I. Just-in-Time (JIT) and Lean Production (LP): The Evolution from Origin to Theorization
Just In Time (JIT) production is the survival wisdom of the Japanese manufacturing industry in response to the post-war shortage of resources. In the 1950s and 1960s, Toyota Motor faced the triple dilemma of "limited funds, shortage of raw materials, and a small market". The founder, Kiichiro Toyoda, proposed the concept of "producing the required quantity and providing the required products only when needed". This concept directly targets "overproduction", which is the biggest waste in the manufacturing industry (overproduction leads to inventory backlog, capital occupation, and an increase in the defective product rate). For example, the Toyota assembly line adjusts the production volume according to the real-time orders of dealers and never produces an extra car that cannot be sold. This "production on demand" model enabled Toyota to survive the resource shortage and gradually become an industry benchmark.
Lean Production (LP) is a systematic refinement by the United States of Japanese experience. In the 1980s, the Massachusetts Institute of Technology (MIT) organized the "International Motor Vehicle Program (IMVP)" to study why Japanese automobile companies (such as Toyota and Honda) could defeat American giants like General Motors and Ford. The team found that the advantage of Japanese enterprises was not cheap labor, but a "full - chain efficiency system" covering R & D, production, and the supply chain - not only "just - in - time" in the production process, but also "full - value - stream optimization" from customer demand to product delivery. In 1990, the IMVP published the book "The Machine That Changed the World", officially naming this model "Lean Production" and upgrading JIT from a "production tool" to a "corporate business philosophy".
II. Six implementation dimensions of lean production: From process optimization to systematic transformation
(I) Production system: From "fixed division of labor" to "flexible collaboration"
The core of traditional mass production is "detailed division of labor" - workers are confined to a single process (such as screwing or labeling), with single - skill sets, and are unable to meet the market demands of small - batch and multi - variety production. Lean production does the opposite, with the cultivation of "versatile workers" as its core goal: it requires workers to master 2 - 3 skills (for example, being able to operate both a lathe and debug a milling machine). In this way, when changing product models (such as shifting from SUV production to sedan production), workers can quickly fill in the positions, reducing downtime (Toyota once shortened the model - changing time from 4 hours to 10 minutes, thanks to the flexible adjustment of versatile workers).
Meanwhile, lean production integrates quality control into every process – it's not "post-production inspection" (sorting out defective products after production) but "loss prevention during production". For example, Toyota's "Jidoka": Equipment is installed with automatic detection devices. Once a defective product (such as a dimensional deviation of a part) is detected, the production line will stop immediately. Workers must solve the problem before restarting. This "immediate stop" mechanism avoids the waste of "batch defective products" and allows quality problems to be resolved at the budding stage.
(II) Parts supply: From short-term game to community with a shared future
The traditional supply chain is a "zero-sum game" - enterprises reduce prices through bidding, and suppliers can only cut corners to seek profits, ultimately leading to "delivery delays and quality fluctuations." The supply chain logic of lean production is "long-term binding + in-depth collaboration":
Early participation in R & D: Tier - one suppliers of Toyota will join the new car R & D team and discuss component solutions (such as the material selection for the engine block) with the design department. In this way, suppliers can adjust the production process in advance and avoid the cost of later modifications.
Technical and financial support: The enterprise will provide lean production training to suppliers (such as helping suppliers introduce the kanban system), and even prepay the purchase price to relieve their financial pressure.
Shared risks: If there are changes in product design, the enterprise will share the mold modification costs with the suppliers.
This "community with a shared future" relationship gives suppliers the motivation to improve their capabilities. For example, Toyota's suppliers can respond to product changes within 24 hours. The inventory turnover days have been reduced from 30 days to 7 days, and the supply qualification rate has been stably maintained above 99.9%.
(III) R & D system: From linear progression to parallel collaboration
Traditional R & D follows a "sequential process": Design → Process → Manufacturing → Testing. Each department hands over the work to the next one only after completing its own tasks. The problem with this model is the "disconnection between design and production". The design department may produce "drawings that cannot be mass - produced" (for example, the precision requirements for parts are too high to be met by existing equipment), which leads to repeated modifications in the later stage and wastes a great deal of time.
