Rotational Molding

Wall Thickness - Rotational Molding Design

Rotational molding produces plastic parts in a wide variety of shapes, sizes, colors, and textures. This manufacturing method also supports undercuts, multiple walls, and molded-in hardware and graphics.

Rotational molding creates hollow plastic parts with low tooling costs and quick tooling modifications. At Gregstrom, this manufacturing method also supports value-added post-mold services like filling plastic parts with polyurethane foam.

How Rotational Molding Works

With rotational molding, powder or resin is loaded into a hollow mold which then rotates on two axes inside an oven until the inside of the mold is coated uniformly. After the mold is cooled, the hollow plastic part is removed. Tooling for rotomolding or rotocasting, as this manufacturing process is also know, ranges from simple two-piece sheet metal molds to multi-piece aluminum molds with articulating features. To learn more, watch this YouTube video.

Rotational Molding Advantages

Rotational molding is ideal for prototyping and for production runs. It’s flexible enough for projects ranging from small, intricate designs to large, complex parts and assemblies. Many rotomolded shapes are impossible to produce by other methods. Plus, because there’s no pressure in this plastics manufacturing process, hardware can be molded-in for strength and durability. Other plastics molding processes can’t support molded-in hardware like rotomolding can.

Additional advantages include:

  • Support for a wide variety of surface textures and colors
  • Support for uniform walls without the thinning in the extremities that’s common to other processes.
  • Rotationally molded parts can also be filled with polyurethane foam for added strength or insulation.

Mold-In Graphics

Custom rotomolded parts from Gregstrom can feature Mold In Graphics, a permanent way to mark, decorate, brand, or label your plastic parts. Traditional stickers and labels don’t adhere well to plastic materials, and some require spray adhesives. Mold In Graphics supports permanent labeling, branding, and marking while also providing better resistance to UV, weather, and chemicals.

Rotational Molding Applications

Gregstrom can create many different types of custom rotomolded parts. Examples from our roto molding services portfolio include:

Rotational Molding Equipment

Rotational Molding EquipmentGregstrom uses Ferry Rotospeed RS-220 and RS2-3300 machines to manufacture your custom rotomolded parts. Each machine has offset arms, and the largest machine has up to 125” swing.  This means we can rotomold plastic parts in a wide ranges of sizes and shapes from intricate spray manifolds to small boats.

High-Intensity Mixing

Gregstrom’s auxiliary equipment for rotomolding includes a Ribbon/Paddle Blender with a 1000-lb. capacity. Our newest machine, a high-intensity mixer with a capacity of 300 lbs., provides even faster mixing cycles and features an optimized vortex for heat generation and shear to avoid agglomeration of the mix material. This new machine “polishes” the resin, which means more uniform colors, reduced porosity and improved overall physical properties.

Polyurethane Foam Filling

Rotational Molding Foam FillingGregstrom also has the equipment and expertise to fill your custom rotomolded parts with polyurethane foam, which provides additional rigidity and thermal insulation. Because rotomolded parts (such as coolers) have hollow cavities, their design is optimal for filling with PU foam.

Rotational Molding That’s Made in the USA

For nearly 70 years, Gregstrom Corporation has been forming and molding plastics at our Made in the USA manufacturing facilities in Massachusetts. To learn how our roto molding services can support your application, contact us online or call (781) 935-6600.