In the multimachine assignment problems, Jones calculated the machine idle time and the operator idle time assuming the frequency of machine breakdowns is of Binomial distribution. Recently, it was statistically proved that the pirn winder machine breakdowns at any random moment and spatial location form the Poisson distribution. To quantify the opimum number of machines per operator, and to evaluate the man-machine system efficiency, machine interferences, operator interferences are calculated in the simulated number of the pirn winder machines per operator, for the machines varying from 10 to 35, A case study was made in one of the leading textile firms in Korea. The results show that the percent of the machine idle time is 14, even if the operator performs the service at exhaustive levee, which coincides with the results made by Jones when M$geq$20. Alternative methods in system improvement and cost reduction are discussed and suggested. Among the suggestions, with computed example, emphasis was made that the high dependency on the so-called cheap labor leads to the high facility cost, and promptly to high production cost. (Received Feb. 28, 1973)