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Abstract. PT XYZ, a wooden furniture manufacturing company, served as the research site for this study which applied the Theory of Constraints (TOC) method to analyze production performance and identify bottlenecks. The company faces capacity imbalances between workstations, resulting in production targets that have not been achieved optimally. Data collection involved direct observation and interviews with related parties in the production area. The analysis was conducted by comparing the required capacity with the available capacity at each production workstation. The findings reveal that solid processing, machining, sanding, assembling, painting, and packing have sufficient available capacities to meet production requirements, thus categorized as non-bottleneck processes. In contrast, the panel processing station is identified as the main bottleneck due to its highest workload among all processes. By implementing the Theory of Constraints, the company can identify major constraints and establish improvement priorities to enhance production flow smoothness. It is expected that improvements in bottleneck processes will increase production efficiency, balance capacity among workstations, and support more optimal achievement of production targets. Keywords: bottleneck; capacity; manufacturing; production performance; theory of constraints   Abstrak. PT XYZ sebuah perusahaan manufaktur furnitur kayu, menjadi lokasi penelitian ini yang menggunakan metode Theory of Constraints (TOC) untuk menganalisis kinerja produksi dan mengidentifikasi bottleneck. Perusahaan menghadapi ketidakseimbangan kapasitas antar stasiun kerja yang menyebabkan target produksi belum terdengar secara optimal. Pengumpulan data meliputi observasi langsung dan wawancara dengan pihak terkait di area produksi. Analisis dilaksanakan dengan membandingkan kapasitas yang dibutuhkan terhadap kapasitas yang tersedia pada setiap stasiun kerja produksi. Hasil penelitian menunjukkan bahwa proses pembahanan solid, machining, sanding, assembling, painting, dan packing memiliki kapasitas yang tersedia yang masih mampu memenuhi kebutuhan produksi, sehingga termasuk kategori non-bottleneck. Sebaliknya, stasiun kerja pembahanan panel diidentifikasi sebagai bottleneck utama karena memiliki tingkat beban kerja tertinggi di antara seluruh proses. Dengan penerapan Theory of Constraints, perusahaan dapat mengidentifikasi kendala utama dan menentukan prioritas perbaikan untuk meningkatkan kelancaran aliran produksi. Diharapkan perbaikan pada proses bottleneck dapat meningkatkan efisiensi produksi, menyeimbangkan kapasitas antar stasiun kerja, serta mendukung pencapaian target output perusahaan secara lebih optimal. Kata kunci: bottleneck; kapasitas; kinerja produksi; manufaktur; theory of constraints

This study aims to analyze the effect of cutting parameters on surface roughness in the turning process of AISI 1045 steel. The investigated parameters include cutting speed, feed rate, and depth of cut. A quantitative approach was employed using multiple linear regression analysis with SPSS software. The dataset consisted of 30 simulated experimental observations with varying cutting parameter conditions. Prior to regression analysis, classical assumption tests including normality, multicollinearity, and heteroscedasticity tests were conducted to ensure the validity of the model. The results indicated that all assumptions were satisfied. The findings reveal that simultaneously, all independent variables have a significant effect on surface roughness with a coefficient of determination of 82.1%. Partially, Feed rate and cutting speed significantly influence surface roughness, while depth of cut does not show a significant effect. Feed rate is identified as the most dominant variable affecting surface roughness, where an increase in Feed rate leads to higher roughness values. In contrast, increasing cutting speed tends to reduce surface roughness. This study highlights the importance of controlling cutting parameters, particularly Feed rate and cutting speed, to improve machining quality. The results provide practical implications for manufacturing industries in optimizing machining parameters to achieve better surface quality and process efficiency.

