Scientific Bulletin Series C, Volume XXXV (2021)

The Behavior of the Lubricant Film to Dynamic Stress at a Radial Bearing with HD Lubrication

Ioan Marius Alexandrescu, Radu-Iacob Cotetiu, Adriana-Gabriela Cotetiu

Abstract: The researches regarding the behavior of HD radial bearings in the conditions of operation with shocks and vibrations, are performed considering known the functional characteristics of the bearing in static regime. In the presented experimental research, the functional characteristics of the bearing in static regime are considered known, the measurements focusing on determining the minimum electrical resistance of the lubricant film, which estimates the minimum thickness of lubricant in the bearing.

Keywords: film resistivity, lubricant thickness, bearing

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Reverse Engineering in the Automotive Industry

Mihai George Ardelean, Vasile Năsui

Abstract: Reverse engineering is a method that is used in order to make an improvement of an old component or assembly by taking the old component and measure it, redesign it and then re-execute it with the new modifications. The reverse engineering evolution in the automotive industry in the past years had a major change in the way that the development of new products is done. By using the new technology of 3D scanning, the work of improving or creating a new prototype is more easy, faster and achievable. 3D scanning is the fastest way to make a 3D high precision model of the existing parts and you can modify and simulate them with a dedicated software. After the scanning and modifying is done, you can easily print the new model with a 3D printer. By using a 3D printer, you can choose the material that you want to use for the prototype, materials such like plastic, powders, resins, metal, carbon fiber and so on. The development of the product in the initial phases is easier to be done because you are able to choose any kind of material. By selecting any material and printing it with the 3D printer, it gives the development a great flexibility in the process of improving the product. Using this technology helps all developers to reduce the time of development and also to reduce the costs of the prototype. Using this technology helps the developers to develop faster, cost efficient and more reliable products.

Keywords: 3D printer, 3D Scanner, 3D modeling, material, reverse engineering, automotive

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Novel Sample Creation Methods and Mechanical Modeling of Dry Friction Fibre Reinforced Hybrid Composite Clutch Facings

Roland Biczó, Gábor Kalácska

Abstract: Fibre pull-out among other dangerous failure modes and flammability of modern fibre reinforced hybrid composite dry friction clutch facing materials were considered to examine suitable sample creation methods for such complex and sensitive materials with mechanical material property identifications in mind. Abrasive water jet machining was found to have the smallest mechanical property modifying effect even if moisture levels caused by the method itself are considered. Tensile test according to DIN 53455 has been carried out on test samples cut with 1515 MAXIEM OMAX water jet machine and sorted into three different groups based on their moisture level: moist, dried, and untreated categories. Force-displacement curves prove that the method doesn’t modify the mechanical properties of the samples cut from the fibre reinforced hybrid composite dry friction facings: maximum forces vary among values between 1600 – 2000 N at about 0,7 mm displacement. Samples then are created to examine mechanical material properties of the hybrid composite separately for the fibre reinforcement and the matrix (a short fibre reinforced composite itself) component groups based on the rule of separation, since some elements of the matrix are part of industrial secret. Tensile test, Iosipescu shear test and two directional strain measurements are carried out accordingly for Young’s modulus, shear modulus and Poisson’s ratio respectively. Stiffness matrices created this way are then united in a stiffness tensor of a quasi-laminate via the rule of mixtures. Tough the list of phenomena taken into consideration by this modeling method lacks fibre-fibre adhesion or fibre-matrix adhesion, abrasive water jet cutting is then utilized for thermal property investigation sample and pin-on-disc tribological specimen creation.

Keywords: hybrid composite, stiffness matrix, water jet cutting, clutch facing

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Optimization of Linear Electromechanical Actuators

Ionut Ciprian Birsan

Abstract: This paper includes a part of expression and fundaments of a new concept regarding the improvement of the parameters of linear actuators, experimental research on the dynamic behavior of these systems within all the assemblies where they are used. Optimization of characteristic parameters of linear electromechanical actuators, aimed at raising the parameters characteristic of the actuators, high yields, reliability, tribological optimization, cost reduction, they must be miniaturized, non-polluting, silent, with a low number of moving parts. The main purpose of this research is the development of a modularized family of linear actuators, intended for the operation of high-performance systems specifics to fine mechanics and mechatronics.

