Development of a Value Stream Map to Optimize the Production Process in a Luxury Metal Piece Manufacturing Company

Abstract

The current market is highly competitive, and customers are increasingly demanding. In this context, organizations need to adopt tools that enhance process efficiency to ensure competitiveness. This report aims to implement Lean tools, specifically Value Stream Mapping (VSM) and complementary tools, to optimize the production process in the metal treatment industry. A case study was conducted, beginning with a brief sector and process recognition, followed by an analysis of production stages using VSM. Value-added activities, non-value-added activities, and waste were identified. The current VSM revealed a Lead Time (LT) of approximately 336 h (14 days), value-added activities (VA) of 21 h, and a process cycle efficiency (PCE) of 6.29%. Improvement actions were proposed to reduce waste and increase competitiveness. After implementation, the LT decreased to approximately 318 h (13 days), VA increased to 23 h, and process efficiency improved to 7.15%. Despite the limitations of VSM in discontinuous flows, its use increased process efficiency, demonstrating its applicability in complex industrial contexts.

1. Introduction

In the global context of increasingly competitive and dynamic markets, operational efficiency and customer satisfaction have become essential for companies wishing to stand out. The adoption of techniques and philosophies such as Lean Manufacturing is a strategy being used around the world to address challenges and optimize production processes [1]. Introduced by Ohno in Toyota Production System: Beyond Large-Scale Production in 1978, this revolutionary approach has demonstrated its ability to improve efficiency and reduce costs by eliminating waste, becoming a global benchmark for operational excellence [2,3]. The successful implementation of Lean tools, such as 5S, Kaizen, Kanban, Value Stream Mapping (VSM), and Poka-Yoke, has significantly improved the performance of companies in various industrial sectors [4]. VSM, in particular, makes it possible to visualize information and material flows, identify and analyze waste and non-value-added activities, and help suggest improvements [5].

This study focuses on the application of VSM to optimize the production process in the metal processing industry for luxury fashion brands. Currently, the turnaround time is relatively high, indicating that it can be improved by eliminating waste. By conducting observations and interviews and collecting data, the aim is to build a VSM of the process, identifying waste and suggesting improvements for optimization. Key issues addressed include the identification of production steps, associated tasks, information and material flows, time metrics, process bottlenecks, and waste elimination strategies. Given the complexity and variability inherent in the industrial production of metal parts, this optimization is crucial to meeting quality requirements and reducing delivery times [6].

The main objective is to address the themes of Lean Manufacturing, in particular VSM, to identify industrial challenges and opportunities for improvement. By defining the process through employee interviews and process observation, followed by time analysis, the aim is to create and follow the VSM methodology. The subsequent analysis will lead to proposals for improvement and the development of an optimized future state. This study aims to contribute by reducing time, standardizing work, and eliminating waste, thereby making the process more efficient. The methodology comprises four implementation phases: product selection, current state map, future state map, and action plan. This approach aims to improve the ability to deliver high-quality products efficiently, demonstrating the effectiveness of Lean Manufacturing, particularly VSM, in improving production processes.

2. Literature Review

This chapter provides a comprehensive overview of Lean Manufacturing, with a special focus on Value Stream Mapping (VSM) and complementary tools for reducing time and waste. The literature review was conducted based on a selection of articles relevant to the topic, covering everything from the fundamentals of Lean Manufacturing to the evolution and practical application of Value Stream Mapping.

2.1. Toyota Production System and Lean Manufacturing

The Toyota Production System, or TPS, was conceived and implemented shortly after the Second World War, but it was only later that it came to prominence. The TPS gained recognition for revolutionizing the traditional approach to mass production, with the essential focus being on the human factor and product quality. In contrast to Taylor and Ford’s methods, TPS seeks to eliminate waste, enabling efficient production without excessive stocks (Just-in-Time) and maintaining high-quality standards [2].

The Toyota Production System (TPS) integrates methodologies such as Kanban, Heijunka, standardized work, Jidoka, and Kaizen to enhance efficiency and facilitate continuous improvement. These methodologies emphasize the importance of fostering a culture of perpetual enhancement and engaging all employees in the process. The foundational principles of TPS are articulated through the 4P model: Philosophy, Process, People and Partners, and Problem Solving. This model highlights the critical role of nurturing a culture of continuous improvement and ensuring the active involvement of all employees in achieving organizational excellence [7].

Lean Manufacturing, which derives from the Toyota Production System, is a more production-oriented approach. Still, all terminologies have a common goal: to optimize the use of resources by reducing waste as much as possible [8].

The Lean Manufacturing approach, adopted by several companies globally, seeks to reduce costs by eliminating activities that do not add value. The key areas of Lean Manufacturing include flexibility, eliminating waste, optimization, monitoring processes, and involving people [3].

2.1.1. The Origins of Lean

The origins of Lean Manufacturing can be traced back to the Toyota Production System (TPS), developed in Japan in the 1940s and 1950s, just after the Second World War. This system gained prominence, especially after the 1973 oil crisis, which fueled the search for greater production efficiency [2]. In the 1990s, James P. Womack and Daniel T. Jones introduced the concept to the West, popularizing the term ‘Lean Manufacturing’ with their book The Machine That Changed the World [9].

