Advanced Materials Research Vol. 1136

Abstract: In recent years, the recycling of resources has become important because of the aggravation of global environmental concerns. In light of this, it is necessary to minimize the resource needs of current production systems. This concept is called sustainable development. When this concept is applied to machine tools, the assumption is that small parts should be processed using small machines. Additionally, the diversification of consumer needs and the ephemeralization of product life cycles are progressing in industry. As a result, the overall production system has changed from high-mix low-volume production manufacturing, to variant types in variable quantity. In this background, the cell production system is receiving attention as a production system that can achieve variant types in variable quantity. The cell production system also requires miniaturization and process consolidation of machine tools, which has given rise to the need to consolidate heat treatments, especially as part of the process consolidation of machine tools. Laser beams have proved to be effective heat sources when integrated into heat-treatment processes, such as quenching and tempering on machine tool tables. On the other hand, In the case of the thin plate, it is well known that the deformation of a plate occurs due to laser irradiation, as named a laser forming. The laser forming is also effective to generate the complex shape without a press die set. Thus, we propose that the hybrid process of laser heat treatment and forming of thin plate with a small power semiconductor laser, and demonstrate that the proposed method makes it feasible to generate the hardened sheet metal products with a compact machine tools. Moreover, considering the power consumption in laser quenching and forming process, we investigate an appropriate laser irradiation condition from a view of reducing the environmental burden.

Abstract: Micro/nanoscale diamond cutting tools used in ultra-precision machining can be fabricated by precision grinding, but it is hard to fabricate a tool with a nanometric cutting edge and complex configurations. High-precision geometry accuracy and special shapes for microcutting tools with sharp edges can be achieved by focused ion beam (FIB) milling. However, in the FIB milling process, the surface properties of the substrate (such as a diamond substrate) are affected by the amorphous damage layer caused by the FIB gallium ion collision and implantation and these influence the diamond cutting tool edge sharpness and increase the processing procedure. In this study, to reduce the diamond cutting tool edge sharpness and processing procedure, FIB milling beam current and tilting angle characteristics of single-crystal diamond were investigated, along with method for decreasing the FIB-induced damage on diamond tools by platinum (Pt) coating on the diamond substrate. Experimental results revealed that optimize beam current, tilting angle and platinum (Pt) coating could lead to relatively few processing procedure and sharp cutting tool edge. The obtained results are an endeavor to enhance the controllability of the diamond cutting tool FIB milling.

Abstract: The drilling of microholes in hard and brittle materials by ultrasonic grinding was carried out using polycrystalline diamond (PCD) micropins fabricated by electrical discharge machining. They can be employed as micro-grinding tools because the convex parts of discharge craters formed on the tool surface can serve as cutting edges of abrasive grains in grinding wheels. In the drilling of crown glass, the increase in the grinding force and the generation of cracks and chippings at hole edges were suppressed owing to the high wear resistance of PCD. Under suitable conditions, drilling was also successfully performed in silicon, which is apt to exhibit cracks and chippings at hole edges.

Abstract: A technique for ordered fabrication of periodic freestanding micro/nanostructures on the crystalline germanium (Ge) <100> surfaces with 1064 nm wavelength ultrashort laser pulses under ambient conditions is presented. The laser radiation fluence used for obtaining the structures is close to the melting threshold (0.1 J/cm²) of Ge. The dimensions of structures range from hundreds of nanometres to a few microns. The orientation of the periodic surface structures depends on laser beam polarization direction. Arrays of structures are formed in rows parallel to the sample movement direction for samples machined with s-polarized laser pulses, but formed in the direction perpendicular to the movement for p-polarized pulses. The structures are fabricated under variable temperatures on sample surface owing to the changed interference between incident and reflected laser beams. A micro-Raman analysis of the processed surfaces shows a minor change in the spectral intensity as compared to the unprocessed surface and the material retains its crystallinity after laser irradiation.

Abstract: In our previous research, precise groove machining could be achieved on a cemented carbide workpiece by utilizing a combined method of EDM and grinding using only a single tool, i.e. a rotary PCD disc tool acting as an electrode for EDM and as a wheel for grinding. In this study, the authors applied this method to forming a 3D shape on a cemented carbide workpiece. Firstly, an EC-PCD disc-shaped tool of φ33.4mm was mounted on a spindle of the EDM machine vertically to the workpiece. And the tool was rotated to make a spherical concave on the workpiece by EDM. The surface roughness of the workpiece was Rz=6.4μm and no electrode wear resulted at all. Secondly, the EDMed surface was ground with the same PCD tool. As a result, the improved surface roughness of Rz=1.7μm was obtained on the workpiece maintaining the precise tool profile and dimension.

