A - Lean Manufacturing

Lean Manufacturing is a system of philosophies and tools for continuously detecting and eliminating waste in business operations, aiming to optimize value for customers while minimize waste. Operating according to Lean Manufacturing method helps enterprises to improve competitiveness in a sustainable way in terms of productivity and quality.

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1. Introduction to Lean Manufacturing

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1.1. The history of development and application of Lean Manufacturing

Since the 1950's, Toyota founder - Kiichiro Toyoda - began to develop Tyota Production System (Toyota Production System (TPS) with many principles and methods that Lean Manufacturing later inherited. Together with Taiichi Ohno, TPS has been widely deployed throughout Toyota's system and has brought remarkable achievements to the automaker in terms of productivity and quality.

On a global scale, the concept of Lean Manufacturing - and with it the system of principles and methods - was really widely accepted when Professor James Wommack wrote and published the book "LEAN - The Machine" That Changed The World" (roughly translated as "LEAN") in 1990. Since then, Lean Manufacturing has been widely applied, along with Six Sigma methodology, all over the world. as a basic strategy to help enterprises improve their operational capacity towards the perfect model (Operational Excellence). Typical examples of pursuing Lean Manufacturing with recorded successes and lessons learned include General Electric, Boeing, Lockheed Martin, Intel, ABB, ...

In Vietnam, along with the process of deep integration into the global supply chain, the principles and methods of Lean Manufacturing are also being pursued and implemented in enterprises such as Garment 10, Toyota Ben Thanh, and Vietnam Hospital. France and a number of enterprises participate in large supply chains in the fields of automobiles, motorcycles, electricity - electronics, and apparel.

Traditionally, Lean Manufacturing is applied mainly in enterprises operating under the assembly model with characteristics of many stages and a high proportion of manual operations such as automobiles - motorcycles, electrical - electronics, furniture. wood, garment, …. However, the successful experience in these fields along with the in-depth study of the principles of Lean Manufacturing have helped the application of Lean Manufacturing to be gradually expanded and promoted effectively in many fields of production and service. other services such as hotels, healthcare, finance - banking.

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1.2. The goal of Lean Manufacturing

Lean Manufacturing is a strategic approach with a system of methods and tools to continuously eliminate waste in production and business activities of enterprises through increasing productivity, reducing costs and shortening time. production/service provision (Lead time/cycle time). With the motto "Produce exactly what the customer requires, in the quantity and when the customer requires it, at the lowest possible cost", some of the basic goals of Lean Manufacturing include:

a) Reduce errors and waste

Minimize errors and material waste in the production / service provision of the business, including reducing raw material usage, preventable errors, cost of handling defective products, develop product features that are not required by the customer.

b) Shorten production time

Shorten order lead time (from order to delivery), production cycle time (from raw material to finished product). This is done through shortening the lead time between production stages, production preparation time, conversion time between orders/products.

c) Reduce inventory levels

Minimize inventory levels at all stages of production, especially inventory of semi-finished products between production stages. Reducing inventory levels will have a significant contribution to reducing demand and increasing working capital efficiency.

d) Improve labor productivity

Improve labor productivity through minimizing waiting time, optimizing operations (removing redundant steps and redundant operations). This is an important driving force in improving the value of labor power, thus, increasing the earning capacity of employees.

e) Efficient use of infrastructure

More efficient use of equipment resources and workshop space by eliminating capacity "bottlenecks", optimizing the efficiency of existing equipment and reducing machine downtime. This, on the one hand, improves production capacity, on the other hand, contributes to reducing the cost of depreciation of equipment and workshops per unit of product.

f) Increased flexibility

Improve flexibility in adjustment to produce different products with the lowest cost and time for switching between orders/products. This result allows businesses to better respond to the trend of diversifying product categories and increasingly smaller order sizes of customers.

g) Overall productivity increase

By achieving the above objectives, the enterprise can significantly improve the overall productivity on the basis of existing resources.

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1.3. Fundamentals of Lean Manufacturing

a) Identify wastes:

The starting step with Lean Manufacturing is to identify value-creating and non-value-creating stages/operations from the customer's point of view. From there, all materials, processes, and characteristics that are not necessary for creating value for customers should be reduced and eliminated.

