8 research outputs found

    Usporedba kvalitete površine i životnog vijeka alata pri blanjanju lameliranih elemenata za prozore

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    The quality of the surface of wooden elements, that have been planed, has a crucial importance in the whole production process, since the obtained effects affect the quality of wooden surface after finishing (painting). The occurrence of defects is usually the reason for qualifying a workpiece as scrap or for requiring additional work. This paper presents the selected results of research of the effect of the cutting tool wear on the surface quality of elements after planing. Research experiments were conducted on the SCM Superset Class machine tool. Glulam elements of pine wood (Pinus sylvestris L.) were researched. The raw material samples (semi-finished products), 6 m long before planing, had been machined by suppliers also by planing. These workpieces were selected according to the plant requirements, e.g. their moisture content, straightness, and other defects. This paper presents the measuring results of surface roughness and some examples of surface profiles, as well as the dependence of total length of the planed elements on the type of blade material. From an economic point of view, the results showed that the use of solid carbide blades were more cost effective.Kvaliteta površine drvenih elemenata obrađenih blanjanjem ima presudnu važnost u cjelokupnome proizvodnom procesu jer kvaliteta blanjanja utječe na kvalitetu površine drva nakon završne obrade (nakon bojenja). Zbog nastalih grešaka elementi za prozore najčešće se kvalificiraju kao škart ili se moraju obaviti dodatni poslovi radi uklanjanja tih grešaka. U radu su prikazani odabrani rezultati istraživanja utjecaja zatupljenja alata na kvalitetu površine elemenata nakon blanjanja. Istraživanje je provedeno na stroju SCM Superset Class. Kao uzorci odabrani su lamelirani elementi od borovine (Pinus sylvestris L.). Uzorci lameliranih elemenata (poluproizvoda), duljine 6 m, već su prije eksperimentalnog blanjanja kod dobavljača također obrađeni blanjanjem. Ti su elementi selektirani prema zahtjevima tehnološkog procesa, npr. prema sadržaju vode, ravnosti i postojećim greškama drva. U radu su navedeni rezultati mjerenja kvalitete površine elemenata, kao i neki primjeri profila površine te ovisnost ukupne duljine oblanjanih elemenata o vrsti materijala oštrice alata. Rezultati su pokazali da je s ekonomskog stajališta isplativija uporaba alata s oštricama od tvrdog metala

    Analiza kuta smicanja pri ortogonalnom rezanju borovine

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    The determination of energy effects for wood machining processes, such as cutting power and cutting forces, is very useful in designing of manufacture process of wooden products. A more accurate prediction of cutting forces requires a correct determination of the shear angle value, which can be determined using various models. In this article, shear angle values for an orthogonal linear cutting process of pine wood are determined. The pine wood analysed was represented by two groups of samples with different moisture content levels, 12 % and 20 %. Three different models were used to determine the shear angle values: the Merchant model, which is based on the rake angle and the angle of friction, model based on chip compression ratios and Atkins model based on material properties (elements of fracture mechanics). The values obtained have been analysed for comparison. Results showed that the values of the shearing angles determined from the chip compression ratios turned out to be higher than the values from Merchant equation. The shear angles determined from the Atkins model are, as expected, lower than those determined from the Merchant model. Furthermore, the shear angle values for moisture content of 20 % are higher than for moisture content of 12 %.Određivanje energijskih veličina tijekom procesa obrade drva, poput snage rezanja i sile rezanja, vrlo je korisno pri projektiranju procesa proizvodnje drvenih predmeta. Za točnije predviđanje sila rezanja potrebno je ispravno odrediti vrijednost kuta smicanja, što se može postići primjenom različitih modela. U ovom su članku određene vrijednosti kutova smicanja za ortogonalno linearno rezanje borovine. Analizirano borovo drvo predstavljeno je dvjema skupinama uzoraka različitog udjela sadržaja vode, 12 i 20 %. Za određivanje vrijednosti kuta smicanja primijenjena su tri različita modela: Merchantov model utemeljen na prsnom kutu i kutu trenja; model zasnovan na omjerima kompresije strugotine i Atkinsov model, kojemu su glavna polazišta svojstva materijala (elementi mehanike loma). U radu je prezentirana usporedba dobivenih vrijednosti. Na temelju rezultata uočeno je da su vrijednosti kutova smicanja određene iz omjera kompresije strugotine veće od vrijednosti dobivenih Merchantovom jednadžbom. Kutovi smicanja određeni prema Atkinsovu modelu očekivano su niži od onih određenih uz pomoć Merchantova modela. Nadalje, vrijednosti kuta smicanja za uzorke sa sadržajem vode od 20 % veće su od kutova smicanja za uzorke sa sadržajem vode od 12 %

