Eight Types of Waste in Lean Manufacturing and Lean Software Development

Lean manufacturing is a systematic method originated in the Japanese manufacturing industry focused in the reduction of waste. Taiichi Ohno, author of Toyota Production Systems that inspired Lean Manufacturing in the US, devised seven types of waste in manufacturing processes: transportation, inventory, motion, waiting, over production, over processing and defects. Some other forms of waste such as unused talent were added later.

Lean software development is an adaption of the values, principles and practices of lean manufacturing and Toyota production systems to the software development domain. Its concepts have been widely accepted by the Agile community. Lean software development is first mentioned in 2003 by Mary and Tom Poppendieck in their book of the same name. In that book, the seven traditional forms of waste in lean manufacturing were translated to the software development domain. These ones are: task switching, partially done work, hand-offs, delays, extra features, extra processing and defects. In addition to them, unused talent can also be added as a type of waste in this domain.

The following table shows the equivalencies of each kind of waste in both domains:

These types of waste are explained with more detail below.

1. Transportation / Task switching

Transport is the movement of products from one location to another. In lean manufacturing, transportation itself does not not transform the product and therefore neither it does adds value nor the customer is especially happy in paying for it. Tips for minimising transportation include designing plant layouts with production lines or cells that contain all of the value adding processes rather than a layout with functional silos.

The equivalent waste in software development is task switching. Every time a person switches among tasks, a significant amount of time is wasted in achieving the necessary concentration for each task. Tips for minimising task switching include assigning resources to one project at a time, prioritising work to do and reducing interruptions.

2. Inventory / Partially done work

Inventory includes raw materials, work in progress and finished goods that are held by the company. Lean manufacturing considers waste when goods and services are produced more than they are required by the customer. In addition to the physical cost, inventory involves storage costs (space, damage insurance, administration) and also increased lead times. It also hides other forms of waste as it may act as a buffer to hide other kinds of inefficiencies. However, if supplier lead times are high and cannot be changed, some degree of buffer inventory may be acceptable

The counterpart in software development is partially done work. A software feature that has not been tested, integrated or properly documented is not finished. To reduce this kind of waste it is very important to limit work in progress (prioritising finishing what had been started and not starting many developments at the same time).

3. Motion / Hand-off

Motion refers to moving more than necessary when doing work. In manufacturing it refers to the ergonomics of the workplace. It includes large and small motions. Generally, in lean manufacturing large motions, such as long walks among work areas, are easily to detect and can be eliminated using common sense. Small motions, such as movements carried out by workers in a specific position are usually more subtle. They are generally harder to identify as waste, as in some cases these motions are considered as a part of the job. Generally speaking, excessive bending, running, walking, turning, etc. should be considered as waste, and preferably everything needed to perform a task should be within arm's reach in front of the worker.

Hand-offs are the counterpart of motion waste in lean software development domain and the amounts of times the work is passed from one person to another person. In the context of software development they could be excessive communication steps from analyst to the designer, from the designer to the developer, from the developer to the tester, etc. Each time a deliverable is handed off, there is a potential knowledge lose. Cross-functional teams with generalising specialists (T-shaped people) that are able to adapt to varying demand by carrying out different types of tasks, face to face communication and shorten feedback loops minimise this type of waste.

4. Waiting / Delays

Waiting times is a common type of waste in both lean manufacturing and lean software development. It is not only the act of doing nothing whilst waiting for a previous step in the process, but also the act of working slowly due to this.

Unbalanced processes are a common cause of waiting and delays. In the context of software development waiting for inputs and delays in reviews, approvals and testing provoke waste.

Face to face conversations and instant messages generally allow immediate feedback and help to mitigate delays. Co-location which foster osmotic communication and regular feedback are also effective methods to prevent it. An inadequate infrastructure (e.g. slow network communications) may also cause delays and distractions.

5. Over production / Extra features

Overproduction is making products in greater quantities before they are actually needed. In a manufacturing context this is the worst of all the wastes because it hides other problems in the process. In addition to tie capital in raw materials, work in progress and finishing goods, it also incurs in storage costs and higher risks of obsolescence. Over production waste is very related to inventory waste.

In the context of software development, over production does not exist (as software can bot be stored and can be easily reproduced at zero cost). However there may be extra features which are those ones that are not needed or asked by the customer. They add unnecessary complexity and can incur in additional failure points. Paretto principle states that for many events, roughly 80% of the effects come from 20% of the cause. Applying to this context, we could say that roughly 80% of the customers only use 20% of the features. Therefore the agile principle of maximising not done work (aka simplicity) helps to reduce this type of waste in software development.

6. Over processing / Extra processing

Over processing is adding more value to a product than the customer actually requires. For instance, it may include the use of too tight tolerances exceeding the customer requirements or painting some areas that are not visible or subjected to corrosion.

In the software development context, extra processing will consist in adding extra steps with no added value, such as too detailed documentation that is not read by anyone or extra management activities that generate bureaucracy.

7. Defects

Defects occur when produced goods or services deviate from what the customer requires and occur in both manufacturing and software development environments. They are the first thing that people have in mind when they think about waste in a process. Defects that are found by the customer may provoke the lose of reputation of the firm.

However, waste caused by a defect does not only depend on its impact but also on the amount of time that has passed since it is detected. The cost of defects can be compared to an iceberg with a only a small fraction of the real cost being visible above the water level. For instance, in addition to the cost of replacing the defective product, there may be costs related with problem solving, paperwork, transport, setups, delivery failure or potentially lost customers.

In a software context, it is quicker fixing bugs if the code is tested immediately rather than doing it weeks later. Therefore the impact is reduced by testing immediately, integrating frequently and releasing into production environment as soon as possible. This can be accomplished much easily if the designed features are of small size. To carry out this, it is important to separate complex requirements into smaller and more manageable parts. It is said that the best way to eat an elephant is dividing it into small parts.

8. Unused talent and skills

The waste of talent is one form of waste in addition to the seven classical forms of waste in both lean manufacturing and lean software development. This waste supposes a failure to make good use of company employees.

Costs related with this type of waste is time wasted to make improvements and meet changing customers requirements. Relying only on 'experts' (e.g. engineers, managers or supervisors) to come up with ideas will make organisation far slower in solving problems. Whilst they may be highly skilled they are small in number compared with other employees.

To prevent this form of waste is necessary to promote a safe environment that assures involvement and loyalty of employees and allows to unlock the intrinsic motivation of knowledge. Therefore is is necessary to provide autonomy, purpose and mission to the employees, in order that the workforce does not feel that there is no point in making suggestions for improvement. Empower employees to implement the necessary changes also boosts the use of all the potential talent in the company.

References

• Leanop - Operations Management Systems
• The Lean Way Blog - What is muda, mura and muri?
• The Lean Way Blog - 8 wastes of lean
• Lean software development - Wikipedia
• Deepti Kalra - Lean Software Development – 7 Wastes of Software Development
• Lean Manufacturing Tools - 7 Wastes

Illustrations were taken from LeanOp