The metallurgical industry, serving as a backbone for numerous segments of the economy, operates under the pressures of a stringent competitive environment, accelerated growth in prices for raw materials and energy carriers, as well as tightening environmental regulation. Under these conditions, improving operational efficiency ceases to be a source of competitive differentiation and becomes a prerequisite for market viability. The Toyota Production System methodology, or lean manufacturing, has demonstrated its effectiveness as a coherent managerial paradigm focused on the systematic identification and elimination of waste. At the same time, the direct transfer of TPS tools from a discrete, assembly context (automotive manufacturing) to the realities of continuous and large-tonnage metallurgical production is associated with significant technological and organizational barriers and requires scientifically grounded adaptation.

The aim of the study is to examine the Toyota Production System methodology in enhancing the efficiency of metallurgical enterprises, as well as to propose a conceptual model of an industry-specific TPS for the metallurgical sector.

To achieve this aim, the following objectives are defined:

A systematic analysis of the scientific literature was conducted to prepare the article. The search and selection strategy was designed to ensure completeness and relevance of the data.

The search was carried out in leading scientometric databases: Scopus, Web of Science, and Google Scholar. To ensure the currency of the study, the publication window was set to 2021-2024. Search queries were formulated in English using the following keywords and their combinations: Toyota Production System AND metallurgy, Lean manufacturing AND steel industry, 6S OR 5S AND heavy industry, operational efficiency AND steelmaking, VSM AND metallurgy.

Inclusion criteria for sources:

Exclusion criteria:

All sources were grouped into several thematic areas to conduct a comprehensive literature review.

Palhau M., Sá, J. C., Ávila P., Dinis-Carvalho J., Rodrigues C., & Santos, G. ( Palhau , Sá, Ávila, Dinis-Carvalho, Rodrigues, & Santos, 2024 ) formulate Toyota Way as the basis of TPS and demonstrate that sustainable growth is ensured by the combination of hoshin kanri, PDCA/kaizen, the discipline of standardized work, and leadership on the line.

Minh N. D. ( Minh, 2023 ) proposes a managerial loop for efficiency improvement based on TPS: loss diagnosis → tool selection (JIT, Jidoka, SMED/TPM) → improvement cycle → verification of metrics (OEE, FPY, WIP, lead time), emphasizing the risks of local optima and the importance of a proper architecture of indicators.

Lara A. C., Menegon E. M. P., Sehnem S., & Kuzma E. ( Lara, Menegon, Sehnem, & Kuzma, 2022 ) conduct a meta-analysis and statistically confirm a positive association between JIT/Lean practices and quality, costs, and lead times. They identify heterogeneity of effects across industries, which is important when transferring TPS to high-capital-intensity thermal processes in metallurgy.

Małysa T., & Furman J. ( Małysa & Furman, 2021 ) using evidence from steelmaking shops show that 5S, visual standards, and standardized work simultaneously reduce muda (motion, waiting) and improve safety by increasing the predictability of operations and eliminating sources of hazards.

Manzanares-Cañizares C., Sánchez-Lite A., Rosales-Prieto V. F., Fuentes-Bargues J. L., & González-Gaya C. ( Manzanares-Cañizares, Sánchez-Lite, Rosales-Prieto, Fuentes-Bargues, & González-Gaya, 2022 ) develop a green 5S strategy for welding processes: they extend 5S checklists with sustainability metrics (waste, energy), linking workplace order to environmental and quality objectives.

Florescu A., & Barabas S. ( Florescu & Barabas, 2022 ) substantiate trajectories of convergence between Lean and Industry 4.0: IIoT sensors, cyber-physical systems, and analytics close the kaizen loop, shorten detection time for deviations, and strengthen pull through more sensitive management of demand and variability.

Price C. R., Nimbalkar S. U., Thirumaran K., & Cresko J. ( Price, Nimbalkar, Thirumaran, & Cresko, 2023 ) show how smart pathways for decarbonization and intensification of thermal processes (heat recovery, heat-transfer intensification, closed loops) integrate with TPS flow thinking, reducing specific energy intensity/CO₂ while increasing the stability of production takt.

Maware C., & Parsley D. M., II. ( Maware & Parsley, 2022 ) systematize barriers to lean transformations: the gap between tools and culture, a deficit of middle leadership, project orientation instead of systemness, weak integration with supply chains. They point to the typical rebound of metrics after pilots in the absence of an established operational routine.

