Viewpoints: Software Can Enhance Machine Safety
Too many manufacturers view safety as a cost burden. Perhaps that's understandable, considering current practices. Conventional machine-safety systems typically provide absolute safety by using various costly additional hardware components, but usually at the expense of business-related issues like productivity and uptime.
In fact, today's safety processes often unwittingly create greater hazards for the conscientious employee, who is frequently tempted to defeat or circumvent safety procedures to keep production moving.
Here's why: to clear a web jam in a press or packaging machine, or align a part being placed by a gantry robot, a machine operator should cut the power, wait for the electrical power to dissipate, clear the jam, unlock the lockout key, reverse the process, then realign the machine and (if it wasn't done right) start over. No wonder so many electricians and shop personnel bypass the safety gates, creating a situation that is more dangerous than if there were no safeguards at all.
That's why the software-based machine-safety standards now being implemented in Europe are beginning to attract attention here. Leading the way in the push for software-enabled safety is safe motion in the drive. In essence, all of the monitoring conditions for safe motion—such as speeds, and travel limits—can be implemented in the drive itself, and monitored redundantly.
Safe motion in the drive is a software-enabled solution that eliminates the reasons to try to defeat or bypass safety. And instead of the inflexible, lockout/ restart procedure described above, software-based systems offer a variety of different choices, ranging from unconditional safety to alternatives that allow safe movement where the part or machine can be moved without the power to cause injury. Being drive-based, this solution mixes and matches with other components regardless of safety certification, giving the machine the safe motion required to protect personnel and the machine itself.
In addition, software-enabled safety systems can remember machine position even if the work is moved to clear the jam. As a result, the operator can clear the jam and get the system back to full operation in much less time than is required by a conventional system.
That's especially true during setup, when most injuries occur. An operator can be in the work zone of a machine equipped with safe motion software, and set up the machine faster and more easily than he or she could on a machine with conventional, absolute-safety protection.
With the significant improvement in productivity and substantial cost savings, why aren't machine builders and their customers demanding software-enabled safety systems? The answers, of course, are never easy.
First, we live in a litigious society. And, quite understandably, both OEMs and machine endusers are reluctant to abandon the absolute safety standard that their own workers frequently bypass. But will this impractical stance hold up in court if an injured worker can prove that a more-effective, safe-motion solution was rejected because of the changes required to implement it? Only time will tell.
Second, the major testing laboratories do not have a certification process for drive-softwareenabled safety systems, and US governing bodies and committees are very slow to adopt new standards. As a result, we are lagging behind our European counterparts in their development of more competitive systems.
Testing laboratories may also be reluctant to certify software-enabled systems, because they are worried about software even in redundant systems. So they're cautious because they, too, fear litigation.
At our company, we're making a concerted effort to at least offer software-based safety alternatives. It's our policy to present these choices, and let the OEMs decide for themselves whether the productivity improvements and real safety enhancements are worth the additional cost.
Our hope is that OEM design engineers will ask their management to begin pressuring the testing labs and OSHA to create standards in this all-important area, lest we fall further behind European machine builders.
I'm convinced that machine buyers will soon begin to demand safe motion software as a way to prevent injuries resulting from bypassed conventional safeguards, prevent damage to workpieces and fixturing, and improve machine productivity. I'm also convinced that foreign machine builders will be selling this alternative. Domestic machine builders will be at a competitive disadvantage when safe motion software from their European competitors finally catches on here.
This article was first published in the September 2006 edition of Manufacturing Engineering magazine.