Machine Tool Operator Research Articles

Behavioral risk factors for the health of machine tool operators as the basis of the company’s social policy

To form a competent social policy of the enterprise, aimed at reducing the risk of chronic non-infectious diseases, early loss of ability to work, information is needed not only about working conditions, but also about the priority behavioral health risk factors for workers. In order to identify the priority behavioral health risk factors for the workers of the machine-building enterprise the characteristics of the lifestyle, information on the awareness and perception of behavioral and occupational health risk factors (by active interviewing method) were obtained. The observation groups consisted of machine-tool workers of the machine-building enterprise with different work experience (Group 1 — ≤5 years; Group 2 — > 5 years). Numerous violations of lifestyle characteristics of machine operators were revealed, priority health risk factors were established: bad habits, low physical activity, violation of quality nutrition, low medical activity. The absence of self-preserving behavior in everyday life and in the workplace was shown. The increase in the prevalence of behavioral risk factors in the dynamics of length of service, and pronounced differences in the understanding of the significance of behavioral and occupational risk factors depending on age have been established. The results justified the need for a differentiated approach to the development of preventive programs to preserve health and longevity of the contingent of workers, taking into account the length of service, age and nature of work.

Application of Chaotic Encryption and Decryption in Wireless Transmission From Sensory Toolholders on Machine Tools

In recent years, several industries have increased their demand for processing precision, automatic detection, and visualization interfaces. Therefore, to keep pace with the Fourth Industrial Revolution, machine tool operators install a large number of sensors on machine tools to obtain more precise physical quantities during processing, and use a variety of sensors to obtain measurements in various situations. However, these additional sensors on machine tools result in complicated wire layouts, which exhibit negative effects on processing. Such problems lead to the birth of wireless data transmission, which is expected to become the new standard in the future. At present, there are more and more interactive integration between relevant embedded system and the machine tool, which allows information communication between each other in the wireless domain. However, generally, the majority of machine tool operators focus on optimizing the sensing conditions during processing, but they disregard the importance of information security. In the current era of the Internet of Things, information security is regarded as a crucial factor. For the wireless communication between the Internet of Things (IoT) equipment for each machine in the machining field, the transmitted data is almost exposed within public space directly due to the loss in constraint and protection of physical wiring. Therefore, such process can easily be intercepted by other devices that capture information on relevant status of the machine, or command messages received by the controller, where intentional individual may possibly control the operating mechanism and progress of entire plant. This leads to theft of relevant secrets in manufacturing technology for the subject company, or intentional shutdown, machine damage and vicious blackmailing attacks. Therefore, introducing the mechanism of safety protection during wireless signal transmission is an inevitable technology to maintain the company interests, and also the necessary study lacking at present. Within the encrypted algorithm under such category, the chaotic system has become the popular option of study based on its characteristic of difficulty in decryption. Therefore, in this study, a signal transmission encryption and decryption system to be used by sensory toolholders during processing was designed. The unpredictability of the chaotic system was utilized, and chaotic synchronization control was used to calculate the encryption and decryption of the key, rendering the key difficult to compromise. Two control methods of the synchronization process were then compared: sliding mode control and proportional-integral-derivative (PID) control. The parameters of the PID controller were calculated using optimization algorithms such as the genetic algorithm, hybrid Taguchi-genetic algorithm, and particle swarm optimization. The experimental results revealed that, compared with the PID control, the sliding mode control featured advantages such as fewer iterations required for synchronization, fewer errors after synchronization, and higher robustness and performance recovery. Thus, the sliding mode control synchronization system was able to generate more complex keys and had superior information security and system stability.

Design of rapid desiccated air-tray dryer machine with ergonomic approach

Occupational Health and Safety is one aspect of increasing work productivity. Increased productivity can be obtained when machine tool operators feel safe and comfortable operating the machine. The study aimed to evaluate the design of a rapid desiccated air-tray dryer using an ergonomic approach with anthropometric methods. Anthropometric data used in the design include shoulder height in standing, arm length when stretched forward, and arm length when stretched sideways. The data obtained were processed and tested for uniformity, data adequacy, and determining percentile. The study results, the length of the existing 170cm machine is close to the recommended size of 175 cm (length of the arm to the side of P50). The height of the existing desiccant tank is 170.9 cm more than the recommended 123.55 cm (shoulder height P5), the height of the existing drying cabinet is 155 cm. Higher than recommended 123.55 cm (shoulder height P5), the door is too wide 72.8 cm. In comparison, side arm span (P5) 64.5 cm, engine setting in squat position (55 cm). a solution that can be done by making a ladder for the process of inserting the desiccant so that the legs can rest higher; make two cabinet doors so that the span of the hands is not too wide; drying cabinet rack and machine setting box are changed to 123.55 height according to shoulder height for comfort when working.

