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For the use of electrical discharge machining (EDM) to drill small, deep holes, many studies have shown that tool electrode vibration and rotation and pump forced flushing can improve machining efficiency or quality. However, these factors are usually studied separately. In this study, a hybrid, rotary, ultrasonic EDMsystem was developed that used these three methods simultaneously. A comparative investigation on different combinations of the three methods was conducted for drilling small, deep holes in Inconel 718 and 41Cr4 workpieces. Results showed that, compared with other combinations for precision drilling under low discharge currents, combinations including these three methods simultaneously achieved more stable machining and higher material removal rates. In addition, the applied current greatly influenced hole depth and the effects of ultrasonics. When a high discharge current was applied, the electrode vibration contribution appeared weak. [ABSTRACT FROM AUTHOR]

A method of generating spherical non-uniform rational basis spline curves based on De Boor’s algorithm is presented in this article. The spherical curve preserves many good properties from non-uniform rational basis spline curves in Euclidean space, such as local modification property, convex hull property, rotation invariant property, knot insertion property, and so on. Construction of closed spherical non-uniform rational basis spline curve will be discussed too. Furthermore, a progressive iterative approximation scheme is proposed to approximate the given points on unit sphere using spherical non-uniform rational basis spline curves. The convergence and curve continuity will be discussed. Since the analytical expression of the spherical non-uniform rational basis spline curve is messy, numerical differentiation is used to test its continuity at interior knots. Finally, several examples are presented to verify the effectiveness of the proposed method. The proposed method is applied on tool path generation of five-axis machining to avoid interference by adjusting fewer directions and obtain smooth tool path simultaneously. [ABSTRACT FROM AUTHOR]

The article discusses nano machining and research regarding various methods for generating complex optical surfaces. According to the article, complex optical surfaces can be used to improve light transmission, reflection, and image quality. Single-point diamond tools and post-production processes such as grinding, lapping, and polishing are mentioned. The Centre of MicroNano Manufacturing Technology at Tianjin University in China is also examined.

Edge chipping is one of the most serious issues during machining process of brittle materials. To find an effective method to reduce edge chipping, the relationship between the distribution of maximum principal stress and edge chipping is studied comprehensively based on 3D finite element analysis (FEA) model of in-process workpiece structure in this paper. Three-level influencing factors of edge chipping are proposed, which are helpful to understand the relationship between intuitive machining parameters and edge chipping at different levels. Based on the analysis, several experiments are designed and conducted for drilling and slotting to study the strategy of controlling edge chipping. Two methods are adopted: (a) adding additional support, (b) improving tool path. The result show that edge chipping can be reduced effectively by optimizing the distribution of the maximum principal stress during the machining process. Further, adding addtitional support method is extended to more complex parts and also obtain a good result. Finally, how to use adding additional support method, especially for complex parts, will be discussed in detail. Several open questions are raised for future research. [ABSTRACT FROM AUTHOR]

A prototype STM system with high aspect ratio measurement capability is developed to fulfill accurate profile measurement of a high step microstructure with 90° steep sidewall. Distinguished from the traditional STM, the new system consists of a long range piezoelectric (PZT) actuator with full stroke of 60 μm as Z-direction servo scanner, a specially customized high aspect ratio STM probe with effective tip length of 300 μm, and an X-Y motorized driven stage for planar scanning. A tilt stage is used to adjust the probe-sample relative angle to compensate the evitable non-parallel effects. Based on the new STM system, sample-tilt-scanning methodology is proposed for eliminating the scanning blind region between the probe and the microstructure. A high step microstructure with height of 23 μm, 90° steep sidewall and width of 50μm has been successfully measured. The slope angle of the sidewall has been achieved to be 85° and the step height at the rising edge and the trench depth at the falling edge are both measured to be 22.96 μm. The whole measuring process only spent less than 10 min. It provides an effective and nondestructive solution for the measurement of high step or deep trench microstructures. In addition, this work also opens the way for further study on sidewall roughness and the tip-sample interaction at the edge of the sidewall, which are highly valuable for fabrication and quality control of high step microstructures. [ABSTRACT FROM AUTHOR]

With a trend toward miniaturization, miniaturized machine tools turn to be more and more reasonable than conventional machine tools in fabricating scaled-down work parts with better quality, higher efficiency, and less expense. In the past 20 years, various miniaturized machine tools have been developed. For the purpose of studying machine tool miniaturization technology and micromachining mechanism, a three-axis desktop milling machine tool is presented in this article. Typical microfeatures such as microgears, microthin walls, and microelectrode made from copper alloy or aluminum alloy have been machined by end milling tools in diameters of 0.1, 0.2, and 0.4 mm. Meanwhile, the profile and roughness of these microstructures are also analysed. By these experiments, the machining performance of this three-axis desktop milling machine tool in aspect of three-dimensional complex microstructures is demonstrated. [ABSTRACT FROM AUTHOR]

