Lihong Qiao

Process planning and scheduling integration with optimal rescheduling strategies

It is of more practical significance to carry out research on the integrated process planning and scheduling/rescheduling (IPPSR) to achieve a global improvement for the performance of a manufacturing system with sustained pursuit and various uncertainties. In this paper, a framework and a unified dynamic rescheduling model for IPPSR with three typical types of situations normally encountered in a production system, i.e. arrival of new jobs, machine breakdown and order cancellation have been constructed. Meanwhile, an improved evolutionary algorithm (IEA) for the integrated process planning and scheduling (IPPS) to generate an optimal initial scheduling plan has been developed. In order to improve the performance of the algorithm for IPPS and facilitate the extension of it to rescheduling situation, new genetic representation for the scheduling plan combined with process plans and corresponding genetic operators are developed. Based on the dynamic rescheduling model and initial optimised result, the integrated rescheduling strategies for the above three types of situations have been developed. In order to verify the feasibility and performance of the proposed strategies, experimental studies were conducted and comparisons were made for different performance measures; the results show that the proposed approaches not only provide more effective result for IPPS but also for integrated rescheduling with the above three types of uncertainties.

Unified variation modeling of sheet metal assembly considering rigid and compliant variations

Variation modeling of sheet metal assemblies is quite critical when specifying and verifying the geometric and dimensional requirements of parts. However, sheet metal parts’ compliant behavior makes the variation modeling approach more complex when coupling both rigid variation in the in-plane direction and compliant variation in the out-of-plane direction. In order to completely model the overall three-dimensional variation of sheet metal assembly, a unified variation modeling approach considering both rigid and compliant variations is proposed in this article. Four types of coordinate systems are defined. In the in-plane direction, homogeneous transformation matrix is used to describe the position and orientation relationships between assembly elements, and differential motion vector is used to represent rigid variation. In the out-of-plane direction, a vector composed of the deviations of selected key characteristic points is used to represent compliant variation, and the method of influence coefficients is adopted to analyze compliant variation. The overall three-dimensional variation of sheet metal assembly is the superposition of both in-plane rigid variation and out-of-plane compliant variation. Three types of variation sources that are fixture locators’ deviations, datum features’ deviations and joint features’ deviations are considered here. A case study is presented to illustrate the proposed approach.

Ontology Model for Assembly Process Planning Knowledge

Assembly process planning is a highly knowledge-intensive work. As collaborative design and manufacturing is getting increasingly popular especially for complex assembly products, assembly process planning knowledge model should be comprehensive, recognizable and reusable. Ontology meets the requirements as a semantic tool providing a source of shared and precisely defined terms that can be utilized to describe both knowledge and concepts. Many researchers have studied the ontology modeling for assembly process planning domain and they mainly focus on the geometry information, tolerance type and manufacture environment respectively. This paper presents an assembly process design knowledge ontology considering assembly requirement, spatial information, assembly operation and assembly resource. It has covered almost every important concept related to assembly process planning knowledge.

A novel representation method of non-ideal surface morphologies and its application in shaft-hole sealing simulation analysis

Assembly process simulation has been recognized as an effective tool for design verification. The representation of actual part surfaces produced by manufacturing processes is an important issue for assembly simulation. Manufactured part surfaces can also be regarded as non-ideal surface morphologies caused by manufacturing errors. This article presents a new approach to describe non-ideal cylindrical surface morphologies. A deviation coordinate system is developed by adding a new deviation dimension along the normal direction of the nominal surface modeled in the cylindrical surface curvilinear coordinate system. Considering characteristics of the cylindrical surface machining process, a unified expression of combined Hermite polynomials and Fourier series is used to demonstrate deviations that commonly appear on manufactured non-ideal cylindrical surfaces. The Hermite–Fourier polynomials constitute multi-morphologies resulting from different manufacturing errors. In the proposed method, a parametric matrix is created from the expansion of the Hermite–Fourier polynomials. Each morphology can be represented by a corresponding matrix. The total deviation of a non-ideal part surface is the sum of deviations caused by each manufacturing error source through a linear combination of various matrices. The effectiveness of the proposed method is verified by a simulation of the sealing function of shaft-hole assemblies.