Cases Integration System for Fault Diagnosis of CNC Machine Tools Based on Knowledge Graph

Due to the time-consuming and labor-consuming maintenance required by appealing to service engineers during the diagnosis of CNC machine tool faults, the CNC machine tool fault diagnosis system has become the economical practical choice of intelligent workshop now, which can help CNC machine tool operators quickly locate and eliminate faults. Knowledge graph technology plays a great role in the use of structured data, and has also achieved a certain degree of research progress and good applications in other professional fields. This article focuses on how to extract semi-structured and unstructured fault knowledge from the abundant CNC machine tool fault cases, fault repair manuals and on-site maintenance logs on the market. A complete system is used to integrate this fault diagnosis knowledge with different formats and content but interrelated, so as to realize the structured application of fault diagnosis knowledge of CNC machine tools. This paper first fully analyzes the content and structural characteristics of these fault cases, and optimizes the design of a set of domain ontology for machine tool fault diagnosis, which contains 8 types of ontoly and 7 types of relation. Using the rule-based knowledge extraction method combined with the BiLSTM-CRF information extraction algorithm to extract effective information from this knowledge. Finally, the structured knowledge is stored through the Neo4J graph database for visualization. Under the application of a good ontology, the accuracy and effectiveness of the composite extraction algorithm have been proved to be greatly improved compared with the single information extraction algorithm in the experimental verification process.

Use of bilateral wrist-worn accelerometers to characterize upper limb activity time, intensity and asymmetry of use in physically demanding and sedentary working task

In the present study, we employed wearable accelerometers to characterize the patterns of mono- and bilateral activity of upper limbs (UL) in 46 individuals of a metalworking company (machine tool, fabrication and administrative departments) who were monitored for 4 h of their shift. UL accelerations were processed to calculate minutes of use and vector magnitude counts for both limbs plus several parameters (i.e. magnitude ratio, mono- and bilateral-arm use index) useful for characterizing the existence of asymmetries. The results show that machine tool operators exhibited marked asymmetry of use in favor of their dominant limb and were characterized by the lowest values of mono- and bilateral-arm use index, which indicate a superior use of the dominant limb in movements involving the use of a single or both limbs. Such evidences suggest that the use of wrist-worn accelerometers may provide essential information for assessing the risk of work-related UL disorders.

Random decision forest based sustainable green machining using Citrullus lanatus extract as bio-cutting fluid

The presently employed synthetic cutting fluids in machining applications lead to skin irritations, hazardous aerosols, ingestion etc., to the machine tool operators. Accomplishing sustainable green machining through bio-cutting fluids, is the key motivating factor behind this work, even though the phenomenon of heat generation is inevitable in the machining process. In the present investigation, Citrullus lanatus extract is chosen as a potential candidate for bio-cutting fluid, since it offers multiple benefits such as increased tool life, cleaner production atmosphere, efficacious heat dissipation, healthy operating conditions, etc. Hybrid LM0-6SiCp-4Grp composite is selected for study since; it has potential applications in marine, aerospace, defence and automotive sectors. Experimentation is carried out with Citrullus lanatus extract as bio-cutting fluid in turning of hybrid LM0-6SiCp-4Grp composite under different processing conditions. The presence of green solution based on Citrullus lanatus extract curtails the rise of temperature significantly during turning operation. Higher magnitude of temperature decrease is observed when the percentage of the concentration of Citrullus lanatus extract is increased, irrespective of depth of turning. Bio-nature and cooling qualities of this green-cutting fluid can contribute its share for green machining and sustainable turning environment. The investigations are further progressed using machine learning algorithms based on the different categories of logical regressions implemented through the Python program. Random forest regression shows better results with 99.8% prediction accuracy compared to other machine learning approaches and the decision tree is constructed through the respective regression model. Decision tree has the ability to handle process parameters systematically and predicts the implications of Citrullus lanatus extract in decreasing the temperature at machine-tool interface during machining operation. This tree structured analysis provides a better inference that delivers flexibility in turning parameters and opens up wider options for operation. Thus, decision tree approach ensures optimized usage of production resources and increases the production capacity through judicial selection of cooling approaches associated with the turning process.

