Power presses

Power presses that shear, punch, form, or assemble metal or other material by means of tools or dies attached to slides. Power presses can be mechanical, hydraulic or pneumatic. In mechanical power presses, tools and dies are mounted on a slide or ram, and move away from the stationary bed containing the lower die. The upper and lower dies press together to punch, shear or form the workpiece.

Improper use of mechanical power presses cause a large number of workplace amputations. Crush injuries and fractures to the fingers, hands and arms are also common injuries.

The two types of power presses are:

  • full revolution (positive clutch) – once activated, it cannot be stopped until the press cycle is completed by lowering and raising of the slide or ram. Presence sensing devices will not work on these machines. Operators must be protected by fixed guards or mechanical interlock guards during the entire operating cycle.
  • part revolution or friction clutch – can be disengaged at any time before it completes the down stroke. Can be guarded with presence-sensing devices.

Figure 1: Punch power press

[Image] Punch power press showing guard correctly positioned to prevent access

Personal Protective Equipment (PPE)

  • Ear protection
  • Eye protection
  • Hand protection
  • Foot protection

Tasks

Task – Insert workpiece and start operation

Hazard

Handling sheet metal

Harm

  • Sharp edges may cut
  • Strain injury

Controls

  • Use mechanical aids to lift materials, when necessary, like automated material handling or robots.
  • ALWAYS WEAR protective gloves.

Hazard

Entanglement when placing workpiece

Harm

  • Deep cuts or amputation
  • Crush injuries

Controls

  • USE closed tools and static fixed guards.
  • FIT interlock safety devices that prevent access and stop machinery movement immediately when opened.
  • USE presence sensing devices.
  • USE light curtains with fixed and interlocked guards on part revolution power presses.
  • USE two handed controls as a back-up system.
  • FIT emergency stops.

Hazard

Contact impact or entanglement during operation

Harm

  • Deep cuts or amputation
  • Crush injuries
  • Bruising
  • Fractures

Controls

Mechanical power presses

  • KEEP interlock guards locked in the closed position, without gaps. They must remain locked until the crankshaft has completed at least one revolution, and stopped.
  • Provide an anti-free-fall device, to prevent involuntary descent of the ram, and/or any other slide due to over-run or fall-back of the crankshaft.
  • COVER the operator foot pedal or two-handed control to prevent accidental start-up. This applies to both fixed and floating foot pedals.

Hydraulic power presses

  • Presence-sensing devices can only be used on hydraulic power presses that are designed and constructed to meet the requirements of AS 4024:3002 – Safety of machinery – material forming and shearing – hydraulic power presses.
  • Provide mechanical back-up protection for an electrical interlock. If this is not possible, use two independent anti-free-fall devices to prevent ram free-fall.
  • USE a fixed or interlocked guard.
  • COVER the operator foot pedal or two-handed control to prevent accidental start-up. This applies to both fixed and floating foot pedals.

Other (non-mechanical) hazards

Hazard

Noise

Harm

  • Hearing damage or loss

Controls

  • REDUCE noise levels by isolating machines or enclosing within noise barriers.
  • ASSESS noise levels.
  • ARRANGE hearing screenings.
  • ALWAYS WEAR hearing protection.

A safe noise level over an eight hour day is 85dB(A). A power press may exceed this noise intensity.

Hazard

Slips, trips and falls

Harm

  • Cuts
  • Bruising
  • Fractures

Controls

  • KEEP up-to-date housekeeping procedures.
  • PROVIDE non-slip mats and suitable flooring.
  • WEAR suitable footwear.

Task – Maintenance, cleaning & repairs

Hazard

Contact, impact or entanglement from moving parts
Faulty or altered machinery

Harm

  • Deep cuts
  • Amputations
  • Bruising
  • Fractures

Controls

  • LOCK-OUT all power supplies, before maintenance, cleaning and repairs.
  • LOCK-OUT procedures that cannot be overridden should be in place.
  • INSPECT and TEST power presses and their safety systems daily, including interlock guards, clutch locks and clutch breaks mechanisms.
  • CARRY out regular maintenance as per the manufacturer’s instructions.
  • ENSURE guards are in place before testing the press’s automatic mode.
  • USE a safety lock, or lock-out the disconnect switch.

Figure 2: Excessive opening size in fixed frontal guard

[Image] Worker's hand positioned under fixed frontal guard, showing gap that is too large
Figure 2: Excessive opening size in fixed frontal guard

Figure 3: Mechanical power press guarded with hinged interlock guard and anti-free fall device

[Image] Worker wearing ear muffs and gloves, operating mechanical power press with hinged interlock guard and anti-free fall device
Figure 3: Mechanical power press guarded with hinged interlock guard and anti-free fall device

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