Optimizing Carbon Footprint and Operational Productivity of Horizontal Boring Machines: An EFBA-Based Approach

In modern-day industries, the presence of bottleneck processes, where the throughput capacity falls short of the workload, can result in reduced efficiency, increased energy consumption, and higher production costs. Such inefficiencies are deemed unacceptable in today’s highly competitive market, coupled with stringent environmental regulations. To address these challenges, many industries have adopted lean and green manufacturing concepts to enhance workflow and environmental performance. This research paper integrates bottleneck analysis with carbon footprinting, specifically employing the EFBA (Energy Focussed Bottleneck Analysis) approach, to identify and eliminate bottlenecks and high energy consumption within the machining section of a press manufacturing industry. The study focuses on improving the setup time, machining time, and carbon footprint associated with the boring operation of the journal head. By implementing the proposed approach, significant improvements were achieved, with setup time reduced by 108 min, machining time reduced by 64 min, and carbon dioxide emissions reduced by 32.2 kg. These outcomes highlight the effectiveness of the integrated EFBA-based methodology in enhancing operational efficiency and reducing the environmental impact of the manufacturing process. The findings of this study offer valuable insights and practical implications for other industries seeking to optimize their production systems, reduce energy consumption, and minimize carbon emissions. By identifying and addressing bottlenecks through a combined bottleneck analysis and carbon footprinting approach, companies can enhance their operational productivity while promoting sustainability in line with environmental regulations and market demands.


Introduction
In order to sustain market position, it is necessary for every industry to lower its manufacturing cost through continuous improvement efforts.The optimized use of available resources plays an important role for any industry to maximize the benefits from its production efforts (Ghatorha et al., 2021).So, every industry must focus on the review of existing operations of its work processes for the identification of the non-value added activities which results in lowering the efficiency of the resources used.
A bottleneck is the stage of congestion in a work process that occurs when the work load at a particular station of the production process is more as compared to the maximum throughput capacity of that station.A bottleneck has a great impact on the work flow of the production process and will result in sharp increase in the lead time and the cost of manufacturing.Thus, every industry must pay attention to its existing production processes in order to find the hidden bottlenecks and develop the opportunity of increasing efficiency through the application of some lean tools for bottleneck elimination (Ghatorha et al., 2020).The common steps involved in the process of bottleneck analysis are: • Data collection of the existing process: The first step is to record the work flow in the process under study in order to get the detailed data of the operations involved.The work flow is represented in the form of process charts which shows all the operations according to their sequence.
• Estimation of the cycle time: The second step is to record the time taken by each operation of the process through techniques like time study.This information of time taken by the operations will lay the foundation for the identification of bottleneck operations.
• Identifying bottleneck operation: The third step is identification of the operations having highest processing time.The operation with higher processing time in the process affects the total cycle time of the process.If the time taken by that operation can be reduced through some means then it will directly result in saving the overall cycle time of the process.
• Detailed investigation of identified bottleneck operation: The fourth step is related to the detailed investigation of the bottleneck operation identified in the previous step.
The aim of investigation is to find out the waste in the operation which can be minimized or reduced through some means so that the processing time of bottleneck operation may reduce.This step demands a lot of analysis and brainstorming for the identification and reduction of the waste in the operation.
There are several potential solutions to eliminate bottlenecks.The selection of solution will depend upon the type of bottleneck identified during the analysis.Some common options that can be considered to eliminate the bottleneck are given as under: • Addition of workstation or staff to the process identified with low production capacity in the production line.
• Adjusting the work flow through elimination or changing the sequence of a particular process where bottleneck develops.
• Elimination of the non-value added activities involved at the bottleneck process to achieve waste-free smooth work flow.The bottleneck analysis not only improves the current workflow of the production line but helps in building knowledge about the production line which will be beneficial in predicting future bottlenecks in the existing production line.That knowledge will be helpful in the decision-making process as well.
But from past few years, the expansion of industry has led to a significant increase in both the need for energy and carbon emissions (Sagar et al., 2023).And manufacturing is responsible for most of the carbon emissions globally (Bin et al., 2023) but manufacturing sector plays a vital role in driving economic advancement for every nation across the globe (Trevino-Martinez et al., 2022).The use of resources at non-sustainable rate has forced the governments to impose strict environmental regulations on the manufacturing industries to safeguard the environment.Thus, these days any productivity improvement effort without improving environmental performance of the processes involved is incomplete.The scientists and technologists are exploring the creation of eco-friendly and energy efficient options to bolster the manufacturing sector (Farooq et al., 2023).Moreover, the two strategies that are lean and green manufacturing used to improve operational and environmental performances complements each other and produces maximum benefits when applied simultaneously as compared to their application in sequence or individually.
The integration of carbon foot print analysis of any process with the lean tools helps in simultaneous application of the two philosophies that are lean and green manufacturing which results in dual benefits of productivity improvement through cleaner operations.
The integration of carbon footprint analysis with bottleneck analysis is important for achieving comprehensive sustainability improvements in organizational processes.Bottleneck analysis helps identify constraints and inefficiencies that limit overall system performance, while carbon footprint analysis quantifies the environmental impact of activities in terms of greenhouse gas emissions.
By integrating carbon footprint analysis into bottleneck analysis, organizations can identify bottlenecks that have the highest carbon emissions.This allows them to prioritize improvement efforts that not only enhance operational efficiency but also reduce environmental impact.By addressing these carbon-intensive bottlenecks, organizations can achieve dual benefits of improving productivity and reducing their carbon footprint.
Moreover, integrating carbon footprint analysis with bottleneck analysis provides a holistic view of sustainability performance.It helps organizations identify opportunities to streamline processes, optimize resource utilization, and implement environmentally friendly practices.This integrated approach enables organizations to make informed decisions that simultaneously enhance operational efficiency and environmental sustainability.
Furthermore, the integration of carbon footprint analysis with bottleneck analysis aligns with the broader goals of lean and green initiatives.It promotes a more sustainable and responsible approach to operations by considering both economic and environmental factors.This integration allows organizations to optimize their processes and resource allocation while minimizing environmental impacts, contributing to the overall sustainability objectives of the organization.

