2.4 Principles of Lean Production
Only an efficient production process is a good production process – this is something that every industrial company would agree with. A popular concept to make a production process as efficient as possible is the so-called “lean production“.
This means the economical and time-efficient use of all production factors, i.e. employees, materials, resources, planning and organization. Other factors are, for example, tight coordination with suppliers or rapid adaptation to market changes.
Lean production is therefore in itself a very comprehensive concept, but it is nevertheless actually a part of something even bigger – namely the approach of lean management. Lean management goes one step further and encompasses the efficiency of the entire value chain.
The value chain is an important term in the production economy and represents all activities of manufacturing – from inbound logistics, through all production processes, marketing and sales activities, to outbound logistics and service. The elements just mentioned are also called primary activities. These are strung together in a value chain. Supporting activities extend across all primary activities. These are activities that are necessary for the primary activities, such as human resources management, technology development, procurement or logistics.
A production process is therefore a primary activity in the value chain of a company. The goal of lean production can now be divided into three aspects:
- Improving productivity: Excess inventory, underutilized capacity and lead times are to be improved.
- Optimization of product quality: The production process is to be checked in terms of quality, faults are to be rectified as quickly as possible, rejects are to be avoided and supplier processes are to be optimized.
- Increasing flexibility: Adaptable production systems are designed to reduce downtime and make capacities more flexible according to demand.
Essentially, lean production (as well as other optimization concepts for production processes) is about avoiding waste. Waste is understood to be, for example, overproduction, standing and waiting times, long distances, complex processes, defective products, multiple data entries or also unused potential or know-how of employees.
Lean production was originally developed to avoid waste in the company. The fundamental goal was defined as eliminating all non-value-adding activities within the production process.
https://www.freepik.com/free-vector/kanban-method-concept-illustration_33756682.htm#query=lean%20system&position=1&from_view=search&track=sph
To avoid waste and achieve the above-mentioned goals, Lean Production now offers various methods and tools that are used in industrial companies:
- Continuous improvement process: With the involvement of the employees, small improvements in the production processes are constantly worked out and implemented in working groups.
- Standardization: The aim is to define the steps of repetitive processes.
- Zero-error principle: Any errors that occur should not be passed on to subsequent work steps but should be rectified immediately.
- Lean operation: Delivering materials as promptly as possible should minimize the effort required for warehousing.
- Orders according to the pull principle: The production processes are carried out demand-oriented (instead of deadline-oriented according to the push principle). Important terms for this are Just-in-Time, Just-in-Sequence or also Kanban.
- Visual management: Processes and workflows are depicted visually. This increases the transparency of important key figures and interfaces for managers and employees.
- Strong involvement of employees: Employees are used as key drivers for innovative concepts and continuous process improvements and are given responsibility in this regard.
A company active in remanufacturing of transmissions for passenger cars, commercial vehicles, and off-road machinery, searched for a solution related to products located in different departments: car transmissions, and steering section. The main motivation to implement lean was to satisfy the customer by reducing throughput times. They observed that operators were walking several kilometres to build one gearbox. The layout was changed to eliminate excessive movement and transportation. Managers suggested that it was people that at first seemed to be the main factor limiting the application of lean within the facility. Employees were stressed about losing their jobs if things would be completed faster. As such, communication played an important part in successfully implementing lean. For example, an ‘introduction to lean’ workshop was organized. Management took part in training together with employees. The workshop covered many lean concepts including waste, Kaizen, pull systems, etc. Besides the workshop, management constantly assured employees that lean is not about reducing headcount. They highlighted that if the product was cheaper, the facility will sell more, and the company will have more work and will create more jobs.
The Kanban system just mentioned during the pull principle is a particularly popular Lean Production tool for inventory management in production processes. The basic principle of Kanban is the linking of individual control loops, which always consist of a production stage and an upstream material store. The production stage independently withdraws the currently required quantities of material, which are automatically replenished by the upstream material store.
Central to this are the so-called kanban cards, which document the withdrawal and consumption of materials along the control loops. While the material is moved in one direction, the withdrawal information of the corresponding kanban card is passed on to the material warehouse in the opposite direction.
For example, the material warehouse always has two containers with a certain quantity of screws. The production stage takes one of these containers, uses up the screws in it as needed, returns the empty container together with the kanban card (on which the exact consumption of screws can be seen) and takes the second, full container with it. The upstream material store now refills the empty container according to the Kanban card. This ensures a constant flow of material according to demand.
