['Machine Guarding']
['Machine Guarding', 'Power Presses']
03/14/2024
Copyright 2024 J. J. Keller & Associate, Inc. For re-use options please contact copyright@jjkeller.com or call 800-558-5011.
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A mechanical power press shears, punches, forms, or assembles metal or other materials by means of tools or dies attached to slides or rams. Metalworking occurs by placing stock on a bottom die and striking it with a top die. The top die is attached to a crankshaft with connecting rods and rotation of the crankshaft is accomplished from a motor, flywheel, and gear power transmission. Typical mechanical power presses fall under two primary categories with respect to their specific clutch system:
- Mechanical Full Revolution Clutch, and
- Mechanical Part Revolution Clutch.
Each of the two types has specific barriers, acceptable guards, and hazards.
Power presses, because of their use in high-production manufacturing and integral operator involvement, result in maximum hazards. Careful operation and safety precautions are extremely necessary.
Scope
OSHA’s standard applies to all employers who have mechanical power presses. Note that the standard does NOT apply to press brakes or hydraulic power presses; these machines are covered instead by OSHA’s General Requirements for All Machines standard, 1910.212.
Regulatory citations
- 29 CFR 1910.217 — Mechanical power presses
Key definitions
- Antirepeat: The part of the clutch/brake control system designed to limit the press to a single stroke if the tripping means is held operated. Antirepeat requires release of all tripping mechanisms before another stroke can be initiated. “Antirepeat” is also called single stroke reset or reset circuit.
- Authorized person: One to whom the authority and responsibility to perform a specific assignment has been given by the employer.
- Brake: The mechanism used on a mechanical power press to stop and/or hold the crankshaft, either directly or through a gear train, when the clutch is disengaged.
- Full revolution clutch: A type of clutch that, when tripped, cannot be disengaged until the crankshaft has completed a full revolution and the press slide a full stroke.
- Inch: An intermittent motion imparted to the slide (on machines using part revolution clutches) by momentary operation of the “Inch” operating means. Operation of the “Inch” operating means engages the driving clutch so that a small portion of one stroke or indefinite stroking can occur, depending upon the length of time the “Inch” operating means is held operated. “Inch” is a function used by the die setter for setup of dies and tooling, but is not intended for use during production operations by the operator.
- Part revolution clutch: A type of clutch that can be disengaged at any point before the crankshaft has completed a full revolution and the press slide a full stroke.
- Pinch point: Any point other than the point of operation at which it is possible for a part of the body to be caught between the moving parts of a press or auxiliary equipment, or between moving and stationary parts of a press or auxiliary equipment or between the material and moving part or parts of the press or auxiliary equipment.
- Point of operation: The area of the press where material is actually positioned and work is being performed during any process such as shearing, punching, forming, or assembling.
- Presence sensing device: A device designed, constructed and arranged to create a sensing field or area that signals the clutch/brake control to deactivate the clutch and activate the brake of the press when any part of the operator’s body or a hand tool is within such field or area.
- Press: A mechanically powered machine that shears, punches, forms or assembles metal or other material by means of cutting, shaping, or combination dies attached to slides. A press consists of a stationary bed or anvil, and a slide (or slides) having a controlled reciprocating motion toward and away from the bed surface, the slide being guided in a definite path by the frame of the press.
- Safety block: A prop that, when inserted between the upper and lower dies or between the bolster plate and the face of the slide, prevents the slide from falling of its own deadweight.
Summary of requirements
Employers must:
- Select the appropriate guarding method(s) for each individual power press.
- Ensure power-transmission components are guarded.
- Ensure there is a red color stop control.
- Protect foot pedals from accidental operation.
- Keep guards appropriately adjusted.
- Train operators on safe operation.
- Ensure employees remove scrap or stuck work with tools even when hand feeding is allowed according to 29 CFR 1910.217(d)(1)(ii). Employers must furnish and enforce the use of hand tools for freeing or removing work or scrap pieces from the die to reduce the amount of time an operator’s hand is near the point of operation.
- Establish a system for regular inspection and maintenance. Inspection certification records must be maintained.
- Inspect and test the condition of the clutch/brake mechanism, anti-repeat feature, and single-stroke mechanism on at least a weekly basis for presses without control reliability and brake system monitoring. Certification records must be maintained of these inspections and the maintenance performed.
- Perform servicing and maintenance under an energy control program in accordance with the Control of hazardous energy (lockout/tagout), 29 CFR 1910.147, standard.
- Ensure there is a proper disconnect switch, motor starter, transformer for reducing the voltage to 120 volts or less, and air lockout valve.
- Report point of operation injuries to OSHA within 30 days of the occurrence.
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['Machine Guarding']
['Machine Guarding', 'Power Presses']
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Copyright 2024 J. J. Keller & Associate, Inc. For re-use options please contact copyright@jjkeller.com or call 800-558-5011.