Key Engineering Materials Vol. 625

Abstract: Smart actuators, such as piezoceramic actuators, magnetostrictive actuators, and shape memory alloy actuators are widely used in applications of micrositioning and vibration control. Piezoelectric (PZT) actuators having the characteristic of infinitely small displacement resolution are popularly applied as actuators in precision positioning systems. However, the tracking control accuracy of the precision positioning systems is difficultly achieved because of its nonlinear hysteresis effect. Hence, it is important to take hysteresis effect into consideration for improving the trajectory tracking performance. In this paper, in order to capture the hysteresis nonlinearity in the PZT actuators, the Hammerstein model is put to use. The fuzzy control algorithm is used to identify the weighing values. The adaptive inverse controller based on adaptive fuzzy inference is used to track the PZT actuator. We firstly identify the weighting values of the Hammerstein model in situ using the multi-mode fuzzy control algorithm based on the error between reference displacement and actual displacement of the actuator, and then calculate the weighting values and threshold values of the Hammerstein model. Finally, we obtain the feed-forward input voltage. The stability of the controller in the presence of the estimated state is demonstrated. The experimental results show the performance is effectively improved under the intelligent control method.

Abstract: This paper introduced about the in-process vibration testing method for small diameter endmill. By this method, the natural frequency and modal parameters such as mass, damping, and stiffness of the milling tool can be determined in the milling process. An oscillation of the vibrator is controlled by the function generator to apply the impact force at the appropriate cutting period. The measurement setup can determine the compliance curve by the measurement signals of the exiting force and tool deformation. To evaluate the feasibility of the new method, vibration tests were performed on a square endmill which has the diameter of 4 mm in the milling on brass material. Results of vibration tests show that modal parameters of the specific vibration mode can be determined by the new developed method.

Abstract: Most optical glasses are in recent years being manufactured by diamond turning processes which has certainly modernized the field of production of optics. Confines of diamond turning for both form and surface finish accuracy have not been reached, yet. In advent of contemporary technology, high precision finishing techniques are of great concern and the need of present industrialized-scenario. This paper presents the development of a small rotary multi-jet abrasive fluid jet polishing tool for use in polishing of optical glasses. The newly designed and manufactured tool has relative angular speed with respect to the spindle of machining centre and is capable of polishing at micro levels. The paper also investigates the optimal polishing parameters for selected, crown optical glass based on experiments conducted using Taguchi’s experimental method. According to the possible number of control factors L₁₈ orthogonal array was used. ANOVA analysis was carried out to determine the main factors which would affect the surface roughness significantly. Consequently, a 2.5 μm size of Al₂O₃ abrasive, 10wt% abrasive concentration, 40 rpm of polishing head rotation, 6 numbers of nozzles, 6 kg/cm² of fluid pressure, 45minuet of polishing time and 40% of step over have been found to be the optimal parameters. It was observed that about 97.22% improvements on surface roughness; Ra, from 0.360 μm to 0.010 μm has been achieved using the optimal parameters. In addition to this; rotation of polishing head, applied fluid pressure and polishing time were found to have significant effect on surface roughness improvement.

Abstract: Micro deep drilling of hard materials is required to involve step feed in process that grows up machining time. To increase the step feed, a method with low frequency vibration (frequency ~190 Hz, amplitude ~10 μm) by oscillating of workpiece has been proposed. Previous study is focused on method of 1-axis drilling process assisted by low frequency vibration. Introducing the method with low frequency vibration to 2-axis drilling process on a curved surface is required to oscillate the workpiece in two dimensions. Purpose of our study is to design fixing system with the 2-dimansional low frequency vibration. Vibration source is needed to change for providing the 2-dimansional vibration. Fixing system for 2-dimensional vibration (FS2DV) consists of two vibration sources in horizontal and vertical directions with spring systems along it action. The 2-dimensional vibration is controlled by amplitude ratio of the vibrations from each source. As a result, we have succeeded low frequency vibration of the workpiece with assigned direction. The resulting vibration is verified (measuring of instantaneous horizontal and vertical displacements).

Abstract: Ultra-precision diamond cutting of ferrous metals has not been successful in application due to significant tool wear. In this work, numerical simulations and experimental investigations are presented in order to study the interface diffusion between diamond tool and workpiece materials. A diffusion model with respect to carbon atoms from diamond tool penetrating into chips and machined surface was established. The numerical simulation results of the diffusion process reveal that the distribution laws of carbon atoms concentration have a close relationship with diffusion distance, diffusion time and the original carbon concentration of the work material. In addition, diamond face cutting tests of die steels with different carbon content are conducted at different depth of cuts and feed rates to verify the previous simulation results. The wear morphology of rake face and flank face of diamond tool were detected by scanning electron microscopy. Energy dispersive X-ray analysis was proposed to investigate the change in chemical composition of the chips and machined surface. The results of this work benefit for a better understanding on the diffusion wear mechanism in single crystal diamond cutting of ferrous metals.

