Overproduction and underproduction are commonly found problems in manufacturing. Producing more products than you can sell means wasting resources that will not turn into a profit. Meanwhile, manufacturing too little means you won’t fully satisfy your customers’ demands – an opportunity your competitors can use to steal your market share. Thus, both problems should be avoided.
Planning production output is always a concern for any plant manager. Yet, what if there’s a way to prevent overproduction and underproduction simultaneously? What if there’s a way to ensure that your plant’s production output is always on point – never too much or too little?
The answer lies in the Japanese philosophy of Heijunka. Yet, what is Heijunka? What is its meaning? And how can you use this powerful philosophy in your plant?
In this article, we will elaborate on Heijunka’s definition & meaning, its principles, supporting tools, and a real-life example of Heijunka in action. At the end of this article, we include a lean manufacturing e-book PDF that you can download for free.
What Is Heijunka?
In Japanese, “Heijunka” means “leveling”. This definition refers to Heijunka’s central philosophy of leveling production. Leveling production means a plant’s production volume should be kept at an average rate based on previous customer demands to avoid production “peaks” and “valleys.” A peak refers to the time when the production volume is far higher than usual, while a valley is when the production volume is far lower than what it usually is.
What Is Heijunka’s Production Levelling?
Here’s a good example of Heijunka’s production leveling: let’s say that you run a plant that produces small leisure boats. Your plant and showroom operate 7 days a week. Here are the boat purchasing orders from last week based on the day they were received:
- Monday: 3 boats
- Tuesday: 1 boats
- Wednesday: 7 boats
- Thursday: 5 boats
- Friday: 9 boats
- Saturday: 20 boats
- Sunday: 18 boats
In total, you received an order of 63 boats last week. Moreover, the number of orders on Saturday & Sunday greatly exceeds those on the weekdays, as weekends are when people generally have the most time for leisure-oriented shopping.
As a manufacturer, you would want to manufacture and deliver your boats to your customers as soon as possible. At the same time, you wouldn’t want to overwork your employees and overburden your production machinery. As the plant manager, what should you do?
In Heijunka, a plant’s production output must be as flat or average as possible. There’s a demand for 63 boats, and your plant operates 7 days a week. To level it, divide the number of orders by the days your plant operates (thus 63 divided by 7). Hence, your plant should produce 9 boats/day
The idea of leveling production is to make the production process as predictable as possible. Additionally, production leveling reduces the likelihood of both overburdening and idleness of your employees and production machinery at the same time.
Overworking your employees will negatively impact their physical & mental health and will correlate to their performance and your organization’s turnover rate. Meanwhile, overusing your production machinery beyond its intended capacity will undoubtedly lead to frequent breakdowns and ultimately shorten its product lifespan.
On the other hand, the idleness of your employees and production machinery is equally bad. If they’re idle, they’re not adding value to your organization. Meanwhile, employee salaries, regular machinery maintenance, and other upkeep costs are still being charged to your organization’s coffers – regardless of whether these employees & machinery are working or not.
The illustration above of a boat manufacturing leveling its production is just a simplified example of Heijunka’s application in manufacturing. In real-life settings, production leveling is much more complicated.
Additional factors such as differing products, varying production machinery, and long-term customer trends must also be considered. In the following sections of this article, we will touch upon the 2 main Heijunka production methods, the tools you need, and a real-life example of a Heijunka-applying company.
Heijunka’ Toyota Origins
Like other lean manufacturing philosophies such as Kaizen, Jidoka, and the Just in Time Production System,
Heijunka originates from Toyota. In 1956, a Toyota industrial engineer named Taiichi Ōhno visited the US. There, he learned about American manufacturers’ production processes and noted aspects that could be further improved when he returned to Japan.
Furthermore, he was inspired by the then-new concept of supermarkets in the US. In supermarkets, customers can simply “pull” the products they want from the shelves. Later on, store workers will re-stock these shelves with new products.
These experiences led Taiichi Ōhno to establish the lean manufacturing doctrine, which includes Heijunka as one of its derivative philosophies. His methodologies are today collectively known as the Toyota Production System (TPS).
The TPS boosts production efficiency dramatically when applied. A McKinsey article by Deryl Sturdevant, a former President and CEO of Canadian Autoparts Toyota (CAPTIN), showcases TPS’s might. Conventionally, changing the die used for fabricating an aluminum alloy wheel takes 4-5 hours. With the TPS in full swing in his plant, he was able to cut this process to less than an hour.
This example of a dramatic increase in production efficiency directly translates into Toyota’s global supremacy in the auto industry. In 2022, Toyota was the world’s best-selling automobile producer, a title it held for three years in a row.
