SIMULTANEOUS MOTION CYCLE (SIMO) CHART
A SIMO chart, often based on film analysis used to record simultaneously on a common time scale the therbligs or groups of therbligs performed by different parts of the body of one or more workers.
The SIMO Chart is the micro-motion form of the man type flow process chart. Because SIMO charts are used primarily for operations of short duration, often performed with extreme rapidity, it is generally necessary to compile them from films made of the operation which can be stopped at any point or projected in slow motion. It is recorded by a â€˜wink counterâ€™ placed in such a position that be seen rotating during the filming.
To prepare such a chart, an elaborate procedure and the use of expensive equipment are required. Investigation in this degree of detail is only justified when the saving resulted from improved method will defray the cost of the work involved.
There are many jobs that have activities, or an inter-relationship of activities which, although they do not need to be examined in fine detail, are still too fast or intricate to be measured recorded accurately without the help of a film.â€™ The production quantities of some jobs may not justify the detail of micro-motion analysis, the job cycle may exceed the 4-minute duration, or the efficiency of a cycle may depend on integrating the work of a team of people.
The filming of these various classes of work can be performed economically and efficiently by Marvin E Mundelâ€™s method of time lapse cine photography known as â€œmemo motionâ€? . This is carried out by attaching an electric time lapse unit to the cine camera so that a picture is taken at an interval of time set at any convenient unit between Â½ seconds up to 4 seconds in frequency. Usually, the time interval chosen is one from a second, which means that a 100-ft reelof film can record an hourâ€™s work. For a very large range and variety of jobs one frame a second misses very little detail of the information that is vital to a study, so that this technique is an extremely valuable tool possessing all the advantages of a film record, and the additional advantages of economic use of film and the ability to record longer periods of work. To avoid difficulties it is necessary to set a wink counter or micro-chronometer in the picture and, also, to take supplementary notes of what is happening while the camera is running Thus, if by some chance the time lapse unit falters, then time continuity will not be lost, or if the cameraâ€™s view of an activity is momentarily obstructed , then the note can be referred to.
Analyzing such a film is much the same as for micro-motion, but the scale of analysis is broader and the therbligs are listed to suit the type of chart that applies. In teamwork, this would be multiple activity charts.
Cyclographs and Chrono cyclographs
In addition to the straight forward use of still photography to make permanent records of work place layouts, string diagrams and models etc, a technique was originated by Gilberth to enable comparatively short motion patterns to be recorded on a photograph of the workplace itself. The record can be made as a continuous or dotted white line, known as cyclograph or chrono cyclograph.
Here we are particularly interested in the motions made by an operator while doing a job. A cyclograph is a technique employed to record of path of movement usually traced by a continuous source of light on a photograph. It is produced by attaching small lights to the workerâ€™s wrists (or where desired) and making a time exposure (on a small lens stop) while single cycle of portion is performed.
A similar photographic procedure is used to make a chronocyclography in which the light source is suitably interrupted at regular intervals so that the path appears as a series of pear shaped spots rather tan a continuous line. This enables both the direction of movement and the speed at any point along the path to be recorded. The shape indicates the direction of the movement and the space between the dots, the speed. This is achieved in following way:
1. The interruption of the light source is arranged to take place at carefully controlled regular interval (usually 10, 20, or 30 times per second).
2. The method of interruption is such that, when the light is being recorded on the film, the movement of the subject results in a per-shaped dot being produced, distinctly tapering off at one end. This is achieved either by means of suitable equipment in the lighting circuit operating at the required frequency, or by exposing the film through a disc rotating at the appropriate speed and of suitably graduated density.
When the frequency of the interruptions is known, the speed and direction of movement at any point along the path can be easily calculated from the number and shape of dots recorded.
The main value of cyclographs and chronocyclographs, lies in the convenience with which different motion patterns can be compared for variations in the method of performing a particular operation.