Ohno emphasized the importance of eliminating waste and implemented Just-in-Time. In his 1978 book Toyota Production System: Beyond Large-Scale Production, he identified seven types of waste: transport, stocks, waiting, overproduction, defects, unnecessary movements, and rework. Eliminating these wastes is fundamental to improving productivity and reducing costs by looking at the Gemba (shop floor) [2].

In 1990, the term Lean Manufacturing gained prominence in the West through the book The Machine That Changed the World [9], which analyzed American, Japanese, and European car production. Womack et al. [9] argued that organizations should eliminate waste in operations to promote more efficient production, highlighting the importance of reducing Lead Time and adapting production systems to deal with small-quantity and large-variety orders [9,10].

In 1996, Womack and Jones [11] wrote ‘Lean Thinking’, identifying five fundamental principles of Lean: specifying the value, identifying the value stream, creating continuous flow, allowing customers to ‘pull’ value, and seeking continuous perfection. They emphasized that Lean is not limited to production, but involves the entire organization [11].

2.1.2. The Eight Wastes

Waste is an action that results in something unnecessary, as explained by Taichii Ohno, who initially identified seven types of waste and later expanded to eight. The categories are [8,9,10,11,12,13]:

i.

Overproduction: Producing more than demand, resulting in excess stock and loss of resources.

ii.

Waiting: Time spent waiting, whether for work, orders, or accessories, jeopardizes the flow of value.

iii.

Transport: Moving materials between locations consumes time and money.

iv.

Over-processing: Doing more than is necessary, generating additional costs and wasting resources.

v.

Inventory: Keeping excessive stocks, increasing waiting time and space, and making it difficult to identify problems.

vi.

Defects: Inadequate final products or services, resulting in rework and additional costs.

vii.

Unnecessary movements: Movements of people or equipment that do not add value, resulting in wasted movement.

viii.

Waste of talent and skills: Under-utilization of workers’ skills, resulting in loss of motivation and ideas. This category was initially defined by [11], with the eighth waste being identified as employee underutilization, indicating that people’s skills and capabilities are not properly used.

2.1.3. Lean Tools

A collection of techniques and tools enriches the Lean approach, the varied application of which is aimed at optimizing processes and eliminating waste. These tools include Just-In-Time (JIT), Single-Minute Exchange of Dies (SMED), Total Quality Management (TQM), work standardization, visual management, Kaizen, Kanban, VSM, and 5S. These techniques, when employed properly, lead organizations to identify and eliminate inefficiencies, improve the quality of products and services, and promote a culture of continuous improvement [12,14].

Lean tools can be categorized in different ways, ranging from analyzing processes to planning, executing changes, and monitoring performance [15]. This subsection will provide a detailed description of the tools that will be practically applied to implement improvements and achieve the desired future state.

Kaizen stands out as a fundamental technique for eliminating waste and promoting continuous improvement at all levels of the organization. It emphasizes not only constant improvement but also addressing problems and inefficiencies along the way, promoting active employee participation and implementing visual management systems to empower workers in the workplace [8].

The 5S method, developed to establish organized and efficient work environments, consists of five steps: Sort, Put in order, Shine, Standardize, and Sustain. Its application results in benefits such as reducing wastes of time and space and improving quality, safety, and hygiene [16].

Kanban, designed to visualize work and optimize flows, contributes to Lean practices and operational efficiency, indicating the right time to replenish materials and facilitating workflow management [16].

Just-in-Time (JIT), introduced by Toyota, aims for efficient production, depending on a significant reduction in tool changes and the practice of leveling production to avoid bottlenecks and safety buffers [2,11].

Standard Work, developed by Taiichi Ohno, seeks to eliminate variations and inconsistencies in results, promoting a culture of responsibility and innovation. Its implementation results in stable and measurable operations, reduced costs, and improved quality [17].

SMED (Single-Minute Exchange of Dies), an essential tool of Lean production, aims to reduce waste by enabling the rapid exchange of tools in less than 10 min. This technique gives companies greater flexibility by minimizing the time needed to change between tasks or equipment configurations. The effective implementation of SMED depends on the precise classification of activities, distinguishing between internal setup (carried out while the machine is stopped) and external setup (carried out while the machine is running) [18].

Time study, which originated with Taylor (1881) and was accompanied by a movement study introduced by Gilbreths in 1885, is used to find the most economical way to carry out a job, standardize methods, and define the time needed to complete a task. To carry out a time study, it is necessary to observe and understand the process, divide the operation into elements, determine the sample size, classify the operator’s pace, and calculate normal and standard time [18].

The PDCA Cycle (Plan–Do–Check–Act), also known as the Deming Cycle or Continuous Improvement Cycle, is a management approach that is based on four stages. The Planning stage involves setting goals and allocating resources appropriately. The Execute stage consists of implementing what has been planned. The Verify stage monitors processes and communicates results, while the Act stage undertakes actions to improve performance if necessary [19].

Quality tools play a key role in the efficient management and continuous improvement of organizations. The 5W2H tool, derived from the PDCA cycle, offers an organized structure for carrying out tasks by answering seven fundamental questions. The GUT Matrix, meanwhile, is a qualitative and subjective tool for prioritizing problems, taking into account severity, urgency, and trend to identify and address critical issues within an organization [20].

Combining these tools with the VSM allows for a complete approach to optimizing processes, reducing waste, and achieving a desired future state, promoting efficiency and operational excellence.

