The Psychology of Quality and More
Flowchart: How to understand it
How to understand it
In order to improve a process, it is first necessary to understand its operation in detail. Describing this in text lacks the clarity of a pictorial diagram, where individual steps are more easily seen.
The Flowchart is a simple mapping tool that shows the sequence of actions within a process, in a form that is easy to read and communicate.
The basic element of a process is a simple action, which can be anything from striking an anvil to making a cash payment, and is represented as a box containing a description of the action. The mapping of 'what follows what' is shown with arrows between sequential action boxes, as in the illustration. This also shows the boxes for process start and end points of which there are normally one each.
Fig. 1. Basic Flowchart elements
Processes become more complex when decisions must be made on which, out of an alternative set of actions, must be taken. The decision is shown in a Flowchart as a diamond-shaped box containing a simple question to which the answer is 'yes' or 'no' as in Fig. 2. More complex decisions are made up of combinations of simple decision boxes.
Fig. 2. Decisions in Flowcharts
Processes often go wrong around decisions, as either the wrong question is being asked or the wrong answer is being given.
Where boxes cannot be directly connected with lines, the separated lines are coordinated with connector boxes containing matching names. This typically occurs where lines cross onto another page, as in the illustration.
Fig. 3. Continuing Flowcharts across pages
By using multiple connector boxes, it is very easy for Flowcharts to become very large, although this is usually self-defeating, as the Flowchart then becomes difficult to understand. The ideal size for a Flowchart is one page, as this gives a single visual 'chunk' that is reasonably easy to understand as a single item.
Large processes can be broken down into a hierarchical set of smaller Flowcharts by representing a lower level process as a single sub-process box. This behaves like a normal action box at the higher level, but can be 'zoomed into' to expose another Flowchart, as in Fig. 4.
Fig. 4. Subprocesses
An additional 'action' box that can be useful when analyzing processes is the wait box, which highlights a delay (i.e. no action), as in the illustration. This is a typical point where the overall cost of a process may be improved by acting, possibly on other processes, to reduce the delay.
Fig. 5. Delay symbol
There are a number of different charting standards which extend this basic set of boxes. They typically include additional boxes for special types of action, such as getting input and producing output.
A confusion that may arise from different standards is that they can use the same box for different purposes or use different boxes for the same purpose. It is therefore a good idea to be clear from the beginning of any exercise on the standard to be used.
A limitation of Flowcharts is that, although they show the action sequence, they do not explicitly show the flow of information or items through the process. This may be done with other tools, such as IDEF0.
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