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STRAIGHTNESS ANALYSIS OF MACHINE TOOL WITH NON-LINEAR KINEMATICS
No full textStraightness of the machine tool affects the accuracy of the workpiece to a great extent. Using wellestablished technics the straightness of linear axis of the machine tools can be determined with a high accuracy. Machine tools with non-linear kinematics are much different in relation to the machine tools with serial mechanisms. It is necessaryto be sure that the existing procedures are appropriate for determining the straightness of machine tools with non-linear kinematics. For that purpose the straightness accuracy of linear axis of a machine tool with socalled O-X glide parallel mechanism, which has non-linear kinematic characteristics, is determined through laser displacement measurements.Editor: Dr Boris Dumnić, full professor, dean
Technical treatment and design: Dr Đorđe Vukelić, full professor
Dr Milana Ilić Mićunović, assistant professor
MSc Aleksandar Milošević, assistan
Kinematics and dynamics
No full textKinematics and dynamics relevant for manipulation, locomotion, postural balance and propulsion in fluids are addressed in this chapter 2. Standard terminology is introduced and several conventional computational and problem-solving techniques are reviewed. The rotation transformation matrix, Rodrigues formula, and Euler angles are also introduced and discussed.These theoretical tools and methods are frequently utilized in Biomechatronics research
CAVITATION RATE OF LASER-SINTERED MS1 STEEL
No full textThe research within this study focuses on analyzing the surface characteristics of samples obtained through laser sintering of MS1 steel powder without subsequent reinforcement (as built). Test samples are produced by an EOSINT M280 machine in a nitrogen environment using the method of Direct Metal Laser Sintering (DMLS). Surface layer characteristics in terms of cavitation resistance were examined using the ultrasonic vibration method according to the ASTM G32 standard. Based on the microstructure of the samples obtained using Scanning Electron Microscopy (SEM), the experiment duration was estimated. The morphology and microstructure of the samples were then examined during and after the experiment, also using SEM. The mass
loss of the samples over time was measured, to calculate the cavitation rate. This research aimed to analyze the potential future applications of laser-sintered MS1 steel powder in the fabrication of machine elements and parts operating under cavitation erosion conditions, due to a series of advantages of the additive manufacturing technology compared to conventional technologies
Dumper Operator’s Workplace Risks: Preliminary Study
No full textThe dumper vehicle is essential for carrying out material handling activities and they are the primary cause of fatal accidents at both construction and mining sites. According to earlier studies, the vast majority of these incidents are caused by the operator’s behaviour. On other side, it is evident that dumper operators are often taking awkward postures and most of them are subjected to high and medium levels of musculoskeletal disorders.Due that fact, the aim of this paper is directed towards preventing accidents and/or incidents in dumper’s operations that originate from the operator’s error and which could be mitigated by the ergonomic adjustment. Specifically, the purpose of this study is to utilize artificial neural networks in order predict the probability of incidents and accidents on the basis of dumper operators’ workplace ergonomic intervention.In this research 40 dumper’s operators participated. Survey started with the 39-item checklist, which is based on prior research and there has been noticed that questions with lowest percent of positive answers are questions related to seat and armrests, so factors such as the seat height adequacy, the seat height adjustability, the seat be horizontal adjustment, the seat back support, the seat lumbar support, armrests availability, armrests height, armrests adjustability, vibrations through the seat, vibrations from the equipment through the floor, vibrations from the equipment through the control devices, the seat attachment to the sub cabin, and possibility to recline and rotate the seat are considered as primary factors in the investigation of the ergonomic adjustment of the dumper operators’ workplace. Poor working conditions originating from organizational factors are also recognized as one of the important focuses of this research. The obtained data were statistically analysed. Surveyed dumper operators came from various age groups and with varied work experience periods in the current study. The research revealed that the average age and height of dumper operator is 36.33 years and 178.35 centimetres, respectively. Moreover, despite the fact that their average weight is 90.33 kg, these body measurements, unlike the others which followed a Gaussian distribution, regardless of the