567 research outputs found
Resource scheduling of workflow multi-instance migration based on the shuffled leapfrog algorithm
Purpose: When the workflow changed, resource scheduling optimization in the process of the
current running instance migration has become a hot issue in current workflow flexible
research; purpose of the article is to investigate the resource scheduling problem of workflow
multi-instance migration.
Design/methodology/approach: The time and cost relationships between activities and
resources in workflow instance migration process are analyzed and a resource scheduling
optimization model in the process of workflow instance migration is set up; Research is
performed on resource scheduling optimization in workflow multi-instance migration, leapfrog
algorithm is adopted to obtain the optimal resource scheduling scheme. An example is given to
verify the validity of the model and the algorithm.
Findings: Under the constraints of resource cost and quantity, an optimal resource scheduling
scheme for workflow migration is found, ensuring a minimal running time and optimal cost.
Originality/value: A mathematical model for resource scheduling of workflow multi-instance
migration is built and the shuffled leapfrog algorithm is designed to solve the model.Peer Reviewe
Intelligent conceptual mould layout design system (ICMLDS) : innovation report
Family Mould Cavity Runner Layout Design (FMCRLD) is the most demanding and
critical task in the early Conceptual Mould Layout Design (CMLD) phase.
Traditional experience-dependent manual FCMRLD workflow results in long design
lead time, non-optimum designs and costs of errors. However, no previous research,
existing commercial software packages or patented technologies can support
FMCRLD automation and optimisation. The nature of FMCRLD is non-repetitive
and generative. The complexity of FMCRLD optimisation involves solving a
complex two-level combinatorial layout design optimisation problem. This research
first developed the Intelligent Conceptual Mould Layout Design System (ICMLDS)
prototype based on the innovative nature-inspired evolutionary FCMRLD approach
for FMCRLD automation and optimisation using Genetic Algorithm (GA) and Shape
Grammar (SG). The ICMLDS prototype has been proven to be a powerful
intelligent design tool as well as an interactive design-training tool that can encourage
and accelerate mould designers’ design alternative exploration, exploitation and
optimisation for better design in less time. This previously unavailable capability
enables the supporting company not only to innovate the existing traditional mould
making business but also to explore new business opportunities in the high-value
low-volume market (such as telecommunication, consumer electronic and medical
devices) of high precision injection moulding parts. On the other hand, the
innovation of this research also provides a deeper insight into the art of evolutionary
design and expands research opportunities in the evolutionary design approach into a
wide variety of new application areas including hot runner layout design, ejector
layout design, cooling layout design and architectural space layout design
Computer Aided Design of Side Actions for Injection Molding of Complex Parts
Often complex molded parts include undercuts, patches on the part boundaries that are not accessible along the main mold opening directions. Undercuts are molded by incorporating side actions in the molds. Side actions are mold pieces that are removed from the part using translation directions different than the main mold opening direction. However, side actions contribute to mold cost by resulting in an additional manufacturing and assembly cost as well as by increasing the molding cycle time. Therefore, generating shapes of side actions requires solving a complex geometric optimization problem. Different objective functions may be needed depending upon different molding scenarios (e.g., prototyping versus large production runs). Manually designing side actions is a challenging task and requires considerable expertise. Automated design of side actions will significantly reduce mold design lead times. This thesis describes algorithms for generating shapes of side actions to minimize a customizable molding cost function.
Given a set of undercut facets on a polyhedral part and the main parting direction, the approach works in the following manner. First, candidate retraction space is computed for every undercut facet. This space represents the candidate set of translation vectors that can be used by the side action to completely disengage from the undercut facet. As the next step, a discrete set of feasible, non-dominated retractions is generated. Then the undercut facets are grouped into undercut regions by performing state space search over such retractions. This search step is performed by minimizing the customizable molding cost function. After identifying the undercut regions that can share a side action, the shapes of individual side actions are computed.
The approach presented in this work leads to practically an optimal solution if every connected undercut region on the part requires three or fewer side actions. Results of computational experiments that have been conducted to assess the performance of the algorithms described in the thesis have also been presented. Computational results indicate that the algorithms have acceptable computational performance, are robust enough to handle complex part geometries, and are easy to implement. It is anticipated that the results shown here will provide the foundations for developing fully automated software for designing side actions in injection molding
A knowledge-based approach for the extraction of machining features from solid models
Computer understanding of machining features such as holes and pockets is
essential for bridging the communication gap between Computer Aided Design and
Computer Aided Manufacture. This thesis describes a prototype machining feature
extraction system that is implemented by integrating the VAX-OPS5 rule-based
artificial intelligence environment with the PADL-2 solid modeller. Specification of
original stock and finished part geometry within the solid modeller is followed by
determination of the nominal surface boundary of the corresponding cavity volume
model by means of Boolean subtraction and boundary evaluation. The boundary model
of the cavity volume is managed by using winged-edge and frame-based data
structures. Machining features are extracted using two methods : (1) automatic feature
recognition, and (2) machine learning of features for subsequent recognition. [Continues.
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