Key Engineering Materials Vol. 679

Abstract: Guidance mechanism such as fast tool servo (FTS) is widely used in precision machining, in the current design method, either the analytic solution or topological optimization, the dynamic feature, namely the stiffness, inertial and frequency, are subjected to the shape and sizing of the designed structure, especially sensitive to the geometric feature of flexure hinge, which caused high machining precision and high cost. In this proceeding, a novel structural design idea for guidance mechanism type micro motion stages based on tension stiffening which allow the dynamic feature adjustable is presented. Firstly, the design of micro motion stages is reviewed on both analytic and topological optimization, and the advantage of the two kinds of commonly used flexure type, the notch type and leaf spring type, are compared, and the latter is chosen as an idea type for guidance mechanism for its uniform deformation and none stress concentration. Secondly, tension stiffening using in the stringed instruments is described, in which the length, tension and linear density is discussed to change the pitch (vibration frequency and amplitude) of the stringed instruments. Finally, a novel structural design idea origin from stringed instruments is discussed, with the assumption that the leaf spring type flexure hinge are symmetrical layout on both sides of the micro motion stage, the stiffness and frequency change rate are also discussed. A numerical method is used to show the efficiency of the presented method.

Abstract: Flexure hinge is widely used in the compliant mechanisms for precision engineering. Generally, compliant mechanisms with flexure hinges are designed using the analytical stiffness formulas, which increases the design complexity. As the development of finite element analysis (FEA) and optimization methods, it is likely to design the flexure hinges directly using the FEA based numerical optimization methods. This paper developed a leaf spring type flexure hinge based micro-motion stage with specific stiffness constraints. Both topology and sizing optimization methods are used in the design of motion stage. The proposed methods is apply to optimal design formed the leaf spring type flexure hinge for a micro motion stage which serves as a guidance mechanism. Further numerical result shows the good stiffness stability of the refined stage.

Abstract: With the double-nozzle NFES process, the uncertainty is more suitable to investigate than the multi-nozzle NFES and also meet higher liquid throughput requirement than conventional electrospinning. Moreover, the key point is to control the deposition characteristics of double-nozzle NFES under the interaction of the nozzles. This paper simulates the change in electric field intensity with the change of nozzle length and voltage. The experiment shows that the deposition distance becomes smaller when needle length increases, however, the influence of voltage is opposite in certain range. According to the study above, the results could be the guidance of the multi-nozzles NEFS in manufacturing process, and also can illustrate the force distribution of the jet with further modification.

Abstract: There are massive reports about near-field electrospinning (NFES) in the literature and the NFES has great tendency for scientific and industrial applications. It is important to improve the machining efficiency of electrospinning. Through the study of the multi-nozzle near-field electrospinning, a new method by adjusting the electrode-to-collector distance (E-C-D) is presented in this paper to make sure the jets with a straight line. The method is divided into two steps: (1) to adjust the E-C-D larger to get the jet at each nozzle, (2) to make the E-C-D smaller enough to get straight jets. Moreover, this paper simulates the electric field density which helps to provide a further understanding on the process of NFES. The experimental results contribute to making a better control on the jets in NFES.

Abstract: In ultra-precision diamond turning (UPDT), axial spindle vibration (ASP) plays a crucial role influencing nanometric surface quality. In this study, a simplified model for ASP is proposed to study its effects on surface generation in UPDT as the spindle is idealized as a mass-spring-damper system. Significantly, the model successfully explains that ASP induces radial patterns at a machined surface. More importantly, this proposed model can be employed to easily predict and understand the effects of ASP on surface generation in UPDT.

Abstract: Optical free-form surfaces are becoming more and more popular in the industry application, which can be fabricated by diamond turning based on fast tool servo (FTS). It is an efficient, precise and low-cost processing method. In order to use diamond turning to fabricate the freeform optics, this paper develops a novel long range fast tool servo which is actuated by voice coil motor. The total range can reach up to 30 mm. The important parts of the FTS have been simulated and analyzed. The transfer function model identification of the FTS has been accomplished. Since the desired tool trajectories are approximately periodic signals in freeform surfaces turning, and the adaptive feedforward cancellation (AFC) control can achieve perfect tracking and disturbance rejection of periodic signals, the AFC control is designed to be added on the IMC-PID controller.

Abstract: It's more and more common to use LED as the light source in automotive lighting. But heat dissipation and low light output of single die light source have restricted the LED to be the mainstream. To use fiber as light-transmitting component could perfectly resolve above weakness. In the paper a design method of LED fiber automotive headlamp is mentioned. And for COB (chip on board) LED, a mathematic model of TIR (total internal reflected) lens is proposed. It could effectively focus the rays emitted from surface light source.

Abstract: Silicon carbide (SiC) is widely used in terrestrial and space applications because of its good mechanical, thermal and optical properties. Nevertheless, traditional grinding and polishing technologies cannot meet the machining requirements due to the high hardness and brittleness. In this paper, Inductively Coupled Plasma (ICP) is utilized to process the SiC optics. The effects of different processing recipes on the removal rate and temperature are investigated. The results show that the removal rate almost keeps stable with processing time and changes with the flow rate of plasma gas, reaction gas, the ratio of CF₄/O₂ and the power. The input power and processing time are the two main influence factors on the processing temperature.

Abstract: Fluid Jet Polishing (FJP) is a promising ultra-precision machining technology which shows great potential with regard to the application value in the generation of freeform surfaces with sub-micrometre form accuracy and nanometric surface finish. The polishing tool influence function (TIF), which is affected by various parameters and commonly assessed in terms of width, maximum depth and volumetric material removal rate, is critically required for corrective polishing and deterministic machining. In this study, a series of experiments was conducted to study the effect of various process parameters on the polishing tool influence function. The polishing machine used is a Zeeko IRP 200 ultra-precision freeform polishing machine, with three linear axes and three rotational axes. All polishing experiments were performed on BK7, which is one of the most common technical optical glass materials for high-quality optical components in the visible range. These specimens were polished using Al₂O₃ (Aluminium oxide) abrasive particles and measured by a Zygo Nexview 3D Optical Surface Profiler. All these experiments were conducted by changing one process parameter and keeping the other process parameters constant. In this paper, the experimental results are described in detail to show the relationships between the material removal and the various parameters (i.e. slurry pressure, standoff distance, impingement angle, etc.), and some interesting experimental results are explained.

Abstract: When the micro lens array machined by an ultra-precision machine was used in 3D computer graphics, a novel format of depth map image was invented with adaptively variable data length for multi requirements of different 3D computer graphics applications. A depth map is an image or image channel that contains information relating to the distance of the surfaces of objects a scene from a viewpoint. Depth maps can be applied for many functions: defocusing, rendering of 3D scenes, shadow mapping and other distance information-related applications.