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 may need to open the operator's gate and remove 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
- 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 (for example, while interlocks have been
removed or bypassed).
- Inadvertently or purposefully reaches
around, under, or over guards into hazardous
- Operates a machine with missing or inoperable
guards or interlocks.
- Is not familiar with the equipment.
- Ensure that an operator's (safety) gate is installed to
block operator access to moving parts while
the machine is in normal production. 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
- Lockout/tagout the machine prior to
servicing and maintenance work.
and Maintenance: Lockout/Tagout
- Electric shock, amputation, or crushing may
result from a service or maintenance worker:
- Removing guards, bypassing safeguards, and
- Relying on interlocks rather than lockout/tagout
- Follow lockout/tagout procedures during service
or maintenance. Some machine guarding safety
devices may be sufficient during normal
operations, but may not be permitted to be used
during servicing and maintenance work. Lockout/tagout
must be performed if activities require the
- Remove or bypass a guard or safety device,
- Place any part of the body into the mold
area or an associated danger zone.
NOTE: The lockout/tagout standard makes a
limited exception for minor service activities
that take place during normal production
operations when they are routine, repetitive and
which are integral to the use of the equipment
for production, provided that the work is
performed using alternative measures that
provide effective employee protection.
Figure 5. An employee follows lockout/tagout procedures for plastics machinery needing repair.
Figure 6. An employee
changes the mold of an injection molding machine.
If exposed to potential injury from hazardous
energy, follow the lockout/tagout procedure.
Manual Feed of Plastics Materials
Figure 7. A guard equipped with safety signs covers the barrel of the injection unit.
- Skin burns from contact with the heated barrel
or burns from splatter of hot plastic and gases/vapors.
- Hands or limbs caught in machine while loosening
trapped materials at feed throat.
- Slips, trips, and falls at material feed location.
- The injection unit and other accessible parts
posing thermal hazards should be insulated or
guarded. 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. Do not place your hand
into the feed throat.
- Wear appropriate personal protective
equipment (PPE), such as a heat-resistant
shirt and eye/face protection, when
- Use a ladder, rolling stairs, platform, or
other safe 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 vapors.
- Consult manufacturer's
material safety data sheets (MSDS).
- Wear heat-resistant personal protective
equipment (PPE) to prevent burns from contact with hot surfaces or splatter
of hot plastic and gases, when necessary.
- 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
and Hearing Conservation Safety and Health