The PLC is an electronic unit which can be programmed to do almost any kind of task. It is often linked to an HMI (human machine interface), principally a keypad and screen, to give and receive instructions to an operator. They are tremendously flexible, powerful, and reliable in the extreme.
The PLC can also be configured to interface with servo amplifiers and motors, giving superb motion control. Complex multi-axis systems can be created, with many advanced functions available. The precise control of the servo system, acceleration, deceleration and speed, means that shock and wear on mechanical parts can be minimised, yet absolutely repeatable positioning is achieved.
Standard Ethernet modules are widely available to fit to the PLC, to allow for the transfer of all machine data to and from your desktop PC,
sitting remotely in your office.
HMI and Scada systems
The HMI (human machine interface) and SCADA (supervisory, control and data acquisition) software packages are the link between the control system and the outside world. These enable users to input production requirements, as well as gather in return information about production parameters, production rates, lost time information etc. Equipment can range from a basic keypad and LCD screen, to very sophisticated PC based systems which can connect into the user's own network.
The HMI can be programmed so that an unskilled operator can be led, in easy-to-follow steps, through all that he needs to do to set up the process or product as required. Most HMIs include "recipe" handling facilities, which, as the name implies, allows for extremely simple management of product types and mixes.
The HMI will also keep the operator informed as to the current status of the process. Gone is the need for a flashing red warning light and the hope that this will eventually lead to a fault being traced ! The PLC / HMI combination is powerful enough (with the correct programming) to isolate and identify faults immediately.
More powerful still, SCADA software can run on a PC connected to the machine's controlling PLC, and carry huge amounts of data to or from the machine or process. The shop floor becomes available on your office desktop PC.
In the modern world, time is money, and information is everything. Modern control systems can be configured with hardware interfaces to talk to almost anything - to each other and to central stations. Different parts of your production process can seamlessly share data in real time. The end result? Less work for you and your staff, more information, more flexibility, more productivity.
Ethernet, Profibus, Modbus, CC-Link, CANbus, DeviceNet and ASI-net protocols are all available to bring real connectivity and intelligence to the shop floor. Couple this network to your desktop PC via SCADA software, and you are fully in control and fully informed.