Machine Guarding eTool
Mechanical Power Presses » Press Safety Considerations
Each mechanical power press must be looked at as an individual system. This system consists of, but is not limited to, the frame, all mechanical parts, clutch and brake assemblies, electrical or electronic systems, hydraulic systems, pneumatic systems, tooling or dies (present and future), tool or die setup, safeguarding, material handling, size or configuration of piecepart, and production requirements.
It is essential that presses and other machinery be thoroughly inspected and that all mechanical, electrical, pneumatic, and hydraulic components and systems, including all collateral equipment, be in first-class operating condition before any equipment is installed. A maintenance and inspection program must be established and implemented to keep machines in first-class condition. This program should include regular periodic inspections of each machine to ensure that, among other things, (i) the clutch and brake mechanism, mechanical linkages, and air counterbalances are operating and used properly; (ii) there is no dirt or water in the air lines; and (iii) the machine is operating at its proper speed (RPM or SPM). Any part of the machine that is worn, damaged or not operating correctly should immediately be replaced or repaired before the machine is used.
Other safety considerations include:
A press system requires the proper disconnect switch, motor starter, transformer for reducing the voltage to 120 volts or less, and air lockout valve.
Mechanical power-transmission apparatus include components on a machine or auxiliary equipment including shafts, crankshafts, splines, pulleys, sprockets, rolls, flywheels, gears, and couplings. These components can create hazards to personnel who work on or around the machines. They must be covered in accordance with 29 CFR 1910.219 Subpart O and ANSI B15.1. All apparatus that creates a hazard up to 7' above the floor or platform must be guarded (covered). This is usually done by the user, either by adding to existing guards or by contacting a local sheet metal fabricator to make a new cover.
Auxiliary safeguarding is used for additional protection from injuries for all personnel in the machine area. It is used in conjunction with primary safeguarding devices. Auxiliary safeguarding also involves the guarding of other components or hazardous openings on machines. One of these hazards is created by auxiliary feeding equipment used with some power presses. Auxiliary equipment includes various types of feeds, shuttles, magazines, stackers, indexing tables, straighteners, reels, cradles, recoilers, scrap choppers, iron hands, robots, etc.
Auxiliary safeguards include such items as point-of-operation side barriers when light curtains are used, pressure-sensitive floor mats, workpiece tables or horizontal light curtains. An additional set of light curtains can be used horizontally to prevent an operator or other persons from standing between the vertical plane of light and the point-of-operation hazard. It is important to remember that light curtains can be used only on part revolution presses.
The two most commonly used safeguards for presses equipped with automatic feeds are guards and presence sensing devices (light curtains). When considering either of these safeguards, arrange them to protect the point of operation as well as the feed. This may require the guard to extend to the right or left of the bolster on OBI presses. If a scrap chopper is furnished, the guarding must also be extended to safeguard it. If a feed and scrap chopper are on the sides of straight-sided presses, the feed and window openings also need to be safeguarded.
When protecting operators and other employees in the press area from hazards created by straighteners, pay-off reels, cradles, iron hands, robots, etc., the perimeter or work envelope of this auxiliary equipment should be safeguarded. This is usually accomplished with guards, presence sensing devices, safety mats or a combination of these methods.
When protecting these areas, keep in mind that access may be required for changing coils and removing scrap, blanks, etc.
Danger signs, used for warning, can be mounted on the machine in a position that is readily visible to the operator, setup person or other personnel. Hand tools are another auxiliary safeguard often used when feeding and retrieving small pieces or removing scrap from the die area. Hand tools by themselves are not a point-of-operation safeguarding device.
When using a light curtain, the mounting brackets for the transmitter and receiver may have to be modified to include safeguarding of the feed. The light curtain's plane of light commonly protects only the front of the press. Additional guards or mirrors are needed to safeguard the sides and back of the machine.
When safeguarding presses equipped with shuttles, magazines, stackers, indexing tables, etc., the previously discussed safeguards can be used. This assumes that the press is operating in either the continuous or automatic single stroke mode. If the press is single stroked by over operator action, other safeguards such as two-hand controls, pullback devices, restraints or gate devices could be used. The back and sides of the point of operation must always be protected as well.