From the perspective of value creation, business activities can be divided into three groups, including:

- Value creation activities:  are activities that directly transform raw materials and other inputs to create the right product that customers require,

- Non-value-creating activities:  are activities that are not required to transform raw materials, creating the right product that customers require. In other words, any activity for which a customer is not willing to pay is considered to be not creating value. Activities that do not create value are considered waste and should be minimized and eliminated.

- Activities that do not create value but are necessary:  ​​are activities that do not add value from the customer's point of view but are necessary to create products, unless the production and business process has a fundamental change. Wastes in this category are often difficult to eliminate in the short term, but can be eliminated in a long-term plan.

According to the research results of the Lean Enterprise Research Center (LERC) of the United Kingdom, the normal rate of these three types of activities in manufacturing enterprises is 5% - 60% - 35%. As such, a typical manufacturing business can eliminate up to 60% of its operations while ensuring customer requirements are met.

In Toyota's production system (TPS), the waste in business operations is divided into 7 basic groups: Excess production waste, Error waste, Inventory waste, Transportation waste, and Waste waste. waiting cost, operation waste and machining waste. Some current research on Lean Manufacturing adds two waste groups, namely Rework Waste and Knowledge Unconnected Waste.

b) Standard processes:

Lean Manufacturing implementation requires the establishment and application of highly detailed production instructions. These instructions, often referred to as Standard Work, have main contents including content, sequence, time (norm) of work performance, and outputs from worker/employee activities. . Standard work helps to minimize variation in how the work is done, and thus minimizes variability in the results achieved.

c) Continuous flow:

A fundamental tenet of Lean Manufacturing is to implement a continuous flow of work, eliminating "bottlenecks", interruptions, rollbacks or waits that occur in the execution of stages. This is achieved by a harmonious combination of manual operations and equipment operations to ensure that, under ideal conditions, the semi-finished products are always manipulated in some form without stopped, wait. With continuous flow production, production time could theoretically be shortened to as little as 10% of initial production time and the wasted waiting time of people, equipment and semi-finished products will be discarded.

d) Pull mechanism in production:

Pull-in manufacturing, also known as Just-In-Time (JIT), aims to produce only what is required and when required. Each stage of production is "pulled" by the latter, and so produces only when required by the latter. The pull mechanism in production is crucial in eliminating unnecessary inventory of semi-finished products between production stages, and thereby significantly reducing errors and waste.

e) In-process quality:

Lean manufacturing pursues the principle of detecting and eliminating defects at the source/point of origin and quality control is performed by manipulators as part of the manufacturing process.

f) Continuous improvement:

Striving for perfection is part of the requirement of Lean manufacturing. Along with the implementation of tools and methods, waste in different aspects and layers is detected and eliminated in turn. This is ensured through a continuous improvement/kaizen mechanism with the active and full participation of those directly performing the work.

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2. BASIC TOOLS AND METHODS OF LEAN MANUFACTURING

2.1. Standard work:

Standard work ensures that processes and instructions are defined and communicated in great detail in order to eliminate variation and incorrect assumptions about how the work is done. This tool helps workers to always perform precise and consistent operations for each and all work cycles.

In Lean Manufacturing, Standard Work typically has some of the following components:

Standard operating sequence:  lists the operations and the sequence that the operator is required to follow. Under ideal conditions, this description should show in detail every hand movement of the person performing the work.

Takt time  is the cycle time to produce a product and is used to explicitly specify the rate at which a process should operate at different stages. of production. The management and monitoring of the operation rhythm at each production process is a basic condition to ensure a continuous flow.

Standard in-process inventory:  is the minimum amount of raw material/semi-finished product inventory required to ensure that the process position is maintained at standard operating rhythms and to avoid unnecessary downtime. . This metric is used to calculate the quantity and cycle of requisitions for the previous stage – which is the basis for Kanban implementation.

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2.2. Visual management:

Large visual images, signs and visual instructions in the workshop/workplace are much more effective at communicating information than written reports and regulations. Visual management keeps workers effectively informed of the process, production status, and other critical information needed to perform operations effectively. Under the condition of good visual management, anomalies are easily detected in a timely manner to take appropriate countermeasures. Groups of visual management tools may include:

Visual order:  visualize 5S results to ensure a clean, orderly production site and easy detection of abnormalities. Manifestations of visual order may include floor plans of factories, locations of tools/tools, production information boards, etc.

