In the paper, the influence of the electrodischarge dressing methods of superhard grinding wheels on shaping their cutting ability are presented. The results of research concerning the influence of dressing conditions using a stationary electrode, rotating electrode and segmental tool electrode on shaping the cutting ability of the superhard grinding wheels are reported. The cutting ability of superhard grinding wheels is assessed using an external tester made of titanium alloy Ti-6Al-4V (with a thermocouple) to determine the grinding temperature and the relative volumetric grinding efficiency of the tool. The results of the research reveal the diversified usefulness of the analyzed methods. At the end of the article application conclusions concerning the adaptation of developed methods of electrodischarge dressing in the industry are formulated.
The paper presents a new, multi-criteria method which allows the numerical evaluation of the machining process in terms of efficiency, quality and costs. Three indicators were developed to assess the operational properties of grinding wheels. Their values are determined on the basis of the results of short grinding tests carried out on a special test stand. The evaluation of the proposed indicators is described. Furthermore, the application exemple of this method in determining the grinding wheel’s operational properties is presented. In the research, the vitrified alumina oxide grinding wheels were used for grinding of constructional and tool steels of various hardness. The results of the experiments show that the proposed indicators are an effective tool for assessing the process and results of grinding for a specific grinding wheel and material within certain tested grinding parameters range. The study also showed that the differences in indicators’ values, observed during tests of grinding specific material type using grinding wheels with different properties, are useful for optimizing the choice of tool type and machining conditions.
This article presents the results of a study of the performance characteristics of ceramic grinding wheels during peripheral grinding of flat surfaces carried out using different methods of supplying cooling and lubricating fluid (coolant). In the study, T1 type grinding wheels were used, differing in the type of abrasive used in their construction. The abrasive consisted of mixtures with different volume percentages of: 1) grains of conventional white electro-corundum, 2) grains of submicrocrystalline sintered corundum produced by sol-gel technology, 3) microcrystalline sintered ceramic grains with RECERAMAX™ RT microclasters from RECKEL. Specimens made of 145Cr6 tool steel (60±1 HRC) were ground using coolant feeding by flood method and MQL (Minimum Quantity Lubrication) method. During the study, the components of grinding force (F n , F t ), radial loss of the grinding wheel and roughness of the ground surface were measured, which made it possible to determine the volumetric wear of the grinding wheel V s , the total grinding power P, and then calculate the grinding indicators G and K s . The obtained values of the G index indicate that, regardless of the type of grinding wheel used, a higher relative grinding efficiency was obtained during grinding with the delivery of coolant by the MQL method. The highest values of this index were obtained in the case of the grinding process carried out with a grinding wheel containing RECERAMAX™ RT abrasive. The K s index confirmed the best performance of the mentioned grinding wheel. Since its value also depends on the total grinding power P and the surface roughness parameter Ra, the grinding process carried out with this grinding wheel is additionally characterized by a better quality of the obtained surface and lower energy consumption.
The subject of research was two kinds of ceramic grinding wheels for machining of holes made of different kind of applied abrasive grains: GE cBN550 and GE cBN100. Operational properties of grinding wheels have been carried out using internal grinding method of holes of bearing rings. In the article the roughness parameters of holes and volume of machined material achieved in different speed of radial feed of grinding wheel has been depicted. It has been ascertained, that in range of applied conditions of grinding process, operational properties of investigated grinding wheels have had very similar values. KEYWORDS: polycrystalline cBN grains, glass crystalline binder, internal grinding, machining Dynamiczny rozwój nowych technologii i materiałów przeznaczonych np. dla przemysłu lotniczego oraz motoryzacyjnego, uzasadnia przyspieszenie prac badawczych nad narzędziami ściernymi do ich obróbki. Aktualnie w obróbkach wykończeniowych coraz częściej dostrzega się konieczność wykorzystania materiałów supertwardych. Świadczą o tym wyniki prac badawczych publikowanych na łamach czasopism z całego świata, dotyczące eksploatacji nowoczesnych ściernic wykonanych z różnych odmian polikrystalicznego cBN [1,2]. Przy projektowaniu takich narzędzi pod uwagę należy brać nie tylko różne odmiany ziaren ściernych, ale także właściwości spoiw ceramicznych. Właściwości te mogą być modyfikowane dzięki wykorzystaniu nowoczesnych materiałów szklano--krystalicznych z różnych układów szkłotwórczych [3÷5]. Zakres wykorzystania narzędzi z cBN ze względu na wysokie koszty ich zakupu jest wciąż niewielki. Obniżenie kosztu i/lub zwiększenie trwałości może przyczynić się do powszechniejszego ich stosowania. Wydłużenie czasu zachowania przez ściernicę z cBN zdolności skrawnej można osiągnąć, m.in. redukując erozję ziaren ściernych poprzez nanoszenie na ich powierzchnię powłok ochronnych [6,7]. Autorzy niniejszej pracy upatrują możliwość zwiększe-nia produktywności operacji szlifierskich wykonywanych ściernicami z cBN poprzez konstrukcję nowych, tańszych ściernic i pełne wykorzystanie potencjału skrawnego zastosowanego w ich budowie ścierniwa supertwardego. Metodyka eksperymentuBadania miały na celu wstępną ocenę celowości wykorzystania tańszej odmiany ziarna ściernego cBN do zastosowań, w których obecnie często wykorzystuje się droższe odmiany cBN. Przedmiotem badań były ścierni-ce wykonane z dwóch odmian polikrystalicznego ziarna ściernego: cBN550 oraz cBN100 firmy GE Superabrasives ze spoiwem szklanokrystalicznym opracowanym w Zakła-dzie Podstaw Nauki o Materiałach i Ceramiki Technicznej Politechniki Koszalińskiej. Jako wypełniacz zastosowano ziarno elektrokorundowe 99A firmy Norton. Wykonano ściernice A i B o charakterystykach: A: 1-30 × 20 × 10 cBN550 B126 C100 Q6 VA; B: 1-30 × 20 × 10 cBN100 B126 C100 Q6 VA. Obróbka termiczna ściernic prowadzona była w następujących warunkach: A -980 °C/2h, B -1000 °C/2h. Temperaturę i czas obróbki wyznaczono na podstawie wartości kąta zwilżania określonego przy uży-ciu mikroskopu wysokotemperaturowego firm...
In the paper the range of requirements concerning grinded surface layers for deposition of protective PVD coatings on magnesium alloys has been presented. Also difficulties concerning the preparation of surface layer and literature review have been depicted. For solving of the problems concerning proper preparation of magnesium alloy surface layer the conventional grinding process using ceramic grinding wheels and the process of cleaning of CSGW during machining has been applied. The machining parameters has been determined and the surface geometrical structure has been assessed using optical profiling in 3D configuration.
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