A New Approach to Prediction of Fault of Manufacturing Quality for FMS

This paper makes a study of the cause of manufacturing fault,develops the and/or- fault-tree of manufacturing quality fault for MC,and presents a new concept of faint manufacturing quality fault(FMQF)and the decision making tree with which the fault of manufacturing system would be found out from FMQF.An approach to identification of FMQF,based on fuzzy set theory,is presented,which can be used for estimating the status of equipment with the deviation of control charts.Based on the study above,an expert system for the flexible manufacturing system's FMQF detection and prediction is built.

STATE SPACE MODELING OF DIMENSIONAL MACHINING ERRORS OF SERIAL-PARALLEL HYBRID MULTI-STAGE MACHINING SYSTEM

The final product quality is determined by cumulation, coupling and propagation of product quality variations from all stations in multi-stage manufacturing systems （MMSs）. Modeling and control of variation propagation is essential to improve product quality. However, the current stream of variations （SOV） theory can only solve the problem that a single SOV affects the product quality. Due to the existence of multiple variation streams, limited research has been done on the quality control in serial-parallel hybrid multi-stage manufacturing systems （SPH-MMSs）. A state space model and its modeling strategies are developed to describe the multiple variation streams stack-up in an SPH-MMS. The SOV theory is extended to SPH-MMS. The dimensions of system model are reduced to the production-reality level, and the effect and feasibility of the model is validated by a machining case.

Numerical Quantification Model and Experiment of External Force on Roller Hemming of Curved Edge Aluminium Alloy with Adhesive

Accurate quantification of external force is the key to improve the high-precision hemming of autobody closure panels.However,the mechanism of external force on forming quality of complex contour sheet metal with adhesive is not clear subjected to geometric curvature and materials.In the present study,taking the curved edge aluminum sheet as the research object,SPH(smooth particle hydrodynamics)is introduced to simulate the viscous adhesive,and the SPH-FEM(Finite element method)coupling model of adhesive and panels considering the viscosity-pressure effect is established.The numerical simulation of the roller hemming process is carried out,then the validity and reliability of the proposed method are verified by measuring the external force in real time using triaxial force sensor.The multi-step forming process and the effect of external force on the roll in/out,surface wave and plastic strain of aluminum alloy sheet under the viscosity-pressure effect are studied,and the relationship between process parameters and external force is discussed.Results show that the coupling SPH-FEM model can well reflect the hemming process of curved edge structure.The normal force is about 2–3 times of the tangential force in the pre and final hemming process.Compared with the case without adhesive,the surface wave of flange part of the hemming with adhesive is slightly larger.The normal force and the tangential force increase about 90 N and 30 N respectively,when the height increases by 1 mm.It provides an important basis for the accurate control of hemming trajectory and the improvement of manufacturing quality of autobody closure panels.

Optimization of fused deposition modeling process parameters:a review of current research and future prospects

Fused deposition modeling （FDM） is one of the most popuIar additive manufacturing technologies for various engineering applications. FDM process has been introduced commercially in early 1990s by Stratasys Inc., USA. The quality of FDM processed parts mainly depends on careful selection of process variables. Thus, identifica- tion of the FDM process parameters that significantly affect the quality of FDM processed parts is important. In recent years, researchers have explored a number of ways to improve the mechanical properties and part quality using various experimental design techniques and concepts. This article aims to review the research carried out so far in determining and optimizing the process parameters of the FDM process. Several statistical designs of experiments and optimization techniques used for the determination of optimum process parameters have been examined. The trends for future FDM research in this area are described.

Research on uncertainty in measurement assisted alignment in aircraft assembly

Operations in assembling and joining large size aircraft components are changed to novel digital and flexible ways by digital measurement assisted alignment.Positions and orientations（P＆O）of aligned components are critical characters which assure geometrical positions and relationships of those components.Therefore,evaluating the P＆O of a component is considered necessary and critical for ensuring accuracy in aircraft assembly.Uncertainty of position and orientation（U-P＆O）,as a part of the evaluating result of P＆O,needs to be given for ensuring the integrity and credibility of the result;furthermore,U-P＆O is necessary for error tracing and quality evaluating of measurement assisted aircraft assembly.However,current research mainly focuses on the process integration of measurement with assembly,and usually ignores the uncertainty of measured result and its influence on quality evaluation.This paper focuses on the expression,analysis,and application of U-P＆O in measurement assisted alignment.The geometrical and algebraical connotations of U-P＆O are presented.Then,an analytical algorithm for evaluating the multi-dimensional U-P＆O is given,and the effect factors and characteristics of U-P＆O are discussed.Finally,U-P＆O is used to evaluate alignment in aircraft assembly for quality evaluating and improving.Cases are introduced with the methodology.