8.4 Production System Design

8.4 Production System Design

1. Plant Layout and Location

1. Plant Location Factors:

   • Primary Factors:

     • Proximity to raw materials.

     • Nearness to market/customers.

     • Availability of labor.

     • Transportation facilities.

   • Secondary Factors:

     • Availability of utilities (power, water).

     • Local regulations and taxes.

     • Environmental considerations.

     • Community attitude.

   • Modern Considerations:

     • IT infrastructure.

     • Supply chain connectivity.

     • Disaster risk assessment.

2. Plant Layout Objectives:

   • Minimize material handling.

   • Reduce production time.

   • Utilize space effectively.

   • Ensure worker safety.

   • Provide flexibility for future changes.

   • Facilitate supervision and control.

3. Layout Types:

   • Process Layout (Functional):

     • Similar machines/operations grouped together.

     • Suitable for job shop, low-volume, high-variety.

     • Advantages: Flexibility, machine utilization.

     • Disadvantages: High material handling, complex scheduling.

   • Product Layout (Line):

     • Arranged by sequence of operations for specific product.

     • Suitable for mass production, high-volume, low-variety.

     • Advantages: Low material handling, simple control.

     • Disadvantages: Low flexibility, high downtime risk.

   • Fixed Position Layout:

     • Product remains stationary, resources brought to it.

     • Used for large products (ships, aircraft).

     • Advantages: Minimum product movement.

     • Disadvantages: Resource scheduling complexity.

   • Cellular Layout (Group Technology):

     • Combines aspects of process and product layouts.

     • Machines grouped into cells for part families.

     • Advantages: Reduced setup time, improved flow.

     • Disadvantages: Requires careful part family identification.

4. Layout Evaluation Methods:

   • Travel Chart: Analyzes material movement distances.

   • Load-Distance Analysis: Minimizes $\sum_{i=1}^{n} \sum_{j=1}^{n} L_{ij} D_{ij}$ where $L$ = load, $D$ = distance.

   • Computer Simulation: Models layout performance under various conditions.

2. Material Handling

1. Material Handling Principles:

   • Plan all material handling as a system.

   • Minimize handling distances and times.

   • Use gravity where possible.

   • Standardize equipment and methods.

   • Reduce, combine, or eliminate unnecessary movements.

   • Consider safety as integral part.

2. Equipment Classification:

   • Conveyors:

     • Belt, roller, chain, overhead types.

     • Continuous movement, fixed path.

     • Best for high-volume, uniform products.

   • Industrial Trucks:

     • Forklifts, pallet jacks, hand trucks.

     • Flexible path, variable capacity.

     • Requires operators and aisles.

   • Cranes and Hoists:

     • Overhead cranes, jib cranes.

     • Intermittent movement, limited area.

     • For heavy, bulky items.

   • Automated Systems:

     • AGVs (Automated Guided Vehicles).

     • AS/RS (Automated Storage/Retrieval Systems).

     • Robots for loading/unloading.

   • Storage Equipment:

     • Racks, shelves, bins, drawers.

     • Pallet racking, cantilever racks.

3. Unit Load Concept:

   • Combine individual items into single unit for handling.

   • Common units: Pallets, containers, totes.

   • Advantages: Reduced handling time, improved space utilization, better protection.

   • Standardization: ISO pallet sizes, container dimensions.

4. Material Handling System Design:

   • Analyze material flow patterns.

   • Calculate handling volumes and frequencies.

   • Select appropriate equipment mix.

   • Design handling sequences and routes.

   • Consider interface with production processes.

5. Cost Considerations:

   • Initial equipment investment.

   • Operating and maintenance costs.

   • Labor costs.

   • Damage and loss prevention.

   • Space utilization efficiency.

3. Production Planning and Control

1. Production Planning:

   • Aggregate Planning:

     • Medium-term planning (3-18 months).

     • Balances demand and capacity.

     • Strategies: Level, chase, mixed.

   • Master Production Schedule (MPS):

     • Detailed plan of what to produce and when.

     • Translates aggregate plan to specific products.

     • Time-phased statement of production requirements.

   • Capacity Planning:

     • Determines resource needs to meet MPS.

     • Identifies bottlenecks.

     • Capacity Requirements Planning (CRP): Detailed machine and labor capacity analysis.

2. Production Control:

   • Scheduling:

     • Determines start and finish times for operations.

     • Objectives: Meet due dates, minimize setup time, maximize utilization.

     • Techniques: Gantt charts, priority rules (FCFS, SPT, EDD), Johnson's rule.

   • Dispatching:

     • Release of production orders to shop floor.

     • Issuing work orders, drawings, instructions.

     • Authorizing material withdrawal.

   • Progress Monitoring:

     • Tracking actual vs planned performance.

     • Collecting data on: Completion times, delays, quality issues.

     • Updating status reports.

   • Expediting:

     • Taking corrective actions for delayed orders.

     • Reallocating resources.

     • Revising priorities.

3. Inventory Control:

   • Types of Inventory:

     • Raw materials, work-in-progress, finished goods.

     • Maintenance/repair/operating (MRO) supplies.

   • Inventory Models:

     • EOQ (Economic Order Quantity): $Q^* = \sqrt{\frac{2DS}{H}}$ Where: $D$ = annual demand, $S$ = ordering cost, $H$ = holding cost per unit per year.

     • Reorder Point: $ROP = d \times L$ Where: $d$ = daily demand, $L$ = lead time in days.

     • Safety Stock: Buffer for demand or lead time variability.

   • Inventory Classification:

     • ABC Analysis: A items (high value, low quantity), B items (moderate), C items (low value, high quantity).

     • Different control policies for each category.

4. Modern Approaches:

   • MRP (Material Requirements Planning):

     • Computer-based system.

     • Explodes MPS into component requirements.

     • Considers lead times and inventory status.

   • JIT (Just-in-Time):

     • Produce what's needed, when needed, in needed quantity.

     • Emphasizes waste elimination, continuous improvement.

     • Requires reliable suppliers and processes.

   • Lean Manufacturing:

     • Focuses on value-added activities.

     • Eliminates muda (waste), mura (unevenness), muri (overburden).

     • Tools: 5S, Kaizen, Kanban, Value Stream Mapping.

5. Performance Metrics:

   • Utilization: Actual output / Maximum possible output.

   • Efficiency: Actual output / Standard output.

   • Productivity: Output / Input.

   • Throughput Time: Total time from start to completion.

   • On-time Delivery: Percentage of orders completed by due date.

   • Schedule Adherence: Actual progress vs planned schedule.