Poka-Yoke Process Applied and Avoiding Errors in Manufacturing Processes Due to Human Intervention - Literature review Example

Literature Review This chapter explores existing literature on poka-yoke systems and factors associated with its implementation and success while noting other associated critical findings and perspectives. 2-1: Principles of Poka-yoke methodology: As explained by Shimbun, in general, poka-yoke is a process applied to avoid errors in manufacturing processes due to human intervention1. Poka-Yoke is a Japanese word, when translated in English becomes ‘mistake-proofing’ 2. It is a form of self-inspecting quality-control mechanism that does not need intervention from quality experts; secondly, this method is real-time approach to quality control and therefore saves time and costs. 2-1-1: History: Literature traces the history and origin of poka-yoke to Toyota’s Shigeo Shingo, who had originally introduced the system of baka-yoke in 1961, which meant idiot-proofing in Japanese; however, due to some opposing views associated with this term that emerged from the employees of Toyota, it was later changed to poka-yoke3. Poka-yoke was introduced into the Toyota Production System to prevent errors from workers in the manufacturing process. Originally, this method used sensors such as electrical, mechanical, or visual, to warn the manufacturing workers about the errors that they made during the process; this warning helped in correcting, or even preventing the error, thereby saving time, cost as well as the error itself. Literature has very little evidence of its application in other countries across the world4. 2-1-2: Types of Poka-yoke systems: According to Shingo, poka-yoke can be implemented in two ways, namely, control type and warning type. The former controls the error or mistake from happening by completely stopping the process; and the latter detects the error either by buzzing some sound, flashing a light or any other type of sensor. Shingo asserts that the control poka-yoke system is very effective as it completely prevents the error from being produced, whereas the warning system might get ignored by the workers5. Therefore, it needs to be understood that poka-yoke should focus on various steps that involve operator’s intervention in manufacturing process along with their constant observation and concentration. In general, potential for defects in activities or tasks involving human intervention lies in many factors: lack of skills, misunderstanding/misinterpretation, sluggishness and poor memory, hurrying and adopting shorter methods of doing things, lack of standards, and also unethical actions/intentions.6 In lean manufacturing, emphasis is mostly on optimizing production or output by minimizing resources, wastage and errors7. The aim of poka-yoke is therefore to achieve zero defects in the manufacturing process. However, achieving such high level of accuracy also depends upon the type of controls in place. Poka-yoke systems usually offer external sources of error identification, in the form of simple fixtures that will help the workers easily identify their errors instead of encouraging the workers to be extra careful by avoiding certain types of errors. Introducing such a system is not always economical because this system might require additional sources and therefore incurs more costs. Moreover, introduction and implementation of poka-yoke fixtures would require technical expertise8. 2-1-3: Poka-yoke implementation: The types of Poka-yoke systems that can be applied practically depend upon the types of possible human errors, and Hinckley provided a comprehensive classification of errors based on the root cause of errors, which is shown below9: Figure 2.1.3: Classification of errors9 Practically, workers are meant to use these systems while performing manufacturing activities. According to Womack, Jones and Ross, the implementation of any lean production system requires strong teamwork, communication, efficient use of resources and continuous improvement10. Therefore, human element stands at the core of any such implementation. Generally, poka-yoke implementation involves seven steps11: i) Identifying the problem: Firstly, various complaints from customers and workers are collated and standards for measuring particular aspect of quality or the product is determined. ii) Observations at work stations: Next, observations during processing are recorded with the help of workers. Causes for these problems are sorted out using root cause analyses techniques. iii) Brainstorming: Ideas to correct the identified issues are generated from workers. iv) Select the best ideas: All options are weighed and the best possible solutions are identified from the lot. v) Implementation plan: A plan to implement the solutions is created, which will include time, resource, monitoring aspects etc. vi) Implementation: Chosen solutions are put into practical application by using required materials, technology and resources. vii) Monitoring and sign off: The final products after implementing the solutions are checked for any defects; if zero-defects are found, then the process is confirmed to be implemented permanently. In their review paper, Patil et al., highlight that the shutdown type of poka-yoke is most effective in producing 100% defect-free outputs compared to the warning method. However, in the warning method, workers might tend to or choose to ignore warning signals, which can lead to defects. Patil et al., point out that implementation of warning method to identify defects and produce defect-free products largely depends upon workers’ natures, attitudes, situations and behaviour12. Due to this reason, the warning method cannot be regarded as a complete fail-proof method. Workers’ attitudes towards quality can be another serious concern. Patil et al., reason that if interdepartmental relationship between production and quality are not strong, then chances of ignoring the warning signals will be extremely high as workers may not be motivated to act according to the warning signal13. 