Keywords: actuator, electromechanical, efficiency

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Optimization of Production Processes on the Rotary Regenerative Air Preheater

Ciobanu Ioana Arabela, Ciobanu Ana-Maria

Abstract: The recovery of residual heat from the flue gases is significant for improving the efficiency of the unit in power plants. In order to achieve good efficiency, an innovative design for preheating the combustion air for power plants has been proposed. The fundamental aim of the research was to present the benefits modernizing equipment to the existing power plants and to investigate the burning process that have a considerable impact on optimizing the production processes of energy environments. Unlike the conventional air preheating system that uses a rotary regenerative air preheater, the new configuration adopts a cascade heating concept, in which the air obtains heat from the feed water, circulating water and flue gases in several exchangers, tubular heat, which significantly decreases the air, leaks and destruction of exergy. The research has definition technological solutions for accommodation structures that have a
considerable the impact on improving the efficiency of the technological process in thermal power plants and energy fuel. This action can be beneficial for improving the air preheating system and in order to advance energy production.

Keywords: optimization, modernizing equipment, air preheating system, combustion, coal, energy production

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Measuring the Quantities of Water in the Supply Systems to Domestic Consumers Considering the Real Value of the Coefficient for the Repartition of Consumption

Adriana-Gabriela Cotetiu, Radu-Iacob Cotetiu, Ioan Marius Alexandrescu

Abstract: Starting from the observation that specialists observe some measurement deviations that may appear between two measuring systems – respectively between the general water meter from the building (or staircase) and the individual water meters from apartments – this paper presents some causes of this problem by analyzing of the “k” coefficient for repartition of the water consumption. Also the paper work presents theoretical researches regarding the calculation of these quantities of water, the determination of the error closing formula and sharing it the right way, that loss hydraulic among consumers.

Keywords: water consumption, water meter, error closing

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A Comparative Study Regarding Monoblock CNC Milling Processing

Dinu Daraba, Catalin Daraba, Marius Cosma, Gheorghe-Toma Horincar

Abstract: Milling is the processing with the largest share among cutting operations. Temporary and specific optimization of this operation brings significant reductions of the production costs. In the presented paper, authors make a comparative study on the milling machining of a part using the same type of tool, through two different strategies: the classic milling method and the “Vortex” strategy using the monobloc carbide milling cutter.

Keywords: milling, temporary optimization, carbide monobloc milling cutter, “Vortex”

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Study on Obtaining the 3D Model of a Groove Box Cam by the Reverse Engineering Method

Vlad Diciuc, Ioan Pasca

Abstract: Reverse engineering is an important approach used to obtain objects starting from the same new or used physical objects. There are many techniques that are used in this regard and they are chosen depending on the type of part, its functional role and the accuracy with which it is desired to obtain the duplicate. One of the most commonly used copy / multiplication methods is 3D scanning. This paper presents a situation in which 3D scanning was not efficient and recourse was made to the reconstruction based on photography and measurements of a groove box cam, part of a machine tool. The goal was to obtain the 3D model of the part so that later, based on a CAM approach, the necessary part of the machine tool may be obtained.

Keywords: 3D scanning, 3D reconstruction, groove box cam

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Temperature Control of Liquid Working Medium Operated Heating Plates

Viktor Erdélyi, László Földi, János Buzás, János Tóth

Abstract: It is extremely important to be able to produce the right quantity and quality of meat under large-scale conditions. In addition, due to rising energy prices and environmentally conscious thinking, there is an increasing focus on operating with the highest possible energy efficiency and using renewable energy sources. In pig farming, contact heating plates used in piglet nursery are typically using either liquid as working medium or they directly using electric heating solutions. The thermal utilization of solar energy provides an opportunity to reduce the energy needs of liquid working systems from fossil fuels. The main problem with this solution is that the temperature of the heating plates inside the barn can vary depending on the load and other environmental parameters, due to the central control, which impairs the comfort of the animals. This paper examines the possibilities of controlling contact heating pads with liquid as working medium. A block-oriented modelling framework is used for the mathematical models that were validated on a small-scale model.