Background and novelty of the case study
The study took place at a small and medium-sized enterprise (SME) in the press manufacturing industry, located in northern India.According to industry forecasts, there was a promising outlook for future growth.However, the company faced challenges related to expanding production capacity and complying with stricter environmental regulations to enhance operational cleanliness.The company's main focus was on enhancing productivity and environmental performance by examining the current production processes across various manufacturing departments.
Given this context, a case study was conducted within the company to evaluate the existing production processes and identify opportunities for eliminating waste related to efficiency and environmental impact.The study specifically highlights the improvements made in the machining section through the implementation of an integrated approach known as energy-focused bottleneck analysis (EFBA).This approach combines carbon footprint analysis of the production processes with bottleneck analysis to enhance both operational efficiency and environmental performance simultaneously.The implementation of EFBA was specifically applied to the machining operations involved in producing the journal head component.
This research is novel because it involves a unique approach, where the combination of bottleneck analysis and carbon footprint assessment is applied to the machining shafts using a horizontal boring machine, a methodology that has not been previously explored.

Literature review
Bottleneck analysis is a critical component in process improvement and optimization.It involves identifying the stages or resources within a system that limit overall throughput and hinder efficiency.Understanding bottlenecks is essential as they dictate the maximum capacity of a process or system.By pinpointing these constraints, organizations can focus their efforts on resolving them and improving overall performance.Bottleneck analysis helps in streamlining workflows, reducing lead times, minimizing idle resources, and increasing productivity.It enables businesses to allocate resources effectively, prioritize improvements, and enhance customer satisfaction.By addressing bottlenecks, organizations can unlock untapped potential, optimize operations, and achieve higher levels of efficiency and profitability.Below are some of the pertinent case studies: Lan et al., (2009) conducted a study focused to optimize the assembly line of a lamp production company.Analysis of the production process identified bottleneck processes and an unbalanced production line.To address these issues, the MOD method in work study and the ECRS principle were utilized.Implementation of these methods resulted in a streamlined and simplified operating process, reducing the number of workers and improving production line balancing.The yield of the A model lighting assembly line increased from 9.97 to 12.19 pieces.Furthermore, the optimization efforts led to a reduction in the workforce from 21 to 18 employees, resulting in a slight decrease in costs.
Al-Saleh, (2011) focused on enhancing the bottleneck inspection point at a Motor Vehicle Periodic Inspection (MVPI) station by implementing applications to reduce inspection time.Specifically targeting inspection point no. 1, which caused delays in the inspection lanes, the study utilized motion and time study tools, along with ARENA software for simulation and prediction, to explore potential solutions.The suggested alternatives showed a projected improvement of 174.8% in production capacity.The research emphasizes the use of simple methods to optimize work processes in vehicle inspection, including reducing component time, improving flow, and expediting the overall process.Additionally, the costs and benefits of adding an extra inspector were assessed, highlighting a substantial increase in output.By implementing these proposed changes, a significant 174.8% increase in vehicle inspection throughput is anticipated, with minimal or no increase in fixed costs.Kumar et al., (2013) investigated the application of lean manufacturing in the sheet metal industry, specifically focusing on enhancing productivity and meeting customer demands for timely delivery.The study examined M/s ABC, a company involved in manufacturing automotive rims, which has faced productivity challenges.Analysis of the production process and lead time for rim manufacturing reveals that the plant operates at only half of its production capacity due to excessive inventory and work-in-progress.Moreover, low employee morale contributes to decreased production rates.The paper emphasizes the positive impact of implementing lean manufacturing to identify weaknesses and improve lead time.Through data analysis and observations, it was evident that production levels are low in a demotivating environment.Despite having double the operational capacity, intentional slowdowns occur.The paper identifies three specific areas for improvement and proposes strategies to reduce waste and enhance productivity by approximately 50% when implemented comprehensively.
Pisuchpen and Chansangar, (2014) enhanced the productivity of the CR39 plastic vision lens production line through modifications.Techniques such as work study and line balancing were employed to address bottlenecks in the manufacturing process.Standard time measurements revealed productivity gains of 1,257 pieces per day, with labour productivity rising from 82 to 88 pieces per man-hour.However, the production capacity remained below the target level.Three alternative approaches were proposed and assessed using simulation models, with the best scenario involving additional labour and machines at the bottleneck point, resulting in a 44% productivity improvement and reaching the desired capacity of 25,138 pieces per day.Economic analysis indicated a payback period of 2.33 years.This study underscores the potential for improving production line efficiency and meeting customer demands, and future research could explore other cost factors and apply the findings to similar case studies.Duran et al., (2015) performed a study on a tea glass manufacturing firm, specifically examining the work and time aspects of the model production process.Efficiency of tea glass models was evaluated through a time survey, which facilitated the calculation of standardized time.By comparing actual time with standardized time, inefficiencies were identified and necessary improvements were implemented.The study revealed that waiting time negatively impacted the moulder's work, resulting in inefficiencies.However, the application of work and time study techniques increased work/time efficiency by 53%, leading to a model production capacity of 237 units.This research highlights the importance of addressing unavoidable time constraints to optimize production efficiency, enabling businesses to enhance productivity and effectively meet the challenges of globalization and competition.
