Krzysztof Nadolny

New Ceramic Abrasive Tools for Rough and Finishing Grinding in One Pass

A new type of ceramic abrasive tools prepared of aluminium oxide (alumina), designed to realise the one-pass process of inside diameter grinding. Distinctive feature of these tools is the gradient distribution of the abrasive grain zones with different sizes and structure which enables to carry out the rough (efficient) and finishing grinding in one pass. An influence of the grinding speed vS and the quantities of the working engagement ae on the worksurface roughness and the grinding power were determined.

Analysis of Flatness Deviations for Austenitic Stainless Steel Workpieces after Efficient Surface Machining

Abstract The following work is an analysis of flatness deviations of a workpiece made of X2CrNiMo17-12-2 austenitic stainless steel. The workpiece surface was shaped using efficient machining techniques (milling, grinding, and smoothing). After the machining was completed, all surfaces underwent stylus measurements in order to obtain surface flatness and roughness parameters. For this purpose the stylus profilometer Hommel-Tester T8000 by Hommelwerke with HommelMap software was used. The research results are presented in the form of 2D surface maps, 3D surface topographies with extracted single profiles, Abbott-Firestone curves, and graphical studies of the Sk parameters. The results of these experimental tests proved the possibility of a correlation between flatness and roughness parameters, as well as enabled an analysis of changes in these parameters from shaping and rough grinding to finished machining. The main novelty of this paper is comprehensive analysis of measurement results obtained during a three-step machining process of austenitic stainless steel. Simultaneous analysis of individual machining steps (milling, grinding, and smoothing) enabled a complementary assessment of the process of shaping the workpiece surface macro- and micro-geometry, giving special consideration to minimize the flatness deviations

The Use of Focus-Variation Microscopy for the Assessment of Active Surfaces of a New Generation of Coated Abrasive Tools

Abstract In this paper, the selected results of measurements and analysis of the active surfaces of a new generation of coated abrasive tools obtained by the use of focus-variation microscopy (FVM) are presented and discussed. The origin of this technique, as well as its general metrological characteristics is briefly described. Additionally, information regarding the focus variation microscope used in the experiments - InfiniteFocus® IF G4 produced by Alicona Imaging, is also given. The measurements were carried out on microfinishing films (IMFF), abrasive portable belts with Cubitron™ II grains, and single-layer abrasive discs with Trizact™ grains. The obtained results were processed and analyzed employing TalyMap 4.0 software in the form of maps and profiles, surface microtopographies, Abbott- Firestone curves, and calculated values of selected areal parameters. This allowed us to describe the active surfaces of the coated abrasive tools, as well as to assess the possibility of applying the FVM technique in such kinds of measurements.

MICRO-DISCONTINUITIES OF THE GRINDING WHEEL AND THEIR EFFECTS ON ITS DURABILITY DURING INTERNAL CYLINDRICAL GRINDING

The article depicts the kinematic parameters of micro-discontinuities and how their shaping methods impact upon the active surface of grinding wheels. It also details the construction of a special device which makes it possible to obtain micro-discontinuities with specific and defined surface configurations and shapes. Experimental research into the effects of shaping the micro-discontinuities of the grinding wheel active surface was realized in the internal deep traverse grinding process. Grinding wheels with a ceramic bond, made from micro-crystalline sintered corundum grains, were utilized in the research. The research investigated the duration of the durability period of the grinding wheels. It also looked at the grinding power, as well as the machined surface roughness, when using grinding wheel with or without micro-discontinuities shaped upon the active surface. As a result of the research undertaken, it was determined that the implementation of micro-discontinuities extends the grinding wheel durability period by at least three times its original duration, while maintaining the desired quality of the machined surface.

The method of assessment of the grinding wheel cutting ability in the plunge grinding

This article presents the method of comparative assessment of the grinding wheel cutting ability in the plunge grinding kinematics. A new method has been developed to facilitate multicriterial assessment of the working conditions of the abrasive grains and the bond bridges, as well as the wear mechanisms of the GWAS, which occur during the grinding process, with simultaneous limitation of the workshop tests range. The work hereby describes the methodology of assessment of the grinding wheel cutting ability in a short grinding test that lasts for 3 seconds, for example, with a specially shaped grinding wheel, in plunge grinding. The grinding wheel macrogeometry modification applied in the developed method consists in forming a cone or a few zones of various diameters on its surface in the dressing cut. It presents an exemplary application of two variants of the method in the internal cylindrical plunge grinding, in 100Cr6 steel. Grinding wheels with microcrystalline corundum grains and ceramic bond underwent assessment. Analysis of the registered machining results showed greater efficacy of the method of cutting using a grinding wheel with zones of various diameters. The method allows for comparative tests upon different grinding wheels, with various grinding parameters and different machined materials.

Experimental study into the grinding force in surface grinding of steel CrV12 utilizing a zonal centrifugal coolant provision system

In order to efficiently remove heat from the machining zone, grinding fluids are used in the majority of grinding processes. Intensive cooling periods make it possible to efficiently influence the machining heat conditions, and through lubricating fluid components, limit the friction of active cutting vertices of unspecified geometry and a frequently negative rake angle. The obtained grinding results are considerably influenced by the amount of grinding fluid and the way it is delivered, which directly influences its effectiveness in reaching the zone of contact between the grinding wheel and the machined surface. The following article presents a new solution, as far as centrifugal grinding fluid delivery is concerned, through a special grinding wheel grip and the channels formed in it. Moreover, the system recommended here is also characterized by zonal grinding fluid delivery into the grinding wheel, which is aimed at additionally increasing the efficiency of grinding fluid delivery into the grinding zone. The results of tests evaluating the effect this system has upon grinding force values are presented. The reference methods employed in these tests were centrifugal grinding fluid delivery without zonal limitation, delivering grinding fluid using the flood method, as well as dry grinding. The results of the experiment showed that using the method recommended here enables the creation of conditions in the grinding zone similar to, or even more advantageous in certain conditions, than when delivering grinding fluid using the flood method. It also leads to a general reduction in grinding fluid expenditure by as much as 10 times.