It is traditionally known that monocrystalline diamond tools cannot be employed to machine steels due to excessive chemical tool wear. In this study, two different materials are preprocessed by turning, grinding, and polishing, respectively, and then are nitrided to gain the compound layer for diamond turning. Tool wears are significantly reduced by two to three orders of magnitudes and the surface roughness are ranged from 4.2 to 20 nm in Ra depending on the elements and qualities of the workpieces. It is also found that Ni, Cu, Si, and Al are beneficial to improve the tool life, while Mn, Cr, and Mo play the negative role. [ABSTRACT FROM AUTHOR]

Advantages of focused ion beam (FIB) technology in micromachining are high feature resolution, capable of maskless processing, rapid prototyping, and adaptive for various materials and geometries. FIB was extensively used to fabricate a variety of microtools for ultraprecision machining and micromachining with typical dimensions ranging from 10 to 40 μm and a curvature radius of 25 nm or even smaller. The microtools with controlled geometries, such as arc and sawtooth shapes, were shaped using FIB milling technique corresponding to different cutting requirements. The FIB milling is able to shape desired tool geometries with microscale features by means of controlling suitable ion beam parameters and precise orientation of the tools with respect to projection direction of ion beam. The cutting microtools used here are made from hard alloy. Testing experiments were carried out using a microtool with arc-shaped cross section to machine concentric rings and an annular plane in planar metal workpiece. Another microtool with sawtooth-shaped cross section was used to fabricate microdiffractive optical elements. The machining results demonstrated that the FIB-fabricated microtools can accurately machine desired microstructures. This fabrication method shows significant advantages of higher precision and lower cost than that of the conventional tool lapped finishing methods. It is promising to be an effective method for fabricating the microtools with complex shapes. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) analysis at the nanometric scale is a powerful tool for understanding the deformation mechanisms of materials when undeformed chip thickness is at atomic or nanometric scale. Until now, two-dimensional and 2.5D MD models have been employed in the MD analysis. With advances in computer performance, it is possible to simulate larger-scale MD in a reasonable time. This article presents a three-dimensional (3D) tool with a cutting-edge radius of 3 nm and a nose radius of 25 nm to reduce computation time. Taper cut is carried out on monocrystalline silicon to verify the model proposed. A smooth surface is achieved before fracture surfaces occur when the depth of cut is below a critical value. The 3D model is also verified by comparing with results obtained by other studies. [ABSTRACT FROM AUTHOR]

The molecular dynamics (MD) analysis at the nanometer scale is a powerful tool for understanding the material removal mechanism. In simulating the nanocutting process, various boundary conditions of the workpiece modeling can be applied. The influence of these workpiece boundary conditions (WBCs) to cutting results is systematically studied, including the boundary conditions of only bottom, bottom and cut-in side, bottom and cut-out side, and bottom and both side and full scale WBC or not. The results of the simulation confirm that the boundary condition of bottom and closed cut-out side is best suited to the nanometric cutting process. According to the above-mentioned results of boundary conditions, the MD simulation experiment was carried out with the undeformed chip thickness from 1 to 5 nm. It is indicated that the undeformed chip thickness has strong influence on the cutting, that is, with the deepening of cutting, cutting force becomes stronger, whereas the ratio of the normal force to tangential force becomes less. However the variation of the ratio does not vary much. [ABSTRACT FROM AUTHOR]

To precisely control the nanotube probe's length and orientation, focused ion beam (FIB) milling and irradiation processes are utilized in the study. The carbon nanotube (CNT) probes' length is optimized by FIB milling and the end of the CNT probe after FIB processing is found to be a round end with a fullerenelike cap. Using ion beam irradiations method, the carbon nanotube probes are bended and aligned to the desired orientation due to the strain introduced by the ion beam and CNT's excellent plastic ability as well. The evaluation of carbon nanotube probe's metrology performance is also made by correlating CNT probe structures with the probe's atomic force microscopy (AFM) images resolution. It is found that the CNT probe can well overcome the bending response effect on the image resolution if its lateral force constant is larger than 0.086 N/m and CNT probe's angle is less than 30°. The nanotube probe after FIB alignment shows high image resolution, and it can detect an edge with vertical angle of 88.374°, which a common pyramid-shaped AFM probe is not capable of doing. It is also confirmed that the probes with fullerenelike cap end show higher imaging resolution than those with an open end. [ABSTRACT FROM AUTHOR]

Since no physical approach can be employed to study the mechanism in micro cutting, the molecular dynamics simulation is becoming more and more important. In this study, the results of molecular dynamics modeling and analysis on the nanometric machining on silicon surface are presented. According to the simulation, some phenomena in the nanometric cutting process are found. First, surface elastic rebound happens on the cut surface after cutter moving away. The value of the surface elastic rebound is calculated in the simulation. Second, the atoms near the corner of work piece swirl up following the cutter moving direction at the initial stage of removing atoms from the work piece. Third, the simulation results show that no matter how small material removal is, the burr is always formed at the edge of work piece. [ABSTRACT FROM AUTHOR]

