Papers by Author: Kai Cheng

Abstract: On the basis of geometrical characteristic of the mirco/nano-transmission platform(MNTP), its kinematics model and input/output motion are established by the theory of coordinate transformation. The stiffness model was derived using elasto-dynamics and Lagrange equation. In terms of ANSYS, the output displacement and stiffness of different degrees of freedom(DOF) was simulated. Actual output displacement about x axis and stiffness along z axis were obtained by experimental testing, the results of them obtained by theoretical computation, ANSYS simulation and testing were compared. A good agreement was achieved, which shows that the kinematics model, stiffness model, the design principle and experiments of the MNTP are correct.

Abstract: The purpose of this paper was to generate several possible configurations of micro/nano-positioning stage with bridge-type mechanism based on graph theory. The structural characteristics of stage were discussed first. Then, these modules made up of micro/nano-positioning stage were abstracted. Thus the stage could be described with a tree-graph. According to the spanning tree theory, several possible configurations of stage are enumerated correspondingly. Subsequently, the configuration synthesis of six bridge-type mechanisms was investigated and 720 results were obtained. Rules for generating structures with symmetry are established. On the basis of this, several innovative structures are presented. Furthermore, the result of this paper provides a practicable approach for the structural design of stage and the design method based on graph theory is effective.

Abstract: Numerical optimization method is increasingly applied into the design of machine tools so as to improve their performance. This paper employs Monte Carlo optimization method to predict and reduce the errors of ultra-precision machine tools in term of motion errors between cutting tool and workpiece closely associated with machine processing of ultra-precision machine tools. Using a quite different origin position of location coordinate system from traditional in that every ideal frame on current body is coincided with the reference actual one on the adjacent body, the motion errors are expressed in homogeneous matrix defined with adjacent bodies’ residuals in multi-body system analysis. This expression clearly shows that the final position errors are decided by the motion accuracy of the guideline, and gesture errors are affected by accuracy of the spindle assembly. With geometric errors extracted from the matrix, a new optimization method of error allocation is presented to maximize the machine precision by reasonable distribution of tolerances key parts. Using variables intimately related to motion errors and under constrained by cost, optimization model is established, then it is solved with Monte Carlo simulation method to compute top ten key factors contributed to errors and obtain distribution probabilities of both position error and gesture error. Case study formulated is reported to illustrate the method proposed and to evaluate its effectiveness.

Abstract: In this paper, a 2-D vibrating platform is designed using dual flexure hinge structure and four significant structural parameters are optimized with the integrated model of Abaqus and Isight so as to improve the platform performance. The natural frequency is increased from 496.3 Hz to 2360 Hz after optimization while the distance of travel and the stress satisfy the constrains. The optimization results are confirmed with the test data. The optimized 2-D vibrating platform is applied into the micro milling and the machined surface quality is improved. Therefore, the optimized 2-D vibrating platform is a valid equipment to carry out 2-D vibration-assisted micro milling and study the cutting mechanism.

Abstract: Two dimensional vibration-assisted machining is applied into micro-milling to improve cutting accuracy and prolong tool life. In this paper, the tool tip path of two dimensional vibration-assisted micro-milling (2-D VAMM) with different vibrating parameters is simulated and analyzed. And the computation module of chip thickness in 2-D VAMM is proposed, based on which the chip thickness characteristics is investigated using two evaluating indicators: free time ratio (FTR) and amplitude ratio (AR). The effects of vibrating parameters on FTR and AR are studied with the help of Full Factorial Design and analysis of variance. It is found that FTR can be increased by increasing the ratio of amplitude in normal direction to the feed and the ratio of frequency in normal direction to spindle speed, while AR will be enlarged with increase of the ratio of amplitude in feed direction to the feed and the ratio of frequency in feed direction to spindle speed. The simulation studies are the foundation for calculating cutting force, tool wear and surface roughness in 2-D VAMM and can also guide the further experiment.

