Accumulator Head Blow Molding

  • Intermittent extrusion process
  • Bottles: Large drums, garbage cans, gasoline tanks
  • Typical Resins: HDPE, PP, PPO
  • Machinery: Davis-Standard, Uniloy, Kautex, Jackson Machinery, R&B Plastics
  • Typically single layer
  • Dies are not polished – glass filled grades are generally safe to use
  • Largest area of concern when purging is the accumulator head – this is a low pressure area where it can be difficult to get sufficient scrubbing action.
  • Clean the extruder before the accumulator
  • Insufficient cleaning of the accumulator head leads to die lines and color/burn streaks in the final parts.
  • When cleaning the accumulator:
    • fill to 100%, then push out 25%
    • fill to 100%, then push out 50%
    • fill to 100%, then push out 75%
    • Fill to 100%, then push out the full 100%
  • “Disco purge” – changing screw speeds, as well as stopping and starting screw rotation, allow for better screw cleaning.
  • Use either an aggressive glass-filled mechanical purge, or a chemical purge with good foaming action.
  • Seal the extruder and accumulator head with a sealing grade commercial purging compound during extended downtime events.