Safety Precautions for Injection Molding

Safety is critical in manufacturing operations, and the injection molding process presents its own set of hazards and safety concerns. High temperatures, high-pressure hydraulic circuits, and hazardous fumes all pose a risk to operators, and the popularity of injection molding provides many opportunities for accidents. There are methods to prevent safety breaches, but they all involve education on how injection molding works and where the danger lies in the process.

This article will help educate readers by detailing various safety precautions for injection molding, covering machine and operational procedures.

Below is an image of an injection molding machine as used in an industrial setting.

Plastic injection molding involves mechanical and thermal hazard sources, where users can experience burns, crushes, impacts, and other dangers. Not only do improper safety procedures jeopardize the longevity of machines, but they can also lead to operator injury, so it is essential to define a working protocol for all aspects of the injection molding process.

The American National Standards Institute (ANSI) defines a safety standard for all horizontal and vertical clamp injection molding machines in its ANSI/PLASTICS B151.1-2017 – Plastics Machinery – Safety Requirements for Injection Molding report. It defines the potential danger zones of injection molding divided into classifications defined as mechanical/thermal, electrical, and other hazards.

A summary of these potential hazard areas appears below for each classification:

Mechanical/Thermal Hazards

• Mold Area
• Clamping mechanism area
• Core and ejector drive mechanism areas
• Nozzle area
• Injection unit area
• Feed hopper/opening area
• Heater bands/heat source areas
• Parts discharge area
• Hoses and manifolds in/around the machine
• Inside the guard and outside mold areas
• Part insert and removal areas

Electrical Hazards

• Electromagnetic component disturbances
• Stored/residual energy areas

Other Hazards

• Vapors and gasses

The standard also states that the risk responsibility of injection molding machines is attributable to multiple parties but is principally determined by whether the machine is in use or not. Existing machines in use must be kept safe by the users (manufacturing company, business, etc.), and this includes everything from installation to operation to maintenance. Responsibility for machines currently being repaired, manufactured, or upgraded is shared by both the user and the technician/repair person/service supplier.

They also operate the control panel, provide manual feeding of material, as well as service and maintain the machine using lockout/tagout procedures and additional measures— all of which can expose them to risks.

With automation entering the injection molding sphere, these considerations may quickly become outdated. However, it is still important to understand the operative dangers of injection molding.

The list found below cannot encompass all considerations for every injection molding operator. Still, it does provide the general steps to ensure proper safety precautions while operating an injection mold machine:

1. Before even touching the machine, all operators must be adequately trained in machine operation, workspace management, and proper lockout/tag-out protocol.  
2. Operators should never reach over or under machine guards, stick appendages into the hopper/granulator, or stand directly below a suspended mold.
3. PPE such as safety glasses, safety shoes, and respirators (if required) should always be worn during operation, and proper lifting techniques should be learned (e.g., upright back, lift with legs).
4. Operators should never free climb on the machine, horseplay around the area, or leave catwalks/railed platforms when needing to climb the machine.
5. Training must be provided on the chemical hazards associated with the injection molding process, both with regard to the material and any supporting chemicals such as mold release, lubricant, etc., used in the injection molding process.
6. Safety measures should not be bypassed, modified, or altered on any or all safety equipment for the sake of expediency.
7. Every worker should know the location and route to fire extinguishers, fire exits, and other emergency tools.
8. Operators should double-check that the nozzle tip is firmly in place and correctly centered prior to molding.
9. When changing materials, operators should understand the possible chemical reactions and related issues between the two materials (some thermoplastics will produce toxic gases when mixed).
10. No steel tools are to be used on the mold cores when cleaning/performing maintenance, opting instead for copper, aluminum, or bamboo tools that will not scratch the mold.
11. If there is a shutdown, heaters must be turned off, and plastic in the plasticizing cylinder must not be further heated.
12. Operators must remain vigilant of sharp ejector pins and corners and frayed wires near the nozzle heater bands.
13. It is strictly forbidden for operators to open the safety door at unauthorized times. The front gate should have mechanical, electrical, and hydraulic devices to prevent closing when the gate is open.
14. Double check that the mold is firmly aligned on the platen and the head plate.
15. Report any and all issues to relevant supervisors, including open junction boxes, leaks, frayed wires, loose water, or injuries.

There are many more model-specific safety precautions to be taken—this list only provides a general overview of the minimum requirements for safety when performing injection molding. Be sure to understand the specific safety requirements and recommendations for your machine, and if you are unsure, reach out to the manufacturer or service provider for safety protocols.