August, 2016
www.us-tech.com
The Case for PC-Based Machine Control over Traditional PLCs
By Michael L. Martel O
ver time, PC-based machine control has encroached upon, and ultimately gained dominance over, traditional, reliable PLC
(programmable logic control) controllers. There are many different reasons, but perhaps the most important benefit directly attributable to this development has been the enabling of advanced manufacturing systems and technologies that would not have been possible had it not been for the evolution of PC control. Many OEMs endeavor to incorporate
advanced capabilities and control into their sys- tems to improve functionality, data acquisition, and analysis, with the goal of giving their systems an added edge over competing sys- tems on the market. Because of this, OEMs are also reluctant to discuss their transition from PLC to PC con- trol for their industrial manufactur- ing or inspection systems. One global supplier of sophisti-
cated inspection and process quality control systems to the bottling indus- try is a good example, though they
Many OEMs are reluctant to discuss the transition from PLC to PC control to keep ahead of the competition.
have preferred to remain anony- mous. The company’s machines per- form multiple functions, including glass container inspection. The com- pany’s flagship line of inspection machines have been entirely PC-con- trolled to date, using a multifunction analog/digital I/O PCI card from Oregon-based Sensoray, a designer and manufacturer of OEM electron- ics for video imaging, data acquisi- tion and industrial control. The OEM’s designers incorpo-
rated Sensoray’s Model 626 con- troller into their products due to the greater flexibility and functionality of the PC over PLC control. But now, the emergence of Sensoray’s new Model 826 controller with its much greater capabilities has allowed this OEM to launch a software technology advancement that improves and sim- plifies container inspection for its entire flagship line. This advanced PC control enables multi-complex data acquisition and analysis needed for machine vision automated inspec- tion, which is the heart of these sys- tems’ inspection capability.
Traditional PLC: Simple and Reliable
A programmable logic controller
(PLC) is a digital computer used for the automation of typically industrial electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in many machines and in many industries. First introduced in the 1970s and still in widespread use today, PLCs have dominated the process and automation control markets. Since the early 1990s, however,
PC-based control has been encroach- ing on the PLC’s dominance due to, in part, greater capability (increases in processor speed and range) and, quite importantly, greater robust- ness required by the industrial man- ufacturing environment. Greater
Best possible soldering results with and without vacuum
Model 826 multifunction analog/digital I/O PCI controller.
cost-competitiveness (lower cost components) has leveled the playing field somewhat as well. Increasing numbers of applications that use a PC have also accelerated the development of PC-based control.
PLCs began as a basic and reliable alterna-
tive to devices like relays, with limited functional- ity, but in time evolved to include such capabilities as motion control and advanced PID process con- trol, among others. Since they were designed for the industrial environment, when PC control began to compete, safety was the biggest argument in favor of the PLC.
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