What is a Kanban System?

• Kanban is a Just-In-Time production management system based on visualizing work in progress and regulating workflow based on demand. It eliminates waste, reduces waiting times, and improves quality.
• Kanban was developed in the late 50s by Taiichi ōno at Toyota as a way to regulate the flow of parts and materials efficiently, minimizing waste and overproduction.
• Kanban is a key tool in Lean Manufacturing, helping to reduce waste, optimize workflow, improve quality, facilitate visual management , and encourage continuous improvement.
• The four main principles of Kanban are: starting with the current situation, pursuing incremental change, respecting existing processes and responsibilities, and encouraging leadership at all levels.
• The essential elements of the Kanban methodology include visual cues (Kanban cards), defining the right number of cards, Kanban boards (physical or digital), work-in-progress (WIP) limits, and a pull-based system that responds to customer demand.

Kanban Principles

1. Visualize the Workflow

The heart of the system lies in visualizing process steps and work items. Whether through physical whiteboards or digital tools, visual representation ensures clear identification of tasks, expectations, ownership, and current status. Different colored cards signify various work types, organized under horizontal swim lanes for additional categorization.

2. Limit Work In Progress

Kanban systems emphasize efficiency by minimizing work in progress. Teams prioritize completing tasks before picking up new ones, enabling early initiation of dependent tasks, preventing resource idleness, and improving focus.

3. Manage and Measure the Flow

Carefully tracking and illustrating process execution allows pinpointing strengths and weaknesses. Immediate identification of goals not met or bottlenecks facilitates timely resolution and process improvement, enhancing predictability and efficiency.

4. Explicitly Define Process Policies

Well-visualized workflows involve clearly defined process rules, guiding team expectations easily. Kanban board columns designate individual process steps' rules, outlining task expectations and definitions.

5. Improve Continuously

A Kanban system is under constant evolution, viewing each improvement opportunity as a chance to simplify and polish the process flow. Employing incremental feedback loops fosters gradual enhancements, emphasizing early detection and swift correction of failures.

Kanban systems: The essential elements

The key elements of the Kanban methodology are designed to provide greater insight into workflow management, production control, and continuous improvement.

Visual cues

Kanban cards are at the center of this method. Presented as cards or sticky notes, they act as visual cues to organize and guide teams' work throughout the production line.

Each card represents a work unit, a task, or an item to produce. It contains important information such as the item description, quantity, location, process step, etc.

There are two main types of kanban cards, each used for a specific purpose:

• Production Kanban: These cards are used to manage the production of parts or items. They indicate when to produce and how much to produce. When a production stage has completed a batch, it brings back the associated Kanban card at the beginning of the process to trigger the production of the next batch.
• Movement Kanban (or Transport Kanban): These cards manage the movement of materials or products between process stages. Withdrawal cards signal when to move parts from one stage to the other. When parts are consumed, the Kanban card is returned to the previous stage to authorize the withdrawal of new parts.

Defining the right number of Kanban cards

Determining the right number of Kanban cards is critical if the system is to operate efficiently. Kanban cards are designed to balance production with actual demand, minimizing waste while avoiding work overload.

The standard formula for defining the number of Kanban cards is:?

Number of cards = (Daily demand x Cycle time) / Minimum order quantity

Once you've determined an initial number of Kanban cards, monitor the system and adjust as you go. If problems arise, such as delays, bottlenecks, or overstocking, reassess and adjust the number of cards accordingly.

Kanban boards (physical or digital)

The Kanban board is a visual aid that provides an overview of the workflow, enabling the whole team to keep track of work progress. It is divided into columns, each representing a stage in the production process. Kanban cards are moved from column to column as work progresses.

The representation of these traditional Kanban boards can be physical (wallboard, whiteboard, etc.). A digital Kanban system can also be implemented (Kanban software).

Work in progress (WIP) limits

WIP limits are the maximum quantities of work allowed at each process stage. They are set to prevent overloading at a given stage, which could lead to delays and inefficiencies.

When a WIP limit is reached, no new Kanban card can be moved to that stage until one of the current cards has progressed.

WIP limits encourage compliance with the workflow and the reduction of waste .

Kanban System Metrics

Benchmarking and measuring progress are crucial for gauging team success with the Kanban system. Common metrics, providing insights for continuous improvement with a Kanban system, include:

• Lead and cycle time – the time it takes tasks to traverse the entire process,
• Process throughput – the speed at which tasks are completed on the whole,
• Cumulative flow diagram (CFD) - an overview of the trends in processing tasks built up over time, showing overall process condition and allowing to make data-backed forecasts.

How does the Kanban method work?

Pull system and push system

The Kanban process is a pull-based method, meaning production is based on customer demand. Kanban cards, associated with tasks or items, act as visual signals to trigger the production.