. The manufacturer's discontinuation of original spare parts for the 149 cm3 two-stroke cylinder block has had a significant impact, resulting in a shortage of products sought by consumers, creating a market gap for local manufacturers to produce spare parts with equivalent and competitive quality. The production objective is to obtain an ADC12 cast aluminum cylinder block with a diameter of 54.5 mm x a stroke of 59 mm. The production method includes: a series of systematic steps of 3D scanning of the cylinder block for geometric accuracy, making a Resin Sand Casting (RSC) mold whose size has been increased due to the shrinkage percentage ADC12-Machining-Pattern removal slope, making a core for the hollow part from RSC material, a melting process using an LPG furnace in parallel stages using 2 RSC molds, natural cooling for about 60 minutes, cutting the casting bowl channel and cutting the riser, T6 heat treatment, and quality and dimensional inspection. The production results are in the form of an ADC12 cast aluminum cylinder block with a diameter of 54.5 mm x stroke of 59 mm, the tensile strength after heat treatment is around 300 MPa, the total production cost is IDR 375,000/unit, and the process duration is 30 minutes/unit which implies that the need for a cylinder block volume of 149 cm3 for two-stroke motorcycles (takt) can be met, so that this type of motorcycle can be used again.

The unavailability of intake and exhaust valves for 500 cm³ diesel engines manufactured in the 1980s has created difficulties in maintaining and operating agricultural tractors. This study aimed to manufacture replacement intake and exhaust valves using SUH 35 austenitic steel according to the original engine specifications. The production process included design preparation, material selection, raw material measurement, forging, machining, heat treatment, quality inspection, and packaging. SUH 35 steel rods measuring 12 mm in diameter and 105 mm in length were used as the raw material. Forging was performed to form the valve heads, producing exhaust valves with a diameter of 30 mm and thickness of 2 mm, and intake valves with a diameter of 35 mm and thickness of 2.5 mm. After machining, the final dimensions of the exhaust valve were 29.5 mm head diameter, 2 mm thickness, 105 mm length, and 7 mm stem diameter, while the intake valve measured 33.5 mm head diameter, 2.5 mm thickness, 105 mm length, and 7 mm stem diameter. Hardening treatment produced a hardness value of 40 HRC. The manufactured valves met the required dimensional and mechanical specifications. The production cost was IDR 100,000 per unit, with a processing time of approximately 60 minutes per unit. The results demonstrate that replacement valves for 500 cm³ diesel engines can be successfully reproduced, enabling the continued operation and maintenance of older tractor engines.

MMP is a metal manufacturing company engaged in casting, forging, and machining processes with a three-shift work system, including night shifts that may increase mental and physical workload due to disruptions in workers’ biological rhythms. This study aims to analyze the mental and physical workload of die casting machine operators during the night shift and to propose improvement measures using the Fault Tree Analysis (FTA) method. The study involved 23 operators, with mental workload assessed using NASA-TLX and physical workload measured using CVL. The results indicate that mental workload falls into high to very high categories, with WWL values ranging from 46.6 to 97.3, where 12 operators experienced very high mental workload. The dominant contributing dimensions were effort, physical demand, and temporal demand. Meanwhile, physical workload ranged from 19.48% to 36.36% CVL, with most operators not experiencing fatigue. Although physical workload remains within acceptable limits, the high mental workload indicates the need for improvements. FTA analysis identified key contributing factors, including work methods, work systems, ergonomics, machine conditions, and the work environment. Proposed improvements include job rotation, improvements in work methods and task distribution, adjustments to the work system, enhanced machine maintenance, and ergonomics-based workplace improvements.

The rolling process is a material forming method that is greatly influenced by the roll rotation speed parameter. Inappropriate rotation variations can cause various defects such as waves, tears, thickness irregularities, and ovalization. This review aims to compare the effect of variations in the roll machine rotation speed on the quality of rolling results on various types of materials, including Al6061-O aluminum plate, rubber sheets, and hollow and pipe-shaped materials. The method used is a literature study by collecting and comparing data on roll speed, defects that appear, deformation results, and process efficiency from several relevant journals. The results of the analysis show that high rotation speeds increase productivity but also increase the risk of defects because the material does not have time to adapt to deformation. Conversely, low rotation speeds produce more stable shapes and minimize defects, but are less efficient for mass production. Each material has a different optimal rotation range, including 23–36 rpm for Al6061-O plate, 45–72 rpm for rubber sheet formation, 24.4 rpm for hollow and pipe rolling, and around 21 rpm for corrugated plate. Overall, this study confirms that rotational speed control is a critical factor in achieving a balance between deformation quality and machining efficiency.