average value indicate that a substantial proportion of operators are overweight and weigh more than 110 kg. In addition, the vast majority of operators in this survey had less than ten years of experience. Regarding the machines, the age of examined dumpers was less than ten years.In order to reduce the likelihood of accidents/incidents and injuries at work resulting from poor seat design, this study uses questions that covers the most significant factors affecting the quality of the working conditions related to the seat and armrests in dumper’s cabin. Furthermore, neural network was trained to predict the likelihood of injuries based on 14 different responses related to the seat and armrest, as indicated by the research's finding that the questions to which respondents provided the worst responses concerned the cabin's seat and armrest. The training dataset consisted of 80% of the obtained data, while 10% was allocated for validation and the remaining 10% was reserved for testing purposes. Used network has one hidden layer with 12 neurons. The neural network underwent training for a total of 16 epochs. The correct classification of 92.5 percent of the data demonstrates a high degree of accuracy in predicting potential accidents/incidents on sites where dumpers operate.Conclusions from the study indicate the need for additional research into an ergonomically optimized workspace for dumper operators in terms of the possibility of resolving identified issues through the further anthropometric surveys and possible application of modern information technologies, such as the installation of sensors, monitoring, and similar solutions.The sample size is a limitation of this study, and additional data collection is ongoing. The proposal for additional research is to collect additional data to increase the reliability of the analysis, and possibly investigate other types of mining machines to determine if similar problems occur with them
Cavitation resistance of refractory coatings
No full textIn this study, the resistance to the cavitation effect of three types of refractory samples based on
talc with the addition of 10%, 15% and 20% cordierite was investigated. Talc has a fine structure,
low hygroscopicity, insensitivity to temperature changes, low coefficient of thermal conductivity,
low coefficient of linear thermal expansion, great ability to stick and coat surfaces, good
grindability, low hardness. Cordierite has high refractoriness, high hardness, high density, low
value of dielectric constant, low coefficient of thermal conductivity, low coefficient of linear
thermal expansion, high resistance to thermal shock, relatively high melting temperature with the
possibility of application up to 1380°C, high inertness towards liquid metal. Cordierite was added
in order to improve properties, primarily to increase resistance to the effect of cavitation. The
prepared mixtures of refractory powders were pressed under a pressure of 1 MPa and sintered at
1200°C.To evaluate the cavitation resistance properties of the investigated refractory samples, the
ultrasonic vibration method with a stationary sample was applied. The change in the mass of the
samples as a function of the cavitation time was monitored and the cavitation speed was
determined. The formation and development of damage to the surface of the samples was
monitored using a scanning electron microscope. The mechanism of degradation and resistance to
the effect of cavitation of the tested samples was monitored by measuring the mass loss and
morphological analysis of the pits formed on the surface of the tested samples. Research has
shown that the addition of cordierite in the composition of the tested samples based on talc
significantly improves the properties of resistance to the effect of cavitation
ПРОЈЕКТОВАЊЕ, ОБРАДА И ИНСПЕКЦИЈА ГЕОМЕТРИЈСКИХ КАРАКТЕРИСТИКА КВАЛИТЕТА КУЋИШТА РУЧНОГ САТА
No full textОвај рад истражује везу часовничарске индустрије са производним машинством и производном метрологијом. Представљен је процес пројектовања ручног сата са свим његовим стандардним и недстандардним компонентама, као и брза израда његовог прототипа методом стереолитографије. Описана је машинска обрада кућишта сата на машини алатки, укључујући одређивање облика и димензија припремка, избор алата и режима обраде. Урађена је и симулација путање мерног пипка за визуелну инспекцију, верификацијa мерне путање и проверa колизије у софтверу „PTC Creo Parametric 8.0“, што је омогућило генерисање и DMIS фајла или улазне датотеке за реалну мерну машину. Резултат рада је пројектован нови ручни сат, машински обрађено кућиште сата и спроведена симулација геометријских карактеристика кавалитета кућишта.This research article explores the connection between the watchmaking industry, manufacturing engineering, and metrology. It presents the process of designing a wristwatch with all its standard and non-standard components and the rapid prototyping of its model using stereolithography. The machining process of the watch case on a CNC machine is presented, including the determination of the shape and dimensions of the workpiece, tool selection, and processing parameters. A simulation of the measurement probe's path for visual inspection, measurement path verification, and collision check was performed using the "PTC Creo Parametric 8.0" software, which enabled the generation of a DMIS file or input file for an actual measurement machine. The result of the work includes the design of a new wristwatch, the machined watch case, and the simulation of the geometric primitives of the wristwatch case
