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Machine Guarding for Injection Molding Machines. OSHA 10-Hour Outreach Training Program for the Plastics Processing Industry A Presentation of the SPI-OSHA Alliance. (Screen Capture of Website). (Screen Capture of Website). Course Objectives.

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Machine Guarding for Injection Molding Machines

OSHA 10-Hour Outreach Training Program for the

Plastics Processing Industry

A Presentation of the SPI-OSHA Alliance


Course Objectives

  • Identify the types of injuries that can occur while operating injection molding machines
  • Describe the possible causes of these injuries
  • Identify ways to safely operate injection molding machines
  • Recognize the importance of a total safety and health approach

Reasons to Focus on Injuries in the Injection Molding Process

  • High injury/illness rates
  • OSHA citations
  • National Emphasis Program
  • Site-Specific Targeting
  • High workers' compensation costs
types of injuries




Cuts and bruises

Sprains and strains


Electric shock

Types of Injuries

Some Causes of Injuries

  • Reaching around, under, over or through guards into hazardous areas
  • Removing or bypassing guards
  • Reaching into equipment to remove stuck or jammed material
  • Not using LOTO procedures
  • Machine/equipment malfunctions

Causes of Injuries(cont’d)

  • Lack of recognition of job hazards
  • Lack of familiarity with the equipment
  • Inadequate training, comprehension, or both
  • Operating machines with missing or inoperable guards and improper or inadequate machine maintenance

Injection Molding Machinery

  • Horizontal injection molding machine (HIMM)
  • Vertical injection molding machine (VIMM)
  • Combinations of vertical and horizontal clamp and injection configurations of machines
  • Regardless of the configuration of the machine, basic machine guarding and good safe work practices must be applied
    • Point of operation
    • Other moving machine parts


Unique Hazards and Issues

  • Gravity
  • Plastic splatter/missing insert
  • Flying inserts
  • Unexpected bystander interventions


Mechanical Hazards

  • Point of operation
  • Pinch points
  • Nip points
  • Rotating parts

Potential Injuries from

Mechanical Hazards

  • Fatalities
  • Amputations
  • Avulsions
  • Crushing injuries
  • Fractures

Safety Guards and Devices

  • Types of guards and devices
    • Movable guards with interlocks
    • Fixed barrier guards
    • Presence-sensing devices
    • Mechanical safety bars
  • Locations of guards
    • Over/around moving equipment
    • Around electrical hazards
    • Around thermal hazards

Operator’s Gate

  • Equipped with redundant interlocks
    • Electrical
    • Hydraulic
    • Mechanical safety bar
  • Allows the machine to operate only when the gate is closed

Electrical Interlock

  • Allows the electrical system to operate and close the clamp
  • Actuated when the operator’s gate is opened or closed
  • Prevents clamp from closing when the operator’s gate is open

Hydraulic Interlock

  • Actuated by opening or closing the operator’s gate
  • Each hydraulic IMM requires at least one
  • Prevents clamp from closing when the operator’s gate is open

Hydraulic Interlock Operation

After Activation

Before Activation


Mechanical Safety Device

  • Prevents clamp from closing when the operator’s gate is open
  • Must have at least one mechanical device on all IMMs
other guarding
Rear guard

Top guard

Parts discharge guard

Feed opening guard

Electrical system guards

Purge guard

Injection barrel cover

Other Guarding

Rear Guard

  • Prevents clamp from closing when interlocked rear guard is opened
  • Should have at least two interlocks
  • Prevents access to mold areas

Top Guard

  • Required if employees can reach over the top of the machine and into hazardous areas
  • Should be interlocked if movable

Parts Discharge Guard

  • Keeps employees from reaching under the operator’s gate and into hazardous areas

Purge Protection

  • Covers the nozzle and purging area
  • In combination with PPE, minimizes exposure to molten plastic during purging
  • Window allows observation through purge guard, if equipped
  • Should be equipped with an interlock

Purge guard



Barrel cover


Injection Barrel Cover

  • Protects from exposure to high voltage and high temperatures
grinder guarding
Grinder Guarding
  • Guarding by:
  • Enclosure over moving components
  • Anti-kickback flaps in feed throat
  • Proximity guarding – distance from feed chute to rotating knives

Proximity Guarding

abrasive wheel machinery
Abrasive Wheel Machinery

Work rests on offhand grinding machines must be kept adjusted closely to the wheel with a maximum opening of 1/8-inch to prevent the work piece or tool from being jammed between the wheel and the rest, which may result in wheel breakage or wheel explosion.

abrasive wheel machinery35
Abrasive Wheel Machinery

The distance between the wheel periphery and the adjustable tongue must never exceed 1/4-inch.

power transmission apparatus
Power-Transmission Apparatus

Unguarded belt

and pulley

Power-transmission apparatus (shafting, flywheels, pulleys, belts, chain drives, etc.) less than 7 feet from the floor or working platform must be guarded.

presence sensing devices
Presence Sensing Devices
  • Safety mat
  • Light curtain

How to Protect Yourself

  • Recognize the hazards in the job you are doing
  • Understand the requirements for guarding machines
  • Implement guarding solutions

Emergency Stop

  • Know:
    • Where it is located
    • What it controls
    • When to use it

Colors used with Safety Signs have meaning!


White Lettering/Red Background


Black Lettering/Orange Background


Black Lettering/Yellow Background

  • Used to automate repetitive or hazardous tasks
  • Must be guarded to prevent workers from entering or reaching into hazardous areas

References for Injection Molding Safety

  • ANSI/SPI B151.1- 1997 Horizontal Injection Molding Machines - Safety Requirements for Manufacture, Care and Use
  • ANSI B11.19-2003 Performance Criteria for Safeguarding
  • ANSI Standards are available at the following web site:

OSHA's Site-Specific Targeting (SST) Program

OSHA's Site-Specific Targeting (SST) program selects for inspection individual worksites with the nation's highest Days Away from Work Injury and Illness (DAFWII) Case Rate and Days Away, Restricted, or Transferred (DART) Rates. It is based on data reported by more than 80,000 employers surveyed by the agency.

See the OSHA Web site for the most current directive and the rates used to target inspections.

In order to verify the reliability of claims by establishments that

they have achieved low DART rates, OSHA inspects a certain percentage of employers with low rates.


OSHA National Emphasis Program on Amputations

On October 27, 2006, the Occupational Safety and Health Administration (OSHA) revised its national emphasis program aimed at reducing amputations in general industry workplaces. TheNational Emphasis Program on Amputations targets all types of machinery and equipment that are considered a high risk for causing amputations. The plastics processing industry is among the industries under scrutiny for workplace amputations. The twenty-four states and two territories which operate their own OSHA programs are encouraged, but not required, to adopt a similar emphasis program. State Plan State information is available on OSHA’s Web site. The OSHA directive on this emphasis program is available on OSHA's Web site under Regulations and Compliance, subcategory Compliance Directives, No. CPL 03-00-003.

Under this initiative, regional and area OSHA offices will continue to conduct outreach; targeting and selection; and inspections. Area offices will obtain and use additional data to identify and add establishments where serious injuries or fatalities related to these machines have occurred.


The Job Safety Analysis Process

  • The Job Safety Analysis (JSA) process is a very effective means of helping reduce incidents, accidents, and injuries in the workplace. It is a multi-step process.
  • Basic Job Steps
  • Potential Hazards
  • Recommended Safe Job Procedures


  • Injuries can occur while operating injection molding machines
  • Risk areas can be protected by safety guards and devices
  • Protect yourself and operate injection molding machines safely
  • Recognize the importance of a total safety and health approach