Visual controls:  visualize standards, work control requirements to ensure correct operation, assist with monitoring and anomaly detection. Visual control manifestations can include color regulation of hot/cold/oil/steam/gas plumbing, visual indication of temperature/speed/pressure parameters, sanitation plan equipment generation, skills matrix, standard work, limited sample, etc.

Visual management information:  visualize general information about status, trends, developments, causes, ... according to key indicators of each area and function. Visual management information promotes communication and awareness to different levels of personnel.

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2.3. Quality in process

In-process quality (JIDOKA in Japanese) is the guarantee of "Doing it right the first time" through the mechanism of including quality assurance in the production process to prevent the occurrence of defects or if Errors are quickly detected. Some manifestations of quality in the process of Lean implementation can include:

In-process  testing: In-process testing is performed directly by the operator, not by independent testers. In Lean Manufacturing, quality control is part of the manufacturing process and not a stand-alone process. Although independent verifiers still exist, they often have a limited role in confirming the reliability of in-process checks or with the characteristics to be tested in the metrology department.

Check at source:  inspectors not only check to detect defects, but also need to check the cause of defects, including production control conditions. With this approach, the role of the quality control department is emphasized with understanding the root causes of defects to identify countermeasures against recurrence and instructing the operator on these countermeasures.

Clear division of responsibilities among workers:  in Lean Manufacturing, when inventory between stages is eliminated, those performing in the previous stage must take personal responsibility for the quality of the product delivered to the next stage. .

Defect Prevention (Poka Yoke):  In-process quality assessment measures are implemented to ensure that defective materials and products are not transferred to the next stage.

Intentional stoppage:  when a defect is detected, production is stopped until the cause of the defect is detected and treated.

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2.4. Value Flow Diagram

A value flow diagram (VSM) is a tool that helps visualize the flow of materials and information in the manufacturing process with the goal of identifying value-creating and non-value-creating activities. Often, the VSM needs to reflect the current state of the processes rather than what should be done in order to identify opportunities for improvement. In improvement projects, the implementation team needs to develop Current Value Flow Maps and Future Value Flow Maps – once the improvements are implemented.

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2.5. 5S

5S is the field management method to promote work efficiency, safety and easily detect anomalies of the production process. The elements of 5S including Sort, Organize, Clean, Standardize and Maintain are implemented on the principle that one thing has a place and one space for one thing, everything is in a clean condition. - check. In Lean Manufacturing, 5S is considered as the basic foundation for other tools to effectively deploy.

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2.6. Maintain overall productivity

Maintaining total productivity (TPM) starts with a preventive maintenance program to minimize the risk of equipment downtime due to breakdowns or lack of replacement parts. A preventive maintenance program improves equipment reliability and significantly reduces the need for inventory of "safe" semi-finished and finished products.

In maintaining overall productivity, basic maintenance items such as inspection, cleaning, oiling, etc. are assigned to equipment operators with the responsibility of proactively identifying, monitoring, and correcting the causes. cause unnecessary shutdown. The maintenance department, in TPM, focuses on higher-value maintenance activities such as equipment improvements, troubleshooting, operating instructions, etc.

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2.7. Quick conversion

Preparing equipment for production and changing molds and jigs is an important cause of equipment downtime and a significant waste that needs to be addressed and eliminated when implementing Lean Manufacturing. Continuous improvement efforts to reduce equipment preparation and conversion times should be part of the corporate culture. Equipment conversion and preparation time can be shortened through standard configuration settings for production, complete work instructions, reasonable ground layout to be able to fully prepare materials, tools before conversion.

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2.8. Small lot size

The requirement of Lean Manufacturing is to create a continuous flow with the smallest batch/lot size possible (ideal condition is single flow). Small batch sizes reduce wait times between stages, increase the ability to ensure just-in-time production (JIT) on demand, improve the ability to detect and handle quality errors early, and ensure the ability to attach more responsibility to workers because there are fewer people involved in production in small batches.

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2.9. Production and storage premises at the point of use