Simulating machine, robot and process skid operation in software is the best way to test controller code, device settings and HMI configuration—short of actual connection to the completed system. And in many instances simulation is a more practical alternative to testing on an actual system for a variety of reasons ranging from the ability to prototype to the desire to maintain a safe environment by testing in software first.
When the complete machine, robot, skid or system isn't available for test, and sometimes even when it is, simulation can shorten the design cycle, improve performance and greatly reduce startup time. Table 1 lists some of the specific advantages of simulation.
Accurpress America in Rapid City, South Dakota, makes hydraulic press brakes and shears for fabricating sheet metal (Figure 1). Allen Guernsey, machine control development specialist at Accurpress, says the machines can be complicated. "Our current version of the PLC for the press brakes can handle 28 axes, and we can link machines together to work in tandem," he says. "Sometimes the press brakes and shears are parts of cells, and in these cases other machines arrive at the customer from different factories, so simulation is the only way to run the machines together prior to startup."
Simulation has reduced the R&D time. "Being able to watch machine movement in a simulated environment has enabled better PLC code because, in simulations, more fail safes can be tested without risking machine crashes," explains Guernsey. "For example, I can simulate hydraulic cylinder characteristics, introducing errors like a stuck cylinder. So far, I have not run into anything that I could not simulate."
Accurpress uses Beckhoff Automation controllers and TwinCAT automation software. "With TwinCAT, the simulation of machine control is fundamental to the software’s design," says Guernsey. The built-in simulation saves time and cuts cost because it’s not necessary to buy a separate software simulation package, learn how to use it and integrate with the controller and its software.
Dave Perkon, vice president of advanced technology at AeroSpec, a machine builder in Chandler, Arizona, also uses simulation software from robot suppliers. "Most of the top robot suppliers have simulation software," he says. AeroSpec designs and builds a variety of discrete manufacturing equipment, ranging from lean assembly stations to high-speed robotic assembly and handling systems (Figure 2).
"During the concept and quoting stage, simulation software helps keep a project moving in the right direction and keeps the customer engaged as their requirements come to life," notes Perkon. "If the actual equipment doesn’t meet the simulation results, it indicates the program needs more work."
And, once the system is designed, some simulators create code. "Although there are configuration differences, the end product from many of these simulation packages are directly downloadable software programming to the robot," Perkon explains.