Needs, Requirements and a Concept of a Tool Condition Monitoring System for the Aerospace Industry.

In this paper, we describe the needs and specific requirements of the aerospace industry in the field of metal machining; specifically, the concept of an edge-computing-based production supervision system for the aerospace industry using a tool and cutting process condition monitoring system. The new concept was developed based on experience gained during the implementation of research projects in Poland’s Aviation Valley at aerospace plants such as Pratt & Whitney and Lockheed Martin. Commercial tool condition monitoring (TCM) and production monitoring systems do not effectively meet the requirements and specificity of the aerospace industry. The main objective of the system is real-time diagnostics and sharing of data, knowledge, and system configurations among technologists, line bosses, machine tool operators, and quality control. The concept presented in this paper is a special tool condition monitoring system comprising a three-stage (natural wear, accelerated wear, and catastrophic tool failure) set of diagnostic algorithms designed for short-run machining and aimed at protecting the workpiece from damage by a damaged or worn tool.

Virtual reality training platform for a computer numerically controlled grinding machine tool

In-depth training of machine tool (MT) operators is crucial to avoid machine damage due to faulty operation. However, machine-hours are costly and during the training, the MT is unavailable for regular production purposes. Here, virtual real-size models offer a solution by providing basic operation principles to future operators. In this context, it is yet unknown whether a virtual teaching enhanced by real walking is similar to a real teaching scenario regarding the learning efficiency and long-term memory retention. This paper describes a study comparing the learning efficiency of a virtual training session with traditional instructions on a real MT. The learning success of both training groups is objectively and subjectively assessed on a real MT a week later. In this assessment, the task completion time and the number of errors are recorded. We observed that the virtually taught group slightly outperformed trainees taught in reality regarding both objective measurements.

Multi-objective optimization of hard milling process of AISI H13 in terms of productivity, quality, and cutting energy under nanofluid minimum quantity lubrication condition

This paper presents the multi-objective optimization of the hard milling process of AISI H13 steel under minimum quality lubricant with graphite nanoparticle. The cutting speed, feed per tooth, depth of cut, and hardness of workpiece were taken as the process parameters, while surface roughness, cutting energy, cutting temperature, and material removal rate were considered as technological responses. Response surface or Kriging approximate models were applied to generate the mathematical regression models showing the relationship between machining inputs and outputs obtained by physical experiments. Then, multi-objective particle swarm optimization algorithm in conjunction with the Pareto approach and engineering data mining was adopted to figure out the feasible solutions. The research results show that cutting energy can be reduced up to around 14% compared to the worst case. Based on the Pareto plot, the appropriate selection of machining parameters can help the machine tool operator to increase machining productivity and energy efficiency.

Occupational exposures and odds of gastric cancer: a StoP project consortium pooled analysis.

