The Importance of Parting Line Maintenance in Rotational Molding

Do you want to save time and labor costs and reduce scrap in your Rotational Molding secondary operations? Then take a few minutes to review our critical-to-quality operation of mold parting line maintenance that we truly believe can help improve your quality and bottom line.

A rotational mold’s parting line is critical to the overall quality of the end part. Over time parting lines can become a major issue that can increase scrap and cause poor part quality if not properly maintained. We believe that it is very important to place molds on a preventative maintenance program that focuses on parting line fit, parting line clamp / bolt tension as well as repairing any necessary damages that could have occurred while in production. This ensures that the next time it goes into production you are starting with a mold that can produce a first quality part. From there it’s up to the operators to treat the molds with good care to reduce scrap / second quality parts and downstream re-work.

Key Point: During production parting lines should be checked EVERY CYCLE and quickly cleaned if necessary.

  • Use only Plexi-glass or wood to clean parting lines. Do not use any type of metal to scrape the parting line.
  • Sharpen the plexi-glass to about a 30° angle. Only sharpen one side.
  • Use firm pressure against the parting line and push the plexi-glass into (and under) the plastic and burnt material.
  • Keep the Plexi-glass sharp to make scraping the parting lines easier.
  • If the plastic build up is too severe, a Certified Torch Operator can burn it off using a torch.
  • If a mold’s parting line is a problem every cycle and causing too much inline repair work on the machine, we recommend taking it down for repair to keep the overall efficiencies on the machine.

Keep in mind that a properly fit and clean parting line will produce a part with minimal flash and offset. Buildup primarily occurs if material has been spilled onto the parting line when charging a mold, a mold has missing or loose clamps or bolts, parting line has high/low spots, or the vent tubes are clogged. These issues will lead to excessive flash, poor shape and dimensions, and blowholes.

At Entec we are here to help and assist you with properly training and coaching your team in parting line maintenance and care. Your success is very important to us, and we believe that this is one of the critical components to that success. Please feel free to reach out and let us know how we can help!

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