Keywords: Agriculture, Control, Heating, Modelling

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Lamination of Metal Slat Profiles

Ionut – Aurelian Goloman

Abstract: The present paper is intended to be a brief presentation of the current state of rolling of metal slats profiles. The author presents some theoretical considerations regarding the rolling process in the case of metal slat profiles. The first part of the paper presents the rolling process which is the most common process of plastic deformation of cold metal materials with the help of special equipment called rolling mills. The process having the advantage of an efficient processing of the metallic material, in the conditions of ensuring a good dimensional precision and a qualitative surface. Lamination processing consists in pressing the semi-finished product when passing between two cylinders that rotate in the opposite direction and are characterized by the degree of deformation of the material. When the sheet is bent, the surface inside the bend is compressed and the outside surface is stretched. Somewhere inside the thickness of the sheet is the neutral axis, the axis that does not compress or stretch, remaining the same length throughout the bend. Laminating is suitable for obtaining long pieces with a constant section, which cannot be obtained by other processes, but also for obtaining complicated finished products such as geometric shape. For the calculation of structures made of cold-formed steel profiles, specific calculation rules have been developed. Currently, the latest version is in the form of SR-EN 1993-1-3 from 2007. Also, in the second part of the work is presented the way of protection against corrosion of metal slat profiles and advantages of using cold formed steel profiles. The metal slat is made of galvanized steel and pre-painted in electrostatic field, which gives a high resistance to environmental factors, as well as an increased mechanical resistance. Galvanizing and painting the profiles brings an increased degree of corrosion protection of the element in the environment. An application of a 0.04 [mm] thick layer provides the standard protection required by regulations, ensuring a safe life of the structure of approximately 60 years. The third part of the paper highlighted the advantages of metal slats and the field of use of metal slat profiles, namely the use for fence panels that surround buildings, producing in various assortments of colors and sizes.

Keywords: laminating, plastic deformation, pressing, qualitative surface

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A Review of Abrasive Wear by Coupled Finite and Discrete Element Methods

Shegawu Hailemariam, István Oldal, Gábor Kalácska

Abstract: Abrasive wear is defined as a mode of material removal that is caused by hard asperities or hard particles sliding over soft materials. It is very important in several engineering applications. The goal contribution of this study focuses on the model of friction, wear, and fracture and the coupling model of finite element method /smooth particle hydrodynamic and discrete element method to abrasive wear to the mechanical machines. The study may help researchers to select an appropriate abrasive wear modeling software and wear model.

Keywords: Abrasive wear, DEM, FEM/SPH, Fracture

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Research on the Turning of Technical Polymers

Robert Kovács, Peter Korzenszky, Robert Keresztes

Abstract: Nowadays, the role of plastics has grown tremendously both in our daily lives and in the industry. Virtually everywhere we look, we see plastics. It is sufficient to make plastic parts or other products by injection molding or extrusion in many cases. Today, however, the field of application of plastics has become highly diverse. Often, highprecision fitting may also require for plastics. In such cases, machining may be necessary in many cases, with milling and turning being prominent here. In the case of rotating bodies, turning is most likely the appropriate method of cutting. Even in the turning of steels, it plays a significant role in avoiding flowing chips, but this is a more difficult task for plastics due to the nature of the material. For this purpose, lathes, inserts, and other tools specially developed for cutting plastics are already present in the industry. Of course, here, as in any production process, productivity and economy play a significant role, so it is essential to define and adjust the cutting parameters on machine tools properly. The price of
special plastic processing tools is very high. With a low number, they may not be worth buying, in which case machining tools recommended for other materials, such as softer metals such as aluminum, may be considered. Therefore, we used a lathe insert for cutting aluminum in the research.