2-1-4: Objectives of implementation: Hinckley identifies four main objectives of the poka-yoke system. First and foremost is a warning signal to detect and prevent possible error by taking corrective action. Secondly, it prevents operator-controlled errors altogether. Thirdly, to save costs incurred from making errors, performing rework and putting quality-control checks in place Lastly, it reduces scrap and wastage14. In short, most of the literature related to poka-yoke system identifies three objectives of implementation: defect-free production, reduction of wastage and rework and cost-effective production at the earliest possible time. Another perspective of poka-yoke is to combine tasks of production and quality-checking thereby improving efficiency as well as quality. Hinckley also points out that poka-yoke systems improve workers’ knowledge and onus of responsibility towards creating a zero-defect product15. 2-2: Value chain of human resource: Aligning human resources development (HRD) strategy with business strategy requires creation of value chain that was originally put forward by Porter. The main activities identified by Porter in the value chain include inbound logistics, operations, outbound logistics, marketing and sales and service16. From a human resource perspective, its value chain facilitates improving the understanding of various roles of HR and its scope in maximising employees’ worth for an organisation; subsequently, this value chain identifies various areas that would require appropriate intervention to provide maximum benefit for the employees and the organisation through HR development practices. Coordination and efficiency between each of the elements of the value chain determine its effectiveness as well as the profitability and sustainability of the business. This necessitates effective HR practices across the value chain, which will in turn uplift the effectiveness and efficiency of the entire business17. According to Johnson, value chain is created through value congruence, “which aligns diverse human capital values that result in commitment, satisfaction and engagement with diverse organisational goals that value increasing profits as well as organisational reputation”18. Johnson, represents a typical HR value chain as below: Figure 2.2a: HR Value Chain18 A detailed value chain with value-adding activities and practices has been presented by Boselie, as represented below19 Figure 2.2b: The HR value chain in detail19 Much of literature on continuous improvement strategies points at employee commitment as one of the major requirements. And, numerous studies have established the link between HRM practices and employee commitment, which in turn have a positive impact on employee honesty, punctuality, quality work and higher productivity20,21. Any type of lean implementation requires skills and willingness of the employees. Dombrowski and Crespo identify the “method adoption by a worker approach” as ideal for increasing willingness and commitment of employees in implementing lean production system22; this method is ideal because it encourages worker participation and therefore enhances responsibility and empowerment. By doing so, employees serve as sources of strategic knowledge and learning, which also gets multiplied with time. MacDuffie had concluded that employee participation and empowerment are promoted by high-involvement HR work practices, which also have an impact on plant productivity and quality23. Developing an organisational culture that is not only conducive to HRM practices but also supportive of employee learning and development is crucial for achieving high productivity and quality24. In short, HR practices in the HR value chain should also consider the organisational culture, policies and procedures. From policies and procedures perspective, Huselid’s studies found a direct correlation between HR practices and procedures and organisational variables such as turnover, productivity and financial results. This indicates a close relationship between HR procedures and business results. Moreover, these studies also focused on specific HR practices such as employee selection, appraisal, compensation, grievance-handling procedures, employee relations, communication and information-sharing, training and development activities, all of which had positive impact on overall employee performance and business results25. Contemporary employment practices that promote commitment to high productivity and quality are mostly covered under performance management policies; these include systematic behavioural appraisal of performance, pay for performance, growth and promotions based on performance and training activities. These practices focus on shaping employees’ behaviour that is required for achieving organisational objectives26. 