Pal and Rajoria, ( 2015) conducted a research work to decrease the machining time of a manually operated crankshaft in a small-scale industry.A systematic stopwatch time study was conducted to evaluate the processes and calculate the total time involved.The implemented solutions aimed to optimize manpower utilization, reduce lead time, and lower component costs.The study identified certain operations as bottlenecks, particularly rough turning and grinding.To address this, the research suggested maximizing material removal during turning to minimize grinding time and overall costs.Implementing these recommendations reduced the cycle time from 92.73 to 88.63 min, resulting in a 4.1 min improvement and a 4.42% increase in productivity.
Verma and Sharma, (2017) presented a model for implementing lean manufacturing to enhance productivity and quality in a small-scale industry.The study focuses on addressing waste-related issues, equipment failures, and bottlenecks.Value stream mapping is utilized to identify and understand the problems, and the paper proposes the application of lean tools such as value stream mapping and takt time calculation.By making changes in procedures and layouts, the study achieved substantial reductions in lead time and improved productivity without the need for additional resources or increased work pace.
Saetta and Caldarelli, (2020) introduced a model for implementing lean manufacturing in a small-scale industry to improve productivity and quality.The study focuses on addressing waste, equipment failures, and bottlenecks using value stream mapping and other lean tools.By implementing changes in procedures and layouts, the study successfully reduces lead time and improves productivity without requiring additional resources or increased work pace.The paper also discusses the environmental impact of making the production line more environmentally friendly in a foundry industry.Future work includes analysing different binders, implementing changes for shorter storage times, and exploring lean techniques specific to the foundry industry.
The literature review highlights the significance of lean and green models in various industries.These models aim to integrate lean manufacturing principles with environmentally sustainable practices, ultimately enhancing operational efficiency and reducing environmental impact.Studies demonstrate that implementing lean and green strategies can lead to reduced waste, improved resource utilization, energy savings, and cost reduction.The synergy between lean and green concepts offers a holistic approach to sustainability, addressing economic, environmental, and social dimensions.The literature emphasizes the importance of adopting these models to achieve long-term competitiveness, regulatory compliance, and stakeholder satisfaction, making them vital tools for organizations striving for sustainable and responsible operations.Below are some of the pertinent case studies: Bhattacharya et al., (2019) presented a systematic review on the integration of lean and green concepts in organizational production systems.It concludes that integrating lean and green strengthens performance outcomes, but the impact on sustainability performance varies.Integrative adoption of lean-green has a positive effect compared to individual adoption of lean or green concepts.Contingency factors like organizational culture and leadership support influence the relationship between lean-green integration and sustainable performance.Farias et al., (2019) addressed the lack of structure in understanding the relationship between lean and green manufacturing.Through a systematic literature review of 65 articles, the paper identified performance criteria and practices of lean and green.The findings contribute to a conceptual framework for integrated assessment.The paper suggested future research questions based on the review and framework, aiming to advance knowledge in this area.
Caldarelli et al., (2022) examined the potential integration of lean and green approaches in the construction industry.The findings revealed that restructuring the production system led to significant improvements, including reduced lead times, work-in-process stock levels, waste generation, and costs.The results highlight the benefits of adopting a lean and green approach, which can enhance operational efficiency and sustainability in the construction sector.
Oliveira et al., (2022) presented a research work focused on analysing the adoption of lean and green methodologies in Japanese and Brazilian SMEs within a binational context.By comparing the two, the research identified weaknesses in the observed companies and areas where both efficiency and sustainability levels needed improvement.The methodology employed included the use of the Analytic Hierarchy Process and the Technique for Order Performance by Similarity to Ideal Solution.The findings provide valuable insights for enhancing the integration of lean and green practices in these organizations.Ribeiro et al., (2022) assessed the implementation of the lean and green philosophy in manufacturing firms in Portugal and examined the resulting improvements in operational, economic, and environmental performance.The research employed an exploratory factor analysis using data obtained from questionnaires.Cluster analysis was used to classify the firms.The findings indicated that implementing integrated lean and green practices can lead to enhanced performance.The study emphasizes the importance of adopting a combined approach to achieve better results in terms of efficiency, sustainability, and economic outcomes in manufacturing firms.
The role of carbon footprint in lean and green models is crucial for assessing and managing the environmental impact of organizational activities.Carbon footprint represents the total greenhouse gas emissions, particularly carbon dioxide (CO2), associated with an organization's operations, products, or services.In lean and green models, carbon footprint serves as a key performance indicator to measure and track the environmental sustainability of processes and products.It helps identify areas of high carbon emissions, enabling organizations to prioritize improvement initiatives and implement strategies to reduce their carbon footprint.By integrating carbon footprint analysis into lean and green models, organizations can make informed decisions to optimize resource consumption, minimize waste, promote energy efficiency, and contribute to mitigating climate change.