Keywords: turning, polymers, plastics, insert

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Possibilities of Use of Statistical Methods in the Technology of Broaching of Internal Contoured Surfaces

Jozef Martinovič, Jozef Peterka

Abstract: The technology of broaching the inner shaped surfaces makes it possible to increase production in the production process. The tools are called broaching mandrels. Broaching tools are shaped tools that have a series of cutting teeth arranged one behind the other, in which the value of the diameter itself increases more and more. Broaching tools have more cutting edges. The final shape of the inner shaped surface is produced in one rectilinear movement of the broaching tool. The use of broaching technology is suitable in series production. The technology of broaching of internal shaped surfaces represents the technology of chip machining of metals and the use of statistical methods makes it possible to monitor the influence of the broaching process on other parameters. This has advantages in solving the experiment, the research itself and in solving the assignment or customer requirements. As a quality management tool in established series production, it is appropriate to use statistical process control methods. The experimental parts were welded parts of two parts, one part was a sheet metal stamping and the other part of the weldment was a round-shaped hub, which is inserted into the central hole of the sheet metal stamping. In the broaching experiment, the influence of the broaching process on another defined weldment parameter of two parts was statistically monitored. Statistical methods are suitable for experimental tests, technical preparation of series production and evaluation of the results of experiments.

Keywords: Broaching, profile shape, statistical methods

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Roghness of Machined Surfaces in the Technology of Broaching Inner Shaped Contours

Jozef Martinovič, Jozef Peterka

Abstract: This paper provides information on research on the technology of broaching of the internal shaped surfaces. This paper provides information on the research on the technology of stretching of internal shaped surfaces. It is a technology that is used in mass production. Our research was focused on machining of internal surfaces. The difficulty of the research was that it involved internal shaped complex surfaces called grooves. At the same time, the research was carried out under mass production conditions. Another problem is that in broaching, low cutting speed is used and therefore oil is commonly used as the cutting medium. The test specimens were intended for further use in assembly. The effect of changing the cutting medium on the roughness of the machined surface of the newly formed grooves was investigated. The experimental conditions consisted of obtaining data directly from a real production broaching process.
Real production conditions were used and the type of cutting medium was varied. So far, oil has been used. Our intervention was to replace the oil with an emulsion. The research hypothesis was based on the fact that if, with sufficient lubricating properties of the emulsion used, the machining process will be satisfactory in terms of the prescribed surface roughness, then considerable financial costs will be saved for this process. The paper documents the occurrences for the roughness of machined grooves as a function of the change in cutting fluids.

Keywords: broaching, broaching tool, surface, roughness

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Modelling and Simulating a Technological Flow Using the FlexSim Application

Nicolae Medan

Abstract: Today, one of the great challenges for any factory is to be flexible enough to produce a wide range of products. Also, to keep production costs under control. In general, the implementation of a technology for the realization of a new product brings with it high costs for refurbishment, production planning, supply logistics, etc. It is necessary to make the right decisions for refurbishment, in the sense that with minimal investment the new product can be made in the quantity, quality and delivery terms established. The FlexSim software models simulates and predicts systems from a wide range, such as manufacturing, warehousing, health, material handling, logistics, etc. FlexSim visualizes and predicts the results that will take place after the change in the production flow. That is why FlexSim is a powerful tool that allows the optimization of a system, before its implementation in the factory. This leads to a reduction in production costs and implementation time of the new type of product. This paper aims to model and simulate a technological flow using FlexSim software, to present the working methodology, benefits and results that can be obtained.

Keywords: simulation, technological flow

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Energy Simulation Based on a Mathematical Model of a Residential Building

Szabolcs Páger, Antal Veres, Gábor Géczi, László Földi

Abstract: In this paper, we have developed a new approach mathematical model for determining the heat loss of a real residential building, which also takes into account the boundary structures used and installed, heat gain from solar radiation, filtration losses, and heat gain from fixtures in the building. Previous approaches did not take into account the different temperatures of each delimiting space and its fluctuations. It was calculated with only a constant temperature. However, during the construction of the model, it turned out that this fluctuation causes a serious discrepancy. The construction documentation of the building was available for the creation of the model, and the built-in materials and structures as well as the geometrical dimensions were also checked on site. Temperature measurements were performed at several points in the living space, in the attic and basement, as well as in the outdoor environment. The measurement results were performed when not in use, so that we could only inspect the building itself, thus ruling out the influence of the wall user. Based on these measurements, model identification will be performed later. This type of approach also takes into account the temperature of the boundary spaces, which were previously ignored, and their temperature fluctuations. The individual characteristic physical elements where the different heat derivations take place have been determined. We wrote the applied mathematical models on these. The aim was to create a mathematical model in which it will be possible to study the hydraulic connections of different heating and cooling systems from the point of view of energy efficiency.

