Due to the mathematical elements used in AHP, researchers are keen to adopt the technique (Dweiri & Al-Oqla, 2006; Hambali et al., 2008). With the properties of using multi-level objectives, criteria, sub-criteria, and alternatives, AHP is suitable to be used to solve decision problem. Through pairwise comparison, data are obtained using weightage of the importance of the criteria and the alternatives in terms of each decision criteria.
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AHP is also commonly applied in task selection where the method is used not to find the correct answer but to aid decision-makers finding the best answer. Not only for academic studies, but AHP is also widely used in organizations, especially for an organization to explore their strategies and their competitors (Vaidya & Kumar, 2006). AHP is suitable to be used to groups of decision-makers who shared common objectives, worked in a cooperative environment and of the same status.
2.2. Continuous improvement (CI)
Currently, the implementation of sustainable improvement is gaining increase atten- tion (Bhasin, 2008; Hassini, Surti & Searcy, 2012). With that, several guidelines were developed to support continuous improvement implementation (Sundar, Balaji & Kumar, 2014). Strategic Management, Kaizen, Six Sigma, and Total Quality Management are some of the well-known methods used in continuous improvement (Garcia, Rivera & Iniesta, 2013). Each of these methods uses different tools for improvement.
One way for the continuous improvement to be successful, there is a need to include staff involvement. With that, Total Quality Management adopts tools and plan of doing, check, act approach (Moeuf et al., 2016) that are capable of integrating learning culture to drive organization change (Amirteimoori, Despotis & Kordrostami, 2014; Moeuf et al., 2016). On the other hand, Six Sigma approach aims at reducing variability in organiza- tional processes through the defining, measuring, analyzing, improving and controlling improvement cycle are used to support this approach (Garcia, Rivera & Iniesta, 2013). As for Kaizen, this tool adopted scenario that allows continuous improvement in personal, family, social, and work-life (Anand & Kodali, 2008) which aimed to change for the better (Bhasin, 2008; Gupta & Jain, 2013). However, there are researchers that mentioned that Kaizen is not only a continuous improvement tool, but it also serves as the means and result of human and non-human resources management in the pursuit of business excellence (Hassini, Surti & Searcy, 2012).
As such, a vast literature argues that characteristically the tools that support Kaizen are process-oriented and human-based, as Kaizen is incremental, continuous, and participatory (Anand & Kodali, 2008; Moeuf et al., 2016; Zhang et al., 2012). Therefore, Kaizen, as a continuous improvement tool, stressed that efforts of all people involved in the organization are important to achieve the improvements that can contribute to the achievement of superior results (Hassini, Surti & Searcy, 2012; Sundar, Balaji & Kumar, 2014), while understanding management as the maintenance and improvement of working standards (Amirteimoori, Despotis & Kordrostami, 2014).
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This case study was done in an automotive manufacturing company in Pahang. Moving forward towards the lean manufacturing concept, the company is encouraging contin- uous improvement projects and activities. In a lean manufacturing concept, reducing waste and increasing value-adding operation time is the main target. To reduce the waste of walking in the production time, fabrication of tools trolley was proposed to increase the efficiency rate. The project team is planning to fabricate 100 sets of tools trolley (shown in Figure 1) in the assembly shop for the used in the assembly line.
Figure 1: Tools Trolley in an Assembly Shop (Source: Authors’ own work).
As the company, in-house Continuous Improvement (CI) Workshop has the capacity of fabricating the trolley. Therefore CI-engineers need to plan on the design and choose the correct material for the trolley. All fabrication tools and machine such as cutting machine, tightening tools, welding machines, and measuring devices are available in the workshop. The material for the fabrication must be strong to withstand the weight of the tools, equipment, and some fittings parts. Project lead time is short. Therefore the procurement and fabrication lead time must be minimized to ensure the project comple- tion is on schedule. Material cost should also be within the budget allocation. The data collection phase is crucial in any research. Several aspects come into play in the data
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collection process. The three most crucial aspects are the cost of the selected data collection method, the accuracy of data collected, and the efficiency of data collection. In this study, data were collected via structured, face-to-face interviews. The interview session was conducted with the participation of Project Engineers, Project Leaders, Continuous Improvement Operators, and Assembly Operators. All the participants are involved in the tools trolley project. A pilot test to validate the questionnaires was conducted with two Managers, and some amendments have been made based on the given feedback. Besides that, the researcher also reviewed a few products’ catalogs that describe in details about each material specification to developed comprehensive criteria and alternatives. Information collected from the participants via interview is gathered to determine which criteria are the most important in deciding which material to select for tools trolley fabrication. With the information gathered, the AHP method can be performed. AHP is a decision-making tool that involves structuring criteria into a hierarchy and the relative importance of these criteria is then assessed. Alternatives for each criterion are compared, that relies on the judgment of the interviewed participants. An overall ranking scale of the alternatives is determined.
The AHP selection method follows the following steps. Firstly, define the objective of selection, follows by developing a hierarchical framework based on the collected information on criteria and alternatives, construction of pairwise comparison set matrix, calculation of preferences against criteria of pairwise comparison, ranking the criteria, developing an overall priority ranking, performing a consistency check on the result and finally selection of the best alternatives.
4. Results and Discussion
The main purpose of this study is selecting the most suitable material for the fabrication process of the tool trolley in order to produce a good quality product. From the interview conducted with the Project Engineers, Project Leaders, Continuous Improvement Oper- ators, and Assembly Operators, information on criteria and alternatives are successfully gathered. The selected main criteria are Material Strength, Material Cost, Procurement Lead Time, and Duration of Fabrication Process. According to the participants, these four criteria are the most important and needed to be considered when considering which material to use in the fabrication process of the tool trolley. As for the alternatives, Aluminium, Steel Tube, and Square Tube are chosen by the participants as the potential materials that can be considered in order to construct the tool trolley. The defined objective, four different criteria, and three possible alternatives are shown in Figure 2.
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Figure 2: Hierarchy Structure of the Criteria (Source: Authors’ work).
4.1. Pairwise comparison
The score of each criterion was calculated using pairwise comparison. The decision was done by comparing two alternatives against one criterion, and then the indicated preferences will be recorded. The pairwise comparison scale measurement that was used is shown in Table 1.
Table 1: Pairwise Comparison Scale.
Preference Level Numeric Value
Equally Preferred 1
Moderately Preferred 2
Strongly Preferred 3
Very strongly Preferred 4
Extremely Preferred 5
Source: Taylor (2019)
Table 3 depicted the pairwise comparison of alternatives (Aluminium, Steel Tube, and Square Tube) against criteria (Material Strength, Material Cost, Procurement Lead Time and Fabrication Lead Time). The data collected are based on the expert judgment of the participants during the interview.