The drilling of holes in CFRP/Ti (Carbon Fiber-Reinforced Plastic/Titanium alloy) alloy stacks is one of the frequently used mechanical operations during the manufacturing of fastening assemblies in temporary civil aircraft. A combination of inhomogeneous behavior and poor machinability of CFRP/Ti alloy stacks in one short drilling brought challenges to the manufacturing community. The impact of the drilling temperature and time delay factor under various cutting conditions on hole accuracy when machining CFRP/Ti alloy stacks is poorly studied. In this paper, the drilling temperature, the phenomenon of thermal expansion of the drill tool, and hole accuracy are investigated. An experimental study was carried out using thermocouples, the coordinate measuring machine method, and finite element analysis. The results showed that the time delay factor varied from 5 (s) to 120 (s), influences the thermal-dependent properties of CFRP, and leads to an increase in hole roundness. Additionally, the thermal expansion of the drill significantly contributes to the deviation of the hole diameter in Ti alloy.
Nitride hard coatings Al25.5Cr21Si3.5N were deposited on WC-Co substrates with a different thickness and a negative substrate bias voltage by the LAteral Rotating Cathodes Arc technology. The nanoindentation tests were performed for analysis of AlCrSiN coatings in order to determine the most promising combination of parameters for subsequent machining. On the basis of results of nanohardness measurement and Ratio H/E*, which represents the resistance to plastic deformation and cracking, deposition conditions were selected for coating of turning cemented carbide inserts. For the evaluation of coating adhesion to substrate, Mercedes adhesion test was used. Chip forming tests and long-term tool life tests were performed for determination of cutting parameters (cutting speed, feed rate and depth of cut) for AlCrSiN coated cemented carbide inserts when machining austenitic stainless steel material.
The article deals with the tool life of ball nose end mills and surface roughness of steel C45 depending on contouring and copy milling. The aim was to determine and compare the wear of ball nose end mill and surface roughness parameter for different types of ball end milling strategies, as well as to specify particular steps of the measurement process. For tool life test, DMG DMU 85 monoBLOCK 5-axis CNC milling machine was used. In the experiment, the cutting speeds, feed rates, axial and radial depth of cut were constant. The coated cemented carbide was used as tool material. The cutting tool wear was measured on Zoller Genius 3s and laser Blum Micro Compact NT . Surtronic 3+ (Taylor Hobson) was used for surface roughness measurement. The results show different achieved surface roughness parameter of machined material C45 and tool life of ball nose end mills depending on milling strategy.
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