Identical Parallel Machine Scheduling to Minimize Makespan Using Suggested Algorithm Method at XYZ Company

Abstract

XYZ company produce the various shape of motor spare parts product. The company has three
identical parallel spot welding machines that use a random method of production scheduling, based
on machine capacity without any sequence of jobs, and only use daily production targets given to
operators. Based on the data, the actual scheduling of the machines has a very large completion time
difference between each machine, or the machine loading is uneven. As a result, the makespan
becomes longer with a value of 440000 seconds (26 days). This research aims to minimize the existing
makespan by giving proposed scheduling, using the suggested algorithm method, which has a small
number of iterations and has an optimal result. The method begins with the longest processing time
sequence rule which is used as the upper bound for the first iteration, then continued to calculate the
lower bound and machine workload. The calculation stops at the 15th iteration because the completion
time value exceeds the lower and upper bound so that the optimal scheduling taken is scheduled in
the 14th iteration with a makespan value of 914412 seconds (16 days). The proposed scheduling can
minimize the makespan from the actual schedule by 38%.