Gastric cancer pathogenesis represents a complex interaction of host genetic determinants, microbial virulence factors and environmental exposures. Our primary aim was to determine the association between occupations/occupational exposures and odds of gastric cancer. We conducted a pooled-analysis of individual-level data harmonized from 11 studies in the Stomach cancer Pooling Project. Multivariable logistic regression was used to estimate the odds ratio (OR) of gastric cancer adjusted for relevant confounders. A total of 5279 gastric cancer cases and 12297 controls were analysed. There were higher odds of gastric cancer among labour-related occupations, including: agricultural and animal husbandry workers [odds ratio (OR) 1.33, 95% confidence interval (CI): 1.06-1.68]; miners, quarrymen, well-drillers and related workers (OR 1.70, 95% CI: 1.01-2.88); blacksmiths, toolmakers and machine-tool operators (OR 1.41, 95% CI: 1.05-1.89); bricklayers, carpenters and construction workers (OR 1.30, 95% CI: 1.06-1.60); and stationary engine and related equipment operators (OR 6.53, 95% CI: 1.41-30.19). The ORs for wood-dust exposure were 1.51 (95% CI: 1.01-2.26) for intestinal-type and 2.52 (95% CI: 1.46-4.33) for diffuse-type gastric cancer. Corresponding values for aromatic amine exposure were 1.83 (95% CI: 1.09-3.06) and 2.92 (95% CI: 1.36-6.26). Exposure to coal derivatives, pesticides/herbicides, chromium, radiation and magnetic fields were associated with higher odds of diffuse-type, but not intestinal-type gastric cancer. Based on a large pooled analysis, we identified several occupations and related exposures that are associated with elevated odds of gastric cancer. These findings have potential implications for risk attenuation and could be used to direct investigations evaluating the impact of targeted gastric cancer prevention/early detection programmes based on occupation.

Principles of "4p medicine" in occupational hygiene: ethical problems (on the example of "machine tool operator in metalworking")

According to studies carried out in recent years, an absolutely new model of health care is becoming more common -the so-called 4P medicine, the medicine of the future. It is based on 4 fundamental principles: Personalization, Prediction, Prevention and Participation. This model is a priority for the entire healthcare system of our country, which includes such branch of preventive medicine as occupational hygiene. At the same time, the principles of «4P Medicine» in occupational hygiene are difficult to achieve due to the complex of ethical problems. The necessity of new methods and regulations's development for governing such research in the conditions of real production is revealed.

Towards sustainable machining of 17-4 PH stainless steel using hybrid MQL-hot turning process

The use of a minimum quantity of lubrication (MQL) with extremely low consumption of lubricant in machining processes has been reported as a technologically and environmentally feasible alternative to conventional flood cooling. In hot machining, the external heat source is applied during machining that will assist to increase machining performance. Many external heating techniques are available and each type has advantages/disadvantages. 17-4 PH stainless steel (AISI630) is martensitic stainless steel, which is widely used in energy equipment, aerospace and petrochemical industries. The objective of the present paper is to integrate MQL technique, for the first time, with a hot turning process for finding an optimum possible hybrid technique for a particular machining process. The effects of different machining parameters on MQL turning of 17-4 PH stainless steel have been investigated in comparison with dry and wet machining processes. Experiments were also designed for machining using MQL and dry techniques to evaluate surface roughness, tool wear, machined surface morphology, chip morphology as well as chip formation mechanism under different pre-heating temperatures. The results show that applying MQL technique with online thermally enhanced turning (MQL-hot turning) increases the efficiency of machining of 17-4 PH stainless steel. The cutting parameters and pre-heating temperature are important parameters and should be selected carefully when using hybrid MQL-hot turning. In addition, machining with MQL is beneficial to the environment and machine tool operator health as lubricant consumption during operation with MQL is 7-fold lower than in the conventional system.

Integration of cutting force control and chatter suppression control into automatic cutting feed adjustment system design

This study designed an automatic cutting feed adjustment system for computer numerical control (CNC) turning machine tools, which integrate the operational characteristics of cutting force control and chatter suppression control to shorten the machining time and maintain the quality of workpieces. The setting of appropriate machining conditions (such as cutting feed, spindle speed and depth of cut) to consider both machining quality and efficiency often causes difficulties for machine tool operators. Therefore, this study uses cutting force control to design an automatic cutting feed adjustment method for cutting tools, and then, the chatter suppression control design is used to modify the cutting force command to suppress cutting chatter. The experimental results of the CNC turning machine tool show that the use of the cutting force control to adjust the cutting feed can shorten the machining time; however, the cutting chatter results in larger surface waviness on the workpiece surface. When the cutting force command is properly modified by actuating the chatter suppression control, the workpiece shows better surface roughness with prolonged machining time. Therefore, the cutting tests demonstrate that the proposed system is feasible for satisfying the machining requirements of the manufacturing processes of mechanical parts for high speed and high accuracy.

