What is Motion Study? Motion study principles, Micro-motion study

Motion Study

Systematic study of the human motions used to perform an operation

• Eliminate unnecessary motions
• Identify the best sequence of motions for maximum efficiency

An important avenue for productivity improvements

The most-used techniques are the following

• Motion study principles

• Analysis of therbligs

• Micro-motion study

• Charts

Motion study principles

Guidelines for designing motion efficient work procedures

The guidelines are divided into three categories:

• Principles for use of the body

• Principles for arrangement of the workplace

• Principles for the design of tools & equipment

- Eliminate unnecessary motions

- Combine activities 

- Reduce fatigue 

- Improve the arrangement of the workplace 

- Improve the design of tools & equipment

Principles for use of the body

• Two hands should begin & complete their movements at the same time

• Two hands should not be idle at the same time except periods of rest

• Arms motions should be symmetrical, in opposite directions & simultaneous.

• Hand & body motions should be made at the lowest classification

• Momentum should be employed to help the worker, but should be reduced to a minimum whenever it has to be overcome by muscular effort

• Continuous curved movements are to be preferred to straight-line motions involving sudden & sharp changes in direction

• "Ballistic" (free-swinging) movements are faster, easier & more accurate than restricted or controlled movements

• Rhythm is essential to the smooth & automatic performance of a repetitive operation

• Work should be arranged so that eye movements are confined to a comfortable area, without the need for frequent changes of focus

Principles for arrangement of the workplace

• Definite & fixed stations should be provided for all tools & materials to permit habit formation.

• Tools & materials should be pre-positioned to reduce searching

• Gravity feed, bins & containers should be used to deliver the materials as close to the point of use as possible

• Tools, materials & controls should be located within the maximum working area & as near to the worker as possible

• Materials & tools should be arranged to permit the best sequence of motions

• "Drop deliveries" or ejectors should be used wherever possible, so that the operative does not have to use his or her hands to dispose of the finished work

• Provision should be made for adequate lighting, & a chair of the type & height to permit good posture should be provided. The height of the workplace & seat should be arranged to allow alternate standing & sitting

• The color of the workplace should contrast with that of the work & thus reduce eye fatigue

Principles for the design of tools & equipment

• The hands should be relieved of all work of "holding" the work piece where this can be done by a jig, fixture or foot-operated device

• Two or more tools should be combined wherever possible

• Where each finger performs some specific movement, as in typewriting, the load should be distributed in accordance with the inherent capacities of the fingers.

• Handles should be designed so that much more hand surface can contact with the handle. Necessary when considerable force has to be used on the handle

• Levers, crossbars & hand wheels should be so placed that the operative can use them with the least change in body position & the greatest "mechanical advantage".

• Perform multiple operations simultaneously rather than sequentially

• Mechanize or automate manual operations if economically & technically feasible

  

Analysis of therbligs

Basic elemental motions that make up a job.

Break jobs down into basic elements & base improvements on an analysis of these basic elements by eliminating, combining, or rearranging them.

Some common therbligs are

- Search implies hunting for an item with the hands and/or the eyes
- Select means to choose from a group of objects
- Grasp means to take hold of an object
- Hold refers to retention of an object after it has been grasped
- Transport load means movement of an object after hold.
- Release load means to deposit the object

Some other therbligs are inspect, position, plan, rest, and delay.

Micro-motion study

Use of motion pictures & slow motion to study motions that otherwise would be too rapid to analyze.

• Use of the camera & slow-motion replay enables analysts to study motions that would otherwise be too rapid to see
• Provide a permanent record that can be referred to, not only for training workers & analysts but also for settling job disputes involving work methods

Cost of Micro-motion study limits its use to repetitive activities

Charts

Motion study analysts often use charts as tools for analyzing and recording motion studies

Some commonly used charts are

• Activity charts
• Process chart
• Simo chart