Abstract: Oxygen-free copper (OFC) is a popular material used for molds/dies in injection molding of plastic lens because of its high ductility, strong impact strength and good thermal conductivity. nanoprecision polishing is essential as the final process in its fabrication. For this purpose, a novel polishing method using magnetic compound fluid (MCF) slurry was proposed. In this article, the construction of an experimental rig to realize the proposed method was described at first. Then the effects of process parameters including MCF slurry composition, workpiece oscillation parameter f/A_p-p and clearance Δ between workpiece and MCF carrier on work-surface roughness and material removal were experimentally investigated. As a result, nanoprecision surface finish of OFC was successfully attained by polishing with MCF slurry and the optimum process parameters (f/A_p-p=30 Hz/4mm, Δ=0.6 mm with an MCF slurry (45wt.% of CIP, 12 wt.% of Al₂O₃ grain, 3 wt.% of α-cellulose, 40 wt.% of MF) for obtaining the smoothest work-surface were determined.

Abstract: Shear thickening polishing (STP) method was newly developed to achieve high efficient and high quality finishing of complex curved surface. The shear thickening fluid based slurry is one of the key factors in STP process. Viscosity of different shear thickening polishing slurry (STPS) was tested by rheometer in this study. The influences of dispersed particle size and concentration, abrasive material, abrasive particle size and concentration on the rheological property of STPS were analyzed. The results show that smaller dispersed particle (5.5 or 13μm in this study) and relative higher concentration (50-55 wt.%) are better for shear thickening effect of the base fluid. The viscosity of base fluid increases from 0.15-0.3 Pa·s to 0.8-1.1 Pa·s under high shear rate. The participation of Al₂O₃ and diamond abrasive changes the rheological property little, and the viscosity of STPS reaches the highest value 1.8 Pa·s at shear rate 300 s^-1. But SiC abrasive obviously destroys the shear thickening effect. SPTS with different Al₂O₃ abrasive concentration in this study presents almost same viscosity curve. It is inferred that the number of the abrasive particle but not the weight ratio plays the role to effect the rheological property of STPS.

Abstract: There has been the requirement in recent times for environmentally friendly methods for finishing free-form surfaces such as those of molding dies [1]. This has led to interest in the development of a new polishing technology that utilizes less abrasive slurry and magnetic abrasive finishing. However, it is well known that the traditional magnetic polishing method is unstable and produces insufficient surface smoothness. In the present paper, we discuss the causes of the instability of conventional magnetic polishing. We also propose a self-adaptive polishing tool comprising a brush with steel balls and a coating of thin slurry and present the results of its use to polish various incline surfaces on a three-axis machining center. The proposed self-adaptive polishing tool was found to be effective for polishing a free-form surface using less abrasive slurry.

Abstract: To reduce the environmental impact of abrasive polishing, we investigated fixed-abrasive polishing using a compact robot. We used a five-joint closed-link compact robot with a fine diamond stone on the main axis to polish a glass plate and measured the polishing pressure and polishing force. We analyzed the stick-slip vibration of a glass polishing motion due to the low stiffness of the robot arm and estimated the influence of relative speed changes on the friction coefficient between the glass plate and the abrasive stone. We also used various paths to polish the workpiece to examine the characteristics of the polishing equipment. Based on the results, we proposed a method that can estimate a workpiece's surface roughness based on the friction coefficient. Using the compact robot and a fine diamond stone, the workpiece's surface roughness decreased and polishing processes on the glass plate were more stable.

Abstract: Honing experiments were carried out for nickel-based superalloy Inconel718 bore. The significance analysis of the four honing parameters: spindle speed, stroke speed, wedge feed per stroke cycle and grain size on the surface roughness, was studied with the orthogonal design method. And the significant degree under the rated conditions was determined. The results showed that: wedge feed per stroke cycle and grain size have a significant influence on surface roughness while spindle speed and stroke speed had no significant effect. Also, there was a positive correlation between surface roughness and wedge feed per stroke cycle and grain size. Furthermore, the honed surface topography was analyzed by the meaning of microscope.