2.2. Value Stream Mapping

Value Stream Mapping (VSM) is a tool that has been widely used since the late 1990s, mainly in the automotive industry, but also in other industries and the service sector [21]. This subsection will look at the evolution of the VSM tool, as well as its main objectives and application methods.

2.2.1. Historic Evolution

Value Stream Mapping (VSM) originated in the value chain analysis developed by Taiichi Ohno, mentor of the Toyota Production System. The first formal VSM approach was developed by Rother and Shook in 1999. It is a methodology that analyzes an organization’s value stream, providing a comprehensive view of the activities related to a product family [21]. Various authors have contributed to the evolution and improvement of VSM, addressing its limitations and proposing improvements. For example, Hines and Rich [22] described seven tools that, used together, create an effective methodology for identifying and reducing waste. These tools include VSM, the supply chain response matrix, the production funnel, quality filter mapping, amplified demand mapping, decision point analysis, and physical structure. Meanwhile, Brunt [23] provided an in-depth look at current and future state mapping, highlighting the application of VSM in implementing the Lean Management philosophy. This approach was expanded to create a representation of the value flow of a product between three different companies—steel producer, steel service center, and first-line component supplier—to provide a visual understanding of the value flow and identify opportunities for improvement. In 2002, Jones and Womack [24] introduced Extended Value Stream Mapping (EVSM) to complement traditional value stream maps by extending the view to the entire value chain, from suppliers to customers, thereby raising the shared awareness of all participants along a given value chain. Another study by Lian and Landeghem [25] investigated simulation and value stream mapping, visualizing impacts before implementation and enabling organizational transformation with minimal costs. They built simulation models for push and pull (Kanban) systems, emphasizing physical and computer-assisted simulations to validate the current state map and explore future scenarios.

Further advancements include Improved Value Stream Mapping (IVSM), presented by Braglia et al. [26], which deals with products with a complex Bill of Materials (BOM) using a recursive approach to identify opportunities for improvement. Additionally, the Value Stream Mapping Paradigm by Lian and Landeghem [27] integrated VSM with simulation, developing a model generator that automatically creates VSM simulation models. VSM has also been used by Clifford and Golmohammadi [28] to unite the workflow of two companies with distinct processes into a single entity, improving operational metrics. This study highlighted challenges in implementing changes due to significant differences between the current state and the ideal future but emphasized the importance of organizational commitment to the success of the approach. In another example, the implementation of Lean Manufacturing in a small company in the USA highlighted the cost challenges associated with hiring specialized engineers. They used Kaizen events and methods such as 5 Whys to identify and solve problems, resulting in improvements in productivity and operational efficiency [29]. The Value Stream Mapping technique has also been applied to small companies by [30], showing that significant changes are expected in terms of productivity improvement if the proposed future states are implemented. This research suggests that VSM can substantially benefit companies of all sizes. A review by Pagliosa et al. [31] of the connection between Industry 4.0 and Lean Manufacturing highlighted that implementing technologies such as IoT and cyber–physical systems can produce rapid and synergistic results with Lean practices. The application of digitized VSM in manufacturing has been addressed by Horsthofer-Rauch et al. [32], emphasizing that manual VSM analysis becomes inefficient with increasing production complexity. This study explored the potential of process mining to model and analyze production processes, identifying challenges in data requirements, methodology, and visualization. Additionally, various perspectives have been analyzed by [33] to help adopt sustainable development through VSM, concluding that implementing VSM requires strengthening its applications with sustainability and Industry 4.0.

The evolution of the VSM reflects the continuous search for improvements and adaptations to meet the specific needs of different industries and production contexts. Various approaches have been developed to make VSM a more comprehensive and effective tool for managing and improving processes.

2.2.2. VSM Objectives and Associated KPI

VSM (Value Stream Mapping) is a technique that aims to identify and eliminate waste throughout the system, minimize resources used, and optimize organizational performance. It also acts as a proactive tool for analysing and selecting technological approaches right from the start of a project [34].

Silva et al. [20] point out that the VSM provides a detailed ‘door-to-door’ visualization of the production process, identifies waste, establishes a common language for processes, integrates Lean concepts, identifies material and information flows, and underpins decision-making and implementation plans.

The VSM includes concepts such as the pull system, which starts production in response to customer demand. Distinguishing between value-adding activities (VA), necessary non-value-adding activities (NNVA), and non-value-adding activities (NVA) is essential for eliminating waste. NVA is pure waste and should be eliminated, while NNVA is necessary within current procedures [8,21].

Work in Progress (WIP) refers to the inventory between the start and end points of a process. Lead Time is the total period a customer waits to receive a product after placing an order. If demand exceeds the system’s capacity, the waiting time increases beyond the production time [24].

In terms of KPI, there is Takt time, calculated as available time divided by demand [1,8,21]:

Takt time = (Available Time)/Demand

(1)

Process cycle efficiency (PCE) compares the value-added time (VA) with the total cycle time (Lead Time). A process is considered Lean if the value-added time is more than 25% of the total cycle time [35].

PCE = VA/LT

(2)

VSM is an integral tool for optimizing operational efficiency, aligning production with market needs and eliminating activities that do not add value to the end product [8].

2.2.3. VSM Symbols

Value Stream Mapping (VSM) uses a set of universal symbols to graphically represent production processes, providing a common language for value stream analysis and a deeper understanding of the connections in the flow of materials. Symbols adapted from the approach in [22] will be used as they are shown in Figure 1.

