In the plastics industry, injuries resulting from inadequate machine guarding are of concern due to their potential severity. Plastics processing machines are complex pieces of equipment that require guards to protect employees from nip points, numerous moving parts, and exposure to high
voltage and high temperature.

Serious injuries including fatalities, amputations, avulsions, burns, cuts, and bruises can occur during operation. Such injuries may result from guards that are missing, improperly installed, removed, or bypassed.

OSHA and the Society of the Plastics Industry has put together the following information to help keep operators of plastic injection equipment safe.

Thermoplastic injection molding machines produce molded plastic parts by converting plastic pellets into molten material, injecting the molten plastic into a mold, and cooling the plastic material.

The mold consists of two halves. One half is connected to a movable platen and the other is connected to a stationary platen. As the machine prepares to inject molten plastic into the mold, the platens close and press the mold halves tightly together. When the plastic is cooled, the movable platen retracts, and the solidified plastic parts are removed.

The operator opens the operator’s gate and removes plastic parts from the mold. The operator may also be required to operate the control panel interface. Tasks associated with the injection molding
process include:
• Opening Operator’s Gate;
• Servicing and Maintenance: Lockout/Tagout; and
• Manual Feed of Plastics Materials. When opening the operator’s gate, the following potential hazards exist:
• Crushing injuries or amputations may occur if hands or limbs are placed between mold halves or other hazardous areas while machine cycles. This can occur if the operator or other person:
• Reaches into the machine to loosen a part that is stuck (while interlocks have been removed or bypassed);
• Inadvertently or purposefully reaches around, under, or over guards into hazardous areas;
• Operates a machine with missing or inoperable guards or interlocks; and
• Is not familiar with the equipment.

Possible Solutions — Ensure that a safety gate is installed to block operator access to moving parts while the machine is running. Use interlocks (mechanical, electrical, hydraulic) that prevent the mold from closing when the gate is open.

Do not remove, alter, or attempt to otherwise bypass a safety interlock. Do not attempt to reach around, under, or over a guard. If a person standing on the floor can reach over the machine into the mold area, install a top guard that is fixed or interlocked.

Access the mold cavity via the operator’s gate and do not remove a fixed guard during normal operation.

Provide training on the safety hazards and features of the injection molding machine for all employees who will operate or work with it.

Servicing and Maintenance
Potential hazards when servicing and maintaining equipment include:
• Electric shock, amputation or crushing may result from a service or maintenance worker;
• Removing guards that are not interlocked, bypassing safeguards and interlocks; and
• Relying on interlocks rather than lockout/tagout procedures.

Possible Solutions — Follow lockout/tagout procedures during service or maintenance. Machine guarding safety devices can be sufficient during normal operations, but lockout/tagout must be
performed if activities require the employee to remove or bypass a guard or safety device, or place any part of the body into the mold area or an associated danger zone.

Manual feed of plastics materials presents the following hazards:
• Skin burns from contact with the heated barrel or burns from splatter of hot plastic and gases.
• Hands or limbs caught in machine while loosening trapped materials at feed throat.
• Slips, trips and falls at material feed location.

Possible solutions – The injection unit and other accessible parts should be insulated or guarded where maximum temperatures can exceed 80 C. Place warning signs where hot parts are necessarily exposed.

• Place a fixed guard (usually a grid) or a distance guard (usually the hopper) at the feed throat. When needing clearing material from the feed throat opening, follow the manufacturer’s recommended procedures.
Do not place your hand into the feed throat.
• Wear appropriate personal protective equipment (PPE), such as a long-sleeved shirt and face protection.
• Use a ladder, rolling stairs, platform or other suitable means to access the hopper or feed throat area. Do not climb on the machine.

Additional Safety Measures
• Ensure that proper ventilation and exhaust systems are in place to help prevent inhalation of harmful gases and fumes.
• Consult manufacturer’s material safety data sheets (MSDS).
• Wear appropriate personal protective equipment (PPE) to prevent burns from contact with hot surfaces or splatter of hot plastic and gases.
• Follow good housekeeping procedures and keep floors clean to prevent slips, trips, and falls due to spilled pellets on the work floor.
• Apply engineering controls or hearing conservation programs as necessary to control noise.

For more information, see OSHA’s Machine Guarding eTool at www.osha.gov/SLTC/etools/machineguarding/index.html and go to its Noise and Hearing Conservation Safety and Health Topics page.