In manufacturing industries, machining processes play a critical role in ensuring product quality, precision, and production efficiency. However, in the production of swing arm parts, the machining process has been identified as a bottleneck due to its non-optimal cycle time. One of the main issues contributing to this inefficiency is the disorganized handling of circlip inner parts. These components are often scattered without a designated placement system, which creates significant difficulties for operators when retrieving and installing circlips onto the swing arm. Such abnormalities disrupt workflow continuity, extend production time, and reduce overall productivity. To address this challenge, a circlip feeder machine was designed as a supporting device to assist operators and streamline the machining process. The design emphasizes efficiency, integration, and systematic operation by utilizing readily available workshop materials. The developed feeder machine is equipped with a robust frame construction and has a storage dimension capable of accommodating up to 200 circlips. In addition, mechanical analysis demonstrates that the feeder structure can withstand a maximum applied force of 31,475 N, ensuring durability and reliability during operation. The introduction of this circlip feeder machine directly impacts the production process by reducing operator workload, minimizing delays caused by disorganized parts, and ensuring faster and more accurate installation of circlips. Consequently, the overall machining cycle time is shortened, thereby improving production flow and enhancing the efficiency of swing arm part manufacturing. Beyond immediate time savings, the use of the feeder machine contributes to better resource utilization, reduced ergonomic strain on operators, and improved consistency in product quality. This study highlights the significance of simple yet effective mechanical innovations in overcoming production bottlenecks and optimizing manufacturing processes in automotive component industries.

This study aims to analyze the factors that influence students' learning motivation in the Lathe Engineering subject in class XI of the Department of Machining Engineering at SMK Negeri 1 Padang. Several variables studied include learning interest, ideals, friendship environment, and family environment, each of which acts as an independent variable, while learning motivation functions as a dependent variable. The method used in this study is quantitative with a correlational approach, where the research sample consisted of 51 students selected using a saturated sampling technique, namely sampling that covers the entire population in the class. The instrument used in this study was a questionnaire with a Likert scale that has been tested for validity and reliability to ensure that the measuring instrument used is able to extract accurate and consistent data. The data obtained were then analyzed using multiple linear regression techniques with the help of SPSS version 26 to determine the effect of each variable on student learning motivation. The results of the study indicate that partially, learning interest and friendship environment have a significant influence on student learning motivation. Students who have a high interest in the Lathe Engineering subject tend to have better learning motivation, and positive relationships with their friends also increase their enthusiasm for learning. In contrast, the variables of ideals and family environment did not show a significant influence on students' learning motivation in the context of this study. Although ideals and family support are often considered important factors in education, the results of this study indicate that external factors such as friendships are more dominant in influencing students' learning motivation. Simultaneously, all four variables significantly influenced students' learning motivation, with the friendship environment being the most dominant factor.

This study aims to analyze the electrical energy consumption of a bench-type drilling machine, RYU RDB 13, by varying machining parameters in the form of spindle speed and feed rate. Electrical energy is a critical aspect of production efficiency in the manufacturing industry, particularly in machining processes that require continuous power consumption throughout the cutting operation. The material used in this study is aluminum 6061, chosen for its lightweight, corrosion resistance, and wide application in the automotive and aerospace industries. The drilling process was carried out using three spindle speed variations: 620 rpm, 920 rpm, and 1280 rpm, along with three feed rate variations: 0.04 mm/rev, 0.08 mm/rev, and 0.1 mm/rev. Current and voltage were measured using a digital wattmeter in real-time, and energy consumption was calculated in wattseconds (Ws) using power calculation formulas. The results indicate that increasing the feed rate and spindle speed leads to higher instantaneous power consumption. However, total energy consumption tends to decrease at higher speed and feed combinations due to shorter machining times. The optimal parameter combination was found at a feed rate of 0.1 mm/rev and a spindle speed of 1280 rpm, which resulted in the lowest energy consumption of 387 Ws and the fastest drilling time. This demonstrates that selecting the right machining parameters not only improves energy efficiency but also maintains or enhances productivity. The observed power consumption pattern typically shows a sharp increase at the beginning of the drilling process, a stable phase during the main cutting stage, and a rapid decrease towards the end of the cut. These findings contribute to a better understanding of the relationship between machining parameters and energy efficiency, serving as a basis for developing sustainable production strategies in the manufacturing sector that prioritize energy savings and cost reduction.

