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Integration of Design Data into a Design Solution and their Modification in Problems of Geometrical Modelling

https://doi.org/10.38013/2542-0542-2021-1-85-92

Abstract

This article considers an approach to achieving modifiability of design solutions in the form of digital 3D parts and assembly units in CAD systems. This approach is based on a modular principle, according to which a design solution is represented by a system of 3D macro-objects. Such macro-objects are typical of a given subject area, have semantic content and are described by a set of design parameters. The variability of selected parameters forms a class of design solutions, which, although differing in terms of geometry and structure, have common structural and functional specific features. The main advantage of the proposed approach consists in the provision of the semantic integrity of a design solution during its modification and reuse.

For citation:


Tsygankov D.E., Shaykheeva G.R., Gorbachev I.V. Integration of Design Data into a Design Solution and their Modification in Problems of Geometrical Modelling. Journal of «Almaz – Antey» Air and Space Defence Corporation. 2021;(1):85-92. https://doi.org/10.38013/2542-0542-2021-1-85-92

Introduction

With the increasing role of information technology (in particular, geometric modelling) in the production process, computer aided design (CAD) systems have become an indispensable engineering tool for solving technical issues at the research and development stage. The result of CAD implementation is an increase in the effectiveness of accumulation, systematisation and unification of design solutions, which is also reflected in the quality of their reuse [1].

Many papers are devoted to the reuse of design solutions at the design stage [2]. Its relevance and importance in the production process is beyond doubt. Modification is among the ways of reuse, namely, the modification of the closest design solution [3] within the framework determined by its functional purpose. This process is typical [4] for all modern CAD systems (when presenting design solutions in the form of electronic 3D-models), however, it is timeand labour-intensive. An additional difficulty is the impossibility of adding semantic content to the design solution within the basic CAD functionality, leading to errors in its geometry and structure in the process of modification. In other words, there are no mechanisms capable of ensuring the structural and functional integrity of the design solution before and after the modification. Such a mechanism has been developed by the authors as part of their proprietary approach.

As an example of design solutions, a class of coaxial microwave devices, including multiple various products, such as connectors, junctions, plugs, workloads, etc. [5], is considered in the paper. All products differ in design and purpose, yet they are defined by a relatively narrow subject domain and a limited list of normative and technical documentation [6], providing a wide creative scope for the design process, primarily at the level of local design parameters. The set of values for such design parameters determine the design of a product with varying ranges of performance characteristics in terms of functionality, reliability, manufacturability, etc.

Modifiability of products at the Part level

Any designed part (as a component of an assembly / assembly unit), displayed in CAD in the form of a 3D-model, is described by the history of its construction as a sequence of n design operations (DO), ordered in a so-called development tree, which has the form of <DO1, DO2, …, DOn>. One and the same 3D geometry can be constructed in multiple different ways with matching or mismatching composition of DO and their number n. Figure 1 shows a 3D model of a union nut (a component of a coaxial connector) and its development tree. Each element of the tree contains a number of parameters (local and associatively connected to other elements). The management of their values ensures the reconstruction of the resulting design solution.


Fig. 1
. Generated 3D model of the part and its development tree

Compass 3D is used as a CAD system in the given paper.

The 3D model generated as a design solution contains a set of values for all design parameters, and contains them implicitly, i.e. the developer establishes associative links between their idea and CAD functionality, using operations and terms of the latter with no possibility of their further recovery. The single structure capable of storing design parameters and their values is the 3D model development tree [3].

The main difficulty of storing design data comprising a design concept is the impossibility of associating them with the electronic 3D model within the framework of the basic CAD functionality. For this reason, the authors have developed an approach that consists in representing a 3D model of a product by a system of 3D macro-objects, typical for the current subject domain, each of which is, in fact, a class of parametrically defined templates and is described by a set of design parameters. Depending on the values of the parameters, an actual template is selected (through software implementation and/ or branching), at the output of which an instance of a 3D fragment is formed with the principal and fundamental feature of a fixed structural and functional specificity in the context of the product under development (for a given subject domain). Otherwise stated, such an object is no longer abstract in its geometry, but has a design concept [7].

