1 Introduction

Many methodologies have been adopted by enterprises in innovating their products to capture market shares and to be ahead of the competition in the current competitive global market. One of the established methodologies adopted by top enterprises such as Airbus, Rolls-Royce, Samsung, Boeing and many others is TRIZ (also known as “Theory of Inventive Problem Solving”) [1, 2]. Although TRIZ is widely used to enhance competitiveness of enterprises, the inventive principles recommended by TRIZ to solve engineering problems are very abstract and requires a significant contribution from designers to derive specific solutions to any problems. Therefore, it is important to explore a generative design systems framework that would be able to generate conceptual solutions with physical embodiment features to support designers better. This research work will explore combining ARIZ with shape grammars to derive such a framework.

2 TRIZ or Theory of Inventive Problem Solving

TRIZ is a systematic problem-solving methodology developed by Altshuller [3, 4] that can help designers to be innovative in product development. TRIZ is derived based on decades of study on patent information [3,4,5]. Although the current TRIZ tools have increased in number in the last few years, the core tools of TRIZ are still the classical TRIZ tools such as Contradiction Matrix, Physical Contradiction Resolving Strategies (Separation, Satisfaction, Bypass), Scientific Effects, System of Standard Inventive Solutions and ARIZ. Different TRIZ methods have different ways to model and solve design problems and these methods suggest general design solutions based on heuristics from successful patents [6]. ARIZ is selected to combine with shape grammars to derive a framework generative design systems based on the investigation by Ang [7] on some of the classical TRIZ methods. Ang [7] found that ARIZ had the most suitable TRIZ tools to work with shape grammars to derive a generative design system to assist designers to generate solution concepts with physical embodiment. Although solution concepts with physical embodiment will inspire better ideas to designers, extensive knowledge and experience are still needed in the detail design solutions. ARIZ is the most suitable TRIZ tool to be linked to shape grammars (refer to Table 1) because ARIZ encourages designers to look for solutions from existing resources or the system. This requirement is necessary in order to be compatible with shape grammars as shape grammars need a shape of an existing system to evolve. Shape grammars are selected to be combined with ARIZ because it is one of the established formal methods that can define and evolve shapes of products [8,9,10,11,12].

Table 1. Comparing classical TRIZ tools [7]
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3 ARIZ (Algorithm of Inventive Problem Solving)

ARIZ or the algorithm of inventive problem solving is a 9-part algorithm that combines several TRIZ methods for solving a contradiction in sequential step-by-step procedures [13]. ARIZ is considered to be the most powerful TRIZ method because it combines the power of several TRIZ methods and is used for solving “difficult” problems i.e. problems that cannot be solved by other TRIZ methods. There are many versions of ARIZ but only ARIZ-85C is the official version accepted and approved by Altshuller [14]. For this research work, ARIZ-85C is used.

ARIZ specifically considers existing resources available in solving a design problem and explores solutions based on the parameters related to these existing resources [15]. In Part 2 of ARIZ [13], designers are required to identify the parameters of an existing system with a problem to be solved from the aspects of existing substances, fields and resources in a tabular structure. This table, also known as Substance and Field Resources (SFR), will be used to solve the design problem for the existing product or system.

The SFR provides the existing parameters that may include the definition of the existing shape of a product. ARIZ consists of sub-steps that will guide designers to solve a contradiction by making minimal changes to the existing system (hence the term “mini” solution was coined but in this context, it does not mean small [15]). This means the designers need to explore and analyse the existing components of the product, the super-systems, and the sub-systems for solutions including their parameters such as the dimensions and properties of the components in the system. Super-systems are defined as elements in the environment external to the system such as air, moisture and sunlight that interact with the system. Parameters such as dimensions can be used to define the shape of an existing component in the system which can then be combined with shape grammars to generate potential design solutions. Most experts in ARIZ apply up to Part 3 or 4 to complete the problem solving and Part 5–9 include experimental steps in development [6].

4 Shape Grammars

Shape grammars were introduced by Stiny and Gips in 1972 [16]. A shape grammar has a set of basic shapes and rules that are applied to govern how shapes can be arranged or manipulated step by step into their final forms. It can be considered as grammars for design and have been used in many different areas such as paintings, decorative art, architecture, product design, and engineering [9, 10, 16,17,18,19]. Shape grammars have been applied manually and computationally to create new shapes of products based on shape rules derived from existing products to retain the style or brand identity of the existing product [7, 12, 18,19,20]. In addition to that, there were some successes in using shape grammars to visualise new shapes of products with the aim to maintain brand identity whilst meeting functional requirements [9, 11]. These successes were achieved by combining optimisation algorithm and shape grammars with the pre-determined functional requirements such as volume and height. Recent works on shape grammars include using shape grammars to generate a customised design of Thonet chair style based on customer preference before optimising the design based on structural requirements [21], investigating computer-based implementation of shape grammars via graph-theoretic representation in architecture [22], and exploring the possibility of shape grammars linking with materials [23]. In this research work, we apply ARIZ as part of a design method to solve design problems and use shape grammars to define the shape of design solution based on solutions recommended by ARIZ to support designers.

