Powder Coated Tough - Fall/Winter 2007 - (Page 28) Powder Automation: Programmable Logic Control might be pressure sensors, position transducers, temperature sensors, and variable speed motor drives. In most cases the equipment controlled in a hardwired system is essentially the same as in a PLC system. The difference is the flexibility that is afforded. A typical hardwire system will require wiring modifications in order to alter the control of a component. Within a PLC-controlled system, the only change would be to the program stored in the memory. For example, a typical relay has two to four control contacts. The relay is limited in the amount of control or logic it can perform. To expand the relay’s functionality, additional relays would need to be added in parallel. Now compared to a PLC program, a “soft” relay can have hundreds of logical contacts and no additional wiring or component changes are required. But to look at a PLC unit as a relay/timer replacement is to miss a great deal of flexibility and customization capability. BY JEFF HALE, ITW GEMA Applying PLC automation to a powder coating system may significantly reduce operating costs and enhance the operability of the equipment. The following describes functions that can be controlled effectively by a PLC. A ny time you can improve the efficiency of a powder coating line, it is a good thing. One way to utilize automation is to implement a programmable logic controller (PLC) to operate gun controls, gun positioning, airflow controls and other system variables. Simply put, a PLC is an industrial computer that replaces complicated hardwiring with “soft” wiring. This soft wiring is a program that simulates an electrical circuit. A PLC consists of several components: a CPU (central processing unit) and I/O (input/output) modules. The I/O modules provide sensory input and then control output to the system components. Examples of the types of PLC inputs are push buttons, pressure switches, photo sensors or relay contacts. Example outputs can be indicator lights, relay coils, motor starters, while other types of devices that can be monitored and controlled are analog. Examples of these analog devices A PLC can: ✔ Handle complex information. ✔ Perform advanced math functions. ✔ Communicate with high-level computer systems. These capabilities allow for greater flexibility in a controlled system. This flexibility eliminates the dependency of decision making to be made solely on conditions of on or off. Also, data in the PLC can be manipulated, displayed, and applied to control variables. With the addition of color touch screens, touch pads, and touch keypads, system operations are enhanced. Operator interface with the day-to-day tasks are automated and displayed for review. Diagnostic feedback from the system provides the necessary tools for efficient corrections. By applying PLC automation to a powder coating system, the user can significantly reduce operating costs and enhance the operability of the equipment. The following describes functions that can be controlled effectively by a PLC. 28 Powder Coated Tough
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