238,660 research outputs found
Feature-based representation for assembly modelling
The need for a product model which can support the modelling requirements of a broad
range of applications leads to the application of a feature-based model. An important
requirement in feature-based design and manufacture is that a single feature
representation should be capable of supporting a number of different applications. The
capability of representing products composed of assemblies is seen to be necessary to
serve the information needs of those applications. To achieve this aim it is an essential
prerequisite to develop a formal structure for the representation of assembly information
in a feature-based design system. This research addresses two basic questions related to
the lack of a unified definition for features and the problem of representing assemblies
in a feature-based representation. The intention is to extend the concept of designing
with features by incorporating assembly information in addition to the geometrical and
topological details of component parts. This allows models to be assembled using the
assembly information within the feature definitions.
Features in this research are defined as machined volumes which are represented in a
hierarchical taxonomy. The taxonomy includes several types and profiles of features
which cover a general range of machined parts. A hierarchical assembly structure is also
defined in which features form basic entities in the assembly. Each feature includes
information needed to establish assembly relationships among features in the form of
mating relationships. An analysis of typical assemblies shows that assembly interfaces
occur at the face level of the mating features and between features themselves. Three
mating relationships between pairs of features have been defined (against, fits and align)
and are represented in the form of expressions that can be used for evaluations. Various
sub-types of these major mating relationships can be identified (e.g. tight fit, clearance fit, etc.) and represented through the use of qualifying attributes. Component Relation
Graphs, Feature Relation Graphs and Face Mating Graphs have been developed to
represent each level of interaction in an assembly, and assembly relationships are
combined with knowledge on process planning into a Component Connectivity Graph. These graphs are used as the basis for deriving an integrated data structure which is used
for defining classes for each level in the assembly hierarchy.
The implementation of a prototype system has been facilitated by use of an
object-oriented programming technique which provides a natural method of adding
functionality to the geometric reasoning process of features and the complex
relationships between the parts that make up the assembly. The feature-based model is
embedded in an object-oriented solid modeller kernel, ACIS®.
The research demonstrates the possibilities for a single feature representation to support
multiple activities within a computer integrated manufacturing environment. Such a
representation can form the basis of design improvement techniques and manufacturing
planning as well as be a model to support the life cycle of the product
Feature based computer aided process planning
This research attempts to study, plan and develop an integrated feature based CAPP system that generates automated process plans for machining prismatic components. The CAPP system comprises a STEP compliant feature based commercial CAD system and the Smalltalk object oriented system. A library of features has been developed that is based on STEP based form feature taxonomy but modified to communicate the manufacturing intent and feature aggregation. The CAPP system has been developed to represent the product, process and resource domain knowledge with a number of object hierarchies, communication methods, and the user interface that would suit the concurrent engineering needs. In addition, suitable geometric and process reasoning methods have been developed in the CAPP system that use the feature based component design data to generate automated process plans.
The research also attempts to identify the problems in feature based process planning and discusses the possible solutions. A solution to the side feature interaction problem has been implemented in the CAPP system.
The CAPP system test results have demonstrated that the proposed approach has been successful and has a great potential for further improvements in terms of flexibility, modularity, emerging data exchange standards, and case in customising the CAPP system
Review of research in feature-based design
Research in feature-based design is reviewed. Feature-based design is regarded as a key factor towards CAD/CAPP integration from a process planning point of view. From a design point of view, feature-based design offers possibilities for supporting the design process better than current CAD systems do. The evolution of feature definitions is briefly discussed. Features and their role in the design process and as representatives of design-objects and design-object knowledge are discussed. The main research issues related to feature-based design are outlined. These are: feature representation, features and tolerances, feature validation, multiple viewpoints towards features, features and standardization, and features and languages. An overview of some academic feature-based design systems is provided. Future research issues in feature-based design are outlined. The conclusion is that feature-based design is still in its infancy, and that more research is needed for a better support of the design process and better integration with manufacturing, although major advances have already been made
Effect of PAO-based γ-Fe2O3 and surfactant concentration on viscosity characteristic
This is a preliminary study on the viscosity characteristics of polyalphaolefin (PAO)- based γ-Fe2O3 under zero magnetic fields. By varying the concentration of magnetic nanoparticles (MNPs), PAO-based γ-Fe2O3 with different concentrations were synthesized by co-precipitation method. The effect of this factor on the viscosity characteristic of γ-Fe2O3 (< 30 nm) was investigated on the basic of a series of rheological measurement. The use of oleic acid (OA) as a coating agent and surfactant was also investigated by varying its concentration. The results show the concentration of MNPs and the amount of OA has obvious effect on viscosity characteristics of PAO-based γ-Fe2O3. In the case of comparison between the concentrations of MNPs, higher concentration of MNPs increased the viscosity of the PAO-based γ-Fe2O3 and exhibit nearly Newtonian behavior. The large amount of OA also exhibits the increment on viscosity characteristic of MNPs. The experimental data were compared with the Bingham and Casson model and the results revealed that the rheology of the polyalphaolefin (PAO)-based γ-Fe2O3 fitted the Casson model better