According to Nash and Poling [36], VSM consists of three main sections:

• Process or production flow: Shows the flow of materials throughout the production process.
• Communication or information flow: Identifies all communication within the value stream.
• Timeline and distance traveled: Represents the execution time of the process, the total cycle time, and the physical distance traveled by the product or people within the process.

2.2.4. Implementation Method

To effectively apply Value Stream Mapping (VSM), four main steps are followed, according to Oliveira et al. [3] and Hines and Rich [22]:

• Product or Product Family Selection: A product or product family with common processing steps and equipment is chosen. The chosen product family, the number of parts, customer demand, and delivery frequency are documented. Value Stream Mapping involves touring the factory and outlining the processing steps from input to output.
• Drawing the Current State Representation: A map is created representing the current state of the value stream, identifying and mapping each step of the process from raw materials to the final product. This detailed drawing reveals areas of waste, inefficiencies, and bottlenecks. The steps are categorized and associated with metrics such as time, distance, and involvement of people. The process includes gathering customer requirements, detailing the physical flow, mapping the supply of materials, and identifying information flows and push/pull systems
• Value Stream Design (VSD): Once the current state is understood, the desired future state is designed, eliminating inefficiencies and developing an optimized model. This process aims to create a clear and improved vision of the value stream. It explores Takt time, continuous flow, pull systems, production scheduling, and process improvements to optimize operational efficiency and effectively meet customer demands. Strategic questions help to create a production environment aligned with Lean principles, promoting the consistent delivery of value to the customer.
  Questions include [21]:
  • What is the Takt time, considering the available labor time?
  • Should you produce for finished goods stock or directly for dispatch?
  • Where should you implement continuous flow?
  • Where should you introduce pull systems with supermarkets?
  • Where should you plan production in the production chain?
  • How should you level the production mix in the pulling process?
  • What increment of work will be released evenly by the pulling process?
  • What process improvements are needed to guarantee the flow of value according to the future state of the project?
• Drawing up a Work Plan to Achieve the Future State: A detailed work plan is defined to implement the proposed improvements, covering the actions needed to move from the current state to the future state, with clearly defined responsibilities and deadlines.

2.2.5. Advantages and Limitations of VSM

Value Stream Mapping (VSM) is widely recognized as a powerful tool for analyzing and optimizing processes, but it has both advantages and limitations that must be carefully considered. Among the main advantages of VSM is its ability to serve as the basis for implementing Lean Production. Organizations can identify and eliminate waste by mapping and analyzing value flows, promoting operational efficiency. In addition, VSM establishes a valuable connection between internal manufacturing processes and the entire supply chain, providing an integrated view that facilitates a comprehensive understanding of processes and ensures that decisions are informed by detailed production and inventory data [25,26,37]. This tool also directly links product planning and demand forecasting to production scheduling and shop floor control, promoting a coordinated approach to integrated optimization.

VSM is particularly effective in continuous production layouts, such as assembly lines, where it can favor the fluidity and efficiency of process data [25,26,37]. However, VSM also has significant limitations. Its application in high-variety, low-volume manufacturing systems can be challenging, as it is less suitable for these settings due to their specific characteristic data [25,26,37]. In MTO (Make to Order) environments, the application of VSM can be even more complex. Conventional VSM is primarily designed for MTS (Make to Stock) environments and may not adequately address the logistics objectives of an MTO environment, such as schedule reliability. In these environments, production is more flexible, and customer demand is more variable, which can make it challenging to implement Lean principles such as FIFO (First In, First Out) [38]. Thus, the application of VSM in MTO environments can be hampered by the variable and dynamic nature of production, jeopardizing its effectiveness [39].

To address these limitations, alternatives have been developed such as the Waste Identification Diagram (WID), the Manufacturing Cost Deployment (MCD), the Manufacturing Critical-Path Time (MCT), and the Project Time Deployment (PTD). The WID aims to overcome some of the shortcomings of the VSM by allowing a more comprehensive representation of production units. WID can represent not only the flow of a product family but also entire production units, visualizing the layout and assessing all types of waste visually and intuitively. In addition, it offers detailed quantitative information on the performance of workstations, such as cycle time, changeover time, and the utilization of the workforce in value-adding and non-value-adding activities. However, WID still faces challenges, such as the lack of representation of the flow of information from Production Planning and Control (PPC) and the absence of links to suppliers and customers [40].

MCD focuses on systematic cost reduction through a rigorous and structured approach. This tool uses five matrices (A-matrix, B-matrix, C-matrix, D-Matrix, and E-matrix) to classify losses, clarify cause and effect relationships, convert losses into manufacturing costs, suggest improvement actions, and present the efficiency of the investment associated with each action. The MCD is effective in identifying and eliminating inefficiencies, highlighting opportunities to increase efficiency and effectiveness in reducing losses. Its implementation has been successful in various industries, especially in the automotive sector, where it has been integrated into the World-Class Manufacturing (WCM) model [41].

MCT is a time-based mapping approach that graphically represents the flow of an order and calculates the corresponding delivery time. It highlights the longest critical path of order-fulfilled activities, helping to identify non-value-adding activities that consume significant time and offering a robust metric for continuous improvement projects [41].