In the manufacturing industry, surface roughness is one of the important quality parameters in machining results, especially in the vertical milling process. This study aims to optimize the concentration of soluble oil coolant and feed rate on the surface roughness of ST 37 steel using the Taguchi method. The material used is ST 37 steel with dimensions of 10 mm × 17 mm × 50 mm, processed using a Dixon XZ7550CW vertical milling machine with a 10 mm diameter HSS endmill. Variations in the concentration of Randocut 500 coolant (3%, 5%, 10%) and feed rate (24, 40, 65 mm/min) were tested with fixed parameters such as a depth of cut of 0.5 mm and a spindle speed of 580 rpm. Surface roughness values (Ra) were measured using a surface roughness tester and analyzed using the Taguchi method and ANOVA. The results showed that a coolant concentration of 5% and a feedrate of 24 mm/min produced the lowest surface roughness (2.24 µm) with the highest S/N ratio (-7.01 dB). ANOVA analysis revealed that feed rate had the most dominant influence (62.4%) on surface roughness, followed by coolant concentration (36.8%). The optimal combination to minimize surface roughness is a concentration of 5% and a feed rate of 24 mm/min..  

Learning activities can run smoothly if accompanied by the availability of appropriate learning media. Learning in the Machining Technology course requires direct practical activities, for example in understanding the use of lathes. The limitations of students' mastery of knowledge when facing the teaching and learning process that tends to be lecture-oriented, causing students' lack of understanding during practice. Learning media that is less interesting causes failure in delivering material, thereby reducing students' interest in learning. This study aims to examine the effectiveness of Real Time Augmented Reality (RT-AR) Lathe media in the learning process of the Machining Technology course in the D-III Study Program, Department of Mechanical Engineering, Faculty of Engineering, Padang State University (FT-UNP). RT-AR media is designed to present interactive visualizations that describe the lathe work process in real time, so that it is expected to improve students' conceptual understanding and practical skills. The study used a quasi-experimental method with a pre-test and post-test design in two groups: the experimental group using RT-AR media and the control group using conventional learning methods. The results showed that there was a significant increase in the learning outcomes of students in the experimental group compared to the control group. In addition, RT-AR media is also able to increase students' motivation and active participation during the learning process. These findings indicate that RT-AR Lathe media is an effective and relevant learning innovation to be applied in vocational engineering education, especially in mastering lathing material.

This study aims to determine the effect of Virtual Reality Box (VR BOX) as a learning medium on students' motivation, interest, and learning discipline in welding practice for grade XI students of the Machining Engineering Department at SMK Negeri 1 Tanjung Raya. The research method used is quantitative with a quasi-experimental design applying the non-equivalent control group design approach. Data were collected through tests and observation and analyzed using validity tests, reliability, normality, homogeneity, t-tests, ANOVA, and coefficient of determination. The results showed that the use of VR BOX significantly influenced students' motivation, interest, and learning discipline. The implementation of VR media created interactive learning, increased student engagement, and reduced fear in welding practice. It can be concluded that VR BOX is an effective instructional medium to improve the quality of vocational practice learning in vocational schools.

This study aims to reveal how symbolic interaction between principals and teachers is interpreted as a social strategy in improving the employability of vocational high school students, especially in the Mechanical Engineering Expertise Competence. Using a qualitative case study approach, the research population was conducted at the Center of Excellence Vocational High Schools in Pasuruan Regency/City, while the sample was 4 vocational high schools that have mechanical engineering expertise competencies. Data collection techniques include in-depth interviews, participatory observation, and documentation studies. The results of the study indicate that the symbolic interaction that occurs is not only verbal communication, but also reflects shared values, expectations, and visions in preparing graduates who are adaptive to the world of work. The principal builds meaning through symbols of consistent leadership actions, such as involving teachers in strategic decision-making and instilling an industrial work culture. Teachers, on the other hand, respond to these symbols with more contextual and work-oriented learning practices. This interaction forms a productive school habitus that is the basis for improving student employability

