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.