Lean manufacturing often refers to the seven or eight types of waste. These eight types of waste (muda) refer to inefficiencies in production or assembly processes. However, associated manufacturing areas such as materials management or maintenance can also be affected by waste. The goal of certain lean manufacturing approaches is to reduce this waste in value-adding and supporting processes. This reduction can leverage significant productivity potential, but it can also improve manufacturing quality. And as everywhere where waste is eliminated, costs also decrease, as material, time or other effort is saved.
It is therefore worthwhile to know exactly what types of waste there are and which tools can be used to avoid them! In this article, we will gladly share this knowledge with you and show you how digital tools can increase efficiency potential in production and prevent waste.
The eight types of waste in lean manufacturing can be remembered very well by the following mnemonic device:
D O W N T I M E
The individual letters each stand for a type of waste: Defect, Overproduction, Waiting, Non-Utilising Person, Transportation, Inventory, Motion and Extra Process. By eliminating waste, production downtimes can be massively reduced. In the following, we would like to explain each of these wastes and provide you with tools for minimizing them.
Defects — or defects in German — are errors that can occur during the manufacture of a product. There are different causes for defects and additional resources are needed to correct them. Defects in products can never be completely ruled out, but organizational measures can be taken to minimize them.
Processes should always be designed in such a way that defects do not occur in the first place. This principle is called poka-yoke in the context of lean manufacturing. For example, assembly fixtures can be designed so that components can only be installed in one possible orientation. Autonomous quality assurance, the so-called Jidoka principle, can also be used to detect and eliminate defects in good time. Through in-line inspection of certain work steps, faulty assembly can thus be detected directly at the point of value creation and rectified immediately.
Another lean manufacturing method is the use of “standard work”. This method involves the detailed description and presentation of important information about the manufacturing process. It breaks down the work into work steps described in small detail. In German, this is often described as Werkerassistenz. This ensures that the worker can find all the information he needs for a repeatable workflow directly on site and can get help quickly with specific questions.
Overproduction usually occurs when employees on the shop floor do not have an overview of the overall process. They then produce so much at the individual workstations that the following workstations are overloaded. As a result, intermediate storage facilities are quickly overfilled and the material inventory in the work-in-progress increases steadily. Thus, overproduction ties up considerable amounts of working capital and can lead to other types of waste.
The waste type overproduction can be minimized by better planning and coordination of the assembly process. By using a Kanban system, a pull principle can be established in production, which even makes intermediate storage unnecessary.
Publicly displaying takt times and the remaining takt time of all workstations can also help minimize overproduction. Using an Andon board, the takt time and many other key figures can be displayed on large displays on the shop floor. Thus, every employee knows how much time is left until the completion of the work step and bottlenecks become visible and can be eliminated!
Waiting times are fundamentally not value-adding. Employees are idle during this time because they have to interrupt work for some reason. These waiting times can be caused by material deficiencies at the workstations. But malfunctions in operating equipment such as machines or tools can also mean that work has to be interrupted. Last but not least, these interruptions can also be caused by a lack of knowledge on the part of new employees undergoing training if they have questions about certain operations.
Improving communication channels on the shop floor can minimize these wait times. Ad-hoc notifications of missing material can enable materials management to provide the required material as quickly as possible. Likewise, by reporting questions from workers digitally, the shift or production manager can quickly intervene and take countermeasures. In this way, production downtime can be significantly reduced. By evaluating the reasons entered for the interruptions, targeted process improvements can subsequently be implemented. This increases the capacity and quality of the assembly processes. In our whitepaper on alarm management, you will find more information on communication channels in manufacturing environments.
This type of waste is not actually one of the seven original types of waste in terms of the Toyota Production System. Nevertheless, inadequately trained assembly employees have a significant impact on the production quality and capacity of a manufacturing process and the entire organization. However, it is not only a lack of know-how (for example, from new or frequently changing employees), but also unrecognized talents or ignored improvement ideas that harbor considerable potential for waste. If these talents or improvement ideas are not heeded, this has a direct impact on the motivation and commitment of individual employees.
Possible solutions to these challenges include the use of worker assistance systems. With the help of such digital tools, information relating to the assembly process can be accessed directly at the individual workstations via touch panels. This applies, for example, to work instructions in the form of pdf documents, checklists, images or videos. These documents, which are normally only accessible in the form of paper documents, help new employees in particular to familiarize themselves with the assembly processes. But even veteran employees often have a need for such information in the case of rarely manufactured or very complex variants of the products. The fast and uncomplicated provision of these documents ensures that they are used and do not just gather dust in drawers.