Finally, PTD is an iterative structured approach specifically designed for Engineer-to-Order (ETO) production environments. Combining MCT with specific features of MCD, PTD identifies the losses affecting an ETO project and facilitates planning on how to reduce them. It classifies, analyzes, and eliminates losses to reduce production time, focusing on business processes where the causal losses are located [41].

Despite the enhanced capabilities of WID, MCD, MCT, and PTD in terms of detailing and evaluating losses, the choice of VSM in the context of discontinuous flows is justified by its simplicity and practical effectiveness. VSM, although limited in its representation of complex production routes and various types of waste, provides a clear and direct view of the value stream, making it easier to quickly identify areas for improvement in terms of material flow and information flow. The adaptability of the VSM is a crucial factor. It allows the stages of the production process to be visualized understandably and intuitively, which is essential for implementing continuous improvements holistically and simply [40,41].

Therefore, the choice of VSM, even with its limitations, is based on its effectiveness in representing the value stream simply and straightforwardly, ensuring that visualization of processes and identification of waste can be carried out efficiently and practically in a short amount of time and with accessible materials.

3. Case Study

This study was conducted at a prominent entity in the metalworking and metal-mechanics industry, specializing in the processing of metal items such as jewelry and metal components/accessories for bags, belts, and scarves. This entity oversees the entire production process from machining to final assembly, with the finished products exported to other companies within its group.

Originally founded in a garage with just 12 employees, the organization underwent significant changes, and in 2013, it adopted its current name. Initially, the company focused exclusively on polishing metals with around 50 employees. In 2016, the entity expanded by acquiring another company, increasing its workforce to 80 employees. Over the years, it has consistently invested in employee training, new machinery, and equipment to enhance its capabilities and expand its activities to include machining, vibratory polishing, and galvanization, among others, with the primary objective of consolidating the entire production chain within Portugal.

This continuous investment has allowed the organization to grow and adapt, ensuring it remains at the forefront of the industry.

3.1. Selection of the Product Family

To develop the Value Stream Mapping (VSM), the initial step involved selecting the product family. Product E was chosen due to its significant order volume, making it a high runner in the company. This product family includes several variants, differing in stem length, hole configuration, and semicircle diameter.

Product E is considered a semi-finished product, consisting of components such as the Ecrou and Pontet (assembled onto the piece) and other parts included in the kitting delivered to the customer.

Initially, various production processes and areas within the company were observed and understood to gain a general overview of the entire process. To construct the VSM, a batch was tracked from machining to shipment to the customer. It is important to note that the polishing process was simulated in this analysis, as this step is currently outsourced by the company for Product E.

3.2. Productive Process and Flow

The manufacturing process for the Product E family begins with the receipt of stamped pieces from a company within the same group, identified by supplier code RN. This receiving process includes material reception and the issuance of a manufacturing order for the machining section (Usinage). After being stored in the receiving stock, a manufacturing order labeled USI is issued, and the batch is moved to advanced stock in the machining area. According to the weekly planning schedule, the batch proceeds to the CNC machine for machining until the end of each operator’s shift. Once machining is completed, the pieces are placed in the control stock area. After inspection, the batch awaits transportation by logistics operators responsible for moving batches between sections. In this instance, the batch is collected by logistics and sent to a group company for polishing. However, to complete the VSM, the selected sample remained in stock until it was transported to the designated polishing production unit.

The next phase is polishing, which includes Lapidage preparation (of the tongue, sides, and “tongue tip” and the semicircle faces), washing, semi-automatic polishing, washing, manual polishing (around the piece, pre-Avivage, complete Avivage), washing (automatic), and finally a complete inspection. Transporting the batches is managed by two employees responsible for washing, each covering half of the layout.

After polishing, logistics transports the batch to the material reception area to add the Ecrou, a component pre-assembled onto the piece. The Ecrou is partially added to Product E to facilitate full plating in the subsequent galvanoplasty process. The galvanoplasty section includes an assembly area where pieces, previously transported in trays, are placed on a support called Bouclard, followed by the bath area and control area.

After this process, logistics retrieves the batch and performs the initial kitting to assemble all components into the final product. Some components are not assembled onto Product E but are included in the kit for customer assembly into the final product.

Once the kits are completed, they undergo inspection and are transported to the shipping area (with quality control in this area and final inspection by picking) for delivery to the customer. In Figure 2 there is a spaghetti diagram showing the flow of product E.

3.3. Data Collection and Analysis

This section presents the data collected and explains each section and production process, considering that the current production flow can be characterized as push and Make to Stock. To develop the VSM, data such as setup time, cycle time, available time, and actual operation time were collected. A batch of 50 pieces was tracked through the entire process, and a table was created with timed metrics (second/piece; minute/piece; hour/piece; minute/lot; hour/lot; and day/lot). The table also indicates the type of process each activity represents according to the ASME standard, with administrative processes added as needed. From the collected data, Uptime, Takt time, and PCE/efficiency were calculated.

The OEE (Overall Equipment Effectiveness) indicator was not mentioned in the VSM (Value Stream Mapping) analysis, even though it was calculated for the machining process, for various reasons. OEE is relevant for machining processes, but most of the other processes in the company, except electroplating, are manual and highly variable. Electroplating, being a complex electrochemical process, is difficult to control and standardize. The main aim of implementing the VSM was to identify waste and optimize the production process holistically, given that the time available to implement the tool was somewhat limited. Focusing exclusively on OEE could divert attention away from global improvements, concentrating instead on the efficiency of individual pieces of equipment.

