Safe to Operate

By Jim Montague, Executive Editor

Some of the biggest ideas and history-making events just need a little push to get rolling, take off and change the world. Machine safety's evolution from obstacle to opportunity is one of these.

However, despite lip service about its importance, machine safety still is viewed by management and operators at too many manufacturers as a costly drag on production. As a result, it's often ignored or bypassed, and the tragic injuries and deaths that result are just seen as the cost of doing business. Fortunately, it's become increasingly obvious that a little investment in machine safety now can pay huge long-term dividends in reduced downtime and improved production.

Machine safety is a benefit rather than an expense, and this is shown by the fact that many safety features are becoming standard equipment or low-cost options on today's machinery and equipment. One device, the safety PLC, provides designed-in safety features ready for engineers to incorporate into their applications. For instance, all the equipment in our assembly and components divisions has safety built in ahead of time by using safety PLCs," says Michael Douglas, senior manager and consultant for new technology and standards at General Motors (www.gm.com). Douglas also implemented GM's global health and safety designs and programs, such as its Safety 21 Process, throughout the entire lifecycle of its production systems. "In fact. we've been working with Fanuc for about 18 months to implement its Dual Check Safety software in the robots in our component and assembly divisions. This software defines an individually tailored and password-protected 3D space within which we can lock down and limit a robot's movement, so it can't travel outside of that 3D envelope and possibly injure someone.This feature also usually reduces the number of light curtains required between the operator and robot. The operators use a teaching pendant to lock the robot in its 3D space, which can be viewed on the pendant. This password feature really adds to the confidence level of the local plant's health and safety department."

Consequently, six months ago, GM began installing Dual Check Safety on several dozen of Fanuc's R30iA robots at its new Chevrolet Volt plant near Detroit. Besides protecting operators, Dual Check provides safety without the expense of traditional barriers, such as added safety mats or light curtains.
"The next phase will be to remove the external robot cell fencing by incorporating safety vision systems, such as Pilz' Safety Eye and other safe-motion robot capabilities. These safety features make our robots so safe that operators can walk right up and interface with them," explains Douglas. "This holds possible solutions for many industries' ergonomic part loading issues. For example, back in 2005 at our assembly plant in Spring Hill, Tennessee, we spent more than $100,000 in rework on our hood line resolving ergonomic issues. If technologies like Dual Check Safety had been available in 2005, we would have avoided those rework costs and provided a safe work space for our operators free of ergonomic risks. Technologies that allow for operator interface will also eliminate many hazards for our maintenance workers because they will no longer have to maintain interface equipment that was eliminated by adding these new technologies. Many of the safety features mentioned above can be applied to later-model robots. Users can check with their robot manufacturer for software upgrade details."

Preparing for Safety

Of course, good machine safety also means getting ready ahead of time. The staff at Oystar Jones (www.oystar.rajones.com) in Covington, Kentucky, always has been concerned with machine safety and proper due diligence. Consequently, even before ANSI/PMMI B155.1-2006, "Safety Requirements for Packaging Machinery and Packaging-Related Converting Machinery," was approved on April 25, 2006, with an effective date 30 months after, engineers at the packaging machine builder formerly known as R.A. Jones knew they would have to gear up to comply with it. They also needed to review their design to ensure compliance with the European Union's new Machinery Directive 2006/42/EC, which became effective on Dec. 29, 2009. As a result, Oystar Jones formed an in-house safety team to update its standards library, perform new risk assessments (RAs) of its machines and make sure it continues to conform to all applicable safety standards. Two members of its safety team are Electrical Controls Engineer Mike Steele and Mechanical Engineer Marc Koeppel.

"Whenever possible, we maintain a single design standard for both the U.S. and European markets," says Steele. "This isn't too difficult once the standards from both regions are understood. Usually, one is a bit more restrictive in some areas than the other. Therefore, if you comply with the more restrictive, you'll typically be in compliance with both standards. This is the general rule, though there are exceptions."

Assessing a Cartoner

For example, one of the Oystar Jones safety team's main projects was implementing a unified safety strategy for its now year-old Criterion 3 cartoning machine (Figure 1). "We first educated ourselves on all the relevant standards that applied to this type of machine," says Steele. "Any necessary standards not already in our possession were brought in-house for reference. Then, during the new machine development phase, we performed a design-phase RA. This allows us to identify potential safety and design issues early, which gives us the opportunity to solve problems before manufacturing begins. Obviously, once manufacturing begins, efforts to correct a potential problem is more time-consuming and costly."

Next, the machine builders constructed a Criterion 3 prototype and undertook a build-phase RA. "A risk assessment really means looking at a machine as if it had no guarding at all," explains Steele. "The object is to identify hazards, including pinch and shear points, impact locations, burn hazards, electrical shock hazards, possible entanglements and other potential hazards. Then, we use a risk-scoring system to determine the severity of each hazard and the probability the machine user will be exposed to this hazard during normal interaction, whether it's an operator or maintenance personnel. For instance, if a hazard with a potentially serious severity is present in the carton magazine region, where an operator interfaces frequently, then there is a greater probability an injury may occur there than in another section of the machine requiring less interaction. This situation would be considered a high risk on our RA, and we would take appropriate corrective action."