Process Planning and Supply Chain Integration: Implications for Design Process

Collaborative production among multiple enterprises is inevitable for complex product development, typically in aeronautical and astronautical engineering. There are more complex links among product design, manufacturing process and production supply chain in that area. In order to achieve their interoperation and collaboration, it is critical to transmit information between processes correctly and in good time. An initial complete product definition in design is a key to contribute to this purpose. This chapter presents the impact of process planning and supply chain design integration on the design process from three perspectives: design modelling, design methodology and design environment. A service-based collaborative framework is constructed as novel design environment for design process. A unified product information model and model-based information representation are the basis of design. And the design methodologies of design for manufacturing, design for supply chain, and design validation by simulation are adopted. The effect of the three phases as well as the integration of product design, process planning and supply chain design is discussed to sustain lifecycle information integration and consistency throughout product development processes.

Calculation and analysis of assembly clearance based on nonideal surface discrete data

Calculation of assembly clearance is the basis of analysis on assembly problems, and the real assembly surface is the nonideal surface. In this paper, the concept of assembly clearance on nonideal surface is defined and the calculation algorithm of assembly clearance is designed. Based on the calculation, the concept of clearance surface is put forward to express the distribution of assembly clearance on nonideal surface as it can assist the analysis of assembly problems. Finally, the effectiveness of the algorithm is verified by the calculation of the assembly clearance between the surfaces of piston and cylinder.

A Framework for Agile Configuration of Product Structure Data

The application of Product Lifecycle Management (PLM) enables companies to improve the efficiency of product development by considering diversified, personalized and uncertain market requirements. Product configuration, as one of the key functions to enhance mass customization and data management in PLM, manages the product information as well as design experience, and facilitates iterative product development. In this paper, a framework for agile configuration of product structure data is proposed, which enables the customization of product structure, the mapping of configuration process and design knowledge, and the definition of configuration rules. The framework accelerates the design process of new products and improves the adaptation of new products to dynamic and complex product requirement. The creation of configuration template for product structure is illustrated and the implementation of the proposed framework is explained. A case study based on the configuration of a crane structure is proposed as an application for the framework to execute agile configuration of product structure data.

A Model-Based Method for Assisting Decision Making Process in Product Development

Decision-making process during product design and development process has a considerable effect on the enhancement of competitiveness, since it allows cost reduction, quality improvement, and shortening of the time to market. In this paper, a framework of decision support system is investigated and developed throughout the product development process based on the application of a Model-based System Engineering (MBSE) methodology. In the process it will be clearly shown how SysML (System Modelling Language) is used to assist the decision-making process in evaluating candidate design alternatives. The analysis will be carried out in each stage of product development taking in to account the Measure of Effectiveness (MOEs) as a means of setting priorities among alternative product design solutions. At the end of the analysis competent design alternatives will be evaluated through trade-off analysis and ready for decision makers to select the best design solution. The result of the research thus will provide predictions as well as recommendations of the results of alternative solutions to the decision makers, and at the same time provide other appropriate information in order to select the best course of action.

Modeling for assembly simulations: Data description and a data-driven construction framework

Assembly simulations such as assembly process simulation and assembly tolerance simulation have become an effective means to evaluate and analyze product assembly design and assembly process planning. Being core aspect of simulation implementation, building an assembly simulation model is rather time-consuming because of its high complexity. Furthermore, modeling has a significant influence on the popularization and application of simulation technology. In this paper, data needed by assembly process and tolerance simulation are addressed to propose a data-driven approach for assembly simulation modeling. The application process and the architecture of modeling framework for assembly simulation are presented as well. An assembly sequence simulation example is given to illustrate the application of the framework. The framework provides a new idea for the realization of automatic modeling for assembly simulation.

Review of Shape Deviation Modeling for Additive Manufacturing

Additive Manufacturing (AM) is becoming a promising technology capable of building complex customized parts with internal geometries and graded material by stacking up thin individual layers. However, a comprehensive geometric model for Additive Manufacturing is not mature yet. Dimensional and form accuracy and surface finish are still a bottleneck for AM regarding quality control. In this paper, an up-to-date review is drawn on methods and approaches that have been developed to model and predict shape deviations in AM and to improve geometric quality of AM processes. A number of concluding remarks are made and the Skin Model Shapes Paradigm is introduced to be a promising framework for integration of shape deviations in product development, and the digital thread in AM.