3.3.1. Reception

The process starts with material reception, which takes about 3 days for stamping and 120 h for delivery. It is unloaded, verified (4 h), and then organized in stock. The reception area includes a control area, vertical storage modules, shelving areas, and a central logistics area for various tasks like issuing manufacturing orders and kitting. The vertical storage modules are distributed for machining materials, consumables, assembly components, and polishing.

The material arrives already stamped in batches of 2000 from a group supplier, so no reception control is performed. The material is received, counted, and stocked using FIFO for supplying the machining section. Typically, the material stays in stock for about a week. Logistics staff select the material and issue a weekly manufacturing order (USI), which is then divided into batches. The logistics transport worker takes the batch to advanced machining stock. This process takes about 5.2 days, though this can vary depending on stock levels and customer orders. The activities that add necessary value (VA) are material reception and order issuance (4.5 h/batch), while non-value-added activities (NVA) total 120.5 h per batch.

3.3.2. Machining

The machining area consists of three machine sets named B, H, and C. Material processing is performed on CNC machines in set B (machines B4, B5, and B6). Each CNC machine has a rotating panel that performs specific operations in sequence. The first operation (cycle time: 3 min and 14 s) includes shaft roughing, drilling with three bits, chamfering, hole finishing, and code engraving. The second operation (cycle time: 2 min and 50 s) involves creating channels, corner finishing, and additional drilling and chamfering.

Each operator handles three machines, and unplanned stoppages or micro-stoppages are minimal as the CNCs can operate continuously. Quality control is supposed to be hourly, but operators often spend time cleaning burrs, causing unplanned stops and leading to 78% availability (5.75 h). Setup time is 3 h, varying with adjustments and tuner availability. The batch advances by shift, with the operator leaving the production in stock at the end of their shift. The inspection takes about a day, followed by a 10% batch sampling for visual control and stock waiting (40 min) before transport to the polishing unit.

The planned time per shift is 7.33 h with a daily demand of 110 pieces (55 per shift), resulting in a Takt time of 8 min per piece. Considering cleaning and unplanned stops, the efficiency is reduced due to stock waiting times, totaling 163 h of NVA and 6.03 h of VA, leading to 54.48% efficiency.

3.3.3. Polishing

Polishing involves several phases: preparation, washing, semi-automatic polishing, manual polishing, and control. Each product family has different polishing flows. For Product E, initial preparation (Lapidage) takes 80 s per piece. Following Lapidage, the batch is transported for washing (29 min), semi-automatic polishing (33 min per pass, with 2 passes), and further washing and waiting. Manual polishing follows (95 s per piece) and final washing before quality control.

Efficiency is 45%, with transport and waiting times being significant. Activities adding value total 5.36 h, and non-value-added activities total 6.67 h, resulting in a 12 h Lead Time.

3.3.4. Pre-Assembly

Product E requires pre-assembly before precious metal deposition. Logistics transports the polished pieces for pre-assembly, where an Ecrou is partially added (32 min for 50 pieces, 15 s per piece). Following pre-assembly, the batch waits (33 min) before logistics transports it to galvanoplasty. In this process the VA is 0.53 h, with 4.81 h of NVA, resulting in 10% efficiency.

3.3.5. Galvanoplasty

The batch is mounted on Bouclards for a series of ultrasonic, degreasing, activation, and plating baths (0.97 h total). Post-bath, the pieces are rinsed, dried, and inspected before initial kitting. The total VA time is 1.89 h, and the NVA is 10.96 h, with a significant wait for plated components that need to be assembled into the main product. Efficiency is 15%.

3.3.6. Final Assembly

Final assembly involves visual inspection, complete Ecrou insertion, and Pontet attachment (75 s per piece). The batch is checked, kitted, and prepared for shipping. Total VA time is 6.33 h, with various waiting times reducing efficiency.

3.3.7. Shipping

Upon reaching shipping, the batch undergoes final quality checks and kit verification (10 min), is declared in the management software, packaged (1.5 min), and shipped (30 h to the customer). VA activities total 21.17 h, and NVA activities total 315.17 h, resulting in a Lead Time of 367 h and a cycle efficiency of 6.29%.

Overall, the process efficiency is low due to a push-based and discontinuous flow, with significant waiting times and transportation delays. Improving these aspects and eliminating waste can enhance process efficiency and effectiveness.

4. Discussion

4.1. Value Stream Mapping Actual State

Based on the data collected and described in the previous section, the VSM (Value Stream Mapping) of the current state of the product E was constructed.

The production flow is characterized as push, with production made to stock, to always have products available for each production process. This method results in the creation of safety stock to minimize the risk of interruptions. In addition, the flow is discontinuous, with different manufacturing orders for each section, resulting in a fragmented flow in logistical terms. Each section works independently, with a discontinuous flow, generating inefficiencies.

When receiving raw materials, the waiting time is significant (120 days) due to the use of FIFO (First In, First Out) and weekly consumption in machining. The raw material received is kept in stock until it is needed. The receiving process includes unloading, checking, and organizing stock. Receiving time is divided into value-added (VA) and non-value-added (NVA) activities.