Due to its impact on production efficiency, the TPS and lean manufacturing doctrine in general (including Heijunka) are commonly used in countless plants worldwide across all manufacturing sectors.
Heijunka and Lean Manufacturing
Lean manufacturing is a doctrine that aims to remove 8 forms of waste, which are:
To become “lean” and remove all of these 8 waste forms, manufacturers will have to implement these 5 lean manufacturing principles:
Sometimes, the terms lean manufacturing and agile manufacturing are used interchangeably. Even though both terms sound similar to each other, they are, in fact, two separate doctrines with different characteristics.
In lean manufacturing, Heijunka is often associated with the fourth principle: Establishing a Pull System. A pull system means that a product will only be produced once there’s already an order from the customer for the said product.
The pull system ensures that a product will always have a buyer so that it will never be a waste. Additionally, a manufacturer or distributor wouldn’t need to store the product in a storage facility such as a warehouse, as the product will be directly sent to the customer. Directly sending the product removes storage-related costs, such as building or renting a warehouse.
Heijunka’s Production Levelling
The Pull system might seem ideal due to its element of certainty and cost-effectiveness. However, the pull system also has its disadvantages. Demands from your customers always vary from time to time. There are always times when demands are so high (known as “peaks”), and there are times when demands are very low (known as “valleys”).
The Heijunka principle of production leveling seeks to find a balance between these peaks and valleys. It aims to take advantage of the certainty element of the pull system but remains flexible enough to fulfill market demands based on past sales statistics.
During peak times, production demands can be extremely high, to the point where your employees are overworked, and your production machinery overburdened. Overworking your employees will detriment their physical & mental health and lower their work performance.
Safety is also another concern. Exhausted employees are more prone to commit errors and cause workplace accidents. According to the National Safety Council, 13% of all workplace injuries in the US are attributed to fatigue-related causes.
In addition, constantly overworking your employees will surely increase your turnover rate. Hiring new employees will also be challenging if your organization has a reputation for continuously overworking its employees.
At the same time, pushing your production machinery beyond its intended capacity also has its risks. Overburdened machines tend to break down faster, thus requiring more frequent maintenance. Furthermore, it will also reduce the machinery’s lifespan.
On the contrary, production demands can be very low during valley times. Thus, some of your employees and production machinery will be idle. This is equally bad as overburdening. When employees are less productive than they should be, your organization still has to pay employee salaries, routine machinery maintenance, and other upkeep costs.
Therefore, Heijunka seeks to avoid the extremities of overburdening and idleness through production leveling. Leveling your production means finding the average production output between these peak and valley times and planning your production output based on this average rate.
Leveling the production in Heijunka can be divided into two methods: leveling by production volume and leveling by product type. Here’s how both methods work:
Production Leveling by Volume
Leveling your production output by volume is the simplest form of product leveling in Heijunka. Here, past customers’ order statistics on a given period are presented on a table to be visualized. Depending on the industry, the period can be days, months, or even years.
In industries where a good is produced quickly (such as fast-moving consumer goods and the textile industries), it’s recommended to use shorter periods. For industries where producing a good takes a long time (such as the aerospace industry), it’s better to stick with more extended time periods.
Once the customer order data and time period have been visualized in a table, it’s time to calculate your optimum production volume. The formula is pretty simple: divide the amount of customer orders by the selected time period. Here’s a visualization of the formula:
This optimum production volume is the amount of output your plant should attain in a given time to be fully Heijunka-compliant. Here’s an example to help you understand production volume leveling in Heijunka:
Example of Production Leveling by Volume
Let’s say that Bob is an assembly line manager in a furniture factory. Bob’s assembly line is responsible for producing chairs. At the moment, Bob is planning the monthly production output for his assembly line. How many chairs should Bob’s assembly line produce per month?
The best way to decide this is by analyzing past customer demands, finding the average between the peaks and valleys, and then planning production based on this optimum production volume. Thus, Bob decided to look at last year’s customer orders report. Here’s what Bob found:
Based on this data, Bob sees the peak customer demand in November – most likely due to the Black Friday sales. Meanwhile, the valley of the customer demands is in March – where orders are only 1/14 compared to the peak month. That’s a drastic difference between the peak and the valley.
Calculating the optimum monthly production volume is relatively straightforward. Simply divide the total number of customer orders (60,000) by the number of months (12). Thus, Bob’s optimum production volume is 5,000 chairs/month.
