Papers by Keyword: Ultra-Precision Machining

Abstract: Texturing on the surface of cutting tools is an effective method to improve the friction and resultant machining performances of the tool. In this study, to fabricate nanotextures on various tools used for precision cutting, a patterning method on nanopolycrystalline diamond and cubic boron nitride tools was investigated using focused ion beam (FIB) irradiation and heat treatment. Patterning was possible using this method, and the patterning characteristics were different from those of single-crystal diamond. This method was more suitable for cutting tools compared with direct FIB machining because of its high efficiency and significantly low affected layer.

Abstract: Embossing by patterned rollers is one of the most efficient machining approaches for manufacturing plastic films with patterned microstructures, and the precision roller with patterned microstructures is the key tooling component in the roll-to-roll process. Single-point diamond turning with a slow or fast tool servo is an enabling and efficient ultra-precision machining process to fabricate microstructures through a simple process to achieve optical surface finish directly. Most of the current studies on slow or fast tool servo machining processes either focus on face machining of patterned microstructures, or on tool servo machining of microstructures in the radial direction of precision rollers. Relatively little research work is found in relation to machining patterned microstructures on a precision roller by using the tool servo in the axial direction. This paper presents a pilot study on the development of a tool path generator for machining precision rollers with wavy patterned microstructures by using slow tool servo machining in the axial direction on a precision roller. The machining mechanism is firstly explained, based on which the tool path generator is developed for machining wavy patterned microstructures on a precision roller surface. Preliminary experimental work was conducted to study the generation of wavy patterned microstructures on a precision roller using a four-axis ultra-precision machine. The machined wavy microstructures on the roller surface are measured and analyzed to successfully validate the performance of the proposed tool path generator.

Abstract: The fabrication of ultra-precision freeform surfaces possessing non-rotationally symmetric geometry and sub-micrometre form accuracy requires an efficient positioning method for precisely locating the position of the workpiece on the machine with high repeatability during the manufacturing cycle. This paper presents an initial attempt to develop a fiducial aided positioning (FAP) method for precisely locating the freeform workpiece on multi-axis machine tools in order to improve the accuracy and efficiency in the manufacturing of ultra-precision freeform surfaces. The FAP method makes use of fiducials to establish intrinsic surface features of the freeform workpiece which are used to determine the coordinate transformation between the coordinate frame of the workpiece and the machine in the machining process and the measurement process. A preliminary simulation experiment was conducted to verify the technical feasibility of the proposed FAP method. The results show that the FAP method is technically feasible to establish a link between the machining and measurement process so as to improve machining accuracy.

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: The computerize numerical control (CNC) system is one of the key factors for the development of micro v-groove machine tools to fabrication micro v-groove structures. Based on the investigation on the machining of micro v-groove structures, a developed software contains five modules: editing, automatic programming, program control, manual control and human machine interface. A3200 software based motion controller integrated with the machine characteristics is used in this study to develop the motion control functions of the micro v-groove machine tool. Meanwhile, a method is proposed to redefine the instructions of M, T and S by setting monitoring points so as to enhance the scalability of CNC system. The results show that the CNC system software is not only stable and reliable, but also satisfies the basic requirements of the ultra-precision machining of micro v-groove structures.

Abstract: Ultra-precision fly cutting machines have long been the hardest one to compliant and induce great focus of researchers. In this paper, a surface topography model is proposed to predict the surface generation in an ultra-precision fly cutting machine. The building of surface topography model is based on the trace of the tool tip. With the 3D surface profile simulations of workpieces, several influencing factors of surface topography, especially the factors related to micro waviness error, are studied.

Abstract: This paper presents a technique for processing Terahertz radar reflector by SPDT (Single Point Diamond Turning) based on LODTM (Large Optics Diamond Turning Machine). This technique applies single crystal diamond cutting tools for ultra-precision machining, and thus could obtain high-precision optical mirror, which could be used as the Terahertz radar reflectors. An experiment for aluminum sample had been done to demonstrate the availability of the technique, and a pair of Terahertz radar reflectors were obtained. The precision of the reflectors, detected through precision coordinate measuring technology, was better than the designed requirement. The experiment results showed that Terahertz radar reflectors generated by deterministic ultra-precision machining technique based on LODTM would have advantages in figure accuracy and roughness and so on, which could be helpful to improve the precision and low the cost of Terahertz radar system.

Abstract: A focused ion beam (FIB) is an effective means of fabricating micro-to submicro-scale shapes on diamond cutting tools. However, ion irradiation of diamond tools causes ion implantation, defects, and non-diamond phases, all of which degrade the tool performance. To remove affected layers from FIB-irradiated diamond tools, heat treatment in air was applied, and the effect of the heating parameters on the etchability of the irradiated area was investigated. It was found that the affected layer could be etched and removed from the diamond tool surface, even at 500 °C. In machining experiments on aluminum alloy and nickel phosphorus, machining performance was improved by the applied heating technique, and the cutting forces and machined surfaces were similar to those obtained with the non-irradiated tool. These results indicate that the proposed heating technique is effective for diamond cutting tools shaped by FIB.

Abstract: The paper analyzes the precision coaxial processing requirements and the characteristics of high automatic online compensation, and builds the electric control system based on Delta series products. The system uses a bus controller and absolute encoders servo constitute nearly closed-loop servo control system, combined with torque limiting grading feeding, dressing real-time compensation, stable and high-speed precision machining ceramic ferrule.

Abstract: There are numerous parameters and steps involved in a computer controlled ultra-precision polishing process (CCUP). The success of CCUP relies heavily on the understanding and optimization of material removal when new materials and new surfaces are polished. It is crucial to optimize the polishing parameters to enhance the effectiveness of the polishing process and to assess the impact of different process parameters on the material removal rate of particular difficult-to-machine materials such as CoCr alloys, which is commonly used in orthopedic implants. This paper aims at studying the process parameters and optimization of the parameter to enhance the material removal rate and quantify the contribution of process parameters.