Methodology used
The stages involved in the methodology adopted to undertake the study are given in the Fig 1 .1.

Data Collection
The case study focuses on a particular industry that comprises three machining sections, each differentiated by capacity, machine types, and the products they manufacture.This specific case study centres on the third machining section, where the industry sought to enhance the shop's capacity.In this section, horizontal boring machines are utilized for crucial operations such as milling, boring, drilling, and turning on various machined components.
The initial stage of the methodology involves gathering data concerning the machining time and carbon footprint associated with the components machined within the studied machining section.The analysis of this collected data reveals that the machining time and carbon footprint for the journal head component significantly surpass those of other components.Consequently, the journal head is recognized as a critical component, prompting the collection of specific data related to its machining operations.Direct observation, method study, time study, carbon footprint calculations, and personal interviews with supervisors and operators are employed to gather the necessary data on the machining operations of the journal head.Subsequently, a machining process chart for the journal head is created based on the information collected during this phase.

Carbon footprinting of processes
The carbon footprint of the machining processes was calculated based on the equation (1) (Choudhary et al., 2019) given below: The CP parameter represents the carbon footprint indicator, expressed in kilograms of CO2 emissions (Kg of CO2) per kilowatt-hour (KWh) of electricity consumption.It is calculated by multiplying the electricity consumption during a machining operation in KWh by the standard emission factor of 0.82 (source: www.cea.nic.in)(Choudhary et al., 2019).The electricity consumption during a machining operation in KWh is determined by multiplying the machining time by the hourly electricity consumption requirement of the electric motor used in the machine.

CP ( )
(1) Based on the data obtained from the company, it was determined that the electric motor utilized in the horizontal boring machines (HBM) consumes approximately 37 KWh of electricity.