Abstract: The manufacturing of molds with diffractive structures requires new approaches in terms of grinding wheel geometry and preparation. To be able to manufacture small geometric features such as widths and depths in the micron range on the mold, ideally sharp edged grinding wheels should be used. This paper will present dressing procedures to create sharp edged grinding wheels by using metal alloy blocks. The results and achieved tip radii of the dressed resin bonded and metal bonded fine grained grinding wheels will be presented. Finally, grinding tests of a tungsten carbide mold with a diffractive structure are conducted and the results of the achieved form accuracy and surface roughness are presented.

Abstract: The optical structure has a large number of micro-structures, which has multiple arrays, complex free-form surface features. But those can not be achieved the requirements with traditional turning and grinding processing, it require to use high-frequency and micro-feed to get ultra-precision machining precision. After creating the 3D digital model of micro-displacement platform using Pro/Engineer, and analyzing the motion and the force, the paper studies the influencing factors about the rigidity and acceleration and explores the motion characteristics of the micro-displacement platform in the high-frequency control, and it the establishes the corresponding dynamics equation. The stiffness and linearity data is accessed after the micro-stage is simulated used by Admas and Ansys software. According to the above data, the structure of micro-stage is optimized in order to meet the ultra-precision machining accuracy and the quality of the workpiece. The research takes advantage of the favorable conditions of the Nanofabrication Laboratory, and it has completed the physical production of the micro-displacement platform supported by the introduction of innovative R&D team program of Guangdong Province, those provide a reliable experimental conditions for future in-depth study.

Abstract: Recently, the development of electronic devices, such as smartphones, has meant that printed circuit boards (PCBs) have become complex multi-layer ones to provide both multiple functions and be compact. Blind via holes (BVHs) connecting the layers of the multi-layer board are processed by using a CO₂ laser. The many benefits of direct processing by CO₂ laser include a lower disconnect of the hole position as a result of the base drilling process in the inner layer circuit pattern. Also, efficiently dissipating heat from components improves the quality of the product as digital home appliances are increasingly compact, lightweight, and thinner. Using PCBs raises the radiation performance by the addition of alumina filler at the insulated layer. However, adding alumina filler means that laser processing is difficult, processing efficiency is reduced, and debris on the surface around the drilled hole increases. We consider what causes the changes in the processing hole by changes in the alumina filler content on the basis of data on drilling phenomena gathered with a high-speed camera. We found that the insulating layer material didn’t effect the diameter of the drill hole per laser spot diameter. The cross-section processing is done in a cone initially, and the truncated cone is then processed. And, we found that the hole depth and processing overhang was reduced, and the amount of scattering increased with the amount of alumina content filler.

Abstract: This paper introduced a kind of fast tool servo (FTS). Base on in the frame rack, flexible hinge, piezoelectric ceramic driver, tool base, diamond tools and so on. Laser interferometer is used for displacement measuring of the fast tool servo. The structure simulation was done to the FTS and the nature frequency was obtained. The output displacement of FTS was measured by Laser interferometer. Four kinds of different sin wave sign were given and the frequency of driving voltage ranged from 10Hz to 400 Hz. The relation of the displacement and the driving voltage frequency and the relation of displacement and the driving voltage had been established by experiment.

Abstract: Research on Micro air vehicle (MAV) has been carried out by many researchers to gather information in environmental monitoring, security and so on. When the earthquake, fire, smoke take place, it is difficult for human beings to investigate the detail because of dangerous condition. However, MAV has possibility to investigate the detail because MAV can fly freely around. Recently, dragonfly is highly focused by many researchers because dragonfly has high flight performances those are high efficiency flight, unintended acceleration, rapid turn and hovering. In general, these characteristics have root that wing is corrugation shape. We focus on microstructures on wing and its aerodynamic characteristics because there are many unique microstructures. We focused on micro spikes on dragonfly wing. Over three thousands of spikes exist on two sides of wing. The length and shape of spikes are 10 to 100 micron meters and oblique circular cone. It is important to clear the aerodynamic effect of the oblique circular cone. Artificial wing was fabricated by following processes. We fabricated micro spikes utilizing electro polishing. Fabricated micro spikes were set on plate utilizing micro spot bonding. We investigated the flow around the artificial wing and found that the flow around wing was controlled by micro spikes on wing. In this paper, we focused on comb shape of leading edge of wing. Comb shape is fabricated utilizing micro-EDM. We investigate flow characteristics of comb shape.