In machining, setup time is relatively high due to the fine-tuning and adjustments required for each machine. The production cycle includes two main operations with several steps, from roughing to chamfering and drilling. Waiting time for control is significant (73 percent of total time), varying according to shifts and production priorities. Efficiency is reduced due to stock waits and unplanned stops, representing 163 h of NVA against 6.03 h of VA, resulting in an efficiency of 54.48 percent. There are opportunities for improvement, such as reducing setup time through tools such as 5S/SMED to minimize time and effort in fine-tuning and adjustments (See Figure 3).

In polishing, the process includes several phases such as Lapidage, washing, semi-automatic polishing, manual polishing, and control. Each phase has associated waiting and transport times. Lead Time is 8.97 h, with 3.61 h dedicated to waiting and transport. This process is carried out externally for strategic reasons and takes 432 h to complete. Internally, polishing efficiency is 45 percent, with value-added activities accounting for 5.36 h and NVA 6.67 h (See Figure 4).

Before pre-assembly, logistics adds the component needed for assembly and transports the parts. Assembly time is 0.53 h, with the main difference between actual and theoretical time due to burr cleaning and visual control. It represents 10% efficiency, with 4.81 h of NVA.

In galvanoplasty, the process includes assembly in the Bouclard, plating, and control, with a total time of 1.89 h and 0.97 h of waiting. Process efficiency is 15%, with value-added activities totaling 1.89 h and NVA 10.96 h, including a significant 9 h wait for components (See Figure 5).

In the final assembly, the process includes visual control, final assembly of the Ecrou, and adding components. Part conformity caused a significant delay. The assembly time is 6.33 h, longer than expected due to doubts about quality parameters. Value-added activities totaled 1.75 h, while NVA accounted for 0.42 h.

The final dispatch process includes a final sample check, kit verification, computerized closing, packing, and wrapping. Transport time takes around 30 h for the batch to reach the customer after dispatch (See Figure 6).

The VSM shows that there are relatively long waits between each of the processes. Internally, in each of the processes, there are also NVA activities, indicating that the times represented as VA on the timeline are not entirely value-added. The main causes of waste identified include waiting and transport between the different phases, as well as inefficiencies in the setup and quality control processes.

4.2. Improvements

After analyzing the current state and considering the guidelines for the future state proposed by Rother and Shook [21], several areas for improvement and actions to be taken in each section of the process were identified.

The main problem identified was in final assembly, where the current cycle time exceeds the Takt time; it is essential to reduce the cycle time to match customer demand. The most appropriate approach is to maintain the push flow in machining but create a pull system between electroplating and final assembly. In addition, it is proposed to implement a Kanban system to control the stock of final products.

4.2.1. Machining

In machining, SMED needs to be implemented to reduce setup times. To identify opportunities for optimization, the setup process was monitored and timed. As shown in

Table 1. SMED. Operations classification.

#	Operation	Time (min)	Cumulative Time	Internal	External	Observations
1	Check Tools	6.78	6.78	x		Team Leader
2	Removing Tools	1.20	7.98	x		Team Leader
3	Select Tools in the Cabinet	2.00	9.98	x		Team Leader
4	Preparing the tool	16.00	25.98	x		Team Leader
5	Measure Tool	2.67	28.65	x		Team Leader
6	Place Tool	2.00	30.65	x		Team Leader
7	Insert parameters (x,y,z)	10.13	40.78	x		Team Leader
8	Zero point	11.48	52.26	x		Shift Leader/Tuner
9	Insert Program	7.75	60.01	x		Shift Leader/Tuner
10	Make 1st Part-Validation	58.00	118.01		x	Shift Leader/Tuner
7–8	Wait Time	61.58	179.59	x		Wait for tuner. One part of the process is done by the team leader, another by the tuner or shift leader. This wait is also for the shift change. Tuner busy.
Total		180

, the setup consists of 10 operations.

It was observed that all the activities are internal, except for the validation of the first part, which generally requires adjustments. This means that they are carried out with the machine stopped. In addition, a waiting time of around 1 h was identified due to waiting for the tuner, who was busy, and due to the shift change.

Although some SMED mechanisms are already in place, it is possible to transform some of the internal steps into external ones. For example, operations 3, 4, and 5 in Table 1 can be carried out while production is taking place, allowing the team leader to prepare the tools; it is suggested that a tool shelf be installed like what already exists on the H needed for the next batch. In addition, machines are used to reduce tool changeover time. By implementing these improvements and maintaining the waiting time for the tuner, it is possible to reduce the internal setup time from 3 h to 2 h and 40 min.

4.2.2. Polishing

In polishing, a quick change of sandpaper is suggested, switching to self-adhesive sandpaper, which significantly reduces the changeover time and associated costs.

The sandpaper change process involves several steps, the time for which has been calculated as a standard 90 s. In the production of E, each batch of 50 units requires four sandpaper changes, totalling 36 min per day. Adopting self-adhesive sandpaper reduced the changeover time to 51 s, saving 15.6 min a day and resulting in monthly savings of 327.6 min, representing a time reduction of 43%. Financially, this change meant a monthly saving of around EUR 3 per operator and glue booth. In addition to the financial benefits, self-adhesive sandpaper contributes to a more sustainable approach, improving air quality and freeing up space in the industrial environment.

Additionally, it is proposed to standardize and speed up changing Brosses (groups of fabric assembled to create a rotating wheel for polishing). This can be achieved by creating kits of pre-prepared Brosses and establishing standards for the use of cloths to optimize the process.