Lean R & D adopts Concurrent Engineering: the design, process, manufacturing, and quality departments participate in the project simultaneously. For example, design engineers and manufacturing engineers discuss "the machinability of parts" together to avoid the problem of "good-looking design but impossible to manufacture". At the same time, the "Shusa Responsibility System" is adopted - an experienced "Shusa" (such as the project leader at Toyota) leads the whole process and coordinates the contradictions among different departments (for example, the design department wants to reduce the weight while the manufacturing department wants to cut the cost) to ensure that the R & D progress is not delayed. Toyota has shortened the R & D cycle of new cars from 5 years to 2 - 3 years, and Concurrent Engineering and the Shusa System are the keys.
(IV) Circulation stage: From "promoting production" to "driving production"
Traditional circulation is a "push" model - enterprises produce according to plans (for example, planning to manufacture 100,000 cars this year regardless of market demand), which leads to inventory backlogs (such as cars piling up in the parking lots of 4S stores that can't be sold). The core of lean circulation is "pull production": deriving the production plan from customer demand and using "Kanban" to transmit demand signals
- The distributor places an order with the factory using a kanban ("I need 10 white sedans").
- The factory places an order with the supplier using a kanban ("I need 10 sets of engine parts").
- The supplier places an order with the raw material supplier using a kanban ("I need 10 tons of steel").
Each link only produces "the quantity needed by the next link", with no excess inventory. For example, Toyota's finished product inventory once decreased from "30 days' sales volume" to "3 days' sales volume" because the "pull system" made production fully match demand.
(V) Human resources: From extension of machines to full participation
Traditional factories treat workers as the hands and feet of machines, only requiring repetitive movements and no thinking. Lean production, on the other hand, regards workers as problem solvers:
QC Group (Quality Control Group): Workers voluntarily form groups to solve daily production problems (e.g., "How to reduce the defective rate of lathes"). The groups hold regular meetings to discuss solutions, and the enterprise provides training and financial support.
Proposal system: Workers can put forward improvement suggestions (e.g., "Move the tool rack next to the work - station to reduce the time for fetching tools"). If their suggestions are adopted, they can receive a bonus (for example, if a proposal saves 10,000 yuan, the worker gets 10% of it).
Multi-skill training: The enterprise provides free training for workers to master multiple skills. For example, an assembler can operate 3 pieces of equipment simultaneously, so that they can fill in when someone takes leave, avoiding the shutdown of the production line.
This "full participation" model has transformed workers from "passively executing" to "actively contributing." Toyota's workers submit over one million improvement suggestions annually, and 80% of them can be implemented, directly leading to cost reduction and efficiency improvement.
(VI) Management concept: From "being satisfied with the status quo" to "continuous improvement"
The core of lean management is "never being satisfied" – not regarding the existing production methods as "the best", but as "objects to be improved". For example:
Pursue extreme goals: It's impossible to truly achieve zero defects, zero inventory and zero waste. However, in the process of pursuing these goals, enterprises will discover hidden problems (such as substandard products caused by inadequate equipment maintenance and long waiting times caused by redundant processes).
Eliminate the "Seven Wastes": Lean production defines seven major wastes in the manufacturing industry - overproduction, inventory, handling, waiting, over - processing, unnecessary movements, and defects. The goal of management is to "eliminate these wastes one by one". For example, by optimizing the layout of the production line, the handling distance can be reduced; by improving the equipment, the waiting time can be reduced; by training the workers, the number of defects can be reduced.
III. The five core components of a lean enterprise: From elements to ecosystem
(I) Product: Streamlined design centered around "customer value"
For the products of a lean enterprise, value is defined by customers. It's not about "what the enterprise wants to do" but "what the customers need". For example, when customers buy an electric fan, what they need are "air blowing" and "silence", not "fancy functions with a Bluetooth speaker". If a product has functions that customers don't need, it's a "waste" (increasing costs and weight and possibly reducing reliability).
