Key Engineering Materials Vols. 407-408

Abstract: Diamond is one of the most important engineering materials for its extreme hardness, high thermal conductivity value and chemical inertness. Due to its high hardness and strength, it can be ideal candidates for AFM probe or micro-needle. In this research, micro cone-like shaped diamond tips with high aspect ratio formed using reactive ion etching (RIE) method. The scanning electron microscope (SEM), transmission electron microscope (TEM) and micro-Raman spectroscopy were used to study the surface morphology and sub-surface micro-structure before and after RIE process. The results showed that gold could be adopted as mask material during the RIE process. Different microstructures could be obtained using different RIE parameters such as etch duration and reactant gas. After RIE (O2 50sccm, 200W) for 5min the micro cone-like structures (aspect ratio~8) could be observed on the surface if a thin layer of gold was applied as mask. However, under the same RIE conditions, the irregular pillar-like microstructures started to emerge if the etching time was stretched longer.

Abstract: In micro drilling, the run-out of drill due to rotational motion error of spindle or eccentric chucking of drill causes machining error and larger radial forces which may break the drill. Furthermore, because the spindle speed is very high, rotating bending fatigue of drill may dominate the tool life. In the previous work, relationship between bending deflection and radial cutting force, and fatigue fracture of drill were investigated theoretically and experimentally. The objective of this paper is to investigate more in detail the relationship between the radial cutting force/deflection of drill and its fatigue life. A series of pseudo rotating bending fatigue tests was performed by using three types of ultrafine grain carbide drill blank with 0.1mm diameter. The main results obtained are as follows, (1) Rotating bending fatigue curve did not depend on cobalt content and tungsten carbide grain size. This differs from the results of conventional cemented carbides. (2) The fatigue fracture surface was dominantly occupied by fast fracture regions.

Abstract: A gelatin stone having a new polishing mechanism that can polish a free-form surface is proposed in this study. The gelatin based stone can easily control the hardness and the melting point by changing the density, the cooling condition and the kinds of additives. The main conclusions obtained in this study are as follows. The proposed gelatin stone can polish the surface of various materials. The high density of gelatin is suited for a gelatin stone. Surface roughness improves as the polishing time gets longer. Polishing by gelatin stone needs a high-speed relative motion.

Abstract: Tools coated with TiBON films of varying boron concentrations were made, and the influence of boron concentration on tool wear was investigated. The TiBON coating film acts as a lubricant at high temperature. Tools coated with such films were applied to the machining of difficult-to-cut materials (Ti-6Al-4V and Inconel 718), where　the cutting temperature increases rapidly and heavy adhesion occurs. In the experiment, turning and interrupted cutting were performed. In cutting of Ti-6Al-4V, the tool coated with a film of high boron concentration showed long tool life. In turning of Inconel 718, the tool coated with a film of a boron concentration of 15% showed the longest tool life-about four times longer than that of a tool coated with TiAlN.

Abstract: The measuring method for thermal effects in NC machine tools was drawn-up as ISO 230-3 in 2001. After that, this international standard was introduced as JIS B 6193 in 2003. In connection with this, the measurement of thermal effects becomes achievable also not only in a machine tool builder but in a user side. Therefore, in this research, practical measurement and evaluation of thermal behavior in CNC lathe are performed from a user's viewpoint. Primarily in the experimental measurement, the spindle speed required for turning of the workpiece for a trial-production was given as a load pattern. Then the thermal displacement between cutting tool and workpiece was measured based on the above-mentioned standard and the evaluation result was reported. Secondarily, the consideration was done for the modification of the turning process of the most influential thermal effect. The thermal behavior by applying the modified load pattern was re-measured successively, and comparative evaluation was carried out. As a result, it was verified that an extensive reduction of the thermal effects was possible in the sensitive direction to the accuracy.

Abstract: Based on the screw theory, the force analysis of the 3-RPS parallel machine is illuminated. Been equivalent to a 6-chain parallel machine, the deformation harmony equation of the parallel machine under the outside generalized force is interpreted. The instantaneous stiffness model of the parallel machine, which includes the change of the force Jacobian matrix, is established. Considering the deviation of the position and orientation of the moving platform, which is resulted from the distortion of the PRS chains of the parallel machine, the influence of the change of the Jacobian matrix to the instantaneous stiffness model of the 3-RPS parallel machine is analyzed, and furthermore, it is verified with an instance.

Abstract: Two machining methods for non-circular isometric profile are introduced. The profile modeling technology and the numerical control technology are analyzed. The dynamic property of in a series profile modeling technology system is revealed, and the design principle for in a series profile modeling technology system is put forward, the value range of damping ratio is instanced at near 0.7. The turning machining system adopting linear servo motor as drive element is brought forward.

Abstract: After using plated CBN hard gear-honing-tools with standard involute tooth profiles, there will be the middle concave errors generally around pitch circle on the machined gear tooth surfaces. For the factors caused to errors are much complicated, it is difficult to calculate them accurately by the analytic method. Therefore, Using Pro/E and ANSYS software, the engaging situation between gear-honing-tool and gear was simulated and analyzed. Based on the results of the analysis, the abrupt changing extent of the compression stress was determined near pitch circle. Along the number of the machined gear teeth was changed, the abrupt changing extent of the compression stress was varied accordingly, which was also coincided with the middle concave errors. Those provided the theoretical foundation for the tooth profile modification of the hard gear-honing-tools, it was proved useful to reduce or eliminate middle concave error in practice.

Abstract: On the base of deep cryogenic treatment(DCT) and drilling experiments of W9Mo3Cr4V, W6Mo5Cr4V2 and W4Mo3Cr4VSi HSS twist drills, the influence of deep cryogenic treatment on hardness, wear resistance and microstructure was studied. The experimental results indicated that deep cryogenic treatment induced transformation of retained austenite to martensite and formation of fine carbide particles, so the toughness, wear resistance and hardness values of HSS twist drill were improved. Life of DCT drills was 2 to 4 times more than untreated drills.

Abstract: For ultraprecision machine tool of the next generation, two novel positioning devices are invented by the authors. The first positioning device of nanometer and sub-nanometer resolution with long stroke is the Twist-roller Friction Drive (TFD). For long stroke with 1nm of positioning resolution, the TFD is driven by a servomotor, and it is driven by a piezoelectric actuator for short stroke with 0.1nm of positioning resolution. The second positioning device of short stroke picometer resolution is an active aerostatic guideway employing the Active Inherent Restrictor (AIR). The stroke of the active aerostatic guideway is in the order of 0.1μm, however, the positioning resolution can be 50pm. These positioning devices are integrated into a tri-mode positioning system and each positioning mode is controlled by a numerical control system.