Surface Roughness after Milling of the Al/CFRP Stacks with a Diamond Tool

The Effect of Clearance Angle on Tool Life, Cutting Forces, Surface Roughness, and Delamination during Carbon-Fiber-Reinforced Plastic Milling

This study aimed to investigate the effect of the clearance angle of the milling tool on wear, cutting forces, machined edge roughness, and delamination during non-contiguous milling of carbon-fiber-reinforced plastic (CFRP) composite panels with a twill weave and 90° fiber orientation. To achieve the objective of the study, it was first necessary to design suitable tools (6 mm diameter sintered carbide shank milling cutters) with a variety of clearance angles (8.4°, 12.4°, and 16.4°) and all the machinery and measuring equipment for the research to be carried out. Furthermore, measurement and evaluation methods for cutting tool wear, cutting forces, machined edge roughness, and delamination were developed. Last but not least, the results obtained during the research were summarized and evaluated. From the experiments conducted in this study, it was found that the tool clearance angle has a significant effect on tool wear, roughness of the machined surface, and delamination of the carbon fiber composite board. The tool with a clearance angle of 8.4° wore faster than the tool with a clearance angle of 16.4°. The same trend was observed for cutting force, machined surface roughness, and delamination. In this context, it was also shown that the cutting force increased as the tool wear increased, which in turn increased surface roughness and delamination. These results are of practical significance, not only in terms of the quality of the machined surface but also in terms of time, cost, and energy savings when machining CFRP composite materials.

The Correlation of Surface Roughness Parameters of Zirconia and Lithium Disilicate with Steatite Wear

PURPOSE

Various surface roughness parameters are utilized to describe the surface in the tooth to ceramics abrasion and to assess the resulting wear. The use of three-dimensional parameters may offer a better estimation for wear and an improved deduced clinical surface treatment. The aim of this study was to determine the influence of various surface roughness parameters of zirconia and lithium disilicate ceramics on the wear of steatite antagonists.

MATERIAL AND METHODS

Forty zirconia specimens with a diameter of 7 mm and a thickness of 3 mm and 40 lithium disilicate specimens with the dimensions 10×10×4 mm were each divided into five subgroups. Two subgroups were treated with different clinically established diamond burs; a third subgroup was treated with a silicone polishing set. Two additional subgroups were produced by glazing the surfaces after treatment. Surface roughness parameters were determined by laser scanning microscopy. All specimens underwent 1.2 million loading cycles using steatite antagonists. After regular intervals of cycles, precision impressions were made to assess the wear. The correlation between wear and different roughness parameters was evaluated using the Spearman correlation test.

RESULTS

For the glazed zirconia, unglazed zirconia, and glazed lithium disilicate specimens no significant correlations (p > 0.05) between the investigated roughness parameters and antagonist wear could be found. In the unglazed lithium disilicate groups, significant (p ≤ 0.05) correlations with steatite substance loss could be found for several roughness parameters after 1.2 million cycles.

CONCLUSIONS

For lithium disilicate, it seems not sufficient to use only one roughness parameter to indicate the wear behavior of the surface. There was no correlation between wear and the tested roughness parameters of zirconia surfaces.

Investigation of the Surface Roughness and Surface Uniformity of a Hybrid Sandwich Structure after Machining

The parameters of surface roughness Ra, Rz and Rmax as well as surface topography Sa, Sz, Sp and Sv of the two-layer sandwich structure composed of an AW-2024 T3 aluminum alloy (Al) and a carbon-fiber-reinforced polymer (CFRP) were measured to determine an impact of the machining configuration (arrangement of the materials forming a sandwich structure) and the type of tool (presence of the tool coating) on the quality of the surface obtained through circumferential milling. The measurements revealed that milling produced different values of surface roughness for the aluminum alloy and the CFRP composite with values of 2D and 3D surface roughness being higher for the composite layer. The highest value of Ra of 1.10 µm was obtained for the surface of the CFRP composite using the CFRP/Al configuration and a TiAlN-coated tool. The highest values of the Rz (6.51 µm) and Rmax (8.85 µm) surface roughness parameters were also obtained for the composite layer using the same machining configuration and type of tool.

Milling of Three Types of Thin-Walled Elements Made of Polymer Composite and Titanium and Aluminum Alloys Used in the Aviation Industry

The machining of thin-walled elements used in the aviation industry causes may problems, which create a need for studying ways in which undesirable phenomena can be prevented. This paper presents the results of a study investigating face milling thin-walled elements made of titanium alloy, aluminum alloy and polymer composite. These materials were milled with folding double-edge cutters with diamond inserts. The results of maximum vertical forces and surface roughness obtained after machining elements of different thicknesses and unsupported element lengths are presented. The results of deformation of milled elements are also presented. The results are then analyzed by ANOVA. It is shown that the maximum vertical forces decrease (in range 42-60%) while the ratio of vertical force amplitude to its average value increases (in range 55-65%) with decreasing element thickness and increasing unsupported element length. It is also demonstrated that surface roughness deteriorates (in range 100% for aluminum, 30% titanium alloy, 15% for CFRP) with small element thicknesses and long unsupported element lengths. Long unsupported element lengths also negatively (increasing deformation several times) affect the accuracy of machined elements.