Influence of Abrasive Waterjet Machining Parameters on the Surface Texture Quality of Carrara Marble

Abrasive waterjet (AWJ) cutting technology has been used extensively for the cutting and processing of almost all engineering materials because of its precise cutting technique and the lack of damage caused. Currently, the use of abrasive waterjet cutting in the natural stone industry is increasing. However, the effectiveness of abrasive waterjet cutting of natural stones is dependent on the rock properties and machine operating parameters. Consequently, this paper presents the influence of abrasive waterjet machining parameters on the surface texture quality of Carrara marble. The results have shown that the abrasive waterjet cutting process offers better cut surface texture quality of Carrara marble under certain parameter conditions as well as being more environmentally-friendly. The stand-off distance shows the opposite effect on both surface roughness and waviness. With a view to reducing the machining costs, every user tries to select the traverse rate of the cutting head to be as high as possible, but results show that increasing the traverse rate always causes a corresponding increase in terms of inaccuracy, surface roughness, Ra ≈ 93.7 μm, and waviness, Wa ≈ 92.6 μm. The abrasive mass flow rate is not a significant parameter during the cutting process. In all investigations, it was found that the machined surface of the marble is smoother near the jet entrance, Ra ≈ 4 μm, and waviness, Wa ≈ 5 μm, and increasingly becomes rougher towards the jet exit. The result also shows that the micro-hardness value of the Carrara marble was in the range of 122 HV to 124 HV.

Abrasive WaterJet Machining of Thick Carrara Marble: Cutting Performance vs. Profile, Lagging and WaterJet Angle Assessments

This paper deals with an assessment of the machined surface created by abrasive waterjet technology regarding its cutting performance versus profile, lagging and waterjet angle assessments. The results of the experiments presented in this study are with regard to Carrara marble. The machined surfaces were measured in seven different locations across a 40 mm depth of cut by a high precision contact-type profilometer and thus assessed using the standardized amplitude parameters of the profile distribution. The lagging and waterjet angle were also evaluated by creating a digital photo of the machined surface together with a reference gauge. The existence of machining marks on the machined surface has been mostly noticeable in the bottom zone around ~20 mm depth of cut down to jet exit. This investigation leads to a conclusion that, stand-off distance and traverse rate play the roles of the utmost importance in considerations of the machined surface quality in contrast to abrasive mass flow rate. In addition, while the striation zone (rough surface) cannot be eliminated entirely, by selecting proper process parameters, a smooth cutting machined surface can be accomplished.

The Effect of Detergents on the Appearance of Automotive Clearcoat Systems Studied in an Outdoor Weathering Test

The ability to predict the weathering performance of the clearcoat system over a short period of time is essential for the design and development of coating production. Thus, the primary objective of the present study is to investigate whether it is possible to predict the weathering performance of an automotive paint system through determination of surface roughness, Ra, and micro-hardness before and after various weathering exposure times (0, 24, 168, 336, 504, 672 hours) and when employing two different detergent materials (house-use detergent and car wash detergent). The data were analysed using a pair-sample t-Test, with 0.05 level of significance. It was found that the total net of degradation in the clearcoat level during the first 24 hours was Ra ≈ 30.3 nm (for surface roughness) and 1.358 HV (for the μ-hardness) when using the house-use detergent. In contrast, it was found to be Ra ≈ 4.6 nm (for surface roughness) and 1.133 HV (for μ-hardness) when using the car wash detergent. Also, increased time of weathering (up to 672 hours) increases the Ra and μ-hardness values. It can therefore be concluded that the effect of house-use detergent was more severe than that of car wash detergent on the clearcoat system.