Rotational molding, also known as rotomolding, is the process of heating and spinning plastic resin in a mold to achieve a hollow plastic shape. While rotating on two axes, the mold is heated to ensure the resin coats the interior evenly. After the hollow part cools, it is removed from the mold.

The result is a seamless, one-piece product with consistent wall thickness. Rotomolding is a simple yet effective way to produce consistent, quality parts.

The technique allows rotomolders such as Michiana Rotational Molding to deliver customizable and durable products for use in a variety of industries.

We can convert your design into a mold and repair existing molds, if needed.

Rotomolding is a low-pressure process with much lower tooling costs than injection molding, making it cost-effective for short- or medium-production runs and large hollow parts.

Unlike blow molding, rotomolding can achieve complex shapes, uniform wall thickness, and multi-layer structures with minimal waste.

Rotomolding is everywhere, often hidden inside larger products. If you’ve used a cooler, played on a playground, ridden on a pontoon boat, or driven through road construction, rotomolded products were likely involved.

Commonly rotomolded products include:

• Marine tanks, live wells, and dock floats.
• RV water and holding tanks and other recreation equipment.
• Agricultural feeders, bins, and chemical tanks.
• Material handling totes, bins, and carts.
• Kayaks, coolers, and playground equipment.
• Planters, furniture, and pond equipment.
• Road barricades and traffic barrels.

We primarily mold polyethylene, but we also work with polypropylene, nylon, ABS, PVC, and cross-linked polyethylene (XLPE). Options include recycled resins for environment sustainability and UV-stabilized grades for outdoor products and specialty resins for chemical or heat resistance.

Drawing upon our extensive industry experience, we can help advise you on the best material for your product and application. Utilizing standard or customized resin colors, rotomolding allows us to manufacture components that can be used as a finished, standalone product or integrated seamlessly into a larger assembly.

Typical wall thicknesses range from 0.125 to 0.25 inches (3–6 mm), with up to 0.5 inches achievable for heavy-duty applications. Our process provides uniform thickness, though sharp corners or transitions may thin slightly.

With swing capacities up to 135 inches, we can mold very large parts in a single piece. This makes rotomolding ideal for oversized tanks, recreational products, and industrial containers.

For best results, include at least 1° of draft per side, use smooth transitions instead of sharp corners, and consider hollow ribs for strength. Inserts, threads, or graphics can be molded in for added functionality.

Yes. Sequential resin loading allows for multi-layer walls (for example, virgin resin on the outside, recycled on the inside).

General tolerances are about ±1% of dimensions, with a minimum of ±0.02 inches. For critical features, we use robotic trimming or CNC machining to improve accuracy.

We use aluminum and steel molds, chosen based on product complexity and production needs. Aluminum is lighter and cost-effective, while steel supports high-volume runs and detailed surfaces.

Working with our partners, we develop specific molds after product engineering and feasibility testing. Our most common types of molds include:

• • Fabricated molds are made in Elkhart, Ind. These are often used for holding tanks, liners, and other RV applications.
  • Cast tools are made in Minnesota and Wisconsin. These molds provide a Class A finish.
  • Solid aluminum billet molds. As the top of the range in price and results, billet tools also provide a Class A finish.

Yes. Rotomolding’s lower tooling costs make it a great option for prototyping, pilot runs, or limited-volume production.

We run six Rotoline machines in a 150,000-sq-ft facility, operating 24 hours a day. Lead times depend on design and demand, but our scale and flexibility help us turn projects quickly.

Our robotic trimming arm delivers fast, precise finishing. We also provide CNC machining, secondary assembly, spin welding, color mixing, and mold-in inserts. These capabilities help us meet both consumer-grade and engineering-grade requirements.

We provide local delivery with our own trucks and arrange direct shipping for broader needs. All products are shipped with efficient protective packaging to ensure your pieces and assembly arrive on time and in excellent condition.

Tooling is far less expensive than injection molding, which can save hundreds of thousands of dollars in upfront costs. The rotomolding process also produces minimal waste, allows for design flexibility, and supports medium or low volumes without sacrificing strength.

Rotomolded products are seamless, with no welds or joints that could weaken over time. UV-stabilized resins make them ideal for outdoor use, and XLPE provides chemical resistance. Many rotomolded products last 10–20 years or more, even in tough environments.

Rotomolding generates little to no waste. Resin can often be ground and reused, and products can be made with recycled or layered materials. Rotomolded parts are also strong and long-lasting, so they don’t need to be replaced as often, reducing overall material use.