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On Technology and the Human Factor


John Lyman, Ph.D.

The Therblig

The therblig notation evolved from the observation of human movement. It was observed that manual skill could be analyzed into a series of about 16 actions. These actions were called "therbligs" using the approximately reverse spelling of the name of their developer, Gilbreth. The idea was first reported in about 1919 and with some adjustments and minimal modifications has stood up as a usable model to the present time. The names of the movement units were search, find, select, grasp, position, assemble, use, disassemble, inspect, transport loaded, transport unloaded, preposition for next operation, release load, wait (unavoidable delay), sait (avoidable delay) and rest (for overcoming fatigue). Each of these units were observed and timed as they occurred by trained "motion and time specialists" who were highly trained, used stopwatches, motion pictures and various specialized timing devices. Timing was usually in milliseconds but under certain specialized conditions could be in microseconds. Various handbooks, tables, etc. have been generated for typical industrial tasks. Social impacts have been enormous, including work and rest legislation, union-management negotiations, workplace safety, etc., etc..... Detailed time tables for standard workplace tasks are available in technical bookstores and libraries.

© 1999 John Lyman

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