The results of grinding are highly dependent on conditions of workpiece removal process. The material is removed by an unspecified number of abrasive grains of irregular shape and random distribution on the grinding wheel active surface. The interaction between the abrasive grain and the workpiece can be divided into three stages: (i) rubbing, (ii) ploughing and (iii) chip formation. Reciprocal contribution of each stage is dependent on the properties of the workpiece, the grinding parameters, the friction condition between the abrasive grain and the workpiece and the shape of the grains. In the article, the results of numerical and experimental process in the analysis of grinding of Ti-6Al-4V titanium alloy, using a conventional grinding wheel and a newly developed grinding wheel with aggregates of grains, were presented. The analysis of influence of the geometric parameters of the abrasive aggregates and the abrasive grains on the effectiveness of the workpiece removal process is presented. The effects of the geometrical parameters of grains and abrasive aggregates in direction of motion as well as in transversal direction on the size of ridges were determined. It has been observed that increase of the length of sideway material displacement results in the decrease of ridge formation. The results of a numerical analysis were confirmed by experimental research. The analysis of the impact of utilization of abrasive aggregates on the grinding forces, grinding-specific energy and surface roughness was performed. The impact of abrasive aggregates on the decrease of grinding forces and specific energy and the increase of quality of ground surface was observed.
The shape of the cutting blades of the abrasive grains has an influence on the material separation process in the machining zone. The paper analyzes the influence of the geometrical parameters of the abrasive grains (rake angle γ, apex angle ε, opening angle α), as well as width bz and length bb of the cutting zone on the material removal efficiency. The material removal efficiency was determined taking into account the volume of the removed material VG and the volume of lateral piles-up VR. The analyses were carried out on the basis of the results of experimental and simulations using the finite element method. The relationship between the selected geometric parameters characterizing the cutting zone and the coefficient characterizing the efficiency of the material removal process was determined. A strong influence of the opening angle α as well as the width bz and length bb of the cutting zone on the material removal process by abrasive grain was demonstrated. It was observed that the wide cutting edge, and thus the large opening angle α of the grain, reduced the size of the pile-ups and more effectively removed the chip material.
Estimation of the machining capacity of grinding wheels after the conditioning process, during their operation and after the grinding process is an important and complex problem. The article presents a methodology for the evaluation of wheel topography using a new height indicator and sharpness of abrasive grains, which enables determination of the machining potential of the wheel to be tested. Analysis of the developed parameter was carried for three different grinding wheels and for two different state after the conditioning process and after 30 minutes of grinding.
Przedstawiono obrazy topografii powierzchni elementów z tworzyw ceramicznych szlifowanych z zastosowaniem ścier-nic o hiperboloidalnej powierzchni czynnej. Wykazano, że cechy tej metody mają istotny wpływ na uzyskanie długiej strefy szlifowania oraz topografię obrabianej powierzchni. SŁOWA KLUCZOWE: szlifowanie ceramiki, szlifowanie czoło-weThe article presents images of surface topography elements of ceramic materials using grinding wheels with hyperboloidal active surface. It has been shown that the characteristics of this method have a significant influence on the long grinding zone, and the topography of the machined surface. KEYWORDS: ceramic grinding, grinding topSzlifowanie jest najbardziej rozpowszechnioną i wydajną metodą obróbki materiałów charakteryzujących się dużą twardością i kruchością -m.in. ceramiki [4÷7]. W opisywanej metodzie szlifowania płaszczyzn powierzchnię elementów szlifuje się czołem ściernicy, mającym kształt stożka lub hiperboloidy, w której najniżej położona tworząca jest równoległa do płaszczyzny ruchu przedmiotów (rys. 1). Oś ściernicy jest pochylona w dwóch wzajemnie prostopadłych płaszczyznach: pod kątem α w płaszczyźnie prostopadłej do kierunku ruchu posuwowego oraz pod kątem β w płaszczyźnie stycznej do tego kierunku. Pochylenie pod kątem β pozwala uzyskać podczas przemieszczania się przedmiotu w strefie obróbki siłę dociskającą przedmiot do zewnętrznego obrzeża, co z kolei umożliwia obróbkę z wykorzystaniem "mocowania siłami szlifowania".Cechą omawianej metody jest wielokrotne wydłużenie strefy obróbki l s (również dla małej szerokości roboczej b s ) w stosunku do szlifowania czołem ściernicy z nakrojem, a w stosunku do szlifowania obwodem ściernicy -nawet kilkudziesięciokrotnie. Dzięki temu można zapewnić małą prędkość usuwania naddatku, dużą równomierność lokalnego obciążenia przedmiotu w strefie szlifowania, krzyżo-wanie się śladów obróbkowych -postępujące wraz z przemieszczaniem przedmiotu w strefie obróbki -i łagodne wychodzenie przedmiotu ze strefy szlifowania [2]. Efektem wymienionych cech metody jest (w zależności od kątów α i β) zarówno możliwość usuwania dużego naddatku w jednym zabiegu, jak i realizacja operacji mikro-i nanoszlifowania oraz usuwania naddatku rzędu 0,5÷10 µm [3]. Parametry obróbki i charakterystyka obrabianych elementówBadania przeprowadzono dla parametrów szlifowania: prędkości szlifowania v s = 30 m/s oraz prędkości obrotowej stołu v w = 20 mm/s. Szlifowane elementy o średni-cy ⌀7,4 mm i wysokości początkowej h 0 = 1,7 ± 0,1 mm były wykonane z tworzywa ceramicznego N1500 (tabl. I) o twardości 8 stopni w skali Mohsa.Wysokość szlifowanych elementów po procesie obrób-ki powinna wynosić h k = 0,98 ± 0,02 mm. Ze względu na trudności z obróbką elementów z tworzywa ceramicznego, wynikające z własności [6] i struktury [1] materiału, a także z uwagi na dużą wartość naddatku na zeszlifowanie (0,72 mm) cały naddatek był usuwany przez pięć ściernic diamentowych ze spoiwem żywicznym (tabl. II), o promieniu r s = 100 mm, rozmieszczonych na obwodzie toru przedmio...
In this article, a method of grinding small ceramic elements using hyperboloid and conical grinding wheels was presented. The method allowed for machining with a lower material removal speed and extending the grinding zone without reducing the efficiency of the process. In order to assess the process output parameters, numerical simulations were carried out for single-pass machining. This strategy allows for automation of the process. Grinding with a low material removal speed is recommended for the machining of small and thin elements, since this can avoid fracturing the elements. The methodology for selecting process parameters as well as the results of the abrasive grains activity analyses were presented. The analyses also concerned the roughness of machined surfaces and the variability of their textures. This grinding method was applied in the production of small ceramic elements that are used in the construction of electronic systems, and in the processing of small piezoceramic parts. This grinding technique could also be used in other grinding processes, where the removal of small machining allowances with high efficiency is required.
The article presents a methodology of an analysis and modeling of technological systems and the grinding process of conical-like helical surfaces with the use of modern CAD/CAE systems and calculations in the Matlab system. The methodology developed allows one to carry out simulation tests for the accuracy of the grinding process of helical surfaces taking into consideration the deviations of the location and shape of the system's elements, axial and radial striking the spindle of the workpiece machined and the grinding wheel as well as the tool's geometrical features.
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