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.