A method to assess assembly complexity of industrial products in early design phase

Complexity is one of the factors, inducing high cost, operational issues, and increased lead time for product realization and continues to pose challenges to manufacturing systems. One solution to reduce the negative impacts of complexity is its assessment, which can help designers to compare and rationalize various designs that meet the functional requirements. In this paper, a systemic approach is proposed to assess complexity of a product's assembly. The approach is based on Hückel's molecular orbital theory and defines complexity as a combination of both the complexity of product entities and their topological connections. In this model, the complexity of product entities (i.e., components and liaisons) is defined as the degree to which the entity comprises structural characteristics that lead to challenges during handling or fitting operations. The characterization of entity complexities is carried out based on the widely used DFA principles. Moreover, the proposed approach is tested on two case studies from electronics industry for its validity. The results showed that the approach can be used at initial design stages to improve both the quality and assemblability of products by reducing their complexity and accompanying risks

Design evaluation of automated manufacturing processes based on complexity of control logic

Complexity continues to be a challenge in manufacturing systems, resulting in ever-inflating costs, operational issues and increased lead times to product realisation. Assessing complexity realizes the reduction and management of complexity sources which contributes to lowering associated engineering costs and time, improves productivity and increases profitability. This paper proposes an approach for evaluating the design of automated manufacturing processes based on the structural complexity of the control logic. Six complexity indices are introduced and formulated: Coupling, Restrictiveness, Diameter, Branching, Centralization, and Uncertainty. An overall Logical Complexity Index (CL) which combines all of these indices is developed and demonstrated using a simple pick and place automation process. The results indicate that the proposed approach can help design automation logics with the least complexity and compare alternatives that meet the requirements during initial design stages

Comparison of damage sensitivities of autoregressive coefficients and natural frequencies for structural health monitoring of a top tensioned riser

Peer reviewedPublisher PD

A model for complexity assessment in manual assembly operations through predetermined motion time systems

Manual assembly processes are favoured for supporting low volume production systems, high product variety, assembly operations that are difficult to automate and manufacturing in low-wage countries. However, manual operations can dramatically impact assembly cycle times, quality and cost when the complexity of the manual operation increases. This paper proposes a method for assessing the process complexity of manual assembly operations, using a representation of manual operations based on predetermined motion time systems. The purpose of this framework is to provide a tool that can be used practically to assess, and therefore control, the complexity of manual operations during their design

A lightweight approach for human factor assessment in virtual assembly designs : an evaluation model for postural risk and metabolic workload

The assessment and optimisation of postural stress and physical fatigue can be challenging and is typically conducted only after the design of manual operations has been finalised. However early assessment of manual operations and identification of critical factors that are deemed outside of an appropriate envelope can avoid the time and costs often associated with re-designing machines and layout for operator work processes. This research presents a low cost software solution based on a simplified skeleton model that uses operator position and workload data extracted from a simulation model used for virtual manufacturing process planning. The developed approach aims to assess postural stress and physical fatigue scores of assembly operations, as they are being designed and simulated virtually. The model is based on the Automotive Assembly Worksheet and the Garg’s metabolic rate prediction model. The proposed research focuses on the integration of virtual process planning, ergonomic and metabolic analysis tools, and on automating human factor assessment to enable optimisation of assembly operations and workload capabilities at early design stage

The use of a complexity model to facilitate in the selection of a fuel cell assembly sequence

Various tools and methods exists for arriving at an optimised assembly sequence with most using a soft computing approach. However, these methods have issues including susceptibly to early convergence and high computational time. The typical objectives for these methods are to minimise the number of assembly change directions, orientation changes or the number of tool changes. This research proposes an alternative approach whereby an assembly sequence is measured based on its complexity. The complexity value is generated using design for assembly metrics and coupled with considerations for product performance, component precedence and material handling challenges to arrive at a sequence solution which is likely to be closest to the optimum for cost and product quality. The case presented in this study is of the assembly of a single proton exchange membrane fuel cell. This research demonstrates a practical approach for determining assembly sequence using data and tools that are used and available in the wider industry. Further work includes automating the sequence generation process and extending the work by considering additional factors such as ergonomi

Hydrogen fuel cell pick and place assembly systems : heuristic evaluation of reconfigurability and suitability

Proton Exchange Membrane Fuel Cells (PEMFCs) offer numerous advantages over combustion technology but they remain economically uncompetitive except for in niche applications. A portion of this cost is attributed to a lack of assembly expertise and the associated risks. To solve this problem, this research investigates the assembly systems that do exist for this product and systematically decomposes them into their constituent components to evaluate reconfigurability and suitability to product. A novel method and set of criteria are used for evaluation taking inspiration from heuristic approaches for evaluating manufacturing system complexity. It is proposed that this can be used as a support tool at the design stage to meet the needs of the product while having the capability to accept potential design changes and variants for products beyond the case study presented in this work. It is hoped this work develops a new means to support in the design of reconfigurable systems and form the foundation for fuel cell assembly best practice, allowing this technology to reduce in cost and find its way into a commercial space

Tree Shaped in Channels Parallel and Counter Flow Through Heat Exchanger Heat Transfer and Flow Investigation of Characteristic

I n this study, a heat exchanger system capable of working on tree-shaped three-level parallel and counter flow basis was designed and manufactured based on the branched Fractal like flow channel structure. A similar phylum of heat exchanger on discs onto one surface of the lower and upper plates and both surfaces of middle plate, 156 Branched-micro channels with cylindrical sections were opened in three levels symmetrically with each other at different levels and diameters. According to the parallel and counter flow type based open circuit and closed circuit principle, the fluid enters the system at equal thermal capacity ratios from the axial or radial connection points and discharges. In the open circuit operating conditions, the heating water is in the temperature range of 35-45°C and the flow rate is 2,0-4,0 lt / min. Similarly, in the closed circuit operating conditions, the heating water is in temperature range of 45-60°C and the flow rate is 2,0-4,0 lt/ min. During the experimental work, the temperature and hydrodynamic characteristics of the system are controlled through software written in the MATLAB R2013b package program. Experimental and numerical analyzes were carried out using ANSYS-Fluent ready packet programs. In the analysis, in the increasing flow rate, positions of some external and lateral channels are determined as cause of the decreasing in level of velocity. The result, requirement of designation as the bifurcation geometry divides the mass flow rate equally for each level of branching, is obtained. The results show that increase in level of branches is not important on the fluid channels which includes this kind fractal branch channel with tree-shaped. The results also show that, in the branched model heat exchanger, for opened and closed circuits, parallel flow increasing branching levels, heating unit and cooling unit is more efficient than the counter flow increasing branching levels heating unit and decreasing branching level cooling unit conditions

A framework for automatically realizing assembly sequence changes in a virtual manufacturing environment

Global market pressures and the rapid evolution of technologies and materials force manufacturers to constantly design, develop and produce new and varied products to maintain a competitive edge. Although virtual design and engineering tools have been key to supporting this fast rate of change, there remains a lack of seamless integration between and within tools across the domains of product, process, and resource design - especially to accommodate change. This research examines how changes to designs within these three domains can be captured and evaluated within a component based engineering tool (vueOne, developed by the Automation Systems Group at the University of Warwick). This paper describes how and where data within these tools can be mapped to quickly evaluate change (where typically a tedious process of data entry is required) decreasing lead times and cost and increasing productivity. The approach is tested on a sub-assembly of a hydrogen fuel cell, where an assembly system is modelled and changes are made to the sequence which is translated through to control logic. Although full implementation has not yet been realized, the concept has the potential to radically change the way changes are made and the approach can be extended to supporting other change types provided the appropriate rules and mapping