Transport includes all movements of material within a production process. This concerns raw material, individual assemblies but also finished products. Delayed or suboptimal transport of material can cause a variety of problems, including production stoppages. In addition, damage to products can cause product quality to suffer. These negative effects of transportation processes stem from a variety of causes. Poor factory layout can lead to long and confusing transportation chains. In addition, poorly aligned manufacturing processes can cause material to pile up in intermediate storage and hinder the production process.
Communication tools also play a critical role in this type of waste. Manufacturing employees can be slow to report material shortages if the right tools are missing. Logistics employees then react too late to individual transport orders and production has to be interrupted until the material has been delivered.
A value stream mapping can be used to create a picture of the sequential flow of raw materials or assemblies. This makes it clear at which points in production problems with material supply are to be expected. Processes can then be improved on this basis. Another option is to introduce communication tools that allow employees to report material shortages at an early stage. Automatic monitoring of material inventories via sensors at the removal facilities can lead to automatically set driving orders for logistics. By measuring the times between notification and delivery of the required parts, the logistics chain can also be more finely planned and optimized.
Waste in the inventory, i.e. in the storage facilities, is caused by an unnecessarily high material stock in the individual warehouses of the production. One cause is the incorrect planning of safety or reorder stocks. Another cause is that the production speed is not adapted to demand. Unreliable suppliers or long setup times can also be the cause of inventory waste.
By using lean manufacturing tools such as Kanban, material inventory can be adjusted to customer demand. This pull principle can drastically reduce material inventories in the goods-in and goods-out areas, but also between workstations. This significantly reduces the amount of capital required for raw materials, intermediate products and finished products. Material management can also be improved via just-in-time or just-in-sequence delivery to individual assembly stations. Here again, digital communication tools play an important role. By providing needs-based, early feedback on assembly steps, the material required for the next workpiece can be made available with precision.
This type of waste describes unnecessary, non-value-adding movements of material or people in the manufacturing process. A workstation that is not optimally set up, where the distances to necessary tools or components are too great, leads to employees spending a lot of time on non-value-adding movements. This increases cycle times and employee motivation also decreases due to a certain level of frustration. Another consideration of this type of waste is unnecessary walking when reporting malfunctions or material needs. Even looking at printed work instructions or drawings on the shop floor can lead to time being wasted.
Lean production methods such as 5S provide a remedy here. This method ensures that work stations are well organized. The 5 “S” here stand for the Japanese terms
Vor allem der Punkt Seiketsu (Standardisieren) kann durch ein Werkerassistenzsystem mit detaillierten Arbeitsbeschreibungen, Zeichnungen oder Checklisten unterstützt werden. Dadurch wird es neuen Mitarbeitern schnell möglich, sich in die Arbeitsabläufe einzufinden. Aber auch erfahrene Mitarbeiter profitieren durch ein Nachschlagewerk für komplexe oder selten gefertigte Produkte und Varianten.
Excessive processing of products always takes place where an operation is performed twice. This can be caused by poor documentation of production steps or a lack of coordination between processes. For example, data on a work step is recorded twice, the workpiece is cleaned at several workstations or more C‑parts are used than necessary. The standardization of processes can eliminate this type of waste as far as possible. This includes cleaning up processes with a view to unnecessary documentation or duplicate process steps.
This is another area where the Lean Manufacturing method 5S , which we discussed in the previous point, comes into play. By standardizing workstations and selecting unnecessary elements in processes and at workstations, duplicate processes can be easily identified and adjusted. This type of waste can also be addressed through Kaizen and the simplifications of process flows that come with it.
Many of our customers start by making the eight types of waste in lean manufacturing visible. This is usually done via a digital alarm and display system. The workers at the workstations are thereby enabled by means of a touch panel to report errors in or questions about the production process. This makes these messages visible to the production or shift supervisor. The supervisor can then react quickly and take appropriate action. By storing and evaluating the messages, optimizations can be made subsequently to the assembly stations, the operating equipment and the production processes.
A second step for many of our customers is a worker assistance system. Here, documents such as drawings, checklists, pictures or videos are displayed at the individual workstations, describing the production process in detail. In addition, data on the process or the product (e.g. serial numbers, measured values from test systems and much more) can be recorded and made evaluable. The times required for a particular assembly step also become transparent in this way, enabling detailed clocking out of individual workstations and the entire line.
When introducing such digital tools, however, it is important to think big but start small. Otherwise, employees on the shop floor and in supporting areas can quickly become overwhelmed. Furthermore, it is important to involve know-how carriers of the manufacturing processes already in the planning phase. These are above all the employees in production! They know what often causes problems and which process steps are unclear or where errors often occur.