The job or process under investigation often consists of a number of activities. It is with a view to listing them conveniently, we use symbols as a short hand.
The modern system of process charting is an adaptation of one of Gilbreth’s later developments in motion study technique. Originally Gilbreth use a large number of symbols, as a device for visualizing a procedure as a means of improving it. Later in 1947 the American Society of Mechanical Engineers reduced the number of symbols and standardized the technique to its present form. The British definitions are as follows:
Process Charts: Charts in which a sequence of events is portrayed diagrammatically by means of a set of process chart symbols to help a person to visualize a process as a means of examining and improving it. We can devise our own symbols However we follow standardized symbols developed by A S M E since 1947.
Process Chart Symbols:
Symbols used for recording the nature of events:
Indicates the main steps in the process, method, or procedure. Usually the part, material, or product concerned is modified or changed during the operation.
Indicates the movement of workers, materials or equipment from place to place
Indicates a controlled storage in which material is received into or issued from stores under some form of authorization, or an item is retained for reference purposes.
Temporary Storage or Delay:
Indicates a delay in the sequence of events, for example, work waiting between consecutive operations, or any object laid aside temporarily.
Indicates an inspection for quality and / or a check for quantity (This covers measuring weighting or looking for some aspect of quality).
Combined activity occurs simultaneously. Various combinations are possible.
Combined activities can be shown by superimposing their respective symbols so that the outer symbol represents the major activity.
Types of Process Charts:
Outline Process Chart (Operation Process Chart): It gives the bird’s eye view of the whole process by recording in sequence only the main operations and inspections. It, therefore, uses only operations and inspection symbols.
1) Type of chart
2) Job concerned and whether it is the present or proposed method
3) Date of study and name of observer
4) Where chart begins and ends.
5) Adequate and accurate description of all activities on the right and side of the symbol concerned.
6) Number each activity for identification purposes by placing the number within the symbol. The convention for doing this is implied by the chart.
a) Each class of symbol is numbered in its own sequence
b) Numbering begins on the main line of activities which is always placed on the right hand side of the chart.
c) The numbering sequence continues until there is a junction with a subsidiary line, when it jumps to the top of this subsidiary and proceeds downwards from there. The same convention is applied when meeting all other junctions. When combined symbols are used, the first number applies to the outer symbol.
7) Date concerning time, distance, weight, or quantity are shown on the left hand side of the symbol it refers to.
8) A summary of activities is shown at the bottom left hand side of the chart.
9) Use the same scale of breakdown in the analysis of activities so that the comparison of present and proposed methods will not be distorted by appearances.
10) Neatness and clarity in the layout of the hart helps to simplify the process of critical examination.
The outline process chart gives an overall view of a process, from which it can be decided whether a further and more detailed record is needed. It is a graphic representation of the points at which materials are introduced into a process, and of the sequence of all operations and inspections associated with the process.
The chart does not show where work takes place, or who performs it, and since it is concerned only with operations and inspections, only two of the five recording symbols are used.
In the design stage, where it is increasingly the practice to use work study, outline process charts are often used to assist in the layout of plant, and in the design of the product or the machinery for making that product. The charts can be made to record the basic data, which can then be subjected to the complete method study procedure while still on the drawing board. Features in the design of a product which are wasteful of materials or labor can often be eliminated and it is frequently the case that expensive equipment, which otherwise might have been bought proves unnecessary in the light of the investigation.