Article

An investigation on surface roughness of granite machined by abrasive waterjet

Bulletin of Materials Science (Impact Factor: 0.58). 01/2011; 34(4):985-992. DOI: 10.1007/s12034-011-0226-x

ABSTRACT Abrasive waterjet (AWJ) cutting is an emerging technology which enables the shaping of practically all engineering materials.
However, AWJ cutting may cause roughness and waviness on the cut surface. This significantly affects the dimensional accuracy
of the machined part and the quality of surface finish. In this study, the surface roughness of three granites is experimentally
investigated for varying process parameters in abrasive waterjet. The philosophy of the Taguchi design is followed in the
experimental study. Effects of the control (process) factors on the surface roughness are presented in terms of the mean of
means responses. Additionally, the data obtained are evaluated statistically using the analysis of variance (ANOVA) to determine
significant process parameters affecting the surface roughness. Furthermore, effects of the material properties on the surface
roughness are assessed. It was statistically found that the water pressure and the abrasive flow rate are the most significant
factors influencing the surface roughness of granites. Additionally, a consistent relationship between the material grain
size and surface roughness of the granites was observed.

KeywordsAbrasive waterjet–granite–grain size–surface roughness

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    ABSTRACT: Many studies investigating the cutting performances of waterjets for several kinds of materials such as steel, brass, glass, or aluminium are available. However, there are few studies focused on the rock cutting in the literature. In the present study, therefore, it is aimed at investigating the cuttability of granite by abrasive waterjet. The effect of process parameters and the textural properties of granites on the cut depth and surface quality were investigated. The design philosophy of Taguchi was followed to conduct the experiments. Analysis of variance (ANOVA) was used to evaluate the data obtained statistically. Major significant process factors affecting the cut depth of granite were determined. It was disclosed that the traverse speed was the most significant process parameters affecting the cut depth of granite. Additionally, it was found that the depth of cut and surface quality were strongly affected by the grain size and its boundaries with the grains surrounding. Furthermore, consistent relations between some physical and mechanical properties of the granite (e.g., the water absorption, microhardness, the specific bulk density, and the uniaxial compressive strength) and the depth of cut were observed. INTRODUCTION The use of granite as building material is dramatically increasing all over the world. This is mainly due to the excellent properties of the granite, such as resistance to environmental influences, hardness, and aesthetic properties [1]. Nevertheless, the actual stone diffusion such as marble and granite may be further increased par-tially due to the intrinsic difficulty of machining these kinds of materials. In fact the inclusion of seaweed and fossils in a matrix of calcite crystals has pointed out the limits of the traditional diamond removal manufacturing processes. Further requirements are the reduction of discards with a subsequent decreased impact on environ-ment, the improvement of worker conditions, and safety [2]. As a result, the growing interest of granite has stimu-lated the study of innovative manufacturing processes. Among the innovative manufacturing processes, abrasive waterjet (AWJ) can meet the required standards for machining=processing and=or manufacturing of rocks, more specifically dimension stone (e.g., granite). This advanced technology is applied to drilling and excavation of hard rock for winning blocks with opening of holes or slots. In addition, the manufacturing process is used more specifically for end products in the field of dimension stone final beneficiary. AWJ cutting process parameters can be categorized as follows: hydraulic, abrasive, mixing, and cutting para-meters [3]. The performance of AWJ cutting is often evaluated in terms of cut depth, kerf structure, surface topography, and material removal rate. The influences of process parameters on different output parameters for different materials have been studied by numerous authors in the existing literature. Arola and Hall [4] sub-jected the pure titanium samples to a surface treatment with an abrasive waterjet. The surface texture, particle concentration, particle size, and distribution, and net mass loss resulting from the treatments were determined. Hlavac et al. [5] conducted an experimental study to investigate the AWJ cutting quality. The experiments were performed on various samples of materials includ-ing granite and marbles. The use of the declination angle for prediction and control of the abrasive water jet cut-ting quality was presented in their study. Theoretical and experimental works were carried out to verify and specify the physical relationships among parameters of AWJ used for cutting, the properties of cut materials and the output parameters of cutting, usually the depth of the cut [6]. The mechanism of delamination in graphi-te=epoxy composites under AWJ machining was investi-gated by Shanmugam et al. [7]. Surface roughness of different granites in AWJ cutting was evaluated by Aydin et al. [8]. The mechanism of material removal in abrasive waterjet machining process was studied. Representative components of pure aluminum and brass were used in the experimental studies. The processed surfaces were analyzed using scanning electron microscopy [9]. Optimal process parameters were selected based on the principles of fuzzy logic and genetic algorithms as a new approach in AWJ cutting [10]. Although many studies investigating the cutting performances of waterjets for several kinds of materials such as steel, brass, glass, or aluminium are available, there are few studies on rock cutting in the literature. The present study, therefore, is aimed at investigating
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    ABSTRACT: In this study, influence of the textural properties, e.g., grain size and its boundaries, of granite on the cutting performance of abrasive waterjet (AWJ) was experimentally investigated. In the experiments, predimensioned granite samples were cut by an abrasive waterjet. Following the cutting process, the cut depth, surface roughness, and kerf angle of the granites were evaluated. As a result, it was disclosed that the cut depths and surface roughness increased when the grain size of the granites decreased. Contrary to the behavior of the cut depths and surface roughness of the granites, the kerf angle of the granites increased with an increase of the grain size. Conversely, it was concluded that the high number of the grain boundaries led to an obtainment of higher cut depths and surface roughness, whereas it caused a lower kerf angle. Additionally, it was found that the grains horizontally lying through the cutting line resulted in lower surface roughness and cut depths, whereas the grains vertically allocated through the cutting line resulted in higher cut depths and surface roughness.
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    ABSTRACT: This paper presents an experimental and statistical study on the kerf width, used instead of the width of the cut in abrasive waterjet (AWJ) cutting. Pre-dimensioned granitic rocks were sampled for the experimentations designed by using Taguchi orthogonal arrays. The effects of the AWJ operating variables on the kerf width were studied and the rock properties were correlated with the kerf widths. Additionally, predictive models for the kerf widths were developed using multi-variable regression analysis and the developed models were verified through some statistical tests. The results demonstrated that the standoff distance and the traverse speed have significant effects on the kerf widths. The results also showed that water absorption, unit weight, microhardness, the maximum grain size of rock-forming minerals, and mean grain size of the rock have significant correlations with the kerf widths of the tested rocks. Furthermore, the modeling results revealed that the predictive models derived from rock properties, can be successfully used as a practical guideline.
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