Kanban: The Pull System Powerhouse

Kanban is the first system that comes to mind, when people think of lean planning. It's the most basic "pull" system, which signals demand to downstream operations and prevents overproduction.

How it works:

Kanban uses visual signals such as cards, containers, designated spaces etc., to signal for additional production or movement of materials only when required. When a downstream process uses an item, a signal is sent upstream to start the replenishment process of that specific item.

Key benefits:

·Reduced WIP: reduces WIP, freeing up floor space and capital.

·Improved flow: actual demand drives the smooth flow of materials and information.

·Enhanced visibility: bottlenecks and inefficiencies are immediately apparent.

·Empowered teams: Teams self-organize and pull what they need, fostering ownership.

Variations:

While the classic two-bin or card-based Kanban is prevalent, electronic Kanban (e-Kanban) systems are increasingly used to automate signalling and data collection, especially in complex supply chains.

Heijunka: Levelling the Production Load

Heijunka, translated as "production levelling" is critical for achieving stability of production levels in a lean environment. It addresses the customer demand variability which is inherent for all manufacturing companies by distributing production of different products evenly over a particular time period thereby increasing predictability.

How it works:

Instead of running large campaigns of a single product and then switching to another, Heijunka aims to produce a mix of products in smaller, more frequent runs. For e.g. instead of running 10MTThis is often visualized using a "Heijunka Box" or production levelling box, which helps schedule the sequence and quantity of different products.

Key benefits:

·Reduced Mura (unevenness): Smooths out demand fluctuations, preventing peaks and valleys in production.

·Improved resource utilization: Ensures a more consistent workload for machines and personnel.

·Shorter lead times: Enables quicker response to diverse customer orders.

·Supports JIT: Crucial for the successful implementation of Just-in-Time principles.

Practical application:

Companies use Heijunka to create a balanced production schedule, often by mixing different product types or sizes within the same shift or day.

Constant Work-in-Process: A Hybrid Approach

CONWIP offers a powerful alternative or complement to pure pull systems, particularly in environments with high product variety or unstable demand. It maintains a constant amount of work-in-process for a given production line or system.

How it works:

Unlike Kanban, where each part has its own WIP limit, CONWIP sets a single, overall WIP limit for the entire production line or cell. When a finished product exits the line, a signal is sent back to the beginning, authorizing the release of a new order into the system. The specific product released is often determined by the actual customer order.

Key benefits:

·Controlled WIP: Prevents excessive build-up of inventory while still allowing for a level of flexibility.

·Simpler implementation: Can be easier to manage than a complex multi-Kanban system in some scenarios.

·Hybrid flexibility: Combines aspects of both push (initial release) and pull (replenishment based on completion).

·Visibility into bottlenecks: When the WIP limit is reached, it quickly highlights the constrained process.

When to use:

CONWIP is particularly effective in make-to-order environments or where there's a strong desire to keep WIP low while maintaining responsiveness.

MRP (Material Requirements Planning) with a Lean Lens

While traditional MRP/ERP systems are often associated with push manufacturing, they can be powerful tools when integrated with lean principles. The key is to leverage their capabilities for data aggregation and communication while still adhering to pull signals and flow.

How it works:

Instead of using MRP to "push" production based on a master production schedule alone, lean organizations use it to:

·Forecast demand: Provide accurate long-term demand signals.

·Manage supplier relationships: Optimize material flow from suppliers based on pull.

·Track inventory: Maintain real-time visibility into inventory levels, crucial for Kanban replenishment.

·Support value stream mapping: Provide data for identifying waste and optimizing processes.

·Integrate information: Connect various departments (sales, production, purchasing) for seamless data exchange.

Key benefits:

·Holistic view: Provides a comprehensive picture of the entire operation.

·Data-driven decisions: Supports informed decision-making regarding production and procurement.

·Scalability: Can manage complex operations with numerous products and suppliers.

·Compliance and reporting: Facilitates regulatory compliance and accurate financial reporting.

Lean integration:

The success lies in using MRP/ERP to support pull systems and JIT, rather than dictate a pure push approach. This involves configuring the system to respond to actual consumption and demand signals from the shop floor.

Production Boards & Visual Management

While not a "system" in the same vein as Kanban or MRP, visual management, often manifested through production boards (Andon, T-cards, performance boards), is an indispensable planning and control tool in lean manufacturing.

How it works:

These boards visually display key performance indicators (KPIs), production schedules, quality metrics, and problem alerts in real-time. They are typically located on the shop floor, making information immediately accessible to everyone.

Key benefits:

·Transparency: Everyone understands the current status of production and performance.

·Rapid problem identification: Deviations from the plan are immediately visible.

·Accountability: Teams take ownership of their performance.

·Continuous improvement: Facilitates quick problem-solving and immediate feedback loops.

·Empowerment: Allows frontline workers to understand their contribution and take action.

Examples:

Andon lights (signalling abnormalities), team performance boards, hour-by-hour production tracking boards.

Choosing the Right System (or Combination)

There's no one-size-fits-all solution. The optimal planning system (or, more commonly, a combination of systems) depends on several factors:

·Product variety and volume: High-volume, low-variety products might benefit more from traditional Kanban, while high-variety, low-volume might lean towards CONWIP or a strong MRP integration.

·Demand stability: Stable demand makes Heijunka more straightforward to implement.

·Supplier relationships: The maturity of your supplier network impacts your ability to implement true JIT.

·Organizational culture: A culture of empowerment and continuous improvement is crucial for the success of any lean system.

·Technological capabilities: The availability of robust IT infrastructure can influence the adoption of e-Kanban or sophisticated ERP integrations.

Ultimately, the goal of any lean planning system is to create a dynamic, responsive, and waste-free production environment. By understanding the strengths and applications of these various systems, manufacturers can strategically design their operations for maximum efficiency and sustainable growth. The journey to lean is continuous, and the right planning system is your compass.