Plastics extrusion presses

Plastic granules are poured into the extrusion press’ hopper, and heated by friction as the screw applies pressure. Additional external heating helps to raise the temperature.

While this guidance has not been updated to reflect current work health and safety legislation (the Health and Safety at Work Act 2015 and regulations), it may still contain relevant information and practices to keep workers and others healthy and safe.

Please read this guidance in conjunction with all relevant industry standards that apply to you as a PCBU. This guidance will be progressively reviewed and either updated, replaced with other guidance, or revoked.

Plastic granules are loaded from the hopper into a closed auger which passes them through a heater. The heat melts the granules which enables molten (melted) plastic to be forced through a breaker plate, then through a die. The flight of the screw decreases to increase pressure and temperature as plastic nears the breaker plate.

Plastic is extruded through a die, and shaped into either profile or film. Profile could be window frames, rods, pipes or sheet. Plastic is cooled after leaving the die, and processed either by cutting profiles of standard length, or cut to film of standard width.

Figure 1: Plastic extrusion press

[Image] Plastic extrusion press

Figure 2: Plastic extrusion press key parts

[Image] Plastic extrusion press with labels and red arrows pointing to key components

Figure 3: Film forming at extrusion press

[Image] Film forming at extrusion press

Hazards

  • Heavy lifting
  • Pouring granules into hopper
  • Molten plastic/heat
  • Contact, impact or trapping
  • Entanglement
  • Hazardous substances
  • Noise
  • Slips, trips & falls
  • Contact, impact or entanglement from unexpected movement (during maintenance, cleaning & repairs)

Personal Protective Equipment (PPE)

  • Ear protection
  • Eye protection
  • Face protection
  • Hand protection

Tasks

Task – Load & unload

Hazard

Heavy lifting

Harm

  • Strain injury

Controls

  • LIFT loads in quantities that will reduce the chance of strain.
  • USE mechanical lifting aids when necessary.

Manual lifting of granules into the hopper. Mould parts can weigh up to several kgs.

Hazard

Pouring granules into hopper

Harm

  • Risk of cuts to hands

Controls

  • WEAR hand protection.

Task – Extrusion process operation

Hazard

Molten Plastic/heat

Harm

  • Risk of burns

Controls

  • GUARD auger and heating devices from contact.
  • GUARD the nozzle where the end of the auger connects to the die, to prevent melted plastic from squirting beyond the press if there is a leak.
  • ISOLATE any heating, cutting or sealing processes that follow extrusion.
  • WEAR PPE (personal protective equipment) to cover face, hands, and body.

Plastic becomes liquid at about 200°C. Plastic is forced into dies under high pressure, so any leak between the auger and the die may squirt out jets of melted plastic. During servicing, release of melted plastic from a blockage may result in hot plastic squirting out under pressure.

Hazard

Contact, impact or trapping

Harm

  • Crush injuries
  • Deep cuts or amputation

Controls

  • FIX guards to prevent reaching into moving parts. Prime movers and transmissions MUST be guarded.
  • Guards that open MUST BE interlocked.
  • USE mesh within the hopper to prevent reaching through to the moving auger.
  • INTERLOCK GUARDS with two control channels to prevent hazardous movement.

Task – Threading film

Hazard

Entanglement

Harm

  • Crush injuries
  • Deep cuts or amputation

Controls

  • NEVER wear loose clothing or jewellery.
  • KEEP rollers open as far as possible and running as slowly as possible.
  • KEEP an emergency stop within reach of either hand.

Task – Cooling and cutting

Hazard

Entanglement with nips, blades and knives

Harm

  • Bruising
  • Crush injuries
  • Deep cuts or amputation

Controls

  • SHIELD heating devices from contact.
  • ISOLATE any heating, cutting or sealing processes that follow extrusion.

Cooling and cutting operations can present hazards, like entanglement in nips where plastic web passes around rollers. Contact with knives used for slitting webs, and contact with blades used for cutting products to length, can be hazardous.

Other (non-mechanical) hazards

Hazard

Hazardous substances

Harm

  • Breathing problems, lung damage or cancer
  • Worsening of existing health problems

Controls

  • ISOLATE hazardous processes that follow extrusion, such as heating, cutting or sealing.
  • ENSURE that handling and storage processes MINIMISE spills and dust.
  • USE temperatures low enough to avoid toxic vapour formation.
  • CLEAN plastic dust from surfaces where it lands. Blowing dust with compressed air is NOT acceptable.
  • PROVIDE adequate ventilation.
  • ALWAYS WEAR PPE to cover face, hands, and body.
  • KEEP fire extinguishers readily available, and ENSURE staff know how to use them.

Plastics dust can form explosive clouds.

Hazard

Noise

Harm

  • Hearing damage or loss

Controls

  • REDUCE noise levels by isolating machines or enclosing within noise barriers.
  • ASSESS noise levels.
  • ARRANGE hearing screenings.
  • ALWAYS WEAR hearing protection.

A safe noise level over an eight hour day is 85dB(A). A plastics extrusion press may exceed this noise intensity.

Hazard

Slips, trips and falls

Harm

  • Trapping
  • Cuts
  • Bruising

Controls

  • KEEP up-to-date housekeeping procedures.
  • KEEP the area around presses clear of slip and trip hazards.

Task – Maintenance, cleaning & repairs

Hazard

Contact, impact or entanglement from unexpected movement

Harm

  • Bruising
  • Crush injuries

Controls

  • LOCK-OUT ALL power supplies before maintenance, cleaning and repairs.
  • KEEP a written daily safety inspection system, and ARRANGE annual testing by a qualified press technician.
  • KEEP guard interlocks and emergency stops safely maintained.
  • LOCK OUT/DE-POWER presses that fail safety requirements, and DO NOT USE until repaired or replaced.
  • ALWAYS WEAR PPE (personal protective equipment) when exposed to melted plastic or hydraulic oil.

 

If additional safeguards are required, they MUST be fitted by competent suppliers, working to recognised safety standards. Instructions MUST be provided in a language understood by operators.

Download fact sheet

Plastics extrusion presses (PDF 411 KB)