When a step in the process needs more items to meet demand, it "pulls" the corresponding Kanban card, indicating to the previous step that it needs to produce more. This system ensures that only what is needed is created, thus reducing waste and excessive inventories.

It contrasts with the "push" principle, which is based on production forecasts. Items are pushed into the production process according to a schedule or demand forecast. It can lead to overproduction, unnecessary inventories, and delays when demand fluctuates.

How Kanban systems are used in manufacturing?

Step 1: Create workflow visualizations

Workflow visualization involves mapping and visually representing the entire production process. It can be done using physical or digital Kanban boards, maps, or panels.?

Each step in the work process is clearly defined, identified, and activated, enabling the whole team to see how work flows.

Step 2: Limit work in progress?

Strict limits must be set on the number of tasks in progress at each process stage, to avoid overload, maintain a smooth workflow, and minimize waiting times.

Step 3: Manage workflows

Managing workflow involves carefully monitoring the progress of tasks or items through the process. The goal is to ensure that production proceeds smoothly, without delays or interruptions.?

If anything goes wrong, corrective actions must be taken to restore the flow.

Step 4: Clearly define and share work policies

This stage involves defining the policies and rules that govern the workflow, including priorities, quality criteria, deadlines, criteria for moving from one stage to the other, etc.

These policies are communicated to the team to make sure everyone knows and understands them.

Step 5: Implement feedback loops

Team members must report problems as soon as they arise, triggering immediate actions to resolve them.

In addition, regular retrospective meetings are held to review production performance , identify areas for improvement, and make adjustments.

Step 6: Foster collaboration and experimentation for continuous improvement

The Kanban method encourages collaboration between employees, fostering a spirit of experimentation and innovation. Different teams work together to find ways of improving the process, optimizing workflows, and reducing waste.?

New ideas and methods can be tested through experimentation, pushing a step further the mindset of continuous improvement.

The benefits of the Kanban System

Reduced waste and overstock

The Kanban method eliminates waste ("muda") by reducing overproduction, excessive inventories, waiting times, unnecessary movements, work overload ("muri"), quality corrections, and any other form of waste.?

It also allows to better manage the variability ("mura") of demand by adapting to fluctuations, thus making production more stable.

Kanban cards ensure that only the necessary work is done.

Improved flow and yield

Kanban optimizes workflow by avoiding delays, waiting times, and interruptions. The result is more efficient production and faster processes.

Increased flexibility and responsiveness to change

The Kanban method adapts to variations in actual demand. It enables flexible production that can be quickly adjusted to respond to market changes and fluctuations.

Better visibility on production status and bottlenecks

Kanban is a method that offers real-time visibility on the state of production. Through charts and cards, everyone can see where tasks or items are in the process.

This makes it easy for teams to track progress, reduce bottlenecks, and make informed decisions on ways to solve potential problems.

Higher quality

By limiting work in progress and controlling processes step by step, the Kanban method helps to improve quality. Problems are quickly detected and resolved upstream.

Better communication and collaboration

The Kanban system encourages communication and collaboration between team members. Everyone can see what's going on in the production process and make sure they're moving in the same direction.

Kanban challenges and solutions

Demand fluctuations

Demand fluctuations can make it challenging to manage Kanban cards.?

Solution: Adapt WIP limits and ensure that Kanban cards are set to handle demand variations.

Quality problems

Quality problems can lead to production delays.?

Solution: Identify problems from the start, resolve them, and consider integrating quality control measures into the process.

Logistical challenges

Problems with transport or material availability can affect the Kanban system.

Solution: Communicate regularly and align with suppliers so that the logistics flow remains smooth.

Resistance to change

Employees may refrain from adopting the Kanban method.?

Solution: Offer training and coaching sessions . Involve employees in implementing Kanban and show them the benefits of this method.

The role of feedback loops in the Kanban system

Each feedback loop is essential to the Kanban system and plays a vital role for continuous improvement. They allow to detect problems, make adjustments, and ensure the workflow remains frictionless.

Feedback loops comprise 3 different stages:?

1. Problems (e.g., delays, errors, bottlenecks) are detected and reported by team members.
2. Once a problem has been reported, the team resolves it immediately. This prevents the issue from getting worse or impacting the production.
3. Once a problem has been solved, the team reflects on its causes and potential solutions. This leads to improvements in the work processes that eliminate the risk of recurrence in the future.

Reference

1. Implementing Kanban in Manufacturing: The Ultimate Guide for Streamlining Operations - AgileFever: #1 Leading Online Professional Training Platform - Certifications - Bootcamps
2. Kanban Systems – Lean Tools For Your Manufacturing Facility | Tulip
3. What Is Kanban in Lean Manufacturing and How to Use it ( proactioninternational.com )