2-3: Human behaviour faces changes at work place: Any continuous improvement system also entails constant change in the way work is being accomplished, change in hierarchy, change in job roles and change in expectations; and change most often elicits fear and resistance from employees27. Employee involvement has been advocated as the best possible solution to address employee resistance to change28. Vidal points out that many studies concerning employee and organisational behaviour vouch for employee empowerment as one method to improve employee commitment to lean implementation; however, empowerment in lean has its own limitations. Firstly, substantive empowerment requires changes in organisational routines and hierarchy, which is not an objective in lean implementation; secondly, lean methods embrace standardization techniques. Therefore, empowerment in lean methods is a rarity, especially in the manufacturing sector29. While the lean methodology needs to be adopted as a philosophy instead of a practice30, approach adopted in poka-yoke implementation addresses the errors and not their root causes. From a different perspective, Hinckley specifically points out that poka-yoke does not focus on controlling or correcting the root cause of the error, but in addressing the error real-time and preventing it from happening. Basically, poka-yoke system was built on the notion that human errors cannot be prevented31. Despite strong poka-yoke systems, achieving zero-defects remains a challenge due to behavioural factors. For instance, poka-yoke system eliminates the need for any sort of quality control inspections; while this can be a positive aspect for the organisation, it can have negative implications on ground-level workers that are less motivated to use poka-yoke systems for various reasons. However, factors that motivate employees and managers to adopt lean methodologies include personal recognition, better compensation, satisfaction and challenge32. Nevertheless, research, evidence and experiences indicate that employees tend to develop negative attitude towards their jobs and also towards supervisors and management because of lack of consistent and effective communication from the management. Moreover, lack of communication and its skills affect employees’ confidence to communicate with management; lack of proper communicating channels or media is another hindrance in fostering better employee commitment33. Boohene and Williams point out that employee involvement improves communication between management and work groups, which can be an opportunity to let employees feel valued and trusted. Meier points out that poka-yoke can have detrimental effects to operations productivity if the sensors or the systems are too complicated. More often, poka-yoke systems are developed by the engineers but implemented or used by frontline workers that are technically less skilled. These workers tend to spend more time in putting the poka-yoke into use due to complexity and lack of understanding about operating the poka-yoke systems. Resetting the poka-yoke device after mistake-proofing is also seen as a concern, thereby increasing the need for training as well as improving their problem-solving abilities34. Poka-yoke is best suited for repetitive tasks that have high risk for committing errors.35 In a way, poka-yoke systems standardize the work processes thereby requiring minimal or no thinking or creativity. The general notion is that although standardization is an effective way to control quality problems, these uniform methods also become the sources for monotony. This notion was challenged by General Motors and Toyota’s joint venture assembly plant, NUMMI, by actually using standardization procedures to improve learning and hierarchical levels to improve support and encouragement for workers36. This project exemplifies management approach to entice the right, or desired, employee behaviour, commitment and attitude through ‘learning bureaucracy.’ This approach in reality achieved higher overall productivity and quality; improved employee involvement and accountability; and created a cohesion between management and workforce. Adler identifies this approach as the right approach to encourage learning, innovation and to institutionalise continuous improvement37. 2-4: Conclusions of the literature review: Concluding the literature review, it can be said that continuous improvement through lean methodologies is an effort primarily required from employees. Poka-yoke systems, first invented in the Japanese automotive manufacturing industry as mistake-proofing techniques, have proven to be extremely useful in preventing inadvertent errors from workers during the production processes. These systems apply the use of specific technology to alarm the workers of potential defect being produced during production process. Research and evidences indicate that poke-yoke systems have not been completely mistake-proof due to reasons such as level of complexity and workers’ skills, motivation and commitment. Studies related to human resource management point at the need for effective HR practices that can add value to overall organisational elements and business outcomes in addition to adding value to human resources through compensation, learning, development and recognition. 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