda).

4. Improving Delivery Performance: Critical for customer satisfaction in sectors like automotive and electronics.

5. Capacity Utilization: Helps plan investment and manage bottlenecks in infrastructure-constrained environments.

Key Challenges in India:

• Unreliable Infrastructure: Power outages, logistics delays necessitate robust safety stock and flexible schedules.

• Skill Gaps: Requires more detailed work measurement and training.

• Supplier Unreliability: Demands sophisticated inventory management (higher safety stock, vendor development).

• Policy & Regulatory Hurdles: Needs adaptive planning for compliance (e.g., environmental norms).

• Informal Sector Integration: Planning must account for variability in outsourced/contract work.

[!TIP] Common Pitfall: Do not just list generic needs. Always link points to developing economy constraints (infrastructure, volatility, skill).

II. Demand Forecasting and Market Analysis

Sales Forecasting

Definition: The process of estimating future sales (revenue/volume) over a specific period based on historical data, market analysis, and assumptions about future conditions.

Purpose:

• Basis for Production Planning, Master Production Schedule (MPS), and Capacity Planning.

• Guides Inventory Management (procurement, safety stock).

• Supports Financial Planning (cash flow, budgeting).

• Informs Marketing & Sales Strategies.

Fields of Application in PPC:

1. Aggregate Planning: Determining overall production rates and workforce levels.

2. Master Scheduling: Setting finished goods availability.

3. Material Requirements Planning (MRP): Calculating component needs.

4. Capacity Requirements Planning (CRP): Checking if capacity meets forecasted load.

Methods (Brief Classification):

• Qualitative: Delphi method, Market Research, Executive Opinion (used for new products, long-term).

• Quantitative:

  • Time Series: Moving Average, Exponential Smoothing, Trend Projection (uses past sales data).

  • Causal/Associative: Regression Analysis (relates sales to variables like price, income, advertising).

Market Analysis (Short Note)

Components:

1. Market Size & Growth: Historical trends and future projections.

2. Customer Analysis: Needs, buying behavior, segmentation.

3. Competitor Analysis: Market share, strengths, weaknesses, strategies (Porter's Five Forces).

4. Environmental Scanning: PESTEL Analysis (Political, Economic, Social, Technological, Environmental, Legal).

5. Product Analysis: Life cycle stage, substitutes, complementary goods.

Relevance to PPC: Provides the external demand input for sales forecasting. Identifies opportunities/threats that affect production strategy (e.g., new technology may require process change, regulation may alter material requirements).

III. Method Study and Work Measurement

Method Study vs. Work Measurement

Procedure of Method Study (6 Steps):

1. Select: Identify the job/process with high potential for improvement.

2. Record: Document the current method using charts (process, flow, activity).

3. Examine: Critically analyze the recorded data. Question each step's purpose, sequence, location, etc. (Use Principles of Motion Economy).

4. Develop: Design a new, improved method. Eliminate, combine, rearrange, simplify.

5. Install: Implement the new method. Train personnel, change layouts, provide tools.

6. Maintain: Ensure the new method is followed and periodically reviewed.

Principles of Motion Economy & Relation to Workplace Layout

Core Principles (Simplified):

1. Use the Fewest Motions: Combine or eliminate unnecessary movements.

2. Symmetrical & Simultaneous Motions: Use both hands, starting/ending at same location.

3. Rhythmic & Automatic Motions: Establish a smooth, natural pace.

4. Minimize Travel Distance: Place tools/materials in fixed, optimal locations.

5. Use Gravity & Momentum: Let tools fall into position; use momentum to advantage.

6. Design for Comfort: Minimize bending, reaching, twisting. Use proper workplace layout.

Relation to Layout: These principles directly dictate workplace layout design:

• Fixed Locations: Tools/materials placed in "grasp zones" (primary, secondary, tertiary) based on frequency of use and motion economy.

• Sequential Arrangement: Tools/materials arranged in the order of use to minimize travel and search.

• Ergonomic Considerations: Height of work surface, tool orientation, and provision for seated/standing work to reduce fatigue.

Predetermined Motion Time Systems (PMTS): Critical Analysis

Definition: Systems that assign standard time values to basic human motions (reach, move, position, grasp, release, etc.) based on extensive laboratory studies. Total standard time = Σ (time for each motion in the method).

Common Types:

1. MTM (Methods-Time Measurement): Most widely used. Highly detailed (e.g., MTM-1, MTM-2, MTM-3). High accuracy, but time-consuming for complex jobs.

