For machine builders, there's safety in numbers—specifically, the numbers represented by falling costs, increasing port count and greater connectivity options of programmable safety solutions. Uncomplicated setups may still best by served by traditional, nonprogrammable and relatively simple safety relays, but ongoing improvements and greater flexibility have made programmable safety cost-effective for a wider array of situations.
For an example of the impact of programmable safety advances, consider a system from Intelligrated, a Mason, Ohio-based provider of intelligent automated material handling solutions. Intelligrated built a mixed-load palletizing cell with specialized end-of-arm tooling that could handle multiple case sizes in a single pick, integrating advanced software, controls and vision technology to do so (Figure 1).
"Prior to programmable safety, achieving the functional and operational requirements of this kind of solution was costly and problematic," says Matt Wicks, vice president of product development for manufacturing systems at Intelligrated.
Flexible and Safe Movement
"Using programmable safety allows for more complex safety functionality to be implemented cost effectively," says Intelligrated's Wicks. "An additional benefit is that this allows for quicker, less-costly changes to the safety system when there are changes in project scope like layout reconfiguration."
For this particular system, Intelligrated used Rockwell Automation's Allen-Bradley Compact GuardLogix programmable automation controllers. To understand why the flexibility added by programmable safety is important, it helps to realize that an automated palletizing system may consist of multiple robot cells, each with its own point of entry, as well as a discharge transfer system of the finished pallet of material. The final product may go through a stack-and-wrap solution that readies the pallet for shipment.
Each piece of equipment has a potential safety-level interaction with others in the system. Programmable safety can define this interaction, eliminating the time spent on complex safety circuit wiring. Consequently, equipment providers and integrators can make functional changes as needed while minimizing any implementation risk.
That flexibility can be important to end users, Wicks says. "It also reduces risk for our end customers as they may not recognize operational impacts until the system has been implemented," he says.
Intelligrated has used Rockwell Automation programmable safety solutions for years. But for simple setups such technology may be more costly than an approach based upon more traditional controllers and safety relays. Generally, programmable safety makes sense in situations where there are more interactions with other types of equipment and if there are more specialized or unique cases that must be handled, Wicks says. All applications with a PLC or similarly capable controller will need some sort of safety solution, says Tim Roback, marketing manager for safety systems at Rockwell Automation. He adds that an integrated solution that combines control and safety into one programmable product enables optimization because there is information associated with a safety event. Data such as how often a fault occurs or an e-stop activates can be important in devising ways to avoid such halts to production. This data also can help to minimize downtime by pinpointing what caused a fault and why.
hen combined with the right choices early in the design cycle, such programmability can help to improve both safety and productivity. For example, a machine can be zoned into different sections, with staging areas between the zones. As a result, a problem in one area and the opening up of an interlocked door may not mean that the entire manufacturing process has to stop.
"You can continue to produce product in one zone while you clear a jam in another," Roback says. A somewhat similar benefit is that with programmable safety a machine can come to a controlled stop, he adds. For instance, a bottle-filling machine may halt after the current batch of bottles are completely filled, which makes starting up after fixing a fault faster and smoother. Such cases illustrate that programmable safety can make restarting a machine easier and quicker than is possible with simpler and less flexible technology.
Safety and Savings
Another example of the use of and benefits from programmable safety comes from system integrator and tooling manufacturer Five Lakes Automation of Novi, Michigan. Five Lakes Automation works with Tier 1 automotive suppliers, with a focus on welding, riveting or other joining applications, says Project Manager David Jones.