Papers by Author: Liang Li

Abstract: High speed milling is one of the most commonly used machining processes in many fields of the industry. It is regarded as a simple and fast solution to achieve a high material removal rate, which allows an important production of parts. Unbalance is a problem in any machining process but becomes a considerable problem when reaching high speed machining. The vibrations due to an unbalanced tool or tool holder can result in a poor surface quality and a damaged tool. The damping of the vibrations can be achieved with a specially designed tool showing an anti-vibration clearance angle. This paper shows the influence of the anti-vibration clearance angle by a computational model and a set of experiments to see if it can reduce or suppress the vibrations due to unbalance in high speed milling.

Abstract: With the development of advanced automation degree industries, the requirements of network management for workshop tool become more and more urgent. A very important part in network management system is identification technology of the tool. In this paper, 2D (two-dimensional) barcode identification technology is applied in the tool information in real-time query to realize network management. The 2D barcode reading device, which is combined with the local computer decoding software, could achieve communication between production line and the server. By using 2D barcode identification technology, it could achieve network management for workshop tool, improve production efficiency and reduce the artificial error.

Abstract: In order to improve the rough machining efficiency of titanium alloy, experiments were carried out to investigate the influence of feed per tooth on cutting force and cutting power with index-able coated carbide inserts. The curves of cutting parameters, including cutting force and cutting power, were obtained by single factor test. The results showed that, as the feed per tooth increases, the cutting force increases, especially in the direction of cutting width. All forces almost changed linearly with the changing of feed, and the cutting force of feed direction was the smallest force among the three directions of cutting force. The analytical model of tangential cutting force in the x-y plane was established. By calculating average chip thickness and relationships between tangential cutting force and measurements of cutting force to predict the cutting power, the calculation results were accurate which compared with the actual output power of the machine tool.

Abstract: Cutting tools play an important role in the cutting process of titanium aircraft components, but it is difficult to comprehensively evaluate the cutting tool performance, so the selection of appropriate cutting tool becomes extremely important. In this paper, an evaluation method using grey relational analysis for cutting tool performance was proposed. Meanwhile, in this method, a test benchmark with some typical difficult-to-machined features extracted from titanium aircraft components was designed, and the processing route was developed. Grey comprehensive evaluation models of cutting tool performance were established for the rough and finish machining respectively. Finally, the grey comprehensive evaluation models were used to evaluate the cutting tool performance in the milling experiments of the benchmarks. The results show that the grey relational comprehensive evaluation method is convenient and effective to evaluate milling tools performance for titanium aircraft components.

Abstract: The titanium alloy thin-walled structure has been widely used in aircraft construction as one of the main load-bearing components. However, it is difficult to ensure the machining accuracy because of the machining difficulties of materials and structures. This paper takes titanium alloy (Ti6Al4V) thin-walled web as the research object and analyzes the factors of milling deformation. Based on the analysis, the milling process of the titanium alloy thin-walled structure is optimized, including the decrease of cutting force and the increase of processing system rigidity. Furthermore, a reasonable milling scheme is put forward.

Abstract: Titanium alloy is becoming increasingly employed in the aerospace industries due to its good mechanical and chemical properties. As a typical difficult-to-machine material, there are problems of fast tool wear and poor stability of the processing quality in the machining process. Therefore, experiments of high feed milling of TB2 titanium alloy in liquid nitrogen cooling were carried out to measure the cutting force and the cutting temperature. The experimental results showed that under some parameters, liquid nitrogen could decrease the cutting force and cutting temperature in comparison with dry cutting. What’s more, the tool life as well as the surface quality was improved.

Abstract: Laser assisted machining (LAM) is one important solution for machining difficult-to-machine materials. The heat transfer model of quasi steady state in laser assisted micro machining is built, and the simulation software for temperature distribution measurement is developed based on MATLAB. The simulated temperature distribution of the ZrO₂ ceramic heated by pulse laser shows a good agreement of tendency with the corresponding experimental results through the infrared temperature measurement method, while the simulated temperature is consistently overestimated. This difference maybe results from the neglect of the heat loss caused by the heat radiation and the heat convection in the model. The proposed model in this paper could provide reference for the selection of optimal process parameters and improve the machining quality, which are closely related to the temperature distribution.

Abstract: In order to improve the working efficiency of a manufacturing system, tool life estimation is very essential. In this paper, the dominant factors affecting tool life are analyzed by theoretical analysis. According to the nonlinear relationship between affecting factors and tool life, a tool life prediction model based on BP neural network, which is optimized by genetic algorithm (GA), is built up. 15 network patterns are trained to get the best network structure. The accuracy of GA-BP model is verified through computing and compared with the standard BP model. The results show that GA-BP model prediction value is exactly closed to the expected value of tool life and the prediction accuracy can be improved more than 5% compared than the standard BP model. The model is proved to be accuracy and it can be used as an effective method of tool selection decision.

Abstract: Recently the demands for miniature component of varying materials have been rapidly increasing in aerospace industry. Carbon fiber reinforced plastics is widely used as functional or structural material due to its superior material properties. It also is one of the difficult to machine materials because of the poor machinability. This paper presents an experimental study on micro milling of carbon fiber reinforced plastics with self-developed polycrystalline diamond tool. Cutting force and specific cutting energy are analyzed. The minimum chip thickness and carbon fiber diameter are found to have great effect on the cutting force signature peak. Tool wear mechanism of polycrystalline diamond tool also is investigated.

Abstract: Micro cutting offers good potentialities in order to manufacture small and medium lot sizes of micro-parts with arbitrary geometry at an economically reasonable expense. This technology has been widely used in many fields, especially in aerospace field and biological medicine. The slit grating which is used for X-ray telescope is difficult to machine because of the small critical dimensions, large material removal rates and the high requirement of machining quality. In this paper, two methods are describes to manufacture the slit grating which include micro-milling and flying-cutting. The focus is on the design of micro tool, optimization of machining parameters, the comparison of machining efficiency and precision of slit grating by micro-milling and flying-cutting.