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1

Influence of cutting parameters on the performance of plough during hard rock cutting in coal mining

Palaniappan Sathish Kumar, Chinnasamy Moganapriya, Pal Samir Kumar, Rathanasamy Rajasekar

Journal of Sustainable Mining

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2023

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Vol. 22. iss. 3

185--194

EN

Coal ploughs have proved very successful on many faces in various parts of the world. Recently, there has been a general tendency in longwall working to increase the speed at which the machine progresses along the coal face. An increase in production rate demands enhances either due to depth of penetration or cutting speed. This, in turn, results in increasing power demand and also the force acting on an individual pick. To get maximum efficiency from a cutting machine, a number of parameters need to be investigated. The first and foremost thing of interest is naturally the pick geometry. The cutting force can be expected to depend mainly on the rack angle and clearance angle of the tool. The second parameter is the cutting depth, which when enhanced, increases the rate of advancement and, at the same time, results in enhanced cutting force. This results in large power demand and increases wear of picks. Thirdly, cutting speed, in which higher cutting speed will increase the production rate but at the same time is expected to enhance the power demand and the cutting force. This paper aims at investigating the cutting efficiency of the plough by simulating the coal cutting operation in the laboratory. The effect of three main parameters like pick geometry, cutting depth, and cutting speed, on cutting efficiency have been studied in detail. The cutting force elevates at a faster rate with an increase in depth at higher speeds. The percentage increase in force is nearly 20% for a speed increase of 20%.

2

Probability-statistical estimation method of feed influence on the tangential cutting force under turning

Krupa V., Tymoshenko N., Kobelnyk V., Petrechko I.

Journal of Achievements in Materials and Manufacturing Engineering

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2022

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Vol. 114, nr 1

22--31

EN

Purpose: This research aims to develop the mathematical model and propose a method for estimating the feed stochasticity impact on the tangential cutting force during turning. The main reason for this research is that the existing models for determining the tangential component of the cutting force do not take into account the stochasticity of the feed rate. Design/methodology/approach: Measurements of tangential cutting force during turning on general-purpose lathes with known feed dispersion parameters were made. The mathematical model was developed, and dispersion characteristics (mean value, dispersion and mean square deviation) of the tangential cutting force component depending on the corresponding dispersion characteristics of the feed rate were obtained. The method of assessing the impact of stochasticity of the feed rate on the tangential cutting force is proposed. Findings: As the result of the carried-out investigations, it is proved that the stochasticity of the feed rate affects the dispersion of the tangential cutting force during turning. For specific conditions, the share of feed stochasticity in the dispersion of tangential cutting force component is from 40 to 60% and should be taken into account while prescribing rational cutting modes. Practical implications: The obtained results make it possible to adjust the cutting modes, particularly the amount of feed, under the conditions of real equipment to ensure certain power characteristics of the cutting process to prevent overloads during cutting. This investigation benefits to the establishment of additional factors affecting oscillations in the cutting process. Originality/value: The probabilistic-statistical approach is used in this investigation in order to prove that the stochasticity of the feed rate affects the dispersion of the tangential cutting force component.

3

Nowe podejście do optymalizacji procesów technologicznych na obrabiarki sterowane numerycznie. Cz. 2, Optymalizacja procesu technologicznego poprzez korektę prędkości skrawania

Niesłony Piotr, Jarosz Krzysztof, Löschner Piotr

Stal, Metale & Nowe Technologie

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2021

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nr 3-4

40--47

PL

W poprzedniej części artykułu autorzy skoncentrowali się na przybliżeniu metodologii funkcjonowania dostępnego oprogramowania do komputerowej optymalizacji procesów technologicznych. Poruszona została głównie tematyka optymalizacji procesu poprzez korektę prędkości skrawania vc wraz z potencjalnymi korzyściami płynącymi z optymalizacji procesu pod kątem tego parametru. W kolejnej części artykułu opisana zostanie optymalizacja toczenia poprzez korektę kolejnego parametru technologicznego, jakim jest głębokość skrawania ap.

4

The impact of shearing and flexibility of cultivator tines on the vertical forces value

Owsiak Z., Lejman K., Pieczarka K., Sekutowski T.

Agricultural Engineering

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2018

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Vol. 22, No. 2

69--78

EN

The paper presents the outcomes of the research on the impact of shearing depth and flexibility of cultivator tines with cultivator points on the value of vertical forces acting thereon. The object of the research consisted in "S" tines with the flexibility coefficient of 0.0061; 0.0711; 0.0953 and 0.1406 m·kN-1 . The investigations were carried out in field conditions in sandy clay soil with moisture of 11.2%. The forces were measured for the assumed shearing depths which were 5, 9 and 13 cm at the shearing speed of 3 m·s-1 . A stand for measurement of forces acting on soil shearing tools in the field conditions was used. It was found out that the increase of the shearing depth causes a linear increase of the vertical force, but the force gradient decreases with the growth of the tine flexibility. Moreover, it was found out that the increase of the tine flexibility at the beginning causes the increase and then the decrease of the vertical force regardless the shearing depth. The impact of flexibility on the vertical force value was described with the parabola equation. The tines flexibility, at which the highest value of vertical force may be expected, grows with the reduction of the shearing depth.