5 The Novel Framework that Combines ARIZ with Shape Grammars

ARIZ has been identified to be more suitable to be combined with shape grammars due to two key characteristics of ARIZ. The two key characteristics are that existing resources may include components with shapes which can be a potential source of design solutions and the Substance and Field Resources (SFR) analyses provide crucial linking locations for shape grammars. The novel framework combining ARIZ with shape grammars was derived in our earlier work and it is shown in Fig. 1 [7] where a link to shape grammars is introduced during the SFR analysis in Part 2.0. The resources in SFR with parameters that can be used to define a shape will have their shape rules derived in Part SG.1. It is important to stress that only if a design solution which has parameters that depict a definitive shape will undergo transformation of shape rules to generate new variants of design solutions.

Fig. 1.
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A novel framework linking ARIZ with shape grammars [7]

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At any time, a design solution is found either in Part 3.0, or Part 4.0, or Part 5.0, the designers can proceed to Part SG.2 and then to Part 7.0, 8.0 and 9.0 if required. The efficacy of the novel framework that combines ARIZ with shape grammars is verified via a case study to solve a chemical liquid leakage problem at a hose joint. In this case study, solutions were derived in Part 4.0 to verify the novel framework, thus the case study would not proceed into Part 5.0 - Part 9.0.

6 Illustrative Case Study: Using Novel Framework to Solve the Problem of Hose Joint Leakage

The problem of leakage at hose joint is not new. Many industry appliances use some form of hose joint to transport chemicals or liquids from a source to a container. These joints usually have threaded surfaces to facilitate the connection. The model of the engineering system and the cause-and-effect chain analysis (CECA) for the problem is shown in Figs. 2 and 3.

Fig. 2.
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The function model for the joint leakage

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Fig. 3.
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The Cause-and-Effect Chain Analysis (CECA) for poor fitting problem

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Using the novel framework that combines ARIZ with shape grammars to solve the hose joint problem, the problem-solving process started by defining the problem statement and modelling the engineering system from the aspect of the components and functions. CECA is then applied to determine the root cause of the poor fitting. These steps are critical preliminary steps before applying ARIZ to solve any problem. CECA shows that there are several possible root causes that can cause a joint leakage but in this case study, the poor fitting (under-tightening and over-tightening) of the joint is identified to be the root cause. With the root cause determined, the process of applying the new framework (refer to Fig. 1) that combines ARIZ with shape grammars can proceed to Part 1.0 (Table 2), Part 2.0 (Table 3), Part SG.1 (Table 4), Part 3.0 (Table 5), Part 4.0 (Table 6) and finally to Part SG.2 (Table 7).

Table 2. Details of Part 1.0
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Table 3. Details of Part 2.0
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Table 4. Details of Part SG.1
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Table 5. Details of Part 3.0
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Table 6. Details of Part 4.0
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Table 7. Potential solutions (showing the details of shape rules used for incremental diameter size and modifications on the thread depth) based on local quality inventive principle derived in Part SG.2
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7 Discussion

This research work explores how ARIZ can be combined with shape grammars to derive physical embodiments of the specific solutions from solution concepts derived from ARIZ. A novel framework that combined ARIZ with shape grammars was derived and was verified in a case study to solve joint leakage design problem which cause liquid to leak. The case study on joint leaks has shown that the framework can generate potential specific solutions based on TRIZ inventive principles. The case study also showed that the designers can make better decisions based on the final design solutions due to the improvement in visualisation of the possible variety of specific solutions derived by a shape grammar. The designers in this case study has decided to select specific solutions generated by a shape grammar based on the inventive principle ‘Local Quality’. This inventive principle has two potential shape configurations of the thread that could solve the problem of liquid leak due to over and under-tightening of the joint threads. The first shape configuration involved modifications on the joint thread to create incremental diameter size of the thread and the second shape configuration required the end thread of the joint to be made mismatched (refer to Table 7). The final decision was to modify and create a smaller end thread (decreasing the depth of the end thread to act as a stopper) of the joint to solve the problem.

8 Conclusions

The findings from this research work has demonstrated that ARIZ can be combined with shape grammars as a framework to construct shapes of a design solution. ARIZ was chosen because it is the most suitable TRIZ tool to be combined with shape grammars. When ARIZ is combined with shape grammars within a specific domain of a design problem, the conceptual solutions from ARIZ can be transformed by shape grammars to detail out potential specific design solutions. With this novel framework, the designers can visualise the specific solutions better and make better decisions to choose the best solution for a design problem. This framework can also be a basis for generative design systems.