Minimizing makespan of a flexible machine under tooling contraints

Computer Number Control (CNC) milling and lathe machines are widely used in manufacturing due to their flexibility in producing parts with a wide variety of geometries. Each flexible machine has a tool magazine capable of holding a set of tools. As machining requirements for each job change, tools can be removed and different ones can be inserted so that the next job can be processed. The existing literature on the job scheduling and the tool loading can be divided into four main areas. The first area is the tool loading for a pre-specified job sequence where the objective is to determine the optimal tool loading by minimizing the number of tool switching. In addition to tool loading, the second area also focuses on sequencing the jobs too; however, the objective is the same as the first one. Rather than to minimizing the number to tool switching, the focal point of the third area has been shifted to minimizing the makespan in presence of multiple process plans. However, the main assumption is that the magazine can hold all tools needed to process all jobs and tool switching is not required. The fourth area considers the geometric and mechanical properties of the tool, assuming a tool switching may be required due to tool life. The job scheduling and the tool loading literatures do not consider multiple process plans or tool life into their problem. Therefore, the first part of this thesis provides a Dynamic Programming method to determine the optimal makespan for a pre-specified sequence of jobs, assuming tool switching may required due to multiple process plans, the capacity of the tool magazine and due to the tool life. In the second part, the assumption for fixed job sequence is relaxed and a heuristic approach is used to first sequence the jobs and then Dynamic Programming is applied to find the optimal makespan for that particular job sequence.

Minimizing makespan of a flexible machine under tooling contraints

Computer Number Control (CNC) milling and lathe machines are widely used in manufacturing due to their flexibility in producing parts with a wide variety of geometries. Each flexible machine has a tool magazine capable of holding a set of tools. As machining requirements for each job change, tools can be removed and different ones can be inserted so that the next job can be processed. The existing literature on the job scheduling and the tool loading can be divided into four main areas. The first area is the tool loading for a pre-specified job sequence where the objective is to determine the optimal tool loading by minimizing the number of tool switching. In addition to tool loading, the second area also focuses on sequencing the jobs too; however, the objective is the same as the first one. Rather than to minimizing the number to tool switching, the focal point of the third area has been shifted to minimizing the makespan in presence of multiple process plans. However, the main assumption is that the magazine can hold all tools needed to process all jobs and tool switching is not required. The fourth area considers the geometric and mechanical properties of the tool, assuming a tool switching may be required due to tool life. The job scheduling and the tool loading literatures do not consider multiple process plans or tool life into their problem. Therefore, the first part of this thesis provides a Dynamic Programming method to determine the optimal makespan for a pre-specified sequence of jobs, assuming tool switching may required due to multiple process plans, the capacity of the tool magazine and due to the tool life. In the second part, the assumption for fixed job sequence is relaxed and a heuristic approach is used to first sequence the jobs and then Dynamic Programming is applied to find the optimal makespan for that particular job sequence.

Online Education: A Learner’s Perspective During COVID-19

The global health disaster COVID-19 has imposed a self-refrainment from social gathering to contain the disease, because social distancing is the only shield from community spread. Home and work places are altogether giving an unanticipated, unpredicted and unpleasant milieu due to global spread of COVID-19. The teaching–learning process is no exception, with the closure of all educational institutions as a protective step to save lives. The teaching–learning process has been reflecting a very wide and deep impact of COVID-19. With all teachers and learners confined to their places of stay, learning has been impacted to a large extent, with a sense of uncertainty, insecurity and dilemma around effective learning. In fact, the COVID-19 pandemic has thrown the mission and rigour of teaching–learning out of gear. With all classrooms shut, the pandemic has exposed teachers and learners more towards the online learning mode, with no other option perceptible at this point of time. Though online education has always been embraced by academics as a supporting tool, switching over completely to the online mode of learning has raised some serious concerns pertaining to its efficacy and the reluctance of learners in embracing it as a substitute of the regular mode of learning. This study reveals the perception of 2,895 learners on the efficiency of online learning as a substitute of the regular mode of learning. The results show the acceptance of online learning only as a supporting tool to regular learning instead of as a substitute of the regular learning mode on the basis of various factors of effective learning, such as content, pedagogy, assessment and rigour.