Not "Only A Movie"
Virtual commissioning of assembly lines—not just the geometry and the kinematics, but the control logic, as well—can make a huge difference.
"It's only a movie. It's only a movie."
If you've seen a really scary film, you might have repeated this phrase to assure yourself that what you're seeing isn't real. Yet that phrase comes up in a discussion of assembly system simulation with Kenneth David, senior applications engineer, Dassault Systèmes DELMIA Corp. (www.3ds.com
). Chances are good that at some point during the past 10 or so years you've seen a computer simulation of an assembly line. Robotic arms reaching. Conveyors carrying. Weld tools engaging. If everything was working as it should, it was a visual orchestra in action; if not, if, say, a stanchion interfered with a movement, then that could be changed. Then things would seem to be working as they should. It looked convincing.
"It was only a movie," David says, explaining that what was being seen was only part of the assembly system in action. It was a validation of the mechanical portion of the system. "This is reality." What he's talking about is a virtual commissioning system that DELMIA has developed so that more than just kinematics, there is the ability to determine whether the control architecture and programming are working as they should—before the system is physically built. It is called DELMIA V5 Automation.
"The current method of commissioning control systems is labor-intensive," David says. One reason is the way that large assembly systems are built. The systems builder constructs the pieces that will become the line. Then, before it is shipped to the customer's plant, there is a runoff to make sure that the system—typically represented by a cell, given that the line is too massive to be contained within the system builder's facility—does what it is supposed to within cycle. The customer may force faults to determine how quickly they can be ID'd and fixed.
But, David points out, a system is more than the sum of its parts. It is how all those parts work together in the system. And the system isn't fully built until it is on the customer's floor. This is usually near the start of production. It is at this point that the control engineer has the first opportunity to exercise and physically validate the controls logic for the entire system (having been able to do pieces of it earlier). And if there are problems at that point—and there are likely to be—then it is time consuming and costly.
The DELMIA Automation system consists of three modules. There is the Smart Device Builder. This is where the actuators, sensors, motors, and drives that make up a system are modeled using existing 3D CAD models (or if there aren't existing models, they can be designed, then put in a digital library for later use). Although DELMIA is part of Dassault, the system is multi-CAD capable. Then there is the LCM Studio module. This is a programmable control (PLC) programming environment that uses standard programming languages. The control engineer can use this to generate a PLC program for the system. Third is the Controlled System Simulator, which is where the virtual assembly line is put through its paces so that it can be validated long before the actual line is built. Failures can be forced in the virtual world. The PLC can be virtual, or the DELMIA Automation system can actually drive physical PLCs. Consequently, when it is built, the likelihood that the line will run without the level of debugging that is ordinarily experienced.
Which means that production can be up and running and ramped far earlier than might otherwise be the case. As David points out, "When a line is down for an hour because of a control problem . . ."
Just as digital models of parts and assemblies make all the difference for design validation, this can do the same for the manufacturing engineering side of the product-process continuum.