Abstract ~ The continuous and large-scale transfer of materials in industrial processes is challenging if solely relying on human labor. Therefore, the use of transport machines such as conveyors is essential to support production efficiency. This study focuses on the development of a conveyor system, particularly the conveyor adjuster component used to regulate the slope at the base. The conveyor adjuster is made from SUS 201 steel, a type of steel with 0.15% carbon content, and is formed into various shapes. The manufacturing processes involved include milling to form the surface and set dimensions, turning to shape cylindrical surfaces and threads, welding to join components, CNC machining for mass production and time efficiency, followed by assembly and quality control stages. Machining calculations for the milling process yielded a cutting speed of 478 rpm, a feed rate of 9.56 mm/min, and a feeding time of 2.4 minutes. These results indicate optimized parameters for efficient production. Purpose~ This research aims to design and manufacture a conveyor adjuster to support the efficient and consistent transfer of workpieces in a grinding machine system. Design/methodology/approach~ The study applies a sequence of manufacturing techniques including milling, turning, welding, CNC machining, and assembly. The approach also includes quality control and machining parameter calculations for the milling process. Findings~ The research found that the optimal machining parameters for the milling process were a cutting speed of 478 rpm, a feed rate of 9.56 mm/min, and a feeding time of 2.4 minutes, which are suitable for mass production. Originality/value/Novelty~ This study presents a practical contribution to improving production line efficiency through the design of a custom conveyor adjuster using SUS 201 steel, integrating conventional and CNC machining processes for optimized output.

This research aims to develop and test the feasibility of products in the form of heyzine flipbook-based learning media in the subject of Lathe Machining Engineering class XI at SMK Kemala Bhayangkari 1 Jakarta. This learning media was developed using the R&D (Research and Development) method using a 4D model consisting of define, design, develop, and disseminate. In the process of assessing the feasibility of this learning media, it provides a validation assessment questionnaire instrument to material experts, media experts, and media feasibility tests to students in grade XI of Machining Engineering as respondents. Learning media is validated by experts with a score of 100% for the material aspect, 94% for the media aspect. And for the results of the feasibility trial, the learning media got a score of 91% of the results of the trial of 53 students. From the results of the test, it can be concluded that the heyzine flipbook-based learning media in the Lathe Machining Engineering class XI subject at SMK Kemala Bhayangkari 1 Jakarta is "Very Feasible" to be used for Lathe Machining Engineering learning activities. The focus of this study is at the stage of development and feasibility testing of the developed media only, as for the results of this study, there are several recommendations that can be given, including the following, heyzine flipbook-based learning media can be implemented and utilized optimally in the learning process of Lathe Machining Engineering at SMK Kemala Bhayangkari 1 Jakarta and other schools where there are Lathe Machining Engineering subjects. And heyzine flipbook-based learning media in the subject of Lathe Machining Engineering needs to be further researched such as the effectiveness of heyzine flipbook-based learning media in the subject of Lathe Machining Engineering.

The increasing demand for skilled human resources in the field of automation by the workforce has encouraged vocational education institutions to align their graduates' competencies with industry needs. Students must be equipped with up-to-date skills in line with technological advancements. Currently, the availability of technical expertise programs in vocational high schools (SMK) that include industrial automation curricula is very limited. This situation does not align with the growing industrial demand for SMK graduates with automation competencies, such as wiring and PLC programming skills. Based on these circumstances, this automation system training based on PLC was conducted as part of a community service program. The activity aimed to enhance the skillsets of vocational high school students, particularly in the machining engineering department. The training utilized PLC-based automation systems with Omron CP1E E30-DR-A controllers. The PLC logic programming was performed using CX-Programmer software. The results of the program showed that most participants could grasp the material well. Moreover, all participants gained new insights and skills in industrial automation systems, which serve as valuable support when entering the workforce.