The creation of 3D macro-objects is implemented by structural and functional decomposition [8] of design solutions in a given subject domain. As to their type, they are divided into structural and functional base (CFB), which sets the design basis for the future product, and structural and functional fragment (CFF), which contributes to the typical purpose of the product. Figure 2 shows the 3D model tree of a nut (see Fig. 1) as a system of 3D macro-objects, and an entry window for design parameter values. The development tree contains one CFB and an arbitrary set of CFF, while the parameters describing the CFB are initial for all CFF.


Fig. 2
. 3D model development tree as a system of typical macro-objects

Some of the design parameters are set by entering values under the constraints of minimum, maximum and invalid values; the other parameters are selected from a set of pre-defined discrete series values. Allocation of parameters and subsequent establishment of associative links, as well as the 3D macro-object parametrisation on their basis, are performed algorithmically in the process of software implementation. Macro-object (МcОb) is formally represented in the form МкОб = <прк1, прк2,...пркn, прв1, прв2,...првn>, where прк – an input parameter comprising a design concept, прв – an internal parameter used by CAD for the construction of 3D geometry, for which the following record is true: првi = φ(прк1,...пркn), .

Upon considering the constraints on the input values, it is necessary to check the structural and functional integrity, implying not only the fulfilment of the conditions for the values of each прк parameter, but their joint correlation as well, excluding the original design intent violation, embedded in the 3D geometry. The 3D macro-object is not formed until the integrity is confirmed.

The nominal values of design parameters are set in the process of 3D model generation at the level of corresponding macro-objects. The generated design is further modified by changing the required parameters, while all changes concerning several macro-objects are performed synchronously, thus ensuring the correctness of the design at the level of geometry and design intent. Figure 3 shows the configuration process of the 3D model of a nut (see Fig. 1) according to the values of the allocated design parameters. Despite the differences in design, all parts are generalised in accordance with their functional purpose. Obviously, such level of automation cannot be achieved within the framework of basic CAD parametrisation.


Fig. 3
. Configuration of the 3D model of the part by design parameter values

The modification of a design solution by changing the values of macro-object parameters corresponds to the modular principle [9], the advantage of which lies in unification of typical elements, contributing to the minimisation of time spent on generating a new design solution. The design solution under modification retains the correct design (not only that of geometry and product structure, but of its semantic content as well) due to the preconditioning system set at the macro-object level.

The design data input into the design solution at the 3D macro-object level allows switching from CAD terms to the terms of the narrow subject domain.

Modifiability of products at the Assembly Unit level

The configuration process of the component parts design (see Fig. 3) defines the variability of products at the assembly unit (assembly) level, determined by the range of required characteristics. Figure 4 shows the structure and assembly drawing of a 5-part coaxial connector (plug). Such 3D assembly is relatively simple (in terms of modelling) and contains ~10 interfaces between components.


Fig. 4
. Development tree (structure) of an assembly 3D model (sub-assembly).
Legend: 1 – housing, 2 – rim, 3 – gasket, 4 – ring, 5 – nut; d – internal thread, D – external thread, l – length of add-on section (with external thread)

The variability of the given assembly, caused by the differences in design parameters at the level of its component parts, is shown in Figure 5. As can be seen, the assemblies differ in the configurations of the Housing parts (item 1) and Nut parts (item 5). They have different connecting (to the mating surface of the housing) dimensions as well. The local parameters, such as Grooving type, Number of end face grooves, etc. are set at the level of the corresponding parts. The special parameters, such as Distance between nut and housing and Length of threaded section (regulated as per standard [6]), which describe an assembly unit (assembly) directly, are specified only through its development tree and subsequently determine the values of component parts’ local parameters.


Fig. 5
. Configuration process of an assembly 3D model (sub-assembly)

Another vital aspect lies in the pairing of assembly components not to the geometrical elements, but to the structural mutual elements, ensuring the correct design during its reuse (modification) that involves changing the original geometry, thus negating the need to redefine all pairings anew. It is relevant to highly complex assemblies under development, since considerable time and labour are required for their design. It is also relevant for the cases when the components structure is altered due to inevitable disruption of the assembly integrity.