2. MODAPTS (Modular Arrangement of Predetermined Time Standards): Uses "MODs" (0.129 sec) as base unit. Faster to apply than MTM, slightly less accurate.

3. WF (Work Factor): Older system, uses "WF units" (0.00001 min). Less common now.

Critical Analysis for Man-Machine Systems:

• Applicability:

  • Excellent for repetitive, short-cycle, manual operations (assembly, small parts handling).

  • Useful for method comparison and ergonomic assessment (identifying inefficient motions).

  • Can be adapted for semi-automatic operations by timing machine cycles separately.

• Limitations:

  • High Setup Cost & Expertise: Requires certified analysts and software.

  • Poor for Non-Repetitive/Complex Jobs: Long-cycle, variable tasks are difficult to break down into basic motions.

  • Ignores Fatigue & Allowances: Provides only basic motion time; must add personal, fatigue, and delay allowances separately.

  • Machine-Dependent Tasks: Difficult to apply when operator pace is dictated by machine cycle (e.g., injection molding). Better to use machine time study.

  • Cultural/Pace Differences: Standards are based on a "trained worker" at a defined pace (often 100-120% of normal). May need adjustment for local conditions.

[!TIP] Exam Key: For "man-machine system," emphasize that PMTS times only the manual portion. Machine time is added separately. It's less suitable if the operator is idle waiting for the machine.

Synthesis from Standard Data (Short Note)

Concept: A work measurement technique where the standard time for a new, similar job is built by combining standard data (time values) for its component elements (e.g., "load part," "tighten bolt," "inspect") from a database of previously timed jobs.

Application:

1. Build Database: Collect standard times for a wide range of basic elements (reach, grasp, move, position, tool use, etc.) from time studies or PMTS.

2. Analyze New Job: Break the new job down into these standard elements.

3. Synthesize: Sum the standard data for each element. Add necessary allowances (personal, fatigue, delays).

4. Adjust: Apply frequency factors (for repetitive elements) and performance rating if needed.

Advantage: Much faster than conducting a full time study for every variant. Ensures consistency. Ideal for batch production with many similar items.

IV. Production Planning

Information Required for Effective Production Planning

1. Demand Forecast: Expected sales volume (by product, period). Source: Marketing.

2. Inventory Status: Current stock of raw materials (RM), Work-in-Process (WIP), finished goods (FG).

3. Capacity: Available machine hours, labor hours, shifts per period. Source: Engineering/Production.

4. Lead Times: Procurement time for RM, manufacturing cycle time for FG.

5. Bill of Materials (BOM): Hierarchical list of components and quantities needed to make one unit of finished product. Source: Design/Engineering.

6. Routing/Process Plan: Sequence of operations, work centers, and standard times for each step. Source: Industrial Engineering.

7. Resource Availability: Status of key machines, skilled labor, tooling.

8. Policies & Constraints: Business rules (e.g., "batch size must be multiple of 50"), budget limits, maintenance schedules.

9. Supplier Reliability: Delivery performance data for purchased parts.

[!TIP] Exam Tip: When listing, group logically: Demand Inputs (1), Internal State (2,3,8), Technical Data (5,6), External Factors (4,9).

Master Production Schedule (MPS) (Short Note)

Definition: A time-phased plan that specifies what finished goods are to be produced, in what quantities, and when (typically weekly) over a planning horizon (e.g., 3-18 months).

Role: The central link between forecast/planning and execution/scheduling.

• Translates aggregate plan into specific end-item quantities.

• Drives Material Requirements Planning (MRP) by exploding the BOM.

• Provides a commitment for capacity loading.

• Serves as a communication tool between sales, production, and procurement.

Inputs: Sales Forecast, Customer Orders, Inventory Records, BOM, Lead Times, Production Policies. Outputs: Planned order releases for finished goods, projected on-hand inventory, available-to-promise (ATP) quantities.

V. Scheduling and Line Balancing

Scheduling Situations and Methodologies

Types of Scheduling Situations:

• Forward Scheduling: Starts from current date, schedules jobs as early as possible. Good for make-to-stock or urgent orders. Can lead to high WIP.

• Backward Scheduling: Starts from required delivery date, schedules jobs as late as possible. Good for make-to-order. Minimizes WIP but is sensitive to delays.

• Infinite Loading: Ignores capacity constraints when creating schedules. Assigns jobs based on priority, assuming infinite capacity. Used in MRP for initial rough planning.

