New machinery safety standards coming this year replace the drop bar — a mechanical safety device that stops the clamp on a horizontal-clamp injection molding press from closing accidentally — with what equipment industry leaders say is the superior controls technology available today.
The change to ANSI/SPI B151.1 applies only to new injection presses. ANSI is the American National Standards Institute. The Washington-based Society of the Plastics Industry Inc.'s effort was coordinated by the Injection Molding Safety subcommittee, part of SPI's Equipment Council.
The decision is to eliminate the ratcheted drop bar, also called a jam bar, on new machines. All existing machines still must have the jam bar.
Also, vertical-clamp injection molding machines are still required to have the mechanical drop bar, because of the effect of gravity.
“It's a physical barrier that stops the unintended closure of the clamp,” said Stan Glover, who chairs the safety standards subcommittee. That's a big safety issue in plants where workers must reach into the molding area when they open the operator gate.
Glover said SPI is the standards-writing body for plastics machinery. SPI works with ANSI in the United States, and, for global standards, the International Organization for Standardization, or ISO.
Glover is director of sales at Zeiger Industries Inc. in Canton, Ohio. He is vice chairman of SPI's Equipment Council, as well as chairing the safety standards group.
For the first time ever, SPI hosted an ISO meeting on Nov. 3-5 in Niagara Falls, Ontario. More than 40 world safety experts came from about a dozen countries.
SPI members and safety experts from the across the global machinery industry discussed how to better harmonize safety standards. Husky Injection Molding Systems Ltd. hosted a plant tour at its headquarters in Bolton, Ontario.
Jim Pilavdzic, Husky's manager of product safety, emphasized the importance of plastics industry leaders getting involved with ISO and the standards-development process. He said the experience opens their doors to world safety experts and meet fellow professionals.
Co-sponsoring the tour with Husky were the Canadian Plastics Industry Association and SPI.
A ‘redundant redundancy'
After a recent third-party risk assessment of the mechanical device, subcommittee members then determined that the jam bar was “a redundant redundancy” on horizontal machines.
Pilavdzic said the SPI Safety subcommittee is reconsidering if the mechanical device for horizontal injection presses are in full compliance with the latest revision of the B151.1 standard.
Committee members fully debated the issue, Pilavdzic said.
“In essence, these findings confirm our longstanding opinion that the mechanical device is an additional redundant option, which does not reduce residual risks, and only adds mechanical complexities,” he said in a written answer to questions for this story. “The European Community and a large portion of the world have never required the mechanical device to be installed in horizontal injection molding machines, and most importantly, we could not cite any safety accidents related to the operator's gate, where having the mechanical device would have prevented the accident.”
Here is the Husky expert's explanation: Modern injection molding presses, he said, have “multiple independent safety circuits.” The first circuit is based on the interlocking guards having two position sensors, one in positive mode and one in negative mode. “We are using two position detectors to ensure that safeguarding cannot be defeated,” Pilavdzic said. And the closing platen movement is immediately stopped after the guard opens wide enough to pass a hand through the guard, thanks to an additional safety device in the power supply.
The jam bar is the third redundant system.
“Cycling the guard will definitely recognize fault in the safety system and cause the machine to stop, and turn the power off until the fault is corrected,” Pilavdzic said.