Hence, for this year, it’s ideal for Bob’s assembly line to produce 5,000/chairs per month. With this monthly production volume, his assembly line will be prepared to face the demand surge in November without the need to overwork his employees and overburden his machinery. This monthly production volume also ensures that Bob’s employees and machinery are always productive, even in months with low demands.
Be aware that the product leveling by volume method only works if your assembly line produces only 1 type of product. If it makes multiple products or product variants, you must follow the second method: production leveling by product type.
Production Leveling by Product Type
Another method of production leveling is through product type. This method is more advanced than the leveling by production volume method, as it adds one extra variable: product variation. This method is used in production facilities that make multiple types of products.
To use this method, simply count the optimum production volume for each product. The formula is still the same as the previous method: simply divide the amount of customer orders by the selected time period. Do this calculation for each product type. Here’s an illustration of production leveling based on product type:
Example of Production Leveling by Product Type
Tom is the manager of a plant that produces dairy products. His plant produces 3 types of dairy products: bottled milk, butter, and ice cream. His production output is measured in liters. Tom is planning the monthly production output of his plant. And similar to Bob in the previous example, he consulted the sales statistics from last year. Here’s what the statistics display:
Calculating the optimum monthly production volume is an easy task. Just divide each product’s total yearly sales volume by the number of months (12).
- For milk, it’s 600,000 liters divided by 12 months. Thus, the optimum milk monthly production volume should be 50,000 liters/month.
- For butter, it’s 360,000 liters divided by 12 months. Thus, the optimum milk monthly production volume should be 30,000 liters/month.
- For ice cream, it’s 120,000 liters divided by 12 months. Thus, the optimum ice cream monthly production volume should be 10,000 liters/month.
Notice how ice cream sales peaked significantly in the summer months of June to August and slumped drastically in the winter months of December to February. Meanwhile, demands for milk and butter remained mainly stable throughout the year.
This fluctuation in ice cream sales is logical; when the weather is warm, people want to cool off by eating ice cream. If it’s cold, people are less likely to eat ice cream and would opt for something warm instead. The ice cream industry is a good example, where the customer demand’s peak and valley differs dramatically.
Now that Tom has done the calculations above, he can plan his monthly production volume. His plant should produce 50,000 liters of milk, 30,000 liters of butter, and 10,000 liters of ice cream each month.
The example above is a simplified illustration of leveling production according to product type. In real life, there can easily be tens of products in a single table.
Moreover, the production time period used in the table can vary depending on the industry and product complexity. They range from minutes for simple, mass-produced goods like canned soda to months for highly complicated & capital-intensive products such as an airplane.
Implementing production leveling, especially production leveling by type, is indeed a complex task, especially if your plant produces multiple kinds of products. But worry not; several tools can help you, such as:
A Heijunka board, often called a Heijunka box, is a commonly used tool. A Heijunka board is a shelf with many boxes in it. The top horizontal axis of the shelf displays the time period, be it minutes, hours, days, weeks, or even months. The vertical axis shows the name of each product made in this plant/assembly line.
When starting the production process of a product, insert documents related to this product into a brightly-colored folder and place this folder on the correct box based on the product type and selected time period. Remove this folder from the shelf once the product’s production process is complete. Repeat this same process for each product.
Using a brightly-colored folder makes your Heijunka board more visually intuitive, as bright colors can easily be spotted from a distance. Employees can see how many products are being produced in each time period by looking at the number of folders on the shelf.
The image above is a perfect example of a Heijunka board in a real-life setting. On the horizontal axis of the shelf, 6 days of the week are written. Meanwhile, the vertical axis shows different car variants.
The boxes on the shelf contain the files and details of each car being worked on. Employees would instantly know which car to process each day and their progress.
Other than the Heijunka board, another helpful tool is the Kanban board. It’s a board that is divided into several sections. Each section in a Kanban board represents a specific production phase, which often goes along the lines of “to do,” “in progress,” “testing,” “done/completed”, and “backlog/stuck.”
After that, gather some post-it sheets. Each post-it sheet should contain the name of a product. Then, stick the post-it sheet to the corresponding section in the Kanban board. Continually update the Kanban board by moving the post-it sheet on the shop floor according to the production process.
Like Heijunka boards, Kanban boards help visualize your plant’s ongoing production process. With just a glance, every employee will know the production progress of each product. Learn more about how to use a Kanban board.
Real-Life Heijunka Example in Manufacturing
Although originating from Toyota, Heijunka is used as good as every sector globally. FPZ is an excellent example of a Heijunka success story – where a company has integrated Heijukna ideals into its manufacturing process and reaped concrete benefits.