Abstract: The dynamics of customer requirements in the global domain are dictating a need for the reconfiguration of existing conventional manufacturing systems in order to adapt and respond to the changing functional requirements. This study presents the investigation of the feasibility of adapting a hydraulic cam system to a power press for uphill sheetmetal piercing. The surface topography of sheared edges of blanks and slugs was analyzed using Zygo New View 200 Scanning White Light Interferometer. The piercing force in each trial was monitored and analyzed via computer-press interface data acquisition system (DAS). The average piercing force, 10721N, obtained was found to be nearly constant throughout the experimental trials.

Abstract: This paper presents a greedy search placement algorithm which incorporates backtracking for the leather stock cutting problem. In the leather manufacturing industry the efficient cutting of component parts (stencils) form a hide is of prime importance to maintain profitability. Consequently, the development of new approaches for generating cut-plans that minimise material waste and which can handle problem constraints have practical value. The unique feature of the greedy placement algorithm method presented in this paper is that it incorporates backtracking which allows previous placement steps to be retraced in situations where no placement solution can be found. The underlying encoding method is based on the use of the no-fit polygon (NFP) which describes the boundary around a stencil shape such that a second stencil shape can be placed while just touching the first but without overlapping. A material coverage of 64% can be achieved when taking placement constraints into account.

Abstract: Globalisation in large engineering, procurement and construction companies has lead in many cases to the establishment of a number of global centres for activities such as process design, detail design, procurement and fabrication. A company with a number of such resources then faces the problem of maintaining a high percentage utilisation in each of these resource locations, multiple projects need to be processed through each of these offices and which project is handled by which office is generally more reliant on available capacity than geography, particularly in the case of engineering centres. This paper considers this problem as an extension of the well studied Resource Constrained Project Scheduling Problem (RCPSP) and utilises a modified form of our existing genetic algorithm to optimise the utilisation of multiple resource locations when scheduling multiple projects. The unique aspect of this genetic algorithm implementation is its use of stochastic resource assignments to simulate the assignment of certain of the project activities to different global facilities. The stochastic resource assignment is processed as an extension to the main chromosome and is therefore optimised along with the scheduling sequence.

Abstract: With the fast deploying and development of information sharing technologies, the Internet has been extensively applied by modern enterprises to pursue a good, efficient communication with their customers and thus research activities supported by global companies zealously motivate onto the Internet which can be used to advertise their products and provide relevant information within design and manufacturing process. Modern enterprises of manufacturing utilize the benefits of global resource from Internet to make the solution which could cut cycle time and reduce costs during the procedure of product design, development and manufacturing. Due to positive development of graphic technologies and 3D modelling tools, Internet is used as an infrastructure to develop new system and explore potential market by modern enterprises on account of the power of sharing text, value and data but also supports dynamic media such as delivering of high quality and interactive 3D graphical content. In the meantime, much work has been done by companies and numerous modelling systems have been developed to build three-dimensional detailed solid which focuses on designing useful parts and shapes using CAD/CAM technologies. Regarding to the increasing quantities of 3D models and requirement of designers based on design reuse in practice, the investigations suggest the achievement of shape data retrieval is viable and a characteristic 3D model search tool is welcome. This paper presents the framework of web-based system and technologies applied in design and the related barrier to implementation is identified. A method for collection 3D data is described and inevitable recursive analysis and relevant equation are induced.

Abstract: This paper presents a customer-centric strategy for e-manufacturing in apparel industry. This strategy integrates 3D body scanning and 3D visualising techniques to allow automatic pattern alterations, based not only on human body measurements, but also on the fabrics’ dynamic properties and features. The 3D virtual try-on integration will actually present the exact idolised avatar of the customer virtually dressed. Scan data and patterns will be automatically transferred through ERP web-enabled interfaces direct to the enterprise’s manufacturing operations and facilities, and will be stored separately for each customer in order to create its ID profile which will be applicable for future purchases or reorders.