The design principle of lean products is "eliminating redundancy": never use two parts when one can solve the problem; never add extra decoration when the basic functions can be met. For example, the design of Apple's iPhone—there are no redundant buttons and no complex interfaces, but the core functions (communication, Internet access, entertainment) are taken to the extreme. This is a model of a "lean product".
(II) Production process: Process optimization targeting "response speed"
The core of the lean production process is "speed" - to respond quickly to market changes. For example, when customer demand shifts from "large-screen mobile phones" to "small-screen mobile phones", enterprises need to adjust the production line, replace the molds, and purchase raw materials in the shortest possible time.
To achieve "speed", lean production uses two methods:
Concurrent engineering: Shorten the R & D cycle (the time from design to mass production is reduced from 12 months to 6 months);
Kanban system: Shorten the production and supply cycle (reduce the raw material inventory from "one month's usage" to "one week's usage").
For example, a household appliance enterprise used concurrent engineering to develop new products, shortening the time from "design to market" from 18 months to 9 months. It just caught up with the "peak sales season for air conditioners in summer" and earned 30% more profit than its competitors.
(III) Factory layout: A compact design guided by "space efficiency"
The layout principle of a lean factory is "occupy less land and achieve more output" - land is a non-renewable resource. Lean enterprises should occupy as little fertile land as possible while maximizing the use of space.
U-shaped production line: Arrange the equipment in a ring shape, and the workers operate in the middle to reduce the material handling distance (for example, originally one needed to walk 10 meters to get parts, but now only 2 meters).
CELL production unit: Concentrate the equipment for producing a product into "small units" (for example, the "assembly unit" for producing mobile phones includes screen pasting, battery installation, and testing). The unit can be quickly adjusted (for example, switching from mobile phone production to tablet production).
Flexible equipment: Purchase equipment with "multiple uses in one machine" (for example, a machine tool can process a variety of parts) to reduce the number of equipment and save space.
(IV) Organization: A flat structure centered around "synergy"
Traditional enterprises have a "pyramid-style" hierarchical structure (general manager → department manager → supervisor → worker), and information transmission is slow (for example, it takes 3 days for front-line problems to reach the general manager). Lean enterprises, on the other hand, have a flat structure.
- Reduce intermediate levels (for example, the general manager directly connects with the "project team", skipping the department manager).
- Establish a "cross-functional team": For example, the "new product R & D team" includes personnel from design, process, sales, and after-sales departments to solve problems together (for example, considering "the convenience of after-sales maintenance" during the design process).
- Visual management: Hang a "progress bulletin board" at the production site so that everyone can see "how many units need to be produced today and how many have been completed". Problems can be exposed in a timely manner (for example, if "the progress of a certain workstation is slow", the supervisor can immediately go to help).
(V) Environment: Green operations with sustainability as the responsibility
The environmental responsibility of a lean enterprise is not "passively treating pollution" but "actively reducing pollution" - because "wasting resources = wasting costs = polluting the environment".
Energy-saving design: Produce low-fuel-consumption vehicles (such as the Toyota Prius hybrid model, whose fuel consumption is 50% lower than that of traditional vehicles) to reduce carbon emissions.
Resource recycling: Recycle the scraps (such as steel and plastic) in production and reprocess them into parts to reduce raw material extraction.
Pollution prevention: Adopt low-pollution processes (such as replacing oil-based paints with water-based paints) to reduce exhaust gas emissions.
Conclusion: Lean is not a "tool" but a "way of thinking"
The essence of lean production is "centering around customers and continuously eliminating waste" - it doesn't mean that purchasing a few new pieces of equipment or setting up a few kanban boards makes it "lean." Instead, at every stage from product design to after-sales service, one should ask: "Does this step create value for the customer? If not, can it be eliminated?"
For enterprises, lean is not a "one-time reform" but a "lifelong practice" - eliminating the waste of "overproduction" today and the waste of "waiting time" tomorrow; achieving a "10-day inventory" today and aiming for a "5-day inventory" tomorrow. This "always moving forward" mindset is the most core competitiveness of lean production.