A knowledge based expert system for moulded part design

In today's competitive market many consumer products are designed with complex curved shapes to meet customers' demands for styling and ergonomics. These styled products are commonly manufactured using moulding processes because they can produce a wide range of freeform shapes at relatively low cost. However, although injection moulding and metal casting allow a great deal of design freedom they also make significant demands on the designer to ensure that parts are designed with due regard for manufacturability. This paper describes a knowledge based moulding advisor that has been developed to provide design for moulding advice to designers during the design process. The main contributions of the research are the development of a hierarchical knowledge representation to allow moulding advice to be generated at different levels of detail and the integration of the expert system with a geometric part description extracted from a Computer Aided Design (CAD) solid model. A demonstrator for the manufacturing advisor has been implemented using the expert system shell CLIPS and integrated with CAD using feature recognition. The moulding advisor is able to generate tailored design for moulding advice for a range of manufacturing processes and materials and evaluate the manufacturability of a designed part at the feature level. The paper provides a case study for a simple moulded test part

Applying Design for Assembly Principles in Computer Aided Design to Make Small Changes that Improve the Efficiency of Manual Aircraft Systems Installations

The installation of essential systems into aircraft wings involves numerous labour-intensive processes. Many human operators are required to perform complex manual tasks over long periods of time in very challenging physical positions due to the limited access and confined space. This level of human activity in poor ergonomic conditions directly impacts on speed and quality of production but also, in the longer term, can cause costly human resource problems from operators' cumulative development of musculoskeletal injuries. These problems are exacerbated in areas of the wing which house multiple systems components because the volume of manual work and number of operators is higher but the available space is reduced.To improve the efficiency of manual work processes which cannot yet be automated we therefore need to consider how we might redesign systems installations in the enclosed wing environment to better enable operator access and reduce production time.This paper describes a recent study that applied design for assembly and maintainability principles and CATIA v5 computer aided design software to identify small design changes for wing systems installation tasks. Results show positive impacts for ergonomics, production time and cost, and maintainability, whilst accounting for aircraft performance and machining capabilities

Understanding the use value dimensions of outsourced maintenance services

Surviving in long-term outsourced maintenance contracts in current financial situation necessitates better understanding of what customers attribute as value and its dimensions. This paper reports on findings from research undertaken with a supplier of automation products and services and its customers. Structured interviewing technique has been conducted in four customer companies from different industrial sectors at different organizational levels. Value dimensions and their role in different decision making levels are identified

Design for Wire + Arc Additive Manufacture: design rules and build orientation selection

Wire + Arc Additive Manufacture (WAAM) is an additive manufacturing technology that can produce near net-shape parts layer by layer in an automated manner using welding technology controlled by a robot or CNC machine. WAAM has been shown to produce parts with good structural integrity in a range of materials including titanium, steel and aluminium and has the potential to produce high value structural parts at lower cost with much less waste material and shorter lead times that conventional manufacturing processes. This paper provides an initial set of design rules for WAAM and presents a methodology for build orientation selection for WAAM parts. The paper begins with a comparison between the design requirements and capabilities of WAAM and other additive manufacturing technologies, design guidelines for WAAM are then presented based on experimental work. A methodology to select the most appropriate build orientation for WAAM parts is then presented using a multi attribute decision matrix approach to compare different design alternatives. Two aerospace case study parts are provided to illustrate the methodology

An Investigation into the Interrelationship between Aircraft Systems and Final Assembly Process Design

Modern aircraft are more integrated with advanced systems functionalities, which result in ever-increasing aircraft complexity, further development difficulties and development delays. These system complexities are mostly in the form of system interactions that make it difficult to understand the overall system characteristics. At the early stages of final assembly line (FAL) design, one of the most important objectives is to arrange the installation and test tasks from components to sub-systems and systems in the proper sequence to meet the designed functions and prevent hazards from the integration process. Improper sequencing of the final assembly process will cause rework, time delays, cost and potential safety risk in development. In the field of final assembly line design, previous research has mostly focused on assembly line balancing or supply chain design based on structural parts assembly. However, these approaches do not consider the early final assembly line definition or test allocation for system functions. In this paper, the research proposes a method based on a systems engineering view and integrated computer aided design (CAD) to help better understand system interactions and generate viable final assembly process sequencing. This research aims to develop a concept of unified master data for final assembly design, which contains 3D geometrical CAD, system functions and interaction characteristics. The paper will present the methodology framework, key concepts and associated industrial software packages for implementation. The paper concludes with further discussion of an initial case study

