The classic approach in the manufacturing industry was highly-efficient production with low-mix mass production since the Industrial Revolution that started in the mid-18th century. Many companies in the manufacturing industry supplied a large quantity of low-cost and high-quality products to the market. They did this by narrowing down the types of product they produced and then mechanizing and automating processes.
However, the competitive conditions in the manufacturing industry have been changing due to changes in the consumer market in recent years (Fig. 1). There is a need for variable-mix variable-lot production to be able to produce and supply only the quantity as needed while frequently changing the specifications of a wide variety of products to respond to the globalization of the market, the individualization of consumer needs, and rapid changes in trends in the information age.
Cell production lines: Suitable for variable-mix variable-lot production, but difficult to improve productivity
An increasing number of companies in the manufacturing industry are building cell production lines to support variable-mix variable-lot production. The cell production line is a production system in which one worker or a small team of workers completes the production processes of a product (Fig. 2). It is possible to produce products independently in each cell. Therefore, simultaneous production in parallel of different products is possible.
Moreover, the range of work taken charge of by one worker is wide. This means that variable-mix variable-lot production is also suited to being able to adjust tasks according to the product item and quantity being produced under the discretion of that worker. The work to replace the parts, materials, and jigs used when switching production items is called "changeover" work. Changeover work is possible mostly without stopping production on cell production lines.
On the other hand, it is difficult to reduce the cost and improve the quality of products on cell production lines. That is because manual work increases. Special purpose machines optimized for specific work used in low-mix mass production can only repeat the same work. Therefore, they cannot be applied to cell production lines (Fig. 3). For example, there are machines and other equipment that shred cabbages in food factories. However, those machines cannot be used either to fry ingredients or to cut meat. This means those machines have a high level of work efficiency and precision due to their inflexibility.
Source: Ministry of Economy, Trade and Industry (PDF)
(Only in Japanese.)
Technical breakthroughs are required to realize variable-mix variable-lot production on cell production lines with costs and quality at the same level as industrial products produced under small-mix mass production. This is the challenge that should be tackled in smart factories.
Dynamic cell production with people and smart machines collaborating
There is an active movement to solve such problems of conventional cell production lines with robots, IoT, artificial intelligence (AI), and other advanced technologies. This new production system is called "dynamic cell production."
It is not uncommon nowadays to have lines for low-mix mass production that have introduced industrial robots. Unlike special-purpose machines that can only perform specific work, industrial robots can handle a variety of work because engineers teach them the movements when working. This means they already inherently possess the nature to be suitable for variable-mix variable-lot production. However, industrial robots have hardly ever been used in cell production lines. This is because there is a possibility of leading to an accident if their hard casing moves at high speed near people.
Nevertheless, industrial robots called "collaborative robots" or "cobots" that enable coexistence with people have been developed in recent years. These are coming to be used on cell production lines and at other production sites. The arrival of cobots has made it possible for people and machines to collaborate while focusing on their own areas of expertise. This has led to an improvement in the productivity and quality of cell production lines. Cobots are equipped with various safety functions. Advanced cobots can handle work safely without injuring people or damaging things while detecting their surrounding environment like self-driving cars. Advanced sensors and AI are used to achieve that.
Coordinating management, marketing, sales, and factory data
The aim of variable-mix variable-lot production is to produce and supply only the number of products needed in a timely manner according to fluctuations in market demand. Companies have appeared in the manufacturing industry looking to build a mechanism that connects core systems in companies, production and quality control systems in factories, and line control systems to realize that aim (Fig. 4).
Production plans of companies in the manufacturing industry are made with consideration for various factors in the company. Typical examples are key performance indicators (KPI) that show the corporate target achievement situation, marketing information (e.g., changes in market needs), product order status, and information on orders of parts and materials necessary for production. Until now, the person in charge has formulated the production plan based on experience gained in the past. It has now become possible to accurately predict the types and quantities of products needed by the market in the future by integrating diverse information possessed by each department in a company in the manufacturing industry and then analyzing that with AI.
It is possible to build a structure that responds promptly and smoothly to changes in the market by connecting the core system (ERP) that manages information in a company with the production system that performs the production schedule and work management in its factories. Such new information systems of companies in the manufacturing industry are also effective in building a resilient business structure. This includes, for instance, the ability to appropriately respond to sudden fluctuations in the supply–demand balance and supply chain disruptions due to disasters and infectious diseases.
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