Nanoscale machining involves changes in only a few atomic layers at the surface. Molecular dynamics (MD) simulation can play a significant role in addressing a number of machining problems at the atomic scale. In this paper, we employed MD simulations to study the nanometric cutting process of single crystal copper. Instead of the widely used Morse potential, we used the Embedded Atom Method (EAM) potential for this study. The simulations were carried out for various tool geometries at different cutting speeds. Attention was paid to the cutting chip formation, the cutting surface morphology and the cutting force. The MD simulation results show that both the tool geometry and the cutting speed have great influence on the chip formation, the smoothness of machined surface and the cutting force. [ABSTRACT FROM AUTHOR]

A compact but practical scanning tunneling microscope (STM) with high aspect ratio and high depth capability has been specially developed. Long range scanning mechanism with tilt-adjustment stage is adopted for the purpose of adjusting the probe-sample relative angle to compensate the non-parallel effects. A periodical trench microstructure with a pitch of 10 μm has been successfully imaged with a long scanning range up to 2.0 mm. More innovatively, a deep trench with depth and step height of 23.0 μm has also been successfully measured, and slope angle of the sidewall can approximately achieve 67°. The probe can continuously climb the high step and exploring the trench bottom without tip crashing. The new STM could perform long range measurement for the deep trench and high step surfaces without image distortion. It enables accurate measurement and quality control of periodical trench microstructures. [ABSTRACT FROM AUTHOR]

For some crystalline materials, a regime can be found where continuous ductile cutting is feasible. Using precision diamond turning, such materials can be cut into complex optical components with high surface quality and form accuracy. In this work we use diamond-turning to machine a monolithic, square-shaped, doubly-resonant LiNbO3 cavity with two flat and two convex facets. When additional mild polishing is implemented, the Q-factor of the resonator is found to be limited only by the material absorption loss. We show how our monolithic square resonator may be operated as an optical parametric oscillator that is evanescently coupled to free-space beams via birefringent prisms. The prism arrangement allows for independent and large tuning of the fundamental and second harmonic coupling rates. We measure 2.6 ± 0.5 dB of vacuum squeezing at 1064 nm using our system. Potential improvements to obtain higher degrees of squeezing are discussed.

A novel method is proposed to fabricate micro Diffractive Optical Elements (DOE) using micro cutting tools shaped with focused ion beam (FIB) milling. Micro tools with nanometric cutting edges and complicated shapes are fabricated by controlling the tool facet's orientation relative to the FIB. The tool edge radius of less than 30 nm is achieved for the nano removal of the work materials. Semi-circular micro tools and DOE-shaped micro tools are developed to fabricate micro-DOE and sinusoidal modulation templates. Experiments show that the proposed method can be a high efficient way in fabricating micro-DOE with nanoscale surface finishes.

The cylindrical coordinate machining method (CCM) is systematically studied in generating optical freeform surfaces, in which the feature points are fitted to typical Non-Uniform Rational B-Splines (NURBS). The given points have the mapping coordinates in the variable space using the point inversion technique, while the other points have their NURBS coordinates due to the interpolation technique. The derivation and mathematical features are obtained using the fitting formula. The compensation and optimized values for tool geometry are studied using a proposed sectional curve method for fabricating designed surfaces. Typical freeform surfaces fabricated by the CCM method are presented.

The effects of IABP on the contractile state of the in situ canine heart was evaluated under control conditions and conditions of regional ischemia by determining the transient slope of the end-systolic pressure-volume line, T-Emax. For comparison, the conventional index reflecting contractility, dP/dtmax and other related hemodynamic parameters were also assessed. The results showed that, T-Emax, rather than dP/dtmax, reflected more appropriately the changes in contractile state during activation of the IABP under both conditions. It suggests that IABP has a positive inotropic influence only in the ischemic-state and this is a positive inotropic influence only in the ischemic-state and this is a result of the improvement in the myocardial oxygen supply and demand relation. In addition, the limitations of the new indicator, T-Emax, is discussed.

The changes in endogenous superoxide dismutase (ESOD) during myocardial ischemia and reperfusion and the efficacy of oxygen free radical scavengers in myocardial protection were investigated in an isolated heart model connected with the recirculating nonpulsatile perfusion circuit. Subjected to a 2-hour period of global ischemia (27 C), the heart was reperfused with 37 C oxygen diluted auto-blood for 60 minutes. Superoxide dismutase plus catalase was added into the cardioplegic solution and reperfusates. ESOD activity was measured by pyrogallol method. The results of the experiment showed that ESOD activity after ischemia and reperfusion was decreased and the addition of oxygen free radical scavengers (SOD and CAT) to the cardioplegic solution and the reperfusates greatly reduced the leakage of myocardial enzymes, coronary vascular resistance, and the ultrastructural damages of the myocardium. These results suggest that the use of SOD and CAT may inhibit myocardial reperfusion injury by scavenging oxygen-derived free radicals.