7/29/2019 2.2 Filming Techniques for Recording Present Practice

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Techniques for recording Present practices

Motion StudyMotion study is a technique of analyzing the body motions employed in doing a task in order to eliminate orreduce ineffective movements and facilitates effective movements. By using motion study and the principles

of motion economy the task is redesigned to be more effective and less time consuming.

The Gilbreths pioneered the study of manual motions and developed basic laws of motion economy that arestill relevant today. They were also responsible for the development of detailed motion picture studies,termed as Micro Motion Studies, which are extremely useful for analyzing highly repetitive manualoperations. With the improvement in technology, of course, video camera has replaced the traditional motionpicture film camera.

In a broad sense, motion study encompasses micro motion study and both have the same objective: jobsimplification so that it is less fatiguing and less time consuming while motion study involves a simple visualanalysis, micro motion study uses more expensive equipment. The two types of studies may be compared toviewing a task under a magnifying glass versus viewing the same under a microscope. The added detailrevealed by the microscope may be needed in exceptional cases when even a minute improvement inmotions matters, i.e. on extremely short repetitive tasks.Taking the cine films @ 16 to 20 frames per second with motion picture camera, developing the film andanalyzing the film for micro motion study had always been considered a costly affair. To save on the cost ofdeveloping the film and the cost of film itself, a technique was used in which camera took only 5 to 10frames per minute. This saved on the time of film analysis too. In applications where infrequent shots ofcamera could provide almost same information, the technique proved fruitful and acquired the name MemoMotion Study.

Traditionally, the data from micro motion studies are recorded on a Simultaneous Motion (simo) Chart whilethat from motion studies are recorded on a Right Hand - Left Hand Process Chart.

Therbligs

As result of several motion studies conducted Gilbreths concluded that any work can be done by using acombination of 17 basic motions, called Therbligs (Gilbreth spelled backward). These can be classified aseffective therbligs and ineffective therbligs. Effective therbligs take the work progress towards completion.Attempts can be made to shorten them but they cannot be eliminated. Ineffective therbligs do not advancethe progress of work and therefore attempts should be made to eliminate them by applying the Principles ofMotion Economy. Table5 gives the therbligs along with their symbols and descriptions.

SIMO Chart

It is a graphic representation of the sequence of the therbligs or group of therbligs performed by bodymembers of operator. It is drawn on a common time scale. In other words, it is a two-hand process chartdrawn in terms of therbligs and with a time scale, see Figure6 making the Simo Chart. A video film or amotion picture film is shot of the operation. The film is analyzed frame by frame. For the left hand, thesequence of therbligs (or group of therbligs) with their time values are recorded on the columncorresponding to the left hand. The symbols are added against the length of column representing theduration of the group of therbligs. The procedure is repeated for the right and other body members (if any)involved in carrying out the operation.

It is generally not possible to time individual therbligs. A certain number of therbligs may be grouped into anelement large enough to be measured as can be seen in Figure7.

Uses of Simo Chart

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From the motion analysis shown about the motions of the two hands (or other body members) involved indoing an operation, inefficient motion pattern can be identified and any violation of the principle of motioneconomy can be easily noticed. The chart, therefore, helps in improving the method of doing the operationso that balanced two-handed actions with coordinated foot and eye motions can be achieved and ineffectivemotion can be either reduced or eliminated. The result is a smoother, more rhythmic work cycle that keepsboth delays and operator fatigue to the minimum extent.

Cycle graph and Chrono cycle graph

These techniques of analyzing the paths of motion made by an operator were developed by the Gilbreths.To make a cycle graph, a small electric bulb is attached to the finger, hand, or any other part of the bodywhose motion is to be recorded. By using still Photography, the path of light of bulb (in other words, that ofthe body member) as it moves through space for one complete cycle is photographed by keeping theworking area relatively less illuminated. More than one camera may be used in different planes to get moredetails. The resulting picture (cycle graph) shows a permanent record of the motion pattern employed in theform of a closed loop of white continuous line with the working area in the background. A cycle graph doesnot indicate the direction or speed of motion.

It can be used for

Improving the motion pattern and

Training purposes in that two cycle graphs may be shown with one indicating a better motionpattern than the other.

The Chrono cycle graph is similar to the cycle graph, but the power supply to the bulb is interrupted regularlyby using an electric circuit. The bulb is thus made to flash. The procedure for taking photograph remains thesame. The resulting picture (Chrono cycle graph), instead of showing continuous line of motion pattern,shows short dashes of line spaced in proportion to the speed of the body member photographed. Widespacing would represent fast moves while close spacing would represent slow moves.The jumbling of dotsat one point would indicate fumbling or hesitation of the body member. A chrono cycle graph can thus beused to study the motion pattern as well as to compute velocity, acceleration and retardation experienced bythe body member at different locations.The world of sports has used this analysis tool, updated to video, for extensively the purpose of training in

the development of from and skill.