Assessing the value dimensions of outsourced maintenance services

Purpose - The purpose of this paper is to investigate the diverse nature of tangible and intangible value dimensions that contribute to customers' perception of value from outsourced maintenance services. Design/methodology/approach - A multiple case study approach has been adopted. Repertory grid, an in-depth structured interviewing technique, has been used in order to draw out the respondents' hidden constructs in evaluating outsourced maintenance services. Data have been collected from four customer organizations of outsourced maintenance services, and a total of 33 interviews have been undertaken. Findings - The paper has identified a range of tangible and intangible value dimensions that are of importance in maintenance outsourcing decision making. The most important value dimensions for maintenance outsourcing were found to be specialist knowledge, accessibility (of the service provider), relational dynamic, range of products and services, delivery, pricing and locality. Although the paper has identified the most important value dimensions the paper also emphasizes the need to take into account the full range of value dimensions in order to understand the whole value pattern in an organization. Practical implications - The results will be of use for maintenance service providers to help them to improve value-adding capacity of maintenance services. The results can also be applied by customers to help them assess the value they receive from outsourced maintenance services. Originality/value - A different perspective on maintenance outsourcing value is provided. The value patterns in different organizations and the viewpoints of respondents in different organizational roles are described. The dynamic nature of these tangible or intangible values over time and their interrelationships has also been explored

An automated maintainability prediction tool integrated with Computer Aided Design

Design for maintainability is an important aspect of aircraft design, with maintenance representing 10 – 25% of the direct operating cost of an aircraft [1]. Design for Maintainability incorporates many aspects including assembly/ disassembly time, accessibility, visibility and ergonomics and it can be challenging for design engineers to consider at the design stage due to the time taken and specialist knowledge required. There are a number of existing tools that can be used to assess individual aspects of maintainability but these were mostly developed as paper based tools that require the designer to visualise the maintenance task while studying the engineering drawings or observing an operator performing the task. This paper presents an automated maintainability prediction tool that is integrated with the CATIA v5 Computer Aided Design software. The tool allows the designer to rapidly estimate the maintenance corrective time for a maintenance task utilising a CATIA product model as its input. It uses elemental maintenance action standard times from MIL-HDBK-472 Procedure V to estimate maintenance task times, and RULA, OWAS and LBA ergonomics methods to apply a time penalty based on the operator ergonomics during the task. In this paper the maintainability prediction tool will be tested on a range of simple aircraft maintenance tasks to assess how accurately it can predict maintenance corrective times. The results from the tool are compared to experimental data from physical trials for each maintenance task and the results discussed

Using remote laboratory experiments to develop learning outcomes in engineering practice.