Abu-Salim T. Y., Agarwal P., Abu Elrub E., Haoum L., & Almashgari M. H. ( Abu-Salim, Agarwal, Abu Elrub, Haoum, & Almashgari, 2023 ) using a hybrid ISM–Fuzzy MICMAC hierarchize the causes of Lean Six Sigma failures: leadership, training, and measurability/data are primary; the logic is transferable to metallurgy, where reliable data-collection loops for downtime, quality, and energy are required.

Fridkin S., Winokur M., & Gamliel A. ( Fridkin, Winokur, & Gamliel, 2024 ) introduce a quality degradation index as an early indicator of process drift; the approach is useful for continuous lines (rolling, heat treatment), where predictive warning of deterioration is required before parameters exceed control limits.

The analysis demonstrated that, despite the large number of studies confirming the effectiveness of TPS, certain contradictions and gaps persist. Most works are case studies at individual enterprises and do not offer a universal, systemic implementation model for the entire metallurgical industry. There is a contradiction between the need for rapid adaptation and the high inertia of metallurgical production systems. Issues of the long-term sustainability of implemented changes and methods for integrating soft aspects (motivation, safety culture) with hard production tools within a single system are poorly covered. It is precisely these problems that this study is aimed at addressing.

As research methods used in writing the article, the following were applied: the comparative analysis method to compare various approaches to TPS implementation; content analysis of scholarly publications to systematize knowledge; the systems analysis method to identify interrelationships among elements of the production system; and the modeling method to develop the author’s conceptual model.

The implementation of the Toyota Production System methodology, adapted to the specifics of the metallurgical industry, demonstrates significant improvements in key performance indicators (KPI). An analysis of successful cases and practices described in the scientific literature makes it possible to systematize the achieved results. The foundation for transformation is a comprehensive approach that begins with the introduction of basic principles of workplace organization and personnel engagement, such as 5S/6S, followed by the deployment of more complex tools, such as Kaizen, value stream mapping (VSM), and the Single-Minute Exchange of Die (SMED) system ( Małysa & Furman, 2021 ; Fridkin, Winokur, & Gamliel, 2024 ).

The practical results of implementation can be grouped into several areas.

1) Increased productivity and efficiency of equipment utilization. A central element here is the fight against equipment downtime. Through the introduction of the Single-Minute Exchange of Die (SMED) it is possible to achieve a reduction in changeover time for rolling mills, converters, and casting machines, which directly increases the useful operating time of the equipment. The implementation of autonomous maintenance principles (Jishu Hozen) within the Total Productive Maintenance (TPM) system makes it possible to reduce the number of emergency shutdowns and increase overall equipment effectiveness (OEE).

2) Reduction of defect rates and improvement of product quality. Systematic work to identify the root causes of problems (the 5 Whys method) and the embedding of quality into the process (Jidoka) yield tangible results. At enterprises that have implemented statistical process control (SPC) and quality circles, a reduction in defect rates is observed for such parameters as nonconformity of chemical composition, geometric deviations, and surface defects ( Abu-Salim, Agarwal, Abu Elrub, Haoum, & Almashgari, 2023 ; Maware & Parsley, 2022 ).

3) Optimization of logistics and production flows. The VSM tool makes it possible to visualize and analyze the entire value stream, from ordering raw materials to shipping finished products. The use of VSM to analyze the production cycle of rolled metal makes it possible to identify bottlenecks and reduce total order lead time, primarily by decreasing interoperation inventories and waiting time.

4) Improvement of safety and employee engagement. The extended 6S concept, in which particular attention is paid to safety and security, forms the basis for changing production culture. Companies that systematically implement 6S report a decrease in Lost Time Injury Frequency Rate (LTIFR) and a simultaneous increase in the employee engagement index, measured through anonymous surveys ( Małysa & Furman, 2021 ; Minh, 2023 ).

These results demonstrate that the TPS methodology is not merely a set of tools but a holistic production philosophy capable of fundamentally transforming a metallurgical enterprise.

It is important to note that achieving the described results is associated with overcoming a number of systemic barriers. The analysis conducted has demonstrated that the principal obstacles are:

Overcoming these barriers is directly linked to critical success factors. Successful cases demonstrate that a key role is played by:

Thus, the outcomes of TPS implementation—are not solely the consequence of applying technical tools, but the result of profound organizational transformation.

