Photo: A steel heavy-duty adjustable screw device added to octagonal-shaped die safety block. These screws are needed to prevent any space between the block and die when various dies are used or when the slide is adjusted. [Source: Rockford Systems]
Die safety blocks are called by many names: safety blocks, ram blocks, die blocks or prop blocks. Regardless of the term, die safety blocks all have the same purpose: provide protection to employees working in the die area from a free-falling upper die/slide.
Bureau of Labor Statistics (BLS) data indicate that approximately three-fifths of all work-related amputations involved a worker's finger or arm getting caught or compressed by a piece of machinery such as a press or conveyor. Injury statistics compiled by OSHA indicated that 49% of the injuries from mechanical power presses resulted in an amputation.
This all-too-common accident happens in the event of a brake or counterbalance failure, broken pitman or adjusting screw, or a sudden loss of hydraulic pressure on presses.
"While die safety blocks appear to be simple devices, there are many factors to consider in choosing what type of blocks to use, as well as how many to use or where to put them," explained Carrie Halle, Vice President of Rockford Systems, a supplier of machine safeguarding equipment and solutions. "As a result many organizations struggle with their use."
Die safety blocks are required by OSHA, and in CFR 29, Subpart O, 1910.217 (d)(9)(iv) Mechanical Power Presses, states, "The employer shall provide and enforce the use of safety blocks for use whenever dies are being adjusted or repaired in the press."
While OSHA does not require the use of safety blocks during die setting, safety-focused companies include them during die setting procedures as a best safety practice. Proper use of die safety blocks also satisfies OSHA's lockout/tagout requirements for controlling mechanical energy. It is important to be aware that multiple ANSI B11 safety standards require the use of electrical interlocks with safety blocks since they are only designed to hold the static weight of the slide and upper die, not the driving force of the press itself.
Anytime an employee needs to put their hands in the die area of a press or is required to work on the die, they must follow OSHA regulations without exception. At no time should the employee make any adjustments or service within the die space area without taking proper protection measures that meet OSHA and ANSI requirements. Regardless of how time-consuming, the employer is responsible—and liable—for these procedures in a press shop.
According to ANSI B11.19-2003, safety blocks "shall be interlocked with the machine to prevent actuation of hazardous motion of the machine." The electrical interlock system for die safety blocks must be interfaced into the control system so that when the plug is pulled, the power to the main drive motor and control is disconnected. If the machine has a mechanical energy source, such as a flywheel, it must come to rest before the die block can be inserted.
In recent years, the rate of non-fatal injuries for press operators has significantly dropped, indicating that safeguarding equipment and effective regulations are preventing common injuries. However, a careless press operator can still cause great harm to himself or to others by neglecting to follow proper die safety block procedures.
With the press motor off and the flywheel at rest for mechanical presses, safety blocks are placed between the die punch and holder while the machine stroke is up. The number of safety blocks is determined by the size of the press bed and the weight the blocks must support. On larger presses, the total slide weight must be distributed among the quantity of safety blocks required. As many as four safety blocks may be needed in larger-scale applications.
Rams usually are adjustable, so wedges or an adjustable screw device are offered to provide a proper fit. If the die takes up most of the space on the die set, it may be difficult to find a place to insert the block. To avoid accidentally stroking the press or leaving the safety block in the die after use, an electrical cut-off interlock system should be used. Again, note that electrical interlocking of die safety blocks to the machine's motor and control circuits is required by ANSI B11.19. This critical step breaks the electrical circuit to the main motor and feed drive so it cannot run when the safety blocks are put in the die area.
This article was written and provided by Rockford Systems, a company that provides innovative machine safeguarding solutions for organizations working with industrial machinery. For more information, please visit www.rockfordsystems.com.