• Finite Loading: Considers capacity constraints (machine hours, labor) when scheduling. Jobs are assigned only if capacity is available. Used in Advanced Planning Systems (APS) and detailed shop-floor scheduling.

Detailed Explanation: Gantt Chart (as a Scheduling Tool)

• What it is: A bar chart showing tasks/operations on the vertical axis and time on the horizontal axis.

• How it works:

  1. List all jobs/operations to be scheduled.

  2. For each operation, draw a bar from its start time to its finish time on the time scale.

  3. Bars can be stacked to show resource loading (e.g., a machine's schedule).

• Advantages: Simple, visual, easy to understand. Shows progress, overlaps, and idle times.

• Disadvantages: Static; difficult to update for changes. Manual rescheduling is cumbersome for many jobs. Does not optimize, just illustrates a schedule.

• Use: Excellent for project scheduling (like CPM/PERT) and for visualizing shop floor schedules on a daily/weekly basis.

Heuristic Methods for Line Balancing

Goal: Assign tasks (with given task times) to workstations on an assembly line such that:

1. Precedence constraints (task sequence) are respected.

2. Cycle time (C) is minimized or line efficiency is maximized.

3. Number of workstations (N) is minimized for a given C.

Common Heuristic Types & Rules:

General Rules for All Heuristics:

1. Always respect precedence relationships.

2. Never exceed the cycle time (C) at any station.

3. Assign tasks in the order dictated by the heuristic's ranking rule.

4. Move to next station when no more tasks fit or no eligible tasks remain.

[!TIP] Exam Alert: You may be asked to apply RPW or Kilbridge-Wester to a small problem. Be ready to calculate positional weight/positional count and assign tasks step-by-step.

Role of Factory Executives and Workers in Raising Productivity

VI. Inventory Management

Economic Order Quantity (EOQ) Model

Assumptions:

• Demand is known, constant, and independent (D units/year).

• Lead time is constant and known.

• No stockouts allowed (backorders not permitted).

• Instantaneous replenishment (entire order arrives at once).

• Fixed ordering cost (S) per order, regardless of quantity.

• Constant holding/carrying cost (H) per unit per year (often as % of unit cost).

Derivation (Conceptual):

Total Annual Cost (TC) = Purchase Cost + Ordering Cost + Holding Cost

$$ TC = C \cdot D + S \cdot \frac{D}{Q} + H \cdot \frac{Q}{2} $$

Where:

• $C$ = Cost per unit (Rs.)

• $D$ = Annual demand (units)

• $S$ = Ordering cost per order (Rs.)

• $H$ = Holding cost per unit per year (Rs.)

• $Q$ = Order quantity (units)

To minimize TC, differentiate w.r.t. Q and set to zero:

$$ \frac{d(TC)}{dQ} = -S \frac{D}{Q^2} + \frac{H}{2} = 0 $$

Solving for EOQ ($$\displaystyle Q^* $$):

$$ Q^* = \sqrt{\frac{2DS}{H}} \boxed{} $$

Key Points:

• At $$\displaystyle Q^* $$, Ordering Cost = Holding Cost.

• Number of Orders per Year = $$\displaystyle D / Q^* $$.

• Total Cost (excluding purchase) = $\sqrt{2DSH}$.

Inventory Decisions with Quantity Discounts

Procedure (Price-Break EOQ):

1. For each price break (lower price for larger order), calculate the EOQ using the holding cost based on that price ($$\displaystyle H = i \cdot C $$, where $i$ = carrying cost rate).

2. Check Feasibility: Is the calculated EOQ within the quantity range for that price? If not, use the minimum quantity for that price break as the candidate $Q$.

3. Calculate the Total Annual Cost (TC) for each feasible candidate $Q$ (using its respective price $C$).

4. Select the $Q$ that gives the minimum TC.

Acceptance Criteria: Accept a discount offer only if the TC with the discounted price and corresponding order quantity is lower than the TC at the standard EOQ (or other feasible options).

Reorder Point, Safety Stock, and Inventory Levels

Definitions:

• Reorder Point (ROP): The inventory level at which a new order should be placed.

• Safety Stock (SS): Extra inventory held to protect against uncertainty in demand or lead time.

• Lead Time (L): Time between placing an order and receiving it.

• Procurement Time: Synonymous with Lead Time.

Basic ROP Formula (with constant demand & lead time):

$$ ROP = d \times L $$

Where $d$ = average demand per unit time (e.g., per day).

