Since assembly processes vary in complexity, the types of control systems and related devices employed will also vary. In addition to small and medium sized PLCs or other control systems used to control individual machines, one or more larger PLCs may be employed to collect data and coordinate operation of some or all of the system. This overall coordination may include control of the full range of motor control devices discussed thus far from full voltage starters to AC and DC drives.
The specific PLC model used will be determined by the size and complexity of the application. Examples of Siemens PLC models that may be employed include the S7-300 and S7-400.
Just as it is often necessary to use a PLC to coordinate the operation of multiple machines in an assembly process, it is often also necessary to provide a graphical representation of the current status of this process. In addition to providing this graphical representation, a Human Machine Interface (HMI), such as Siemens WinCC, can provide a custom interface to allow operation personnel to control some or all the process and for maintenance personnel to obtain system diagnostic information.
Since many manufacturing facilities use multiple PLC models and often models produced by multiple companies, WinCC can communicate with many types of PLCs. In addition, WinCC versions are available for computers using Windows 95 or Windows NT operating systems.