A Study of nozzle angle in stone surface treatment with water jets
Highlights
► Surface treatment quality with water jets depends on nozzle angle. ► Surface roughness is small at low and high nozzle angles while it is high at moderate angle. ► Variogram analysis of the profiles indicates the presence of high anisotropy ratios for low and high nozzle angles. ► Surface treatment with water jet between 30° and 75° angles yields better surfaces from the esthetic point of view.
Introduction
Contemporary stone architecture philosophies have definitively consolidated the use of ornamental stones with treated surface, especially rough surfaces, for cladding/facing, paving/flooring and more and more frequently for urban fixtures and in design [1]. Surface treatment is a set of operations performed on the surface, outside borders and edges of stone elements to give a certain appearance and also to provide housing for anchorage devices [2].
There are a number of methods of stone surface processing and finishing such as chiseling, bushhamering, sandblasting, scratching, flaming, grinding, water treatment. The choice of the method depends on the type and the conditions of the material, the esthetic effect, economics of the working, tradition and also market trends [3], [4], [5]. This study is concerned with water jet treatment.
Surface treatment methods based on mechanical tools, sand blasting and flaming lead to undesirable features such as chromatic modifications, production of micro-cracks, mechanical alterations. Water jetting is a relatively new process of stone surface treatment based on the action of very high velocity water jets generated at constant pressure and water jet treated stone surfaces are of higher level of esthetical appearance than the other methods [4], [6], [7], [8], [9].
Researchers [4], [7], [8], [9], [10], [11] have experimentally treated the surfaces with water jet machine. In these studies, the surfaces were evaluated esthetically and compared by other surface treatment methods as flaming, bushhammering, sandblasting. In particular, Bortolussi et al. [10] worked on surface finishing marble with abrasive water jet. Careddu et al. [7] and [9] investigated how the water-jet is suited to treating the surfaces of many non-flammable rocks, with considerable esthetic and economic advantages. Costa [8] worked on superficial surface finishing with water jet technology and analyzed the results esthetically. Gürsel [11] investigated relationships between operating and performance parameters such as specific energy, excavation rate (material removal rate), roughness, luminance on different types of marbles for surface treatment operation with water jet. Careddu [4] showed the technical economic and esthetic results obtained with a new water jet treatment and compared it with competing technologies.
In all these studies, the nozzle angle 30° is considered only and the surface quality is assessed from the esthetic point of view. The purpose of this study is to investigate the effect of the nozzle angle in the range of 15–90° on the surface treatment and also to determine the most suitable nozzle angle. For this purpose, surface treatment operations with pure water jet are performed in six different nozzle angle values (15°, 30°, 45°, 60°, 75° and 90°) on Sardinian Basalt sample. The roughness measurements are performed in two perpendicular directions on all the treated surfaces and the surfaces are assessed by considering statistical and geostatistical criteria.
Section snippets
Material and method
Two main machines were used in this study; water-jet plant for the surface treatment operations and roughness measurement system to evaluate roughness of the treated surfaces.
Experimental studies
The methodology used in this study is given as follows (Fig. 4):
- 1.
Select the samples used in surface treatment operations.
- 2.
Determine the values of the working parameters. The working parameters used in this study are the effective parameters in surface treatment using water jet. The parameters and the values of them were chosen based on the results obtained by Costa [8] and Gürsel [11] about stone surface treatment using water jet. The parameters and their values considered in the experiments were
Analysis of experimental results
The roughness is measured along with several profiles in X and Y directions on the surfaces. The profiles constructed at six different nozzle angles are shown in Fig. 6, Fig. 7. Plot of roughness against nozzle angle is shown in Fig. 8 for each roughness parameter.
Fig. 8 indicates that roughness increases up to 30–60° nozzle angle and then decreases. This suggests that, on average, variability at low and high angles is small while it is high at middle angles. At angles less than 30°, nozzle is
Conclusion
In this study, it is aimed to determine the effect of nozzle angle on roughness by using statistical and geostatistical measures. For this reason, some laboratory studies have been performed by using the water jet cutting-surface treatment machine on natural stone samples commercially named as Sardinian Basalt. The main conclusions drawn from this study are given below:
- •
Surface treatment quality with water jets depends on nozzle angle.
- •
The relationships between roughness parameters (Ra–Ry–Rz–Rq)
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