Morphology of Near- and Semispherical Melted Chips after the Grinding Processes Using Sol-Gel Abrasives Based on SEM-Imaging and Analysis

Selected issues related to SEM-imaging and image analysis of spherical melted chips formed during the grinding process are presented and discussed. The general characteristics of this specific group of machining products are given. Chip formation phenomena, as well as their overall morphology, are presented using selected examples of near- and semispherical melted chips occurring singly or concentrated in clusters on the grinding wheel surface after the machining process. Observation of the spherical melted chips and acquisition of their images were carried out for grinding wheel active surfaces with microcrystalline sintered corundum abrasive grains SG™ after the internal cylindrical grinding process of a 100Cr6 steel and Titanium Grade 2® alloy by use of a scanning electron microscope, JEOL JSM-5500LV. Analysis of the obtained SEM micrographs was carried out by Image-Pro® Plus 5.0 software to determine the selected geometrical parameters describing the morphological features of the assessed chips.

Potential for improving efficiency of the internal cylindrical grinding process by modification of the grinding wheel structure. Part I: Grinding wheels made of conventional abrasive grains

This article offers an overview of 14 grinding wheel construction modifications used in the peripheral grinding of flat-shaped internal and external cylindrical surfaces, when grinding wheels made of conventional abrasive grains are used (Al2O3, sol-gel alumina, SiC, etc.). The text contains characteristics of grinding wheels with mixed grains, glass-crystalline bond, a centrifugal provision of the coolant into the grinding zone, aggregate grains, zones of different diameters, radial rough grinding zone, extended finish grinding segments, active surface macro- and micro-discontinuities, as well as multiporous, impregnated (self-lubricating), sandwich, sectional and segment grinding wheels. Each of the presented structural modifications was described by giving construction scheme, used abrasive grains, range of applications, advantages as well as disadvantages. Modifications of the grinding wheel construction allow for effective improvement of both the conditions and the results of the grinding process. A wide range of the known modifications allows for their proper selection depending on the required criteria of effective evaluation and taking into account the specific characteristics of conventional abrasive grains. As a result, it is possible to obtain positive influence on a number of technological factors of the grinding process. The described modifications of the grinding wheel structure can be also an inspiration and the basis for creating new solutions in this field.

The effect of sulfurization on the grinding wheel cutting ability in the internal cylindrical grinding of nickel superalloys

One possible way of preventing excessive growth of smearings/loads on the grinding wheel active surface is the introduction of compounds such as sulfur, graphite, or wax into the grinding wheel volume which exerts an active influence on adhesion during the process of impregnation. Limiting the formation of smearings/loads on the grinding wheel active surface is of crucial importance to achieve effective grinding of hard-to-cut materials (such as nickel superalloys) which are characterized by considerable ductility and a strong chemical affinity to abrasive grains, among other things. This article presents the results of experimental tests performed on plunge grinding and the influence of sulfur impregnation of grinding wheels on the smearing/load intensity on the grinding wheel active surface during the process of internal cylindrical plunge grinding of openings made from Inconel® alloy 600 and Incoloy® alloy 800HT®. Bearing steel 100Cr6 was included in the tests as a reference material. Grinding wheels were impregnated with a new method of gravitational sulfurization combined with centrifuging. The experiments carried out show that the adhesive properties of sulfur allowed for considerable limitation of smearing/loading of the grinding wheel active surface with machined material. This mainly concerned limiting the formation of the largest and most technologically undesirable smearings/loads of the intergranular spaces. The presence of sulfur in the grinding wheel volume had a minor influence on the intensity of smearings/loads in the microareas of the active abrasive grains’ apexes. The tests also showed an increase of 32%–49% in the value of parameter Sa in the surfaces ground with grinding wheels impregnated with sulfur for all the examined materials.

The effect of active surface morphology of grinding wheel with zone-diversified structure on the form of chips in traverse internal cylindrical grinding of 100Cr6 steel

The article presents the results of experimental investigations to determine the effect of active surface morphology of grinding wheels with a zone-diversified structure on the form and size of chips generated during traverse internal cylindrical grinding of 100Cr6 steel. In the grinding process involving grinding wheels with a zone-diversified structure, chip formation phenomena differ in the rough and finish grinding zones of the tool. In order to expand one’s knowledge of this phenomena, the microtopography measurements of the grinding wheel active surface in the rough and finish grinding zones were made, as well as scanning electron microscopic observations of these areas after the dressing cut and following internal cylindrical traverse grinding. The conducted studies showed that chips in the rough grinding zone of the grinding wheel active surface are usually several hundred micrometers in length. In the finish grinding zone, however, mainly micro-chips were generated whose length does not exceed 100 µm (usually around 10 µm in length). In the rough grinding zone, shearing-type and flowing-type chips dominate with a few examples of spherical melted chips. Moreover, in the finish grinding zone, mainly slice-type and knife-type micro-chips were observed.