The Brosse changeover process revealed a lack of standardization, both in the number of cloths and the arrangement of the tools. After analyzing the data and interviewing operators, a standard number of cloths was established for each type of Brosse configuration, resulting in kits designated as S, M, and L. These kits were organized in a specific station with a shelf for each configuration, also including the necessary key and reference tables. The standard Brosse changeover time was reduced to 2 min, saving 3 min and 24 s. This standardization not only improves efficiency but also guarantees better quality and controlled use of resources.

4.2.3. Assembly and Galvanoplasty

In assembly and galvanoplasty, it is essential to reorganize the layout to create a continuous flow between the two areas, eliminating non-value-adding activities such as transport and waiting. This involves implementing a Kanban production system for final products and creating shelves for pre-assembly and PP assembly, speeding up the workflow and ensuring more efficient production. To optimize the value flow of the product family under study, it is proposed to reorganize the layout between the assembly and galvanoplasty areas. This involves the elimination of logistical steps, the creation of stock between these areas, and the implementation of a pull-type system to create a continuous flow, with the aim of reducing non-value-added activities such as transport and waiting. The new layout will group assembly stages and associate the final assembly with control. A system will be implemented to control the entry and exit of parts, such as the use of a conveyor to guarantee FIFO during electroplating. The flow between assembly and electroplating will be continuous, supported by a Kanban of final products pulled by final kitting. The walls between the sections will be removed to promote a fluid connection. These changes are aimed at improving efficiency, reducing waste, and promoting a continuous and agile flow in the production process.

These actions aim to reduce non-value adding activities, optimize production processes and improve the overall efficiency of the system, in line with the principles of Lean Manufacturing.

4.3. Future State

Based on the improvements identified, the future state VSM was drawn up, which includes various optimizations in the setup, sandpaper changeover, and Brosse standardization processes. Through SMED, it was possible to reduce setup time by 20 min, while changing from traditional sandpaper to self-adhesive sandpaper reduced changeover times, resulting in more efficient cycle times. The standardization of Brosses led to a reduction in changeover times, as well as ensuring greater control and stability in production.

The most significant proposed improvement involves changing the production flow and layout between the assembly and galvanoplasty sections (See Figure 7 and Figure 8). This includes eliminating non-value-added activities, such as transport and waiting, and creating a continuous flow of work. Through this reorganization, it is hoped not only to reduce idle times but also to promote better use of resources and a more agile response to customer demands.

The flow of parts between sections has been redefined, starting with logistics reception and followed by PPP assembly and Bouclard assembly, now carried out sequentially at the same workstation. The flow continues with the bath and quality control stages, before returning to final assembly and control. This reconfiguration allows for smoother integration between the processes and the elimination of waste, such as unnecessary handling and waiting between stages.

With these improvements, it is hoped to eliminate waiting times between batches, guaranteeing a constant and efficient flow.

Once the main sources of waste have been eliminated, the future state shows an increase in efficiency of 0.86% and a reduction in Lead Time of 18.31 h with the following values:

• VA = 22.75 h
• NVA = 295.39 h
• LT = 318.14 h
• PCE = 7.15%

The future state VSM reflects these improvements, providing a clear view of the optimized value flow and the activities required at each stage of the process. These changes not only increase operational efficiency but also improve product quality and customer satisfaction.

5. Conclusions

By applying Value Stream Mapping (VSM) and other Lean tools, waste was identified and proposals for improvement were developed. The VSM allowed for a comprehensive visualization of the entire process, identifying waste and suggesting changes for the future state. Key wastes identified included waiting, unnecessary transport, and over-processing. Improvement proposals included the implementation of self-adhesive sandpaper, standardization of brushes, and reorganization of the production flow.

The current state was characterized by (1) Lead Time: 336.45 h; (2) value-added time: 21.17 h; (3) process cycle efficiency (PCE): 6.29%.

After implementing the proposed improvements, the following changes were observed:

• SMED reduced setup times by 20 min.
• Self-adhesive sandpaper reduced unnecessary movements by 0.04 h.
• The most significant improvement was the restructuring of the layout and flows, with the creation of component stock, which eliminated approximately 14 h of non-value-added (NVA) time.

The new state improved the process by achieving: (1) Lead Time: 318.14 h; (2) value-added time: 22.75 h; and (3) PCE: 7.15%.

This analysis resulted in significant operational improvements and cost reduction (details undisclosed due to institutional confidentiality). Thus, this research work stands out for its specific application in a discontinuous process context within a sector characterized by independent sections operating with entirely different processes. VSM focus is on continuous production processes, and this study offers an innovative approach by applying VSM in an industrial environment where the variable nature of processes presents unique challenges. Despite the challenges, VSM was successfully implemented in a complex industrial setting, achieving the initial objectives. By analyzing how VSM can effectively be applied in discontinuous processes. This study could fill a gap in the existing literature and establish standards for the practical application of conventional VSM, providing accessible insights for dynamic industrial environments.

Future research is suggested to assess VSM’s applicability in the complex context of other surface treatment process industry discontinuous flow and to evaluate the effectiveness of the implemented improvements. Future work should include applying SMED actions, analyzing the processes of different product families to create FIFO or Kanban systems in centralized areas like washing. Additionally, conducting detailed time studies for each VSM activity is necessary to ensure the replicability of this research.