Assessment of the safety of use of portable machine tools

The article presents safety issues related to on-site machining with the use of portable machine tools. Their advantage is the possibility of machining elements at places in which they are used. This especially refers to large-size constructions, welded elements and any items whose disassembly is technically difficult. The authors present tasks performed by the operators of portable machining equipment, working conditions, construction and characteristic features of portable machine tools on the example of a portable boring machine, milling machine and flange facing machine. The presented characteristics can influence the safety of work with these machines. The information given in the article were used to asses risk at the position of a portable machine tool operator. The assessment was conducted using the Risk Score method taking into account four stages of using portable machine tools, i.e. transport, assembly/disassembly, machining and maintenance. The result of the conducted risk analysis is the proposal of possible risk reducing actions. Due to the specificity of the operation of portable machine tools which significantly impedes the development of a machine tool which would be safe in and of itself, the proposed actions refer mainly to organisational solutions. The work presents also the thesis that it is possible to decrease the risk at this position thanks to the use of numerical control in a portable machine tool. Such a solution may reduce exposure to some identified threats. The issue is presented on the example of a prototype of a portable flange facing machine developed in the Institute of Mechanical Technology ZUT in Szczecin.

Special Issue on Active and Passive Vibration Damping in Machine Tools

Automation of machine tools has made them more productive, thereby providing an advantage for sustainability and the welfare of mankind. However, in many cases, the successful automation of machine tools requires the avoidance of self-excited chatter vibrations, resulting in a reliable stable state for cutting. Machine tool operators tend to use the machines close to their power thresholds, thereby unknowingly driving them toward the limits of their stability. Much progress has been made in the last few decades concerning the understanding and prediction of such vibrations, and this has led to improvements such as higher cutting rates and chip thicknesses. Several countermeasures such as active and passive damping are available for avoiding chatter vibrations in machine tools. However, their industrial use is not common yet. In fact, the industry is somewhat unfamiliar with many of these countermeasures. The hesitant attitude of the machine tool builders to apply such countermeasures is a result of several factors: active and passive damping devices are additional system components that require design, tuning, and maintenance. Furthermore, they are associated with a risk of failure, resulting in additional down times of the machines. Additionally, if a machine requires such devices to achieve the desired specifications, the customer’s opinion regarding it can be negatively affected. This situation is challenging for machine tool builders, users, and academia as well. Therefore, we decided to dedicate a special issue of IJAT to this topic. This special issue focuses on both active and passive damping measures, particularly the measures that are systematically designed and deliberately implemented to increase the chatter-free depth of cut in machine tools. The papers in this issue identify successful applications or at least a vision for them. Additionally, models demonstrating the effects of the chosen active or passive damping systems are presented. Some of these models can also be used to systematically select the parameters of the system. Some of the systems can be easily applied as low-cost patch-up solutions to improve the behaviors of the machines already in use. I hope that this special issue delivers a valuable overview of the existing approaches to introduce additional damping in machine tools. I would like to sincerely thank all the authors for their dedication and the well written and illustrated manuscripts. I would also like to thank the reviewers for their efforts to ensure the quality of this issue. Finally, I am very thankful to IJAT for their immense cooperation and support. I wish you all the best and hope that you can benefit from the content of this special issue.

The Task of Machine Tool Operators in Small and Medium Enterprises in Indonesia

The needs of operators for each type of industry are different because the type and the complexity of the task is different. Small and medium-sized industries require machine operators with better capabilities than operators in large companies, thus it is necessary to identify what tasks are performed by these operators. This study aim at (1) identifying duties of machine tool operators in small and medium enterprises, and (2) identifying tasks carried out by machine tool operators in small and medium enterprises. This study used a descriptive research method. The participants were eight machine tool operators from five small and medium enterprises in Yogyakarta, Indonesia. The data collection used document review, observation, questionnaires and focus group discussions. The data were analysed using descriptive analysis. The results of the study were (1) five duties done by machine tool operators are identified (maintaining safe work environment, maintaining the machine tools, analyzing the blueprint, performing machining operations, cleaning the machines and the workplace), and (2) twenty seven tasks executed by machine tool operators are identified; twenty-two knowledge and skills, seventeen behaviors, and eighteen machines, tools and equipment required by machine operators.