Energy process chart preparation and identification of the bottleneck operations
After completing the data collection stage, a machining process chart for the journal head was generated, as depicted in Fig 1 .2.This chart provides a comprehensive overview of the critical stages involved in the machining process.It specifically highlights the total number of operations, setup time, machining time, and carbon footprint associated with the journal head machining.
According to the chart, the machining process of the journal head consists of five operations, all of which exhibit a 100% uptime.These operations primarily encompass milling, turning, boring, grooving, and drilling.Upon analysing the chart, it becomes evident that operations number 2 and 3 exhibit higher machining times and carbon footprints compared to the other operations within the process.Consequently, these two operations were selected for further examination and study.
To delve deeper into the significance of each activity within these two operations, critical examination chart was prepared.This chart aims to provide a better understanding of the importance and impact of each activity involved in operations number 2 and 3.

Critical examination of bottleneck operations
In this section, the critical examination of the bottleneck operations is presented through critical examination charts.

Critical examination chart preparation for operation number 2 and 3:
The activity chart of operation number 2 and 3 was prepared as shown in Table 1.1.This chart shows the activities involved in the machining operations along with their time taken.During the study, it was found that both the operations are similar and have same machining time.So, only one activity chart as shown in Fig 1 .3for both the operations was prepared.

Spot facing 3
Total 423 After the preparation of activity chart, Pareto analysis was done to find the critical activities of the operations.The Pareto chart is shown in Fig 1 .3.From the Pareto analysis it was found that the activity of machining shaft diameter takes bulk of the total time of machining of the journal head.
To further analyse this critical activity in detail, its critical examination chart was prepared as shown in Table 1.2.   .This was due to the limited approach of the boring bar because of the greater thickness of the conventional chuck (including protruding part) which interferes with the shaft after the machining of 90 % of the shaft length.Then in stage 2, the job setup and tooling setup was changed in order to machine the remaining length of the shaft.This was done through a milling cutter and direct spindle machining as shown in Fig 1 .6.This was done through manual control of the machine as the horizontal machine used was not CNC.

Results and discussion
The use of the new holder has increased the approach length of the boring bar for the machining of shaft of the journal head.Due to this improvement, the two extra setups are eliminated in the machining operation number 2 and 3 which has resulted in the saving of 108 min of the total setup time.In addition to this, the machining of the shaft through boring bar and new holder arrangement in single setup has reduced the machining time of the journal head by 64 min.The reduction in the machining time has helped in the reduction of carbon foot print of the process as well.Earlier, in the old method of machining, the total carbon foot print of the journal head machining was 529.5 Kg of CO2 emissions.But the saving of the 64 min of machining time has reduced the carbon foot print of the process by 32.2 Kg of CO2 emissions.The savings obtained through this kaizen are given in Table 1.2.

Conclusion
In conclusion, this research paper demonstrates the successful integration of bottleneck analysis and carbon footprinting using the EFBA approach to improve the carbon footprint and operational productivity of horizontal boring machines in the machining section of a press manufacturing industry.By identifying and eliminating bottlenecks and reducing energy consumption, the study achieved significant enhancements in setup time, machining time, and carbon dioxide emissions.
The findings emphasize the importance of addressing bottlenecks in production processes to enhance efficiency, reduce costs, and meet the demands of a highly competitive market.Additionally, the integration of carbon footprinting highlights the growing importance of sustainability in manufacturing operations, ensuring compliance with environmental regulations and reducing the overall environmental impact.The research contributes to the body of knowledge in lean and green manufacturing by providing a practical framework for optimizing workflow and promoting sustainability.The proposed EFBA-based approach can be applied in various industries to identify and eliminate bottlenecks, reduce energy consumption, and minimize carbon emissions.Thus, this research contributes to the advancement of sustainable manufacturing practices, fostering both environmental responsibility and economic competitiveness.
In conclusion, the integration of carbon footprint analysis with bottleneck analysis is important as it enables organizations to identify and address carbon-intensive bottlenecks, optimize processes, and achieve sustainability improvements in both operational efficiency and environmental performance.This integration supports the overarching goals of lean and green models by promoting a more sustainable and responsible approach to organizational practices.

Future scope of study
The results of the research can serve as a foundation for future investigations into the machining of components with deep bores, particularly when conventional chucks lead to issues related to overhanging.These findings may also be applicable for expanding research in this area.

Fig 1. 2
Fig 1.2 Energy process chart of the journal head

Fig 1. 3
Fig 1.3 Pareto analysis of machining activities

Fig 1. 5
Fig 1.5 Conventional chuck and boring bar

Fig
Fig 1.6 Machining through cutter

Fig 1. 7
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Table 1 .
1 Activity chart of operation 2 and 3