Q 282. Heijunka is the solution for Mura (unevenness or irregularities). What is Heijunka and what are some of the ways in which it could be implemented? 

 

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Heijunka is a Japanese term and it can be broadly translated as 'Leveling". The main focus of Heijunka is to eliminate unevenness/ irregularities/ fluctuations (Mura).

 

Lean emphasis on the concept of 1 piece flow, but it's easily said than done. This is where Heijunka comes in picture. Instead of 1 piece flow, heijunka takes average demand in consideration. The average demand should be of a fairly small period of time I.e 3days/ 1 week/ 10 days/ fortnight, etc. (Depending on lead time and other factors)

 

Mostly firms don't work upon a single product but they work with a varied range of products. In this scenerio the Production/ Planning team should take average demand of each product for the specified time period.

 

For example, if the firm get 9 orders per week for Product X, 4 orders for Product Y, 6 orders for Product Z on average, team need to level their capacity to produce a total number of 19 products per week.

 

This way team can establish a stable flow of work and meet the average demand by end of the week, thus keeping your equipment utilised all the time and without overburden at the time of peak demand. Other benefits include reduced inventory, reduced WIP, better cash flow, etc.

Heijunka or levelling is defined as balancing work by volume and variety during a period of time, typically a day. The day is further broken down into more manageable units of 2-4 hours  

 

The purpose of levelling is to ensure 

 

• Work is evenly distributed amongst workers by volume and variety 
• No work is waiting in queue 
• No work is released upstream that is not required downstream 
• A pull system of work is established 
• Continuous flow is achieved 
• A visual aid that identifies when and where work is behind schedule 
  
   
  
  Example 
  
  When a car is scheduled for a tune-up, the customer is given a time slot for the expected work to be done. That time slot may not fit your schedule. The scheduler will then attempt to fit you in at some agreed upon time. The Lean approach would be to increase capacity to meet customer demand by doing one or more of the following: 
  
  1.Determine historical demand, by the month, and create capacity for what the historical trend has been (tune-ups, brake problems, electrical problems, oil changes, etc.). 
  
  2.Cross-train more employees to handle the higher volume service jobs. 
  
  3.Increase daily capacity by reducing cycle times for repairs (this could be by implementing a bonus program based on the performance times of repair jobs, evening hours, additional shifts, etc). 
  
  4.Create capacity in bays where usage is not high by purchasing additional testing equipment, using part-time employees, etc. Auto service facilities have well-documented data (i.e., standard work) for servicing cars. They are ahead of many industries in that Lean tool application. 

Benchmark Six Sigma Expert View by Venugopal R

The term Heijunka has emerged from the Toyota Production System and aims to level the irregularity in Production. The Lean Lexicon defines Heijunka as “Levelling the type and quantity of production over a fixed period of time, which enables production to efficiently meet customer demands while avoiding batching and results in minimum inventories, capital costs, manpower and production lead time through the whole value stream”. Heijunka is a pre-requisite for the popular concept of JIT (Just-In-Time).

 

Though Heijunka is referred to as a solution for Mura, it is important to understand how the 3Ms, Mura, Muri and Muda are interrelated. Hence, before we get to discuss Heijunka, let’s take a quick look at the Japanese terms Muda, Muri and Mura.

 

Muda means ‘Waste’ and includes non-value-added activities such as avoidable Transportation, Inventory, Motion, Waiting, Over Production, Over Processing and Defects creation.

 

Muri means ‘Over Burden’ and relates to tasks that are Overbearing, Risky or High stress causing.

 

Mura means ‘Unevenness, Irregularity or Non-Uniform. In Six Sigma terminology, we may refer to it as ‘Variability’.

 

We will understand more about Mura with some example situations.

 

If we have a product whose demand is less during the beginning of the month and very high during the end of the month, we will have unevenness with respect to capacity utilization across the month. This irregularity is Mura. In the beginning of the month, being a low demand period, there will be idle waiting time which is a form of Muda. On the other hand, towards the last few days of the month, the demand becomes higher and is bound to put pressure on the employees to deliver the volumes and this causes Muri or overburden.

