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Understanding the Parting Line

Learn how parting line best practices help to improve mold quality at Waupaca Foundry.

Waupaca Foundry works with a variety of companies with a wide range of casting-design and mold-design experience. Throughout the years, we’ve gathered some best practice tips for designing a parting line that improves moldability, mold performance, and quality of the casting.

We commonly see unequal parting lines, deep offsets, and sharp corners. Understanding and correcting these three areas of parting line design can make a difference in quality and manufacturability. Here are some quick tips:

  1. Equalize your parting line. Sometimes we see a company that offsets the parting line of a 2-inch-thick part to one side, thinking that it’s easier to design around the casting edge. But from a molding standpoint, it’s not. The best approach is to split the parting line right down the middle whenever possible. This helps avoid pitfalls and reduces the chance for imperfections in the mold.
  2. Avoid deep offset pockets. Offset pockets require more close-over clearance in the molding chamber where the swing half closes over the ram half, completing the pocket. With the increase in the required clearance, the chance for imperfections and the difficulty of green sand molding also increases. The molding process becomes more efficient and cleaner with a flatter parting line that is distributed evenly on each side. This also means less scrap, less inclusion, reduced green sand imperfections, less mold crush, and a reduction in flash during the manufacturing process. 
  3. Limit the use of sharp corners. The corners of a mold are where things can get fuzzy. A sharp, square corner can lead to imperfections in the mold and an increase in necessary machining on the casting. Designing with a larger radius corner and a smoother transition between parting lines as they meet the drafted surface will create a better mold, a more efficient manufacturing process, and result in a high-quality casting that requires less finishing.

Some companies have limited interaction with foundries and the nuances of the casting process. That’s exactly why Waupaca Foundry offers Foundry 101. You can learn about parting line designs that improve quality, reduce waste, and reduce cost.

Contact us about Foundry 101 sessions for this exact topic and many more. Visit the Foundry 101 page on our website.