Keywords: Energy simulation, heating, mathematical model, residential building

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Aspects Regarding the Specific Energy and Temperature in Turning of Pure Titanium

Dumitru Panduru, Nicolae Craciunoiu, Emil Nicusor Patru, Marin Bica

Abstract: Pure titanium and their alloys are very used in aeronautical and automotive industry, but also in medicine and other domains, especially due to their high specific strength (strength/density) and excellent corrosion resistance, low conductibility etc., but, in terms of machinability, these materials are very difficult to cut especially due to the low conductibility. As results, a surface quality of the machined parts can be affected. In this paper, in order to appreciate the machinability of these materials the temperature and specific energy are analyze, using different cutting tools (uncoated carbide and ceramics inserts) and different value of the cutting parameters.
All the results are graphically representations and discussion and conclusion about the factors influence are presented.

Keywords: Ceramics inserts, Pure titanium, Specific energy, Temperature, uncoated inserts carbide

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Researches on the Specific Energy and Interface Tool-Chip Temperature During Milling of Aluminum Alloys

Emil Nicusor Patru, Nicolae Craciunoiu, Dumitru Panduru, Marin Bica

Abstract: Due to the importance of aluminum alloys in a various types of industry (automotive, aerospace, naval and maritime, food etc., is important to know the phenomena that occurs in cutting processes of this alloys. One of the most important phenomena is temperature.
For this reason, the main purpose of this paper is to study the thermal aspects in milling of three types of aluminum alloys, both by measuring, using contact method, and calculus of medium temperature at the chip-tool interface as function of the cutting parameters.
For contacts method, six thermocouples, K-type, was used. All the experiments were performed using pre-machining work-pieces, with the drilled holes, necessary for thermocouple installation.
The tools used in this study was carbide end mills and all cutting processes was performed using a conventional milling machine, with digital readout.
The results are graphically representations with discussions and conclusions about temperature and specific energy.
The results show a high values, both for temperature and specific energy, for increasing of cutting speed.

Keywords: Aluminum alloys, Milling, Specific energy, Temperature carbide

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Infill pattern optimization of Fused Filament Fabrication samples for enhanced mechanical properties

Răzvan Cosmin Stavarache, Vasile Ermolai, Marius Ionut Ripanu, Liviu Andrușcă, Marian Mareș, Oana Dodun

Abstract: In recent years, 3D printing has become a manufacturing process used more often in making various parts with functional or non-functional applications. One of the significant factors that influence the manufacturing time and the mechanical properties of printed parts is infill density and their pattern, both factors influencing the manufacturing cost. Printing parts with high filling densities is the most common solution for obtaining high strength parts. In order to reduce the printing time and material usage and maintain the part’s strength, this paper proposes an accessible solution of locally reinforcing the samples by using mesh modifiers to change the inner fill pattern. The research was systematized through a half fractioned factorial setup with five factors controlling the mesh modifier via shape, cross-section, infill grade, infill pattern and extrusion width. The results show that mesh modifiers can significantly increase the tensile properties of regular samples, especially regarding the strain.