PL

Przedstawiono wyniki badań wpływu głębokości skrawania i sprężystości zębów kultywatora zakończonych redliczką na wartości działających na nie sił pionowych. Obiektem badań były cztery esowe zęby o wskaźnikach sprężystości 0,0061; 0,0711; 0,0953 i 0,1406 m·kN-1 . Badania przeprowadzono w warunkach polowych w glebie o uziarnieniu gliny piaszczystej i wilgotności 11,2%. Siły mierzono dla założonych głębokości skrawania wynoszących 5, 9 i 13 cm przy prędkości skrawania 3 m·s-1 . Stosowano stanowisko do pomiarów sił działających na narzędzia rolnicze skrawające glebę w warunkach polowych. Stwierdzono, że wzrost głębokości skrawania powoduje liniowy przyrost siły pionowej zagłębiającej, przy czym gradient siły maleje przy wzroście sprężystości zęba. Stwierdzono również, że wzrost sprężystości zęba powoduje początkowo wzrost, a następnie spadek wartości pionowej siły zagłębiającej niezależnie od głębokości skrawania. Wpływ sprężystości na wartość siły pionowej opisano równaniem paraboli. Sprężystości zębów, przy których można się spodziewać najwyższej wartości siły pionowej zagłębiającej, rosną przy spadku głębokości skrawania.

5

Ocena wpływu naddatku dla obróbki wykończeniowej oraz topografii powierzchni swobodnej na wartość i lokalizację odchyłek

Czerech Ł.

Inżynieria Maszyn

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2012

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R. 17, z. 3

107-118

PL

Wzrastająca dokładność obróbki realizowanej na maszynach CNC powoduje, że coraz częściej powierzchnie obrobione tą techniką nie podlegają dalszej obróbce wykończeniowej i bezpośrednio rzutują na jakość końcową wyrobu. Osiągnięcie wysokiej dokładności geometrycznej wytwarzanych elementów jest problemem, z którym współcześnie spotykają się technolodzy i programiści CAD/CAM. Poniższy artykuł jest częścią pracy dotyczącej badania wybranych parametrów technologicznych obróbki skrawaniem na strukturę geometryczną powierzchni swobodnych wytwarzanych na obrabiarkach CNC. Przedstawiono wpływ wartości naddatku dla obróbki wykończeniowej oraz topografii powierzchni krzywoliniowych na wartość oraz lokalizację odchyłek kształtu.

EN

Increasing machining accuracy realized on CNC machines causes that the more frequently surfaces machined with this technique are not subject to further finishing processing and directly impinge on the final quality of the product. Achieving either geometric accuracy established by the constructor and the repeatability is the problem that modern technologists and CAD/CAM programmers have to faced with. This article is part of the research work of influence of selected machining parameters on geometric structure of the freeform surfaces machined on CNC machine tool. In this paper was presented influence of stock left for finish machining and surface topology on value and the distribution of shape deviations for freeform surfaces.

6

Turning conditions of Ck 45 steel with alternate hardness zones

Stoic A., Kopac J., Ergic T., Duspar M.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 34, nr 1

87-94

EN

Purpose: of this paper is investigation of dynamic impacts on cutting edge during machining of locally hardened steel. Alteration of hardness on a single work piece is a source of impact on tool, which could lead to breakage of cutting tool and work piece surface damage in turning. Influence of material properties (primary hardness) is important when work piece is hardened locally by induction and part of material is soft annealed. Design/methodology/approach: Experimental tests of cutting outputs have been done on specimens after induction hardening to evaluate the rate of variation of cutting forces, surface roughness and chip formation because of hardness alteration. Measured data of main cutting force were analyzed in frequency and time domain. Findings: It was found that chip formation condition, chip thickness and chip shape depends on cutting forces alteration in transition areas in the range of 10 to 15%. Much higher alteration of force signal is recorded when machining is performed with low depth of cutting value as a result of backlash in system. The most important value of cutting force correlates with depth of cutting, and roughness correlates oppositely to the hardness. Research limitations/implications: Results and findings presented in this paper are qualitative and might be slightly different in other cutting condition (e.g. other heat treatable steels or other hardening techniques or other single cutting point processes). There is evident force value alteration in the transition (hard to soft state) zone. Practical implications: Surface roughness is a consequence of both cutting impacts and of tool/work piece loading condition. Originality/value: Originality of the paper is in analysis for stability of turning to heat treatable steel influenced with alternating work piece hardness. It was recorded edge loading shock overcome from hard to soft machining. It was recorded and analyzed self-exited vibration. A new type of chips: horseshoe-type was found.