The cylinder block is a housing of cylindrical tubes in which there is a cooling water channel. In these channels there is also the camshaft housing and the bearing seat tube, which is equipped with holes with various threads for attaching other parts that have to do with the cylinder block. One of the components to bind or connect the cylinder block is the Dowel Pin. The function of the Dowel Pin is to lock and close the connection between the engine block, cylinder block and head. Making Dowel Pins using S45C carbon steel material. S45C carbon steel is a medium steel with a carbon content of 0.48% already in rolled form. The process of making Dowel Pins includes, The cutting process is cutting from the initial length of 12 meters to 109 mm. The turning process is a machining process for the workpiece feeding process where the incision is made by rotating the workpiece, in this process a level lathe is carried out with a length of 109 mm and a width of 16 mm, 14 mm, 11 mm, and 7 mm. Drilling process where this process expands / enlarges the plate hole which can be done with a drill rod with a hole diameter of 4 mm. The grinding process is part of the finishing process used to remove parts of the workpiece that are uneven. And finally, Quality Control is done to check whether or not an item is produced.

Choosing a good machine and process to make a particular product requires basic knowledge about all the possibilities that occur during the production process. Therefore, material selection, machine settings and determining appropriate machining parameters need to be optimized to produce quality products. In the milling process, surface roughness is very important. From this surface roughness, an evaluation can be made whether the workpiece is acceptabel or not. The lower the surface roughness of a workpiece, the better the quality of the workpiece. The higher the surface roughness, the lower the performance of the components of the workpiece pair will be because it will increase friction on the components of the machine elements. This research aims to determine the effect of variations in feeding work movement, spindle rotation, and feed depth on the level of surface roughness resulting from conventional milling machining processes. This research also discusses which influences produce optimal surface roughness values in conventional milling machining processes. This research was carried out three times in one combination. Data collection on surface roughness values was carried out horizontally on the surface of the workpiece by taking data three times on the workpiece. The results of the statistical analysis prove that the feeding movement variable is proven to have a significant influence on surface roughness, while the optimum combination for the lowest level of surface roughness can be obtained with a feeding movement of 249 mm/minute (3rd test)

This study aims to provide an overview of the suitability of machining engineering majors in the world of work. When the Covid-19 case is on the increase, especially in Indonesia, many graduates of vocational high schools have difficulty finding jobs according to the majors they are interested in, especially in the field of machining engineering expertise. This research method uses descriptive quantitative methods with field data obtained from the results of questionnaires distributed to vocational high school students in the field of machining engineering expertise so that 33 respondents can be analyzed. The results of the study show that there is suitability and incompatibility in finding work due to the impact of Covid-19, factors that can cause this such as students' lack of understanding of distance learning when affected by the Covid-19 outbreak and remote practicum which hinders the growth of students' competence that should be obtained to enter the world of work. In addition, the lack of information related to the world of work was also felt by students when the Covid-19 outbreak attacked Indonesia. Therefore, this research was conducted to find out how suitable graduates of vocational high schools are in finding jobs and in accordance with what they are interested in in their areas of expertise

The Government's goal to make Indonesia an Maritime Country must be supported by all elements of society, especially is from the education sector. As one of the maritime education institutions to improve competent human resources in its field, it needs training and supporting facilities and infrastructure. One way to increase competence is to supply cadets with capabilities in the field of operation and maintenance of ship machining. Synchronous generator is one of the important components in ship machining. Therefore, the ability to operate and maintain generators is absolutely necessary for cadets in the world of work. Standard selection of generator in the Shipbuilding Laboratory follows Government standards through the Ministry of Transportation Regulations. To choose the best electricity generator, a special method is needed. The solution to this problem is the use of the Analytical Network Process (ANP) to determine synchronous generators that meet the quality standards and specifications of stakeholders.By implementing ANP, the synchronous generator is obtained according to quality standards with the specifications desired by stakeholders. In applying ANP, weighting is based on criteria, namely: durability, maintenance, spare parts, specifications and price. Then obtained an electric generator with appropriate quality standards and specifications.Results of data processing using the ANP method obtained electical generator alternative selection with each weight is adalah CUMMINS GFS-C30KW 41,6 %, HARTECH HT35Y 33,9 %, and CATERPILLAR C2.2 24,5 %.