Keywords: Fused Filament Fabrication, mesh modifier, local reinforcement, filling pattern, tensile strength

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Influence of Input Factors on Certain Characteristics of the Electrochemical Engraving Process

Ion Surugiu, Margareta Coteață, Laurențiu Slătineanu, Adelina Hrițuc

Abstract: Electrochemical engraving is a process that allows the making of various inscriptions on the surfaces of parts of electroconductive materials. The removal of material from the workpiece occurs due to chemical reactions developed between the workpiece material and an electrolyte in the presence of a direct electric current. Many factors can affect the values of the output parameters of the electrochemical engraving process. The main groups of factors capable of influencing the output parameters of the electrochemical engraving process are the nature and chemical composition of the workpiece material, the shape and arrangement of the workpiece surface to the cathode, some physical and chemical properties of the electrolyte, the shape and the arrangements of the cathode surfaces, duration of the engraving process, etc. Some functional equipment requirements intended to develop experimental research of the process were first formulated to assess the influence exerted by some of the input factors in the engraving process. A test piece and simple equipment designed to meet the functional requirements under consideration were then considered. A planned factorial experiment was designed to highlight the influence of input factors on characteristics that define the results of electrochemical engraving. Empirical mathematical models were generated by the mathematical processing of the experimental result for the modification during the electrochemical processing of some of the test piece zones. These empirical mathematical models provide information on the intensity of the electrochemical processing in different areas of the test piece. Power-type mathematical functions were used for this purpose. The electrolyte concentration, the intensity of the electric current flowing between the electrodes, and the duration of the processing were taken as independent variables.

Keywords: electrochemical engraving, empirical mathematical model, experimental research, input factors, output parameters

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Using the Factorial Experiment to Optimize the Injection Regime of a Coil Body

Aurel Mihail Țîțu, Alina Bianca Pop

Abstract: Nowadays, the statistical processing of experimental or observational data is found in all sciences, from social, medical or economic, to engineering, physics, chemistry, biology or agricultural sciences. This research was developed based on a study conducted within a company whose field of activity is the production of parts from various plastics by injection, for the automotive industry and beyond. The advantage of injection molding is the possibility of obtaining objects with complicated shapes and different sizes, from a very wide range of polymers. The operations are automatic and the machines have a high efficiency. The research method approached in conducting the study consist of the factorial experiment. This paper aims to highlight the optimization of the injection regime of a coil body and thus reduce the waste
resulting from the injection process within the company.

Keywords: injection process, optimization, research method, factorial experiment

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Experimental Assessment of the Wear Preventive Characteristics of Waste-Recovered Biodegradable Total-Loss Lubricants Produced from Sunflower Oil

Petrică Turtoi, Alice Marinescu, Vladislav Cotelea, Traian Cicone

Abstract: Bio-lubricants represent a reliable alternative to classical, petroleum-based lubricants. This paper aims to assess the tribological properties of two bio-degradable lubricants, based on sunflower waste cooking oil. Prior to the tribological tests, the rheo-physical properties of the two lubricant samples were determined. The load-carrying properties of both lubricants were evaluated using a four-ball testing machine by employing methods which covered the load-wear variation and the assessment of extreme pressures. The coefficient of friction (COF) and wear scar diameter (WSD), as well as the influence of lubricant temperature, were evaluated. The results obtained for the bio-lubricant candidates were compared with similar studies from literature, and both tested bio-lubricants were proven to have good potential.

Keywords: biodegradable, four-ball machine, sunflower oil, total-loss lubricants

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Kerf Profile Analysis and Acceleration Modeling Based on Material S235 Thickness CO2 Laser-Cut Sheet Metal Neural Networks

Ciobanu Ana-Maria, Ciobanu Ioana Arabela

Abstract: I believe that laser power, laser cutting speed, position and CO2 pressure with which to cut S235 steel material of different thicknesses have a great contribution to be able to set the best parameters for laser cutting that influences the kerf. I did an experiment to optimize laser cutting with a 4020-watt laser. Three new steps were established to estimate a cutting profile deviation response (KPD) by estimating the total cutting area of the laser cut, characterizing these steps due to the difference between the resulting cutting profile and a straight cut. We concluded that the deviation of the kerf improved by 23.2 for the 2 mm sheet thickness, by 41.8 for the 6 mm sheet thickness, by 13.8 for the 10 mm sheet thickness, by 25.4 for sheet thickness of 15 mm.

Keywords: cutting, kerf, optimization, parameters, S235

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