    Online mjerenje glatkoće površine drva

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    The latest progress in the field of optics and microelectronics resulted in the development of new generation vision systems capable of scanning surface topography with very high sampling frequencies. The blue color of illuminating light as well as novel systems for controlling ultra-thin laser line thickness allows the measurement of the porous surface of wood with a triangulation method. Three alternative sensors were tested here in order to verify their suitability for the determination of surface topography in the industrial environment. The scanning head was installed at the exit zone of the four-side profiling moulder and was set to scrutinize the wood surface shape line-by-line, immediately after profiling. The sensor was also tested for automatic detection of surface defects appearing on the elements after sanding, wetting and painting with various finishing products. The set of pilot test results is presented, together with an original algorithm for real-time surface defects detection.Najnoviji napredak u području optike i mikroelektronike rezultirao je novom generacijom skenera koji mogu skenirati topografiju površine vrlo visokom frekvencijom uzorkovanja. Svjetlost plave boje, kao i novi sustav za kontrolu vrlo tanke laserske zrake omogućuju mjerenje porozne površine drva metodom triangulacije. Testirana su tri alternativna senzora kako bi se potvrdila njihova prikladnost za određivanje topografije površine u industrijskim uvjetima. Glava za skeniranje postavljena je na izlazu četverostranoga profilnoga glodala kako bi se odmah nakon profiliranja pomno linijski skenirala površina drva. Senzor je također testiran za automatsko otkrivanje površinskih grešaka na elementima nakon brušenja, vlaženja i premazivanja različitim premaznim materijalima. Predstavljen je set rezultata pilot-ispitivanja, zajedno s originalnim algoritmom za otkrivanje površinskih grešaka u realnom vremenu

    Surface roughness evaluation in thin EN AW-6086-T6 alloy plates after face milling process with different strategies

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    Lightweight alloys made from aluminium are used to manufacture cars, trains and planes. The main parts most often manufactured from thin sheets requiring the use of milling in the manufacturing process are front panels for control systems, housing parts for electrical and electronic components. As a result of the final phase of the manufacturing process, cold rolling, residual stresses remain in the surface layers, which can influence the cutting processes carried out on these materials. The main aim of this study was to verify whether the strategy of removing the outer material layers of aluminium alloy sheets affects the surface roughness after the face milling process. EN AW-6082-T6 aluminium alloy thin plates with three different thicknesses and with two directions relative to the cold rolling process direction (longitudinal and transverse) were analysed. Three different strategies for removing the outer layers of the material by face milling were considered. Noticeable differences in surface roughness 2D and 3D parameters were found among all machining strategies and for both rolling directions, but these differences were not statistically significant. The lowest values of Ra = 0.34 µm were measured for the S#3 strategy, which asymmetrically removed material from both sides of the plate (main and back), for an 8-mm-thick plate in the transverse rolling direction. The highest values of Ra = 0.48 µm were measured for a 6-mm-thick plate milled with the S#2 strategy, which symmetrically removed material from both sides of the plate, in the longitudinal rolling direction. However, the position of the face cutter axis during the machining process was observed to have a significant effect on the surface roughness. A higher surface roughness was measured in the areas of the tool point transition from the up-milling direction to the down-milling direction (tool axis path) for all analysed strategies (Ra = 0.63–0.68 µm). The best values were obtained for the up-milling direction, but in the area of the smooth execution of the process (Ra = 0.26–0.29 µm), not in the area of the blade entry into the material. A similar relationship was obtained for analysed medians of the arithmetic mean height (Sa) and the root-mean-square height (Sq). However, in the case of the S#3 strategy, the spreads of results were the lowest

    A Critical Reanalysis of Uncontrollable Washboarding Phenomenon in Metal Band Sawing

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    The article analyzes the cutting process of hard bars. Investigations conducted in industrial conditions demonstrated the presence of surface errors in the machined workpieces in the form of washboard patterns. The purpose of this study was to analyze the results of cutting on band sawing machines with different band saw blades. The cutting processes were conducted on three different horizontal band sawing machine types. Analyzed material was an alloy steel Ø40 mm rod with a hardened surface covered with a thin layer of chromium. The hardness of the outer layer was 547 HV with a core hardness of 180 HV. The surface topography measurements of the processed workpieces were carried out with the 3D Optical Profiler, which supplied information on the irregularities of the processed material texture. In each of the analyzed cases, a corrugated surface was obtained after sawing, which is the effect of the occurrence of the washboarding phenomenon, despite the fact that the teeth of each band saw had variable pitches. The washboarding phenomenon when cutting rods with hard surfaces is caused by the phenomenon of wave regeneration. Despite the use of variable pitch saw blades, the cutting process results in rippling of the sawn surface, which is caused by the high hardness of the outer layer of the workpiece, as well as by the type of tool with spring setting of teeth

    Sawing Processes as a Way of Determining Fracture Toughness and Shear Yield Stresses of Wood

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    A new computational model, based on fracture mechanics, was used to determine cutting forces. Unlike traditional computing methods, which depend on many coefficients reflecting the machining of solid wood, the new model uses two main parameters: fracture toughness and shear yield stresses. The aim of this study was to apply this new method to determine these parameters for the tooth cutting edge principal positions and longitudinal and perpendicular cutting speed directions. Samples of beech wood (Fagus sylvatica L.) were sawn. The measurements of energetic effects (cutting power and cutting force) while sawing wood were carried out on two laboratory stands: the sash gang saw and the circular sawing machine. The basic relationships between different sawing methods, such as cutting on a frame sawing machine (sash gang saw) and a circular sawing machine, and the fracture toughness and shear yield stresses were recognizable. The data obtained could be applied to the computation of the energetic effects on other wood cutting methods
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