ROP with Safety Stock (uncertain demand/lead time):

$$ ROP = (d \times L) + SS $$

How to Calculate SS (Statistical Method):

If demand during lead time is variable (normal distribution):

$$ SS = z \times \sigma_{DL} $$

Where:

• $z$ = safety factor based on desired service level (e.g., z=1.65 for ~95% service).

• $$\displaystyle \sigma_{DL} $$ = standard deviation of demand during lead time.

  • If demand per period ($$\displaystyle \sigma_d $$) and lead time ($L$) are independent: $$\displaystyle \sigma_{DL} = \sigma_d \times \sqrt{L} $$.

  • If lead time is also variable, formula becomes more complex.

Inventory Levels (for a cycle with order quantity Q):

• Maximum Inventory Level = $Q + SS$ (just after order arrival).

• Minimum Inventory Level = $SS$ (just before next order arrival, assuming no stockout).

• Average Inventory Level = $$\displaystyle \frac{Q}{2} + SS $$.

[!TIP] Exam Problem Checklist: For a full problem (like May 2024), you must:

1. Calculate EOQ.

2. Compare with discount offer (calculate TC for discount Q=24,000).

3. Calculate ROP given procurement time (lead time) and safety stock.

4. State Min, Max, Avg inventory levels.

Inventory Classification (Short Note) - ABC Analysis

Concept: Classifying inventory items into three categories (A, B, C) based on their annual consumption value (Unit Cost × Annual Usage).

• A Items: ~10-20% of items, but ~70-80% of total consumption value. Tight control, frequent review, accurate records.

• B Items: ~20-30% of items, ~15-25% of value. Normal control, periodic review.

• C Items: ~50-60% of items, ~5-10% of value. Simple controls, large orders, minimal records.

Other Classification Methods:

• VED Analysis: Vital, Essential, Desirable (based on criticality to operations, e.g., spare parts).

• FSN Analysis: Fast moving, Slow moving, Non-moving (based on usage rate).

• XYZ Analysis: Based on forecast accuracy (X=highly predictable, Z=very unpredictable).

• SDE Analysis: Scarce, Difficult, Easily available (based on procurement lead time/difficulty).

VII. Distribution and Logistics Planning

Transportation Problem

Formulation as Linear Programming:

• Objective: Minimize total transportation cost.

• Decision Variables: $$\displaystyle x_{ij} $$ = units shipped from source $i$ to destination $j$.

• Constraints:

  1. Supply Constraints: For each source $i$, $$\displaystyle \sum_j x_{ij} \leq \text{Supply}_i $$ (or = if all supply used).

  2. Demand Constraints: For each destination $j$, $$\displaystyle \sum_i x_{ij} \geq \text{Demand}_j $$ (or = if all demand met).

  3. Non-negativity: $$\displaystyle x_{ij} \geq 0 $$.

Solution Methods (Steps):

1. Northwest Corner Rule (Initial Basic Feasible Solution - IBFS):

   • Start at top-left cell (NW corner).

   • Allocate as much as possible: min(available supply, remaining demand).

   • Adjust supply/demand, move right if demand exhausted, down if supply exhausted.

   • Continue until all allocations are made.

2. Least Cost Method (IBFS):

   • Consider all unallocated cells.

   • Allocate to cell with lowest unit cost.

   • Allocate max possible (min of row supply, col demand).

   • Adjust, cross out exhausted row/column, repeat.

3. Vogel’s Approximation Method (VAM) (IBFS - Often Better):

   • For each row and column, calculate penalty cost = difference between two smallest costs in that row/col.

   • Allocate to cell with lowest cost in the row/col with highest penalty.

   • Adjust supply/demand, recalculate penalties for affected rows/cols, repeat.

4. MODI Method (Optimality Test & Solution):

   • Step 1: Start with an IBFS (from above).

   • Step 2: Calculate dual variables ($$\displaystyle u_i $$ for rows, $$\displaystyle v_j $$ for cols) using: $$\displaystyle u_i + v_j = c_{ij} $$ for allocated cells. Set $$\displaystyle u_1=0 $$ (arbitrary), solve for others.

   • Step 3: For each unallocated cell, calculate opportunity cost (improvement index): $$\displaystyle \delta_{ij} = c_{ij} - (u_i + v_j) $$.

   • Step 4 (Check Optimality):

     • If all $$\displaystyle \delta_{ij} \geq 0 $$, current solution is OPTIMAL.