A flexible programming and verification methodology for reconfigurable CNC woodworking machine
No full textAn advanced flexible programming methodology for CNC woodworking machines was developed. As the research starting base, a three-axis CNC woodworking machine was used. The developed methodology is proposed for programming, simulation, postprocessing, and machining by woodworking machine. This flexible programming method integrates the standard programming based on CAD, CAD/CAM systems, and STEP-NC protocol through different output files, enabling data interoperability during the realization of the machining tasks. The control system for the machine is configured based on the open-architecture software LinuxCNC to verify the flexible programming method and the results obtained. Programming verification was realized by simulation on a configured virtual machine in different programming environments and finally on a virtual machine integrated with the control system. The results obtained from the study were evaluated comparatively
Ball bearing life assessment depending on lubricant contamination level
No full textThis paper investigates deep groove ball bearing rating life, focusing on the systems approach to service life calculation according to the ISO 281 standard. The schematic presentation of the systems approach factor (also known as life modification factor) aISO, depending on bearing size and operating conditions is shown in the figure below. Lubricant contamination can accelerate damages and fatigue on the bearing contact surfaces, reducing bearing service life. The paper analyzes the impact of lubricant contamination on bearing rating life, using empirical data and standard formulas. The analytically derived diagrams are presented, illustrating the dependence of the rating life on bearing size and various operating conditions, such as lubricant viscosity, sealing quality, and load intensity. The research results provide a more accurate understanding of ball bearing rating life assessment under real operating conditions
Evaluating the Limit States: A Case Study of a Hull Girder
No full textThis work explores the impact of selecting critical thresholds (i.e., limit states), on the loadbearing capacity of large structures. Using the hull girder of a typical inland navigation barge as a
case study, this analysis evaluates the structure's capacity to endure high loads. Modeled as an open box girder made of steel, comprised of plates and stiffeners, the structure is assessed under the most critical load it encounters: the vertical bending moment (BM). The maximum BM that the structure can withstand is calculated using various limit states commonly selected during the structural design of such objects: yield stress, collapse stress, industry-standard allowable stress, full-plastic stress, the Caldwell approach, the Paik-Mansour approach, and the progressive-collapse analysis [1]. The first three consider linear-elastic behavior, while the latter four involve ultimate (nonlinear) limit states that can lead to hull girder collapse and the loss of load-carrying capacity. Also, buckling phenomena is included in analysis [2]. The results demonstrate the safety margin between linear-elastic and ultimate limit states, emphasizing how the choice of structural criteria can significantly influence the designed load-carrying capacity of large structures
The influence of welding parameters on the geometric characteristics of surface weld metal obtained by handheld laser welding
No full textThe handheld laser welding process is the latest innovation in welding technology with an increasingly broad range of applications primarily due to the simplicity of the welder's training, the minimal influence of the welder on joint quality, the low heat input, the high welding speed, and lower equipment costs. In this paper, the influence of selected welding parameters (wire feed rate and laser oscillation width) on the geometric characteristics of surface welds on low-carbon steel P235 is presented. Additionally, based on the selected optimal parameters, a butt joint was performed by welding plates made of the same base material. The dependence of these parameters on the weld metal width and the weld metal reinforcement was determined. Furthermore, it was concluded that the use of a device with higher power would most likely result in complete root penetration during butt welding