7

Experimental investigation of dynamic instability of the turning process

Kopač J., Stoić A., Lucić M.

Archives of Computational Materials Science and Surface Engineering

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2009

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Vol. 1, nr 2

84-91

EN

Purpose: Purpose of this paper is consideration of dynamic instability in turning process. There are several sources which lead to instability in turning process (cyclic variation of depth of cutting, inadequate rigidity of machine tool, high passive force component Fp, small tool nose radius and small tool/workpiece contact length, non-uniform stress distribution over contact length). In hard turning, when depth of cutting and feed have low values, lead edge angle and passive force Fp are strongly depend on real time value of depth of cutting. Design/methodology/approach: Experimental tests and numerical modeling of tool/workpiece contact line have been done to evaluate the rate of cutting instability while using and comparing different process monitoring sensors, and acquisition techniques. This data can be used for prediction and compensation of machining errors. Findings: It was found that high chip thickness alteration occurs because of cutting depth vary for a value of some 60 %. Even higher alteration of Fp force signal is recorded when machine tool has inadequate stiffness. Research limitations/implications: Results and findings presented in this paper are qualitative and might be slightly different in other cutting condition (e.g. if wiper inserts are used). Also there are no experiences with coated workpieces or with workpiece material with low deformation energy. Practical implications: Assuming that a hard turning is a semi finishing or finishing process, surface finish is of big relevance. Surface roughness is a consequence of both cutting instability and of tool/workpiece loading condition. Results of test indicates an optimal cutting depth for final pass when minimum surface roughness can be achieved what can be valuable for cutting regime determination. Furthermore, more effective use of the machine tool performances might be achieved. Originality/value: Originality of the paper is in analysis of sources of turning instability (variable depth of cutting combined with lead edge angle and tool nose radius) which lead primary to condition where Fp sensing data does not fit to the normal distribution and secondary to cyclic push-offs of the edge.

8

Dynamic instability of the hard turning process

Kopač J., Stoić A., Lucić M.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 17, nr 1-2

373--376

EN

Purpose: Purpose of this paper is consideration of dynamic behavior of the hard turning process. There are several indicators which could confirm assumption of turning instability (depth of cutting, high ratio of forces Fc/Fp, small tool nose radius, and non-uniform stress distribution over tool/workpiece contact). Lead edge angle and passive force Fp are strongly depend on depth of cutting in hard turning what additionally increase instability. Design/methodology/approach: Numerical calculation and experimental tests have been done to evaluate the rate of cutting instability while using and comparing different process monitoring sensors, and acquisition techniques based on PC platform. Findings: It was found that high chip thickness alteration occur because of cutting depth vary for a value of some 60% and even more if Fp force signal is analyzing when machine tool has inadequate stiffness. Research limitations/implications: Results and findings presented in this paper are qualitative and might be slightly different in other cutting condition (e.g. if wiper inserts are used). Also there are no experiences with coated workpieces or with workpiece material with low deformation energy. Practical implications: Assuming that a hard turning is a semi finishing or finishing process, surface finish is of big relevance. Surface roughness is a consequence of both cutting instability and of tool/workpiece loading condition. Results of test indicates an optimal cutting depth for final pass when minimum surface roughness can be achieved what can be valuable for cutting regime determination. Furthermore, more effective use of the machine tool performances might be achieved. Originality/value: Originality of the paper is in analysis of sources of turning instability (variable depth of cutting combined with side edge angle and tool nose radius) which lead primary to condition where Fp sensing data does not fit to the normal distribution and secondary to cyclic push-offs of the edge.

9

Wpływ głębokości skrawania na stan naprężeń w pile taśmowej bez końca

Wojnarowski J., Kaczmarczyk J.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2005

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z. 29

505-510

PL

W pracy przedstawiono analizę stereomechaniczną ostrzy piły w ustalonym procesie cięcia przy zmiennej głębokości skrawania. Obliczenia numeryczne przeprowadzono przy użyciu metody elementów skonczonych wykorzystując system komputerowy MSC/Patran z modułem liczącym MSC/Nastran. W procesie modelowania uwzględniono nieliniowości geometryczne wynikające z faktu styku (kontaktu) powierzchni skrawającej modelu wycinka piły z modelem wycinka materiału obrabianego. Wybrane wyniki obliczeń zestawiono: na rysunkach, graficznie na wykresie i w postaci barwnej mapy naprężen Hertza.

EN

In the paper, the stereomechanic analysis of cutting edges of a band saw in established cutting process with variable depth of machining was presented. The numerical calculations were carried out with the finite element method using the computer system MSC/Patran with the computational module MSC/Nastran. In modelling process, the geometrical nonlinearities coming from the fact of a contact of cutting surface of the band saw sector model with the machining material sector model were taken into consideration. The selected results of numerical calculations were put together: in figures, graphically in a diagram and in the form of a colourful map of Hertz's stresses.