Selection of reference base points during the determination of locating chart of the assembly unit

Аuthors

Ahatov R. K.^*, Chien H. V.^**

Irkutsk National Research Technical University, 83, Lermontov str., Irkutsk, 664074, Russia

*e-mail: axatob@istu.edu
**e-mail: maimaibenem_0113@yahoo.com

Abstract

Automatization of the selection of the assembly datum surfaces during the design of the assembly tools requires finding an algorithm for searching and selection of reference base points according to the digital mock-up of the assembly unit, which was constructed in a CAD software system.
The criterion for choosing the position setting spacing of the reference base points is the stiffness, which is defined by the admissible deformation w_доп. The value of w_доп is defined according to the following criteria: the finished component error; the assembly unit linkage errors; the errors of the base elements of the assembly tool.
The work contains the classification, which was developed for the low-stiffness details of the airplane airframe structu re. The universal stiffness characteristic D was defined for each type of details. The value of this characteristic depends on the geometrical, physical and mechanical properties of the standard details. D describes the ability of the structure of the standard components to withstand the external loads.
For example, the stiffness characteristic of the structure of a plate-type detail is defined by the following formula:
 
This allows to determine the maximum deflection of the plate under its own weight

The comparison of the maximum allowable deflection wmax with the admissible deformation w_доп allows to define the maximum spacing of position settingof the reference base points or the installation pitch of base fixing members via the following formula:

The problem of definition of lmax for other standard components is solved in a similar way. These components include the following:

• skin panels from semi-finished sheets (flat and three-dimensional structures with single and double curvature);
• details from extruded profiles, which are made aslong-length elements that define the load-bearing frame ofthe structure oract asskin stiffeners;
• integral panels with the load-bearing stiffeners (milled orextruded).

Analysis results allow to automate the procedures of selection of assembly datum surfaces during the design of assembly tools. This automation enables the assembly of the airplane airframe structure at optimal labor costs for the design and manufacturing of tools for the assembly of the products, which consist of low-stiffness components.

Keywords:

reference base points, locating chart, assembly unit, assembly process references

References

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