Method of quantitative assessment of the airframe element manufacturability
Irkutsk National Research Technical University, 83, Lermontov str., Irkutsk, 664074, Russia
Nowadays element design is carried out with the help of CAD/CAM/CAE/PDM systems. Thus it is rational to estimate the manufacturability of element structure at early stages of product launch during element design and manufacturing. The goal of this paper is to provide a method for such evaluation. The paper considers a method of manufacturability calculation and estimation, which allows formalizing the process of airframe element manufacturability evaluation and altering characteristics and parameters of individual indicators.
While refining the airframe element design with the purpose of increasing the airframe manufacturability, one must take into account the manufacturing type and specific features of the manufacturer (manufacturing plant) so that structure of individual elements could be produced with taking the aforementioned factors into account.
The paper proposes a method of quantitative estimation of airframe element structure manufacturability based on interaction of individual indicators with taking into account their weight-coefficients. Also an algorithm for manufacturability control of the element based on its 3D-model is suggested.
Final assessment of industrial manufacturability is carried out according to single individual indicators by comparing the variants of the proposed element with analogues, which are already manufactured at the considered plant. The aggregated indicator value is determined under the conditions of an extremely unfavorable combination of individual indicators based on expert estimates.
The quantitative assessment of element manufacturability during its design is carried out with the help of an aggregated indicator:
where ki is the value of individual element manufacturability indicator i;
ϕi is the weight-coefficient of individual element manufacturability indicator i;
n is the number of adopted indicators, which is defined by the expert and must be no less than 5.
Weight-coefficients of the manufacturability indicators are determined by experts. Part of the indicators can be used again to evaluate other airframe elements while their weight-coefficients should be reidentified based on new expert estimates.
It is difficult and often impossible to fully estimate manufacturability level at early stages of manufacturing process design because of insufficient information. To ensure the structure manufacturability it is possible to make a qualitative assessment via manufacturability properties and carry out the quantified evaluation using individual indicators.
The proposed method was tested on the example of structure design of sheet pressed airframe elements. It was discovered that this method does reflect the real conditions of structure design and manufacturing processes.
The proposed method is based on expert estimations. Thus additional work is required for selecting the appropriate groups of experts to make these estimations less influenced by subjectivity of particular personalities.
Proposed methodology of refining the element structure manufacturability can be successfully applied in practice for calculation of manufacturability and estimation of the quality of the new developed airframe elements. This is especially important since it might be hard and/or impossible to carry out the manufacturability estimation for such elements according to the main indicators of the standards at the early stages of pre-production planning due to the lack of information, while the ability to carry out the estimation according to additional indicators is limited since such estimation would only reflect the structural design aspect.
Technologies and methods of manufacturing design change over time. The proposed system of manufacturability analysis aspires to «isolate» the designer from such changes while still taking them into account during the creation of the model of the element manufacturing process.
Application of structure manufacturability analysis provides for adaptation of the method to the specific manufacturing by accumulating knowledge about its technological basis. This ensures adaptability of the method as a whole and takes into account general and particular characteristic features of manufacturing. The recognition method works with structure models, which are based on solid-body primitives, thus ensuring the invariability of the manufacturability analysis method towards the way the model was built.
Keywords:airframe structure element, product model, manufacturability, structure component, individual indicator of manufacturability
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