FPZ is an Italian company that manufactures blowers, fans, and pumps. In 2007, it began integrating lean manufacturing ideals, including the Heijunka philosophy, into its operations.
It installed tools such as Heijunka and Kanban boards in its plant to support its transition into lean manufacturing. Thanks to these tools, operators know exactly what to do after completing a task – making the shop floor operation much faster. Tools storage was also centralized, reducing the possibility of mistakes and time spent walking between different production stations.
Coupled with other lean manufacturing strategies, FPZ has removed waste that would have otherwise cost the company an estimated EUR 60,000 within the first 3 years of lean manufacturing implementation.
Heijunka Software Solutions
Besides analog tools such as Heijunka and Kanban Boards, digital tools such as Azumuta will also help you comply with the Heijunka philosophy and become a proper lean manufacturer. Here’s how:
Digital Work Instructions
Starting a production leveling strategy by volume or product type is challenging. Your employees must be able to:
- Gather data on past customer orders
- Calculate the optimum production volume
- Adjusting production output to match the set optimum production volume
- Use Heijunka and Kanban boards
All of these tasks are technical and require work instructions that are highly detailed yet brief enough to be easily understood. Meanwhile, the pages of conventional paper-based instructions can only include minimal information. They’re also not intuitive since they primarily consist of text-heavy instructions with little visual elements.
Not to mention that it takes many hours to write paper-based work instructions. Due to their physical nature, paper-based work instructions can be only in one place at any time – meaning that your employees have to take turns and share them.
Our Digital Work Instructions module is the solution to all of this. Thanks to our drag-and-drop interface, you can make multiple pages of work instructions in just a few minutes instead of hours.
Supplement your digital work instructions with visual elements such as videos, symbols, and 3D models. This will make your instructions more straightforward and easily understandable with just a single glance.
And, of course, thanks to its digital nature, our work instructions module is 100% paperless. Not only is it good for the environment, but it will cut unnecessary printing costs each year. Your digital work instructions can be accessible from any authorized PC, tablet, or smartphone, so your employees can use them wherever & whenever they need it.
Audits & Digital Checklists
After implementing Heijunka for some time, it’s crucial to audit your production facility. To know whether it has fully complied with the Heijunka production leveling strategy and to investigate whether the targeted key performance indicators have been achieved.
Our Audits & Digital Checklists module is any auditor’s best companion. With it, you can easily plan, organize, and execute any audit. There is no need to draft the audit documents from scratch, as we already provide pre-existing templates for all your audit needs – saving you precious time. Simply input data into our pre-existing fields, and you’re good to go.
Our audit dashboard will make any audit process a walk in the park. With this dashboard, you can easily track your plant’s audit progress in just a few clicks.
Unlike many other competitors, our lean manufacturing software can be connected with various peripherals, ranging from printers to digital torque wrenches. Your industrial machinery can directly feed data into your PC, tablet, and smartphone.
Using our Quality Management module, this data can be visualized into a centralized data dashboard. Thanks to it, you will have a complete situational awareness of your entire plant – all from the comfort of your desk, without the need to visit all machinery on the shop floor.
In implementing Heijunka, this is a convenient feature. You will know firsthand the production volume of all products in every assembly line. If something is not right, you can instantly spot it and resolve it quickly. Leveling your production volume in accordance with the Heijunka philosophy has never been easier, thanks to our Quality Management module.
Skill Matrix & Training
Before starting any transition into Heijunka, all of your employees must be trained beforehand. This includes training on the Heijunka philosophy, the lean manufacturing mindset, and how to do production leveling on the shop floor.
Our Skill Matrix & Training module is perfect for your employee training needs. With it, you can send training materials, plan short and long-term training programs, and send notification reminders to your employees’ devices for any upcoming training.
Evaluate your employees’ knowledge and skills from time to time and keep track of them using our skill matrix. Use our visually intuitive and automatically color-coded template to monitor your employees’ knowledge and skills. Thanks to our template, you don’t have to spend hours drafting a visually intuitive skills matrix with Microsoft Excel from scratch.
Moreover, our module can generate a personalized report for every employee. That way, you will immediately know if there are employees who are struggling to keep up with your organization’s transition into Heijunka and lean manufacturing.
Free Lean Manufacturing E-Book PDF
Learn more about Heijunka and other lean manufacturing philosophies with our freely downloadable lean manufacturing e-book PDF.
See how Azumuta’s powerful modules have helped a client to have a 100% paperless shop floor, 100%, 60% reduction in data entry time, 35% reduction in documentation time, and achieved 0% operator idle time.