Experimental investigation into the effects of nozzle position, workpiece hardness, and tool type in MQL turning of AISI 1045 steel

ABSTRACTMinimum quantity lubrication (MQL) is a replacement for dry machining in which a minimum quantity of lubricant fluid is mixed up with compressed air and sprayed periodically on the machining area. In this research the effects of different parameters on the MQL turning of AISI 1045 steel have been investigated to evaluate the cutting force, surface roughness, and tool wear in comparison with the wet and dry machining. The research is aimed to study the effect of the MQL nozzle position, workpiece hardness and tool type on the output parameters. During MQL machining experiments, the nozzles were placed in three different arrangements relative to the tool to investigate the effect of the nozzle position. The effect of workpiece hardness and tool type were also studied experimentally for different lubrication conditions. The results indicated that the MQL system significantly increases the cutting efficiency in AISI 1045 steel machining. The experiments results have also confirmed a significant influence of the nozzle position, workpiece hardness, and tool type on the outputs. Machining with MQL is also beneficial to the environment and machine tool operator health as lubricant consumption during operation with MQL is 7-fold lower than in the conventional system.

Modal analysis of the vertical moving table of 4-DOF parallel machine tool by FEM and experimental test

The vibration of the machine tool has important effect on machining quality of parts. So, in this paper, the dynamic behavior and modal parameters of the vertical moving table of the 4-DOF parallel machine tool are studied using the FEM and experimental methods. The prepared model of the vertical moving table in Solidworks is exported to ANSYS environment. Then, its natural frequencies and mode shapes are extracted using the modal analysis. Then having the FEM results, the exact modal data of the vertical moving table is obtained by the experimental tests. The exciting conditions of the machine tool table are obtained through modeling of machining operations. Finally, the resonance situations of the table are found using the modal data of the table and the cutting parameters of the machine tool. The results of this research can help the machine tool operator to avoid the vibration condition through correct selection of the cutting parameters.

Comparative occupational risk assessment in a CNC machine tool operator position

Abstract Law requires from employers to assess occupational risk in workplaces. A well-executed occupational risk assessment promotes the improve-ment of working conditions and reduces a negative impacts on employees’ health and life. Employers by conducting occupational risk assess-ment not only meet legal requirements but also benefit from it in two ways. They eliminate loss of an enterprise connected with employees’ absence, and they also decrease the probability of high compensation pay due to situations that have a destructive influence on the employees’ health. However, in order to benefit from such actions, firstly, it is necessary to select a risk assessment method properly, then to apply it and implement preventive measures. The paper presents the results of the occupational risk assessment carried out on the example of a CNC ma-chine operator by means three-stage methods in accordance with the PN-N-18001, PHA and Risc Score. Despite the subjectivity of the assess-ment, there were differences in the results. Thus, it is advisable to choose a risk assessment method skilfully, for example by comparing several similar methods.

Experimental investigation on the feasibility of dry and cryogenic machining as sustainable strategies when turning Ti6Al4V produced by Additive Manufacturing

The performances of the cutting fluids have recently been under investigation to drive machining operations towards cleaner and more sustainable targets. Several efforts are being made to test new formulations of coolants and to implement cooling strategies alternative to standard flooding. Cryogenic cooling seems to be an efficient solution to enhance the process sustainability when machining difficult-to-cut metals, such as nickel, cobalt and titanium alloys. Among its several advantages, no contaminants are left on the chips and workpieces, hence reducing the chips disposal costs and limiting skin and breath diseases for the machine tool operators. Furthermore, in case of production of surgical prostheses, it can help reducing the cleaning steps before the final sterilization. The present work investigates the feasibility of using dry cutting and cryogenic cooling in semi-finishing turning of the Ti6Al4V titanium alloy produced by the Additive Manufacturing technology known as Electron Beam Melting when compared to standard flood cooling. For this purpose, the effects of the cutting speed and feed rate on the tool wear, surface integrity, and chip morphology were investigated as a function of the applied cooling strategy. The experimental findings show that the cryogenic cooling assures better performances than dry and wet machining by reducing the tool wear, improving the surface finish and the chip breakability, whereas dry cutting provokes more surface defects and severe tool wear. Therefore, from an environmental point of view, cryogenic machining can represent a sustainable process for manufacturing surgical prostheses made of AM titanium alloys.