Goods and services tax (GST) on construction capital cost and housing property price
Good and Service Tax (GST) an indirect broad-based conswnpti.on tax. Following with the implementation of GST in Malaysia on 1st April 2015, it is suspected that the construction capital cost and housing property price will increase accordingly. This study is aim to review the GST effect associated on construction capital cost and it influences towards housing developer and housing property price. Additionally, this study highlights what was the developer point of view on the GST given to them and also the housing price further proposes initiatives to the housing developers. Argument of GST effect is useful for the public administrators so that to re-consider the rate of GST and also beneficial to the construction parties to account with the GST implementation. As conclusion, this study review that GST do give an impact towards the construction capital cost, housing developer and housing property price in terms of knock-on effect
Goods and services tax (GST) on construction capital cost and housing property price
Good and Service Tax (GST) an indirect broad-based conswnpti.on tax. Following with the implementation of GST in Malaysia on 1st April 2015, it is suspected that the construction capital cost and housing property price will increase accordingly. This study is aim to review the GST effect associated on construction capital cost and it influences towards housing developer and housing property price. Additionally, this study highlights what was the developer point of view on the GST given to them and also the housing price further proposes initiatives to the housing developers. Argument of GST effect is useful for the public administrators so that to re-consider the rate of GST and also beneficial to the construction parties to account with the GST implementation. As conclusion, this study review that GST do give an impact towards the construction capital cost, housing developer and housing property price in terms of knock-on effect
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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
Principles for aerospace manufacturing engineering in integrated new product introduction
This article investigates the value-adding practices of Manufacturing Engineering for integrated New Product Introduction. A model representing how current practices align to support lean integration in Manufacturing Engineering has been defined. The results are used to identify a novel set of guiding principles for integrated Manufacturing Engineering. These are as follows: (1) use a data-driven process, (2) build from core capabilities, (3) develop the standard, (4) deliver through responsive processes and (5) align cross-functional and customer requirements. The investigation used a mixed-method approach. This comprises case studies to identify current practice and a survey to understand implementation in a sample of component development projects within a major aerospace manufacturer. The research contribution is an illustration of aerospace Manufacturing Engineering practices for New Product Introduction. The conclusions will be used to indicate new priorities for New Product Introduction and the cross-functional interactions to support flawless and innovative New Product Introduction. The final principles have been validated through a series of consultations with experts in the sponsoring company to ensure that correct and relevant content has been defined
Virtual manufacturing: prediction of work piece geometric quality by considering machine and set-up
Lien vers la version éditeur: http://www.tandfonline.com/doi/full/10.1080/0951192X.2011.569952#.U4yZIHeqP3UIn the context of concurrent engineering, the design of the parts, the production planning and the manufacturing facility must be considered simultaneously. The design and development cycle can thus be reduced as manufacturing constraints are taken into account as early as possible. Thus, the design phase takes into account the manufacturing constraints as the customer requirements; more these constraints must not restrict the creativity of design. Also to facilitate the choice of the most suitable system for a specific process, Virtual Manufacturing is supplemented with developments of numerical computations (Altintas et al. 2005, Bianchi et al. 1996) in order to compare at low cost several solutions developed with several hypothesis without manufacturing of prototypes. In this context, the authors want to predict the work piece geometric more accurately by considering machine defects and work piece set-up, through the use of process simulation. A particular case study based on a 3 axis milling machine will be used here to illustrate the authors’ point of view. This study focuses on the following geometric defects: machine geometric errors, work piece positioning errors due to fixture system and part accuracy
The implementation of uncertainty evaluation model in manufacturability analysis system for miniature machine tool
The development of Manufacturability Analysis System for micro-machining domain (MicroMAS) is intended to address the need of the 4-axis Miniature Machine Tool (MMT) that require such system to assist the user in generating micro-component through manufacturability evaluation. One of the manufacturability aspects being assessed is the impacts from Uncertainty Evaluation Model (UEM) analysis that analyse the influence of the errors stemmed from the MMT construction on the geometrical accuracy of the machined micro-parts. The model has allowed a methodology for the errors in a custom-made MMT to be predicted and to further understand the origin of the errors on the machined micro-part. This paper reports on the implementation of UEM in the development of MicroMAS. Therefore, the results from uncertainty evaluation towards the MMT were integrated in the database which are interactively searched based on IF-THEN clauses in order to determine which rules satisfy the requirements expressed via inputs
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