 

The three components of Heijunka

Leveling – Overall smoothening of the process to reduce the variability

Sequencing – Managing the sequencing of work – Mixed production

Stability – Reduce Process variation

 

If we have a product with demand levels opposite of that mentioned earlier, i.e. whose demand is higher in the beginning of the month and lower towards the end, then by cross training the employees to work on this process and the earlier mentioned process could help to even out the variability in the process and thus reduce Mura and Muda.

Another aspect that needs to be considered is to balance the production line with respect to the resource allocated and time taken for each step in the process. By allocating more resources for the process steps that consume more time, we can balance the process and also prevent building up WIP inventory between the steps.

 

When we have products of varying complexities, but handled by the same set of people in the production line, it is bound to cause variation, idle time and overburden if the products of same complexity levels come together. For example, if all the easy products are processed during the beginning of the month and the difficult ones turn up together towards the end of month, we will see Muda (excess time) and Muri (Overburden) alternatively. If we are able to sequence the flow of products in a mixed manner so that the overall complexity levels at any point of time is more or less uniform, this will help in leveling of the variations.

 

It may also be noted that if we want to have all product mix to be available to the customer uniformly throughout the month, the above point of Heijunka becomes very important and the concept of SMED will play an important role.

 

Many of the Lean concepts are essential for successful Heijunka implementation:

 

Takt Time: The time taken to finish a product to satisfy the customer demand

Volume Leveling: Understanding the variability in demand, maintaining production at levels comparable to long-term average demand and maintaining a buffer inventory in proportion to the demand variability

Type leveling: Maintain product type mix at frequent basis, if possible every day, and reserve capacity for changeover flexibility.

Change over time: We already mentioned the importance of SMED concept

 

Implementation of Heijunka is an important element of the Lean implementation for an organization. Successful implementation requires good understanding and data for the 3Ms (Muda, Muri & Muda), building flexibilities in terms of mixed manufacturing, quick changeover and employee allocation.

Heijunka is one of the underlying concepts of the Toyota Production System (TPS), shown in below Figure. Levelling any work isn’t easy, but it's the inspiration of Toyota’s celebrated production system. The Japanese coined this idea as Heijunka, extending the concept to include the requirement for ‘standard work’ – the processing of work consistently.

 

 

The TPS consists of two columns – Jidoka and Just- in-Time both are supported by Heijunka. Heijunka involves production and smoothing processing on using levelling, sequencing and standardising . For a process to run smoothly and consistently with many forms of output, it's to average, not just in volume, but also in kinds. So, we'd like to process the unique customer order, as an example, supporting the date they’re received instead of handling the more straightforward cases first and allowing the harder ones to create up and be delayed.

 

Heijunka provides the foundation and involves the subsequent elements;

 

Levelling involves smoothing the amount of production to cut back variation, the trials and troughs that may make planning difficult. Levelling pursues forestall ‘end-of-period’ peaks, where production is initially slow at the start of the month, then again quickens within the last days of an acquisition or accounting period, as an example.

 

Sequencing involves mixing the styles of work processed. So, as an example, when putting in new loans, the loan being processed is mixed to raise match customer demand and help ensure applications are actioned in date order. Managing this method could also be easier in manufacturing, where a producer may hold a little amount of finished goods to reply to the fluctuation in weekly orders. Keeping a tiny low stock of finished goods at the very end of the worth stream, near shipping, this producer can level demand to its plant, and to its suppliers, making for more efficient utilisation of assets along the complete value stream while still meeting customer requirements. 

 

Stability and Standardisation is the third strand of Heijunka. It strives to scale back variation within the way we do our work, which highlights the importance of ‘standard work’, of following a typical process and procedure. This method links well to the concept of process management and also the control plan, where the method owner continuously seeks to search out and consistently deploy best practice. 

 

In the spirit of continuous improvement the ‘best way’ of ending this method will keep changing, because the people within the process identify better ways of doing the work. 

 

Concepts like Heijunka can’t be implemented overnight – as an example, Toyota has taken a few years to attain the successful application of levelling and spreading the load, but is now a paradigm for the growing awareness of lean-thinking principles within the contemporary world.

Sourabh Nandi has provided the best answer to this question for providing the different ways in which Heijunka can be implemented.

 

Another very common tool used for implementing Heijunka is called a "Heijunka Box".

 

Also review the answer provided by Mr Venugopal R, Benchmark Six Sigma's in-house expert.