TPS: the seven types of waste

• The seven types of waste
• The eighth MUDA
• The three “MUs”

The seven types of waste

Much of the success of TPS is due to Toyota's ability to optimise what others found difficult to manage: waste.
Waste consists of all those activities or ways of using resources that do not add value to the product. Therefore, anything that does not serve to increase the value of the product as perceived by the customer and for which the customer is willing to pay is considered waste and, as such, must be eliminated.
Waste is also classified into seven types, the most serious of which is overproduction, as it is the source of other types of waste, particularly inventory, defects and transport.

1. Overproduction

This consists of producing a quantity of components or finished products that exceeds demand. Overproduction is the most dangerous form of waste, as it involves the use of company resources and internal warehouses to store products while waiting for them to be sold.

2. Expectations

This is the most easily identifiable type of waste. It occurs whenever an operator is not performing any work while waiting for materials (from the supplier or warehouse) or means of production.

3. Transport

Every time a product is handled, there is a risk of it being damaged, lost, etc., but that's not all. Since transport does not involve any transformation of the product that the customer is willing to pay for, it is not a value-added activity. Transport often becomes a waste because:

• the layout of the plant is outdated or has been designed incorrectly;
• the space occupied by production lines is excessive in relation to actual requirements;
• the materials are procured and stored in packaging that contains excessive quantities of materials that are not consistent with those actually used;
• The work is organised without precise picking sequences and the equipment is not designed to optimise internal transport.

4. Process

This type of waste occurs when the production process does not have adequate resources (equipment, machinery, operators) and procedures. In the specific case of equipment and machinery, waste is created when, for example, equipment or machinery with production capacities exceeding demand is used, or in the case of operators, when an operator is required to remove finished parts from the machine and stack them in special containers, instead of, for example, using a system whereby the parts are ejected and automatically stacked in a specific container by gravity.

5. Stocks

Materials produced in excess of actual requirements, wherever they are located—on production lines, in warehouses, or on order from suppliers—are considered a waste of both space and financial resources.
The term "stock" refers to everything that is waiting for an event (further processing, sale) and therefore represents time during which no value is added to the product. Furthermore, the continuous movement of stock material from one place to another can cause problems related to damage during transport. But that's not all: stock material can deteriorate in quality and become obsolete.

6. Unnecessary movements

Useful work is that particular type of movement that produces value. All types of movements that involve unnecessary movements due to poorly designed layouts or oversized structures and unproductive actions attributable to workplaces that are not ergonomically designed are to be considered unproductive movements.

7. Reworking

Every time an operation is performed that produces a defective part, the defect must be corrected. A non-compliant product entails significant financial and reputational costs for the company. Defects slow down production and increase lead times. If the defects are detected by the customer, the costs increase further, as it becomes necessary to set up a structure capable of handling complaints and covering the costs of repairs, disassembly, reassembly and delivery.

The main causes of the seven types of waste can be identified in poorly organised layouts, excessively long lead times, inadequate production processes, inadequate maintenance, poor working procedures (technique of Visual Management), lack of staff training (tool Skill Matrix), poor supervision, incorrect product or production process design, lack of performance indicators, inefficient production planning and scheduling, inadequate equipment, and poor workplace organisation (5S methodology) and in the quality of suppliers.

The eighth MUDA – Skills

Staff training

This Muda is not one of the original 7 Mudas of TPS. However, it is a significant waste that affects the active experience of every employee within the company.
Skills are wasted whenever there is a discrepancy between job duties, operator training and personality traits that prevents employees from performing at their best professionally.

Visual Management

The Visual Management methodology, understood as visual management applied to processes, allows the progress of business processes to be visualised using simple tools, making them visible to the actors involved in the process themselves.
The fundamental objective is therefore to make all information related to the progress of the process instantly available, highlighting in particular any critical issues that may arise, so that they can be addressed in real time.
Visual Management methodologies, which can be used not only during the process itself but also during its analysis, significantly reduce the need for intermediate adjustments, as they allow for constant status updates and the consequent definition of improvement activities to be introduced, with a view to reducing waste.
The essential tools of Visual Management can be divided into three main categories, based on function and type.

DISPLAYS
This category includes all charts and diagrams that are useful for performing practical work more effectively. These are visual tools that are always within reach of the worker, providing immediate guidance on how to perform certain tasks.

VISUAL CHECKS
Visual controls allow you to understand when and how to perform a specific action: they can be used to ensure employee safety or to better coordinate individual operations and make the process more organic. In the production department, these indicators are extremely useful and can be represented, for example, by simple traffic lights, where green indicates the time to perform an action or an operation in progress, while red indicates a suspension.
This category also includes Kanban signs, which provide precise and detailed information about the previous steps in the production flow.

VISUAL PROCESS INDICATORS
Visual process indicators are also widely used tools known for their effectiveness. In reality, they can be very simple devices, such as marking specific routes with coloured adhesive strips on the floor, or areas designated for the storage of specific materials or supplies. More generally, this category includes all signage that facilitates work by providing precise indications of areas and processes, quickly and intuitively guiding the correct flow of materials or information.

SKILL MATRIX
The skills matrix is a visual management technique. It consists of a table where the names of the operators are written on the vertical axis, while the required skills are written along the horizontal axis. As the operators' training progresses, markers are added at the intersection of the row with the name and the vertical rows of the skills acquired.
A skills matrix can serve both as a management tool, for example to quickly allocate trained resources to new positions, and as a stimulus to motivate staff to increase their skill level.

The three “MUs”

It should be remembered that Muda is only one of three negative elements that Lean combats in processes, namely the so-called three “MU”:

MUda: waste, loss.
MUri: indicates the overloading of people or resources. Overloading people can, in the long term, lead to the possibility of accidents or occupational illnesses due to the excessive strain placed on workers. In the short term, however, the consequences of overloading can include muscle strains, bruises or similar injuries. The effect is the absence of workers from work for varying lengths of time and general staff dissatisfaction. Similarly, excessive use of machinery can lead, in the long term, to accelerated wear and tear, breakdowns resulting in production stoppages for maintenance and repair, or even the need to replace machinery.
In the long term, the small benefit that can be obtained in the short term by overloading staff and resources turns into a waste of time and money. The goal is therefore to organise work correctly, but also to apply all those small measures that can reduce the workload without decreasing productivity.
MUra: indicates fluctuations, variations, irregularities in the workload (demand). These fluctuations lead to phases in which there is an overload of work (muri) and other phases in which the workforce and machinery are oversized (creating pauses – muda). The production flow is disrupted as a result.