A Process Flow Chart is a pictorial representation of a process, using a variety of symbols connected by lines and arrows. A Process Flow Chart provides a clear picture of each stage of a process, the interrelationship between stages of the process, and the direction of the process flow.
There are a few basic symbols that you should understand prior to starting the flow charting process. Here they are:
A rectangle is generally used to identify a process activity, or an action step, in the overall process. Activities such as machining a thread, grinding a surface, and assembling components are examples of activities that could be represented by the rectangle.
The diamond is used to indicate a decision required in the process. The information contained in the diamond generally takes the form of a question. Decisions such as “make or buy,” “cast or machine,” and “ship or stock” are represented by the diamond. Probably the most common use of the diamond symbol is in quality assurance. If a part meets certain quality criteria, then a subsequent process occurs. If the part does not meet these criteria, then an alternate process occurs. These two alternate processes would be shown as branches running from different points on the diamond.
This symbol is used to represent delays in the process. If a part must be placed in a temporary storage area, awaiting delivery to a secondary operation, this delay would be described by this symbol. It is helpful to see graphical representations of delays in a process, as these are the first areas that should be addressed when trying to streamline the process. In a Process Flow Chart, the fewer the number of delay symbols, the more efficient the process.
The inverted triangle symbol designates a storage activity. If raw material is ordered and brought to a stockroom, this symbol is used. Likewise, if a sub-assembly is taken to the stock room at some time during the overall manufacturing process, then this symbol could represent this activity. The inverted triangle is another symbol that represents non value-added activity, so it should be the focus of any streamlining efforts.
There are other symbols that may be incorporated in Process Flow Charts. A circle serves as a “Go To” symbol and is used when your flowchart gets too big for one sheet of paper (for example, Go to Page 2), or when your flowchart gets complicated and you want to avoid lines that cross each other. A square may be used to denote a specific inspection process. However, the four symbols shown above are the most important and can be used to complete almost any Process Flow Chart.
The following steps should be followed when flow charting a process:
- Clearly define the steps in the process from beginning to end.
- Identify each step by the simplest symbols possible.
- Determine how the steps flow, including any backward flow that may result from outcomes of certain activities.
- Add all lines and arrows to indicate the relationship between steps and the direction of flow.
- Complete the first draft and have if reviewed by those most familiar with the process.
- Modify the Process Flow Chart as necessary.
Once the Process Flow Chart is complete and accurate, begin the procedure of analyzing the overall process. Look for duplication of activities and non-value added steps throughout the process.
The sample flow chart (above, right) shows how the symbols can combine to produce a graphical representation of a process.
Look at some of your own processes and use the simple flow charting technique to identify areas for improvement.