Papers by Keyword: Grinding Wheels

Abstract: Selective laser melting (SLM) is a promising technique to build grinding wheels with complex structures. In this paper, Ni-based self-fluxing alloys are chosen as bond materials to investigate single track formation on a steel substrate under different processing parameters. Results show that irregular and balling tracks are obtained with a low linear energy density (LED). The width of a melt pool increases linearly with LED. For LED values larger than around 0.9 J/mm, keyhole occurs in the melt pool, which is not desirable in the SLM process. Energy dispersive spectroscopy (EDS) mapping is performed to investigate the formation of the melt pool. Through an analysis on chemical distributions, it is found that the melt pool has a mixture of the partly melted substrate and powders. However, in the keyhole region, only the alloying elements of the substrate are detected due to the repulsion of the melted powder materials caused by the recoil pressure. This work can offer guidance on parameter optimization for the fabrication of SLMed grinding wheels.

Abstract: The main purpose of processing of tough-to-machine materials is improving of cutting process of steels with different physicochemical properties and alloying by means of various chemical elements in combination with heat treatment. Producing of high quality surface layers depends on properties of material used to make details, that is why reasons of tough machining were identified: influence of chemical composition and resulting structure. The studies of grinding of tough-to-machine materials were undertaken by means of grinding wheels made from synthetic diamonds as they are most resistant and highly-productive. Based on the studies recommendations for using of characteristics of grinding wheels and tough-to machine steel grades.

Abstract: Efficacy of existing designs grinding wheels is relatively low and one of the main reasons for this situation is the lack of control over the shape of grains included in the composition of these tools and their employees cutting elements. Standard wheels are composed of grains with an arbitrary, varying in the range from isometric to the needle-like species. When only part of the grain has a favorable geometry for cutting and participates fully in aggregate nom cutting process. Arranging grain shape and as a consequence, their geometry can increase the efficiency of each individual grain and thus improve the performance of grinding wheels as a whole. The study on the establishment of the variety of forms of grains for abrasives Russian and German production made standard way - by ebb abrasive ingots, their crushing and screening a number of particle size fractions. Studies have shown that each has its abrasive distribution pattern in the manner that depends on the brand of abrasive characteristics of technology and the manufacture of abrasive grit. The interrelation of grain shape to their geometry as derivation of mathematical models. A pilot batch of grinding wheels with controlled grain shape, are prepared by separating the initial mass of abrasive on a number of fractions with the same shape of grains using the vibratory separator. Experimental wheels were tested on the operating processing bearing rings, and as compared with the following instruments used an arbitrary shape of grains. Found that a differentiated approach to the choice of grain shape allows for a increase resistance grinding wheels in 1,5-3,9 times , reduce roughness of machined surfaces in 1.2 - 3.2 times, roundness - 1.3 times, waviness - 2.3 times the wear sized - 2.0 - 3.0 times.

Abstract: The form wheel generating curve is always a composited curve which is composed of lines and arcs, and the calculation of the envelope surface is more complex than conventional rotary cutter. Therefore, a method of envelope to a two-parametric family of point vectors is proposed, which defines the point and its normal vector on the wheel generating curve as a point vector. Each point vector corresponds to a virtual ball uniquely. The rotation of point vector forms latitude circle and the valid envelopment movement forms sectional circle. The intersection of latitude circle and sectional circle is grazing point; The analytical calculation model is established, in which the geometry parameters of virtual ball can be directly calculated from point vector; An example is presented to demonstrate the effectiveness of the method which can be used for form grinding geometry simulation, accuracy evaluation and optimization of the wheel path.

Abstract: Grinding, a technique for removing abrasive materials, is a chip-removal process that uses an individual abrasive grain as the cutting tool. Abrasive material removal processes can be very challenging owing to the high power requirements and the resulting high temperatures, especially at the workpiece-wheel interface. This paper presents a novel system that uses graphite particles impregnated in an aluminum oxide matrix to form a grinding wheel. This study specifically investigated grinding wheels with a graphite content of 0.5 wt%. The new grinding wheel was compared with conventional grinding wheels by comparing the factors of grinding performance, such as surface roughness, morphology, wheel wear ratio, grinding temperature, and grinding forces, when the wheels were used under two different coolant strategiesdry and with minimum quantity lubrication (MQL) using pure water. This study found that there is a considerable improvement in the grinding performance using graphite-impregnated grinding wheels over the performance obtained using conventional grinding wheels. The use of 0.5 wt% graphite provided better surface roughness and topography, lower grinding temperature, and decreased force; in addition, wheel consumption was lower, resulting in extended wheel life.

Abstract: Grinding of metals is a complex material removal operation involving cutting, ploughing, and rubbing depending on the extent of interaction between the abrasive grains and the workmaterial under the conditions of grinding. In this investigation, various parameters of the process including the number of abrasive grains in actual contact, the number of actual cutting grains per unit area for a given depth of wheel indentation, the minimum diameter of the contacting and cutting grains, the probability of active contacting grains and cutting grains were determined analytically. The analytical work was proved to be practicable by the means of measuring grinding temperature. Research results enable the use of actual number of contacting and cutting grains in the grinding wheel for thermal distribution and wheel wear analyses and contribute to a better understanding on the mechanics of grinding.

Abstract: A series of experiment were performed to test the cleaning ability of different organic emulsion for Si₃N₄ ceramic grinding. The experiment results showed that the grinding fluid made by short chain organic substance and alkane will induces the jam of grinding wheels. At the same time, polar organic substance with long carbon chain can suppress wheel loading phenomenon. The main reason of the jam by alkane is the nonpolar oil film surface possesses the strong attraction to abrasive dust of Si₃N₄, which will lead to jam in the grinding process. The polar oil film relieves the aggregation of abrasive dust in the grinding area to some extant, which is beneficial to decrease jam. By analyzing the cleaning property by some types of polar organic substances, the paper discusses the relationships of molecular structure characters to their cleaning ability.

Abstract: The grinding wheel in the grinding process will surely become duller and duller. To find the reason for it is beneficial to optimize grinding process. The paper draws the graph of the Passivation process of grinding wheel by carrying grinding experiment in the condition of invariable grinding force. The curve can be divided into three parts according to the Passivation rate i.e. initial dull stages, regular dullness stages and rapid dullness stages. In the initial stages, the Passivation rate is lowest and the grinding efficiency is the greatest. The curve figure changes from concave to protruding，which is greatly different from wear curve of grinding process.