The literature review and synthesis of the results of TPS implementation in metallurgy indicate that the success of transformation depends not so much on the choice of specific tools as on the systematic and comprehensive nature of the approach. Many enterprises make the mistake of implementing isolated Lean elements (for example, only 5S or only TPM) detached from the overall strategy, which leads to short-term improvements but does not change the system as a whole. The main problem lies in the absence of a connecting link between the company’s strategic objectives, operational improvements at the shop-floor level, and corporate culture.

To address this problem, we propose the authors’ integrated model PM-6S-TPS for metallurgical enterprises. This model (see Figure 1 ) is a three-level system in which each element performs its unique function.

As can be seen from Figure 1 , the first level is project management (based on DMAIC). This is the strategic level that sets the direction and governs change. Any initiative to implement TPS should be considered as a project with clear objectives, timelines, budget, and team. The DMAIC cycle (Define, Measure, Analyze, Improve, Control) is an ideal framework for managing such projects, ensuring their structured nature and the measurability of results.

The second level, the 6S culture and environment, constitutes the foundation of the entire system. Without a clean, organized, and—critically important for metallurgy—safe workspace, it is impossible to expect employees to engage in

improvement processes. In our model, the classical 5S concept (Sort, Set in Order, Shine, Standardize, Sustain) is deliberately expanded to 6S to reflect the specifics of heavy industry. The new elements are defined as follows:

The third level comprises TPS tools. This is the tactical level, a set of specific methods for solving production problems. The choice of tools (VSM, SMED, TPM, etc.) is dictated by the results of Analyze at the project level.

The practical application of the model can be illustrated by a table linking typical metallurgical problems with the proposed solutions within the PM-6S-TPS model. See Table 1 .

Table 2 will be presented below, in which the advantages, limitations, and future trends in the application of the Toyota Production System (TPS) methodology to improve the efficiency of metallurgical enterprises are systematized.

The proposed PM-6S-TPS model constitutes an original contribution to the development of the theory and practice of lean manufacturing in metallurgy. It closes the gap between strategy and tactics, places safety and production culture at the forefront as the foundation for improvements, and offers a structured approach to transformation management. This enables a shift from piecemeal improvements to building an integrated, efficient, and sustainable production system.

For empirical verification and confirmation of the effectiveness of the proposed PM-6S-TPS model, the following pilot testing plan is proposed:

Selection of the pilot area: Select one production area with clearly measurable indicators and known issues (e.g., a strip finishing line or a continuous casting section).

Stage 1: Baseline assessment (1 month). Collect baseline data on key performance indicators (KPI) at the selected area: OEE, defect rate (%), production cycle time, lost time injury frequency rate (LTIFR), and employee engagement index.

Stage 2: Implementation (4 - 6 months).

Stage 3: Results evaluation (2 months). After completion of implementation, remeasure the same KPI. Compare before and after data, perform statistical analysis to confirm the significance of the changes. Conduct anonymous surveys to assess shifts in production culture.

The expected timeframe for pilot project implementation is 7 - 9 months. Successful completion will confirm the operability of the model and enable the development of a roadmap for its full-scale deployment at the enterprise.

Within this study, the stated objective of developing a conceptual model for adapting the TPS methodology to the metallurgical industry was achieved. The analysis of the scientific literature confirmed the relevance and potential effectiveness of lean manufacturing for enhancing the competitiveness of metallurgical enterprises, yet revealed a shortage of systemic approaches that account for the specific characteristics of the industry.

In addressing the first task, the key TPS tools were systematized and the main barriers to their implementation were identified, such as resistance to change, the high inertia of technological processes, and insufficient management engagement. Addressing the second task made it possible to synthesize practical results and confirm that the greatest effect is achieved in improving equipment utilization efficiency, reducing defect rates, optimizing logistics, and improving safety indicators.

The key outcome of the work, addressing the third task, is the proposed original integrated model PM-6S-TPS. It unifies three crucial aspects of transformation: project management as a methodology for change management, 6S culture as the foundation for safe and organized work, and TPS tools as tactical means for eliminating waste. This model confirms the hypothesis that the maximum synergistic effect is achieved precisely through a comprehensive and systemic approach.

The implementation of the proposed model will enable metallurgical enterprises not merely to copy external experience but to build their own production system capable of adaptation and continuous improvement. This will ensure long-term operational efficiency and create a sustainable competitive advantage in the global market.