Therblig


Therbligs are elemental motions used in the study of workplace motion economy. A workplace task is analyzed by recording each of the therblig units for a process, with the results used for optimization of manual labour by eliminating unneeded movements. Eighteen therbligs have been defined.
The word therblig was the creation of Frank [Bunker Gilbreth] and Lillian Moller Gilbreth, American industrial psychologists who invented the field of time and motion study. It is a reversal of the name Gilbreth, with 'th' transposed.

Elements

A basic motion element is one of a set of fundamental motions used by a worker to perform a manual operation or task. The set consists of 18 elements, each describing one activity.
  • Search : attempting to find an object using the eyes and hands.
  • Use : manipulating a tool in the intended way during the course of working.
  • Find : A momentary mental reaction at the end of the Search cycle. Seldom used.
  • Disassemble : separating multiple components that were joined.
  • Select : Choosing among several objects in a group.
  • Inspect : determining the quality or the characteristics of an object using the eyes and/or other senses.
  • Grasp : grasping an object with the active hand.
  • Pre-position : positioning and/or orienting an object for the next operation and relative to an approximation location.
  • Hold : holding an object.
  • Release load : releasing control of an object.
  • Transport loaded : moving an object using a hand motion.
  • Unavoidable delay : waiting due to factors beyond the worker's control and included in the work cycle.
  • Transport empty : receiving an object with an empty hand.
  • Avoidable delay : pausing for reasons under the worker's control that is not part of the regular work cycle.
  • Position : positioning and/or orienting an object in the defined location.
  • Plan : deciding on a course of action.
  • Assemble : joining two parts together.
  • Rest : resting to overcome a fatigue, consisting of a pause in the motions of the hands and/or body during the work cycles or between them.

    Effective and ineffective basic motion elements

Effective:
  • Reach
  • Move
  • Grasp
  • Release Load
  • Use
  • Assemble
  • Disassemble
  • Pre-Position
Ineffective:
  • Hold
  • Rest
  • Position
  • Search
  • Select
  • Plan
  • Unavoidable Delay
  • Avoidable Delay
  • Inspect

    Sample usage

Here is an example of how therbligs can be used to analyze motion:

History

In an article published in 1915, Frank Gilbreth wrote of 16 elements: "The elements of a cycle of decisions and motions, either running partly or wholly concurrently with other elements in the same or other cycles, consist of the following, arranged in varying sequences: 1. Search, 2. Find, 3. Select, 4. Grasp, 5. Position, 6. Assemble, 7. Use, 8. Dissemble, or take apart, 9. Inspect, 10. Transport, loaded, 11. Pre-position for next operation, 12. Release load, 13. Transport, empty, 14. Wait, 15. Wait, 16. Rest."