In terms of automating the modifiability of design solutions, complete functional units are of the greatest interest due to the possibility to manage their design via the design parameters of the upper level. A coaxial connector is considered as an example of such a unit, namely, the “Ekspertiza” cable plug of the third type as per GOST 20265-83. Its 3D assembly structure is shown in Fig. 6, it contains 2 sub-assemblies and 6 parts. It stands to mention that every structural component of the assembly is a system of 3D macroobjects in the form of . The set of its parameter values defines an instance of the design solution (configuration). In other words, an assembly 3D-model development tree is a system of associatively interconnected parametric 3D templates, controlled by the values of the initial design parameters.


Fig. 6
. Development tree (structure) of an assembly 3D model.
Legend: 1 – plug (sub-assembly), 2 – rod (sub-assembly), 3 – sleeve, 4 – housing, 5 – collet, 6 – gasket, 7 – hold-down clamp, 8 – washer; h – diameter of orifice for cable insulator (braided), H – diameter of orifice for external cable cover

The given plug as a structurally complete product as per standard [6] is described by such parameters as Connector type, Plug type, Cable grade, etc., which are “top-level” as they describe not the local geometry, but the final design in terms of its functional purpose. An instance of the design solution in the form of an assembly 3D plug model and some of its design parameters are shown in Figure 7. As can be seen, the Cable grade parameter defines the design at the level of two components: sleeve (item 3, size H) and collet (item 7, size h), while the first two parameters define the parameters and structures of nearly all components.


Fig. 7
. Design solution in the form of an assembly 3D model

Design solution instances, generated from a single assembly 3D model development tree, differ in the values of design parameters and, consequently, in the structure. They are generalized to the level of semantic similarity class, i.e. similarity in design and functional purpose. Unification and systematization of design solutions based on such similarity level is the upper level of abstraction and is not implemented in the standard CAD functionality.

The generated design solution in the form of the 3D model of a functional assembly subsequently provides an opportunity for automated generation of separate 2D fragments compiling the information images of typical 3D macro-objects displaying their required dimensions, positional designations and other information, presenting a full-fledged design document in compliance with the Unified System for Design Documentation after some manual adjustment.

Conclusion

The configuration process of the 3D models of assembly units by functional parameters within a single class allows to increase the automation effectiveness during the reuse of design solutions in geometrical modelling by preserving the design intent of the original solution [10]. The elimination of errors in 3D geometry and the consequent need for its rearrangement allows to significantly reduce the time and labour intensity of a design solution generation by means of modification.

The preservation of structural and functional integrity of design solutions in the process of modification allows to create unified objects libraries of various levels with a wide range of variability. Such libraries are assigned to design sectors specialising in a narrow subject domain.

The design data input into the design solution and the subsequent modification of their values on the example of a class of coaxial microwave devices are implemented by the developed software package [11], executed as an add-on to the Compass 3D CAD system. Further development of the proposed approach is related to the integration with a CAE system to enable configuration of the product design based on the results of electromagnetic calculation to obtain the required parameters.

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About the Authors

D. E. Tsygankov
Ulyanovsk mechanical plant
Russian Federation

Tsygankov Denis Eduardovich – Cand. Sci. (Engineering), Designer Engineer of the first category. Research interests: design activities, automation methods, modelling and development of coaxial and strip microwave devices.

Ulyanovsk, Russian Federation



G. R. Shaykheeva
Ulyanovsk mechanical plant
Russian Federation

Shaykheeva Gyuzel Rinatovna – Designer Engineer. Research interests: geometric modelling, designing technologies, schematic modelling of radio-electronic microwave devices.

Ulyanovsk, Russian Federation



I. V. Gorbachev
Ulyanovsk state technical university
Russian Federation

Gorbachev Ivan Vladimirovich – Cand. Sci. (Engineering), Assoc. Prof., Head of Educational Department. Research interests: computer-aided design systems, knowledge-based intellectualization of industrial process control.

Ulyanovsk, Russian Federation



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For citation:


Tsygankov D.E., Shaykheeva G.R., Gorbachev I.V. Integration of Design Data into a Design Solution and their Modification in Problems of Geometrical Modelling. Journal of «Almaz – Antey» Air and Space Defence Corporation. 2021;(1):85-92. https://doi.org/10.38013/2542-0542-2021-1-85-92

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