Remote laboratories allow students to undertake experiments using remotely controlled equipment over the internet (de Jong, 2018; Nedic et al., 2015) and have gained a great deal of interest in recent years as a means to deliver hands-on laboratory teaching to distance learning students. Brinson’s (2015) review paper shows that remote and virtual laboratories are being used to develop a wide range of learning outcomes, most commonly developing ‘knowledge and understanding’ but less frequently developing ‘practical skills’. This presentation will present our experience of developing a remote experiment to deliver learning outcomes in both knowledge and understanding and practical skills. The Engineering Council AHEP framework (Engineering Council, 2014) requires that engineering graduates achieve output standards in engineering practice as one of six key areas of learning. The AHEP definition of engineering practice includes the understanding of relevant materials, tools and equipment and a practical knowledge of workshop and laboratory practice. In face to face settings, these learning outcomes are developed through hands-on laboratory sessions supported by a lecturer or demonstrator. Remote laboratories at the Open University are delivered through the OpenSTEM Labs, a major initiative used across the STEM Faculty. Engineering undergraduates use the OpenSTEM Labs throughout their qualification, starting at FHEQ level 4 with observational experiments viewed through a live video stream, and building up to fully interactive experiments from FHEQ level 5. This presentation focuses on a level 5 remote experiment to investigate the strain in a pressure vessel wall, that was developed as part of a course on stress analysis. The experiment develops knowledge and understanding of stress and strain and also practical skills related to the use of engineering equipment, taking measurements and error analysis. The presentation will describe the experiment design and how the student activities were designed to meet the learning outcomes. A key challenge was to design a web interface for the remote experiment that would allow students to develop the required practical learning outcomes, replicating the student experience in a face-to-face setting as closely as possible. The pressure vessel remote experiment was used for the first time in 2019 with a cohort 418 students in the T272 Core Engineering B module. The submission rate for the coursework task associated with the remote experiment was 96 % and the pass rate for the coursework was 80 %. There was a high level of engagement with the experiment and student feedback was generally positive, but further research is required to assess how effectively the learning outcomes were achieved compared to a conventional face-to-face laboratory. References de Jong T, Linn MC, Zacharia ZC. (2013) Physical and virtual laboratories in science and engineering education. Science, 340(6130):305-308. Nedic Z, Machotka J, Nafalski A. (2003) Remote laboratories versus virtual and real laboratories. 33rd ASEE/IEEE Frontiers in Education Conference. Boulder, CO. Brinson, J. R. (2015) Learning outcome achievement in non-traditional (virtual and remote) versus traditional (hands-on) laboratories: A review of the empirical research. Computers and Education, 87:218–237. Engineering Council (2014) The Accreditation of Higher Education Programmes. Third editio

Experimental investigation into aircraft system manual assembly performance under varying structural component orientations

Installation of aircraft wing systems is a bottleneck in the assembly process. This phase is typically composed of many work packages, taking hundreds of man-hours per wing. In addition to this volume of work, tasks are specialized and completed in a difficult environment in terms of access and visibility. In current industrial practice, the wing is mounted horizontally on a transport trolley, which exposes the workforce to prolonged periods of overhead working. Future wing designs may consider a pre-equipping build philosophy, where systems are installed to major structure assemblies before the wing box is assembled. This allows for a change in the orientation and position of the major structure and provides new freedoms in assembly station design and layout. This research presents results of experiments to investigate manual assembly performance of aircraft wing systems, under varying wing structure orientation. A mock-up of a section of an A320 aircraft wing front spar, mounted on a rotation device, functions as the testbed. Manual installation activities are then conducted to emulate real aircraft system equipping for electric harnesses, raceways and hot air ducts. The results show a best-case assembly performance change of 36% for electric system installation activities of cable harnesses and raceway housing components. Tilted and horizontal orientations of the structure show the highest time reductions, with the vertical orientation either non-conclusive or increasing the assembly time. The outcomes of this study are intended to aid in effective trade-off decision making for future wing systems and assembly station layouts from the perspective of structural orientation and assembly task interaction

Using requirement-functional-logical-physical models to support early assembly process planning for complex aircraft systems integration

The assembly line process planning connects product design and manufacturing through translating design information to assembly integration sequence. The assembly integration sequence defines the aircraft system components installation and test precedence of an assembly process. This activity is part of the complex systems integration and verification process from a systems engineering view. In this paper, the complexity of modern aircraft is defined by classifying aircraft system interactions in terms of energy flow, information data, control signals and physical connections. At the early conceptual design phase of assembly line planning, the priority task is to understand these product complexities, and generate the installation and test sequence that satisfies the designed system function and meet design requirements. This research proposes a novel method for initial assembly process planning that accounts for both physical and functional integrations. The method defines aircraft system interactions by using systems engineering concepts based on traceable RFLP (Requirement, Functional, Logical and Physical) models and generate the assembly integration sequence through a structured approach. The proposed method is implemented in an industrial software environment, and tested in a case study. The result shows the feasibility and potential benefits of the proposed method