Kanban Systems

Kanban systems employ various signal types adapted to specific production and logistics requirements. Understanding these variations enables practitioners to select and implement appropriate kanban mechanisms for different operational contexts.

Production Kanban authorizes manufacturing operations to produce specified quantities of specific parts. These signals typically remain at producing work centers, returning to trigger production when supermarket withdrawals occur. Production kanban quantities are calculated based on demand rates, production lead times, and safety stock requirements.

Withdrawal Kanban authorizes movement of materials between locations, commonly from upstream supermarkets to downstream point-of-use locations. Material handlers respond to withdrawal signals, moving only authorized quantities to designated locations. This separation of production and withdrawal authority enables optimized material flow.

Signal Kanban trigger production or replenishment when inventory reaches predetermined reorder points. Unlike circulating kanban that move with materials, signal kanban remain in fixed positions, indicating replenishment need when inventory falls below trigger levels. Signal kanban suit high-volume, low-variety items where continuous replenishment is appropriate.

Express Kanban handle urgent or emergency situations requiring immediate response outside normal kanban cycles. These signals authorize expedited production or delivery when standard kanban cannot meet urgent needs. Excessive express kanban usage indicates system design problems requiring attention.

Supplier Kanban extend pull signals to external suppliers, authorizing shipments to replenish incoming material supermarkets. Supplier kanban require coordination of delivery schedules, container specifications, and information sharing. Electronic supplier kanban enable rapid signal transmission across supply chain distances.

Container Kanban use the containers themselves as kanban signals, with empty containers authorizing replenishment. This approach simplifies administration for items stored in standard containers, eliminating card management while maintaining pull discipline. Container specifications become critical system design elements.

Effective kanban systems require careful design that balances inventory investment against service level requirements. System design encompasses kanban quantity calculations, loop definitions, and visual management elements that support consistent operation.

Kanban Quantity Calculation determines the number of kanban required to maintain flow. The fundamental formula considers average daily demand, replenishment lead time, and safety factor: Kanban = (Daily Demand x Lead Time x Safety Factor) / Container Quantity. This calculation establishes the maximum inventory the system will maintain.

Lead Time Analysis identifies all time elements between kanban signal and replenishment availability. Lead time includes wait time, processing time, transport time, and any delays. Accurate lead time estimation is critical, as underestimation causes stockouts while overestimation creates excess inventory.

Safety Stock Determination addresses variability in demand and supply. Higher variability requires larger safety factors, while more stable systems can operate with minimal safety stock. Statistical analysis of historical variability informs safety stock decisions, balancing service levels against inventory costs.

Loop Definition establishes the boundaries and mechanics of each kanban circuit. Loops define source locations, destination locations, signal types, and trigger mechanisms. Complex value streams may require multiple interconnected loops, each designed for specific material flow requirements.

Container Standardization specifies the packaging used within kanban systems. Standard containers hold specific quantities, protecting parts while enabling visual inventory management. Container selection considers part characteristics, ergonomic handling requirements, and storage efficiency.

Visual Board Design creates central displays showing kanban status across multiple items or processes. Boards reveal which items are in replenishment, which have available inventory, and which face potential shortages. Color coding and arrangement conventions enable quick status assessment.

Electronic kanban (e-kanban) systems replace physical cards with digital signals, enabling faster information transmission, easier system management, and integration with enterprise systems. Understanding e-kanban capabilities enables practitioners to leverage technology while maintaining pull system discipline.

Signal Transmission in e-kanban systems occurs through various mechanisms including barcode scanning, RFID, and automatic sensor triggers. When consumption occurs, systems automatically generate replenishment signals without manual card handling. This automation reduces administrative burden while improving signal accuracy.

ERP Integration connects kanban signals with enterprise planning and inventory systems. Real-time updates provide visibility into kanban status across the organization while supporting capacity planning and supplier communication. Integration requires careful design to maintain kanban simplicity within complex enterprise architectures.

Supplier Communication extends e-kanban across organizational boundaries to trigger supplier shipments. Electronic signals eliminate mail delays and lost cards while providing audit trails of signal transmission and response. Supplier portals enable visibility into replenishment status without direct system access.

Analytics and Reporting leverage e-kanban data for continuous improvement. Systems track signal frequency, replenishment lead times, and service levels over time. This data supports kanban quantity optimization, identifies bottlenecks, and reveals improvement opportunities that physical systems cannot easily measure.

Mobile Access enables kanban management through smartphones and tablets, supporting material handlers and supervisors working throughout facilities. Mobile applications display kanban status, capture transactions, and communicate across teams without returning to fixed terminals.

Hybrid Approaches combine electronic and physical kanban elements to leverage benefits of each. Physical boards may maintain visual simplicity while electronic systems handle data capture and analysis. This combination preserves intuitive visual management while gaining analytical capabilities.

Kanban systems are designed not merely for production control but as vehicles for continuous improvement. Systematic kanban reduction exposes problems that inventory buffers hide, creating improvement pressure that drives organizational capability development.

The Kanban Reduction Cycle represents a disciplined approach to improvement. Beginning with stable system operation, teams reduce kanban quantities slightly, observe the system for problems that emerge, address root causes of problems, achieve new stability, then reduce further. This cycle continues indefinitely as capability improves.

Problem Exposure occurs when reduced kanban reveal previously hidden issues. Quality problems, equipment unreliability, and process variation that were accommodated by inventory buffers become visible disruptions. Rather than restoring inventory, teams address root causes for permanent improvement.

Setup Reduction often becomes necessary as kanban reduction decreases batch sizes. Smaller kanban quantities require more frequent production of each item, making setup time increasingly costly. SMED activities enable the production flexibility that smaller kanban quantities demand.

Quality Improvement follows from defects that disrupt flow in low-inventory systems. Problems that inventory buffers absorbed now create stockouts that demand immediate attention. This pressure motivates investment in quality improvement that prevents defects rather than buffering against them.

Lead Time Reduction enables further kanban reduction by decreasing the time between signal and replenishment. Process improvements, cellular manufacturing, and setup reduction all contribute to lead time reduction that enables lower kanban quantities.

Supplier Development extends kanban improvement beyond factory walls. As internal systems mature, supplier capabilities become limiting factors. Supplier development activities improve delivery reliability, reduce lead times, and enable smaller delivery quantities that support lean operations.