Motion Safety

May 20, 2008
They are the dirty words of the plant floor: stop motion.

They don’t just mean that you have a supply chain issue and ran out of stock, or that your recipe got muddled and you have to waste an entire batch or that a worker put their hand where it didn’t belong and you have more stock that you ought to. Stop motion—the emergency cessation of production on a machine or line or even an entire factory can, and often does, mean all of those things plus the dirtiest words of all: lost productivity.

Until very recently the typical response to an emergency on the production line was to stop motion, which impacted productivity and put a lot of wear and tear on the equipment as torque and inertia had to be managed.
Siemens Energy and Automation is adding safety features directly to the drives in their motion control systems that deliver rapid diagnostics and intelligence to help analyze exceptions and faults and moderate the response to minimize negative impact.

“Safety and motion is becoming a hot topic in the industry,” says Michel Jabbour, who manages safety integration in the United States for Siemens Energy & Automation in Norcross, Ga., adding that innovative work is being done to bring a function that had been stuck in the 1970’s fully into the new millennium.

Starting in 2002, Siemens' started building hardwired safety features into its general industry drives so that PLCs and safety relays could implement safety stop functions. Then, in late 2007, the company released its next evolution in drive integrated safety by providing drive safety functions over networks giving manufacturers the option of remote control or continuing to maintain safety functions internally on the drives, without any external safety relays or safety PLCs.

“To us, safety in motion means that the machine safety is now integrated into the variable frequency drives, and no longer must be a separate, standalone system. This continues the integration of safety into the standard control system so that the application can achieve improved diagnostics, scalability and modularity,” says John Krasnokutsky, motion control marketing manager in Siemens’ Production Machines Business Unit.

According to Krasnokutsky, safety-rated drives deliver significant benefits for manufacturers. “Generally, drives associated with hazardous motion must be safely shut down using suitable protective equipment and devices. This is generally implemented with external circuits that in some cases can be extremely complex. Using the safety functions integrated in the Sinamics S120, in most cases these external circuits can be eliminated which lowers infrastructure costs for users. Less equipment, less wiring, less control systems. And now you can save time on reset because when you do encounter an issue you can ramp down in a controlled, synchronized manner, making restart easier. So it’s great for productivity.”

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