     • If any $$\displaystyle \delta_{ij} < 0 $$, solution can be improved. Select the most negative $$\displaystyle \delta_{ij} $$.

   • Step 5 (If not optimal): Form a closed loop for the selected cell (unallocated) with allocated cells. Reallocate quantities along the loop (add to cells with +, subtract from cells with -) to maintain feasibility. The quantity to reallocate is the minimum of the allocated quantities at the "-" corners.

   • Step 6: Go back to Step 2 with new allocation.

[!TIP] Exam Must-Know: You will likely be asked to solve a problem using MODI. Practice the loop formation and reallocation steps meticulously. Always write the cost matrix, IBFS, $$\displaystyle u_i, v_j $$ table, $$\displaystyle \delta_{ij} $$ calculations, and final optimal allocation with total cost.

VIII. Advanced Planning Systems

Manufacturing Resources Planning (MRP II)

Definition: An extension of Material Requirements Planning (MRP) that integrates all manufacturing resources (machines, labor, tools, budgets) into a single, comprehensive planning system. It is a closed-loop system that includes capacity planning and execution.

Key Components:

1. Business Planning: Overall company goals.

2. Production Planning: Aggregate plan (what product families, how much).

3. Master Production Schedule (MPS): Specific end-items, quantities, timing.

4. Material Requirements Planning (MRP): Explodes MPS to component/RM needs.

5. Capacity Requirements Planning (CRP): Checks if work center capacity meets the MRP-generated load.

6. Shop Floor Control: Executes and tracks orders (dispatching, data collection).

7. Performance Measurement: Reports on schedule adherence, inventory turns, etc.

8. Financial Interface: Links to accounting (standard costs, cash flow).

Surround Failures / Limitations in Manufacturing Management:

• "Garbage In, Garbage Out": Highly dependent on accurate and timely input data (BOM, inventory, lead times). Bad data leads to useless plans.

• Infinite Capacity Assumption in MRP: Traditional MRP ignores capacity during netting. CRP is a separate, often reactive, step. This disconnect causes unrealistic schedules.

• Poor for High-Mix/Low-Volume: Works best for repetitive, batch manufacturing. Struggles with job shops or highly configured products.

• Rigidity: Difficult to handle frequent schedule changes or unplanned disruptions (machine breakdowns).

• Implementation Complexity & Cost: Requires significant organizational change, training, and software investment.

• "Surround" Problem: Focuses on internal planning. Does not inherently integrate with suppliers (SCM) or customers (CRM)—this gap is filled by ERP.

Enterprise Resource Planning (ERP)

Definition: An integrated, enterprise-wide software system that manages and automates core business processes across finance, HR, manufacturing, supply chain, services, procurement, and projects.

Advantages:

• Single Source of Truth: Integrated database eliminates data redundancy and inconsistency.

• Improved Visibility & Reporting: Real-time information across departments.

• Enhanced Coordination: Seamless flow of information between functions (e.g., sales order auto-triggers production, procurement, and finance).

• Standardized Processes: Enforces best practices and regulatory compliance.

• Scalability: Can support business growth and globalization.

• Better Customer Service: Accurate ATP, order tracking.

Disadvantages:

• Very High Cost: Licensing, implementation, customization, training.

• Long, Complex Implementation: Can take years, disrupts business.

• Resistance to Change: Major organizational upheaval; requires change management.

• Customization Dilemma: Too much customization makes upgrades difficult and expensive.

• Over-Engineering: May force a company to adapt to the software's "best practices" rather than its unique strengths.

Implementation Phases (Typical):

1. Pre-Implementation (Planning & Selection): Define requirements, select software/vendor, form project team, get top management commitment.

2. Implementation (Blue Print & Build):

   • Business Blueprint: Document how the company's processes will be mapped to the ERP.

   • Realization/Development: Configure system, develop custom interfaces/reports, migrate data.

   • Testing: Unit, integration, user acceptance testing (UAT).

3. Go-Live & Post-Implementation: Data final migration, cutover, training, go-live support.

4. Maintenance & Optimization: Ongoing support, periodic upgrades, process optimization.

Key Challenges:

• Top Management Commitment: Most critical success factor.

• Change Management: Training, communication, addressing user resistance.

• Data Quality & Migration: "Dirty data" is a major cause of failure.

• Scope Creep: Uncontrolled addition of requirements.

• Post-Go-Live Support: Adequate resources for troubleshooting.