TABLE OF CONTENTS Many processes, particularly those for batch chemical manufacturing, food processing, discrete parts manufacturing, and mechanical assembly operations, must be custom programmed rather than configured from a set of predefined functions offered by the automation system supplier. Programming custom software is a business process requiring organization and management to achieve performance success, on-time completion, and successful long-term support.
Before writing custom programming, an organization must make several decisions. The primary decision concerns the functions to be performed. You must create a document called the manufacturing specification to describe exactly the desired outcome and methods used to perform the automation functions. Unsuccessful projects are usually traced to incomplete definitions of what is to be done and the ways in which the automation system is to accomplish the desired actions. Successful projects spell out in detail every step of the manufacturing operation, what is to be measured, and the exact flow of the manufactured item. In fact, the manufacturing specification is the base document for testing the completed manufacturing sequence to determine if the system has been programmed correctly.
One highly successful form of the manufacturing specification is a stepwise set of instructions, described as though a human would be performing each step. The benefits of this type of document are that it is more easily diagrammed using Sequential Function Chart (SFC) programming methods and it can be more easily understood by people who will later access the document to maintain, expand, and improve the automation system.
