Learn How to Create the Best Rotational Molds
Rotational molding, or rotomolding, is a flexible and cost-effective way to manufacture hollow plastic parts. But the success of any rotomolded product begins long before the material hits the mold. It starts with smart, strategic mold design.
At GVL Poly, we’ve been creating rotomolded parts for over 30 years. We know firsthand that mold design can make or break a project. A well-designed mold not only produces consistent parts but also streamlines manufacturing, reduces defects, and saves time and money in the long run. So, what exactly goes into rotational molding mold design? Let’s break it down.
Understanding Rotational Molding
Before we dive into rotational molding mold design, let’s first take a look at the process. Rotational molding is a highly specialized manufacturing method that’s ideal for creating everything from storage tanks to playground equipment. It’s capable of producing parts within tight tolerances, making it a popular choice to create a wide variety of hollow products. In fact, so many companies rely on this process that the industry is expected to surpass $12.6 billion by 2037.
During the rotational molding process, a polymer is heated inside a mold, which is then spun around two perpendicular axes. The polymer coats the inside of the mold, creating a tight-tolerance, hollow part.
Want to learn more about rotational molding? View our in-depth blog here.
How to Design the Perfect Rotational Mold
Get Clear on Your Needs
Before any mold is designed, we start by understanding the end use of the product:
- Will the part be exposed to chemicals or outdoor conditions?
- Does it need to meet certain weight or strength requirements?
- Are there aesthetic considerations like color, texture, or shape?
- How tight do the dimensional tolerances need to be?
These answers help determine the material, wall thickness, shape, and features that the mold needs to support. Every design decision ties back to how the final part will perform in the real world.
Material Selection
Mold design is closely tied to material selection because different plastics behave differently during the molding process. For example, LLDPE offers excellent flexibility and impact resistance. HDPE delivers strength and chemical resistance. And XLPE requires additional mold considerations due to its cross-linking behavior. The properties of the chosen materials will impact the entire process. An experienced rotational molding provider can help you choose the right option for your needs.
Wall Thickness and Uniformity
Because rotomolding relies on plastic coating the inside of a mold, maintaining uniform wall thickness is key to part performance. Uneven thickness can lead to weak points, warping, or inconsistent quality.
In mold design, we consider a few different things to get the right solution. This might include:
- Ensuring corners are rounded, not sharp, to encourage even material flow
- Avoiding deep recesses or extreme angles that could create hot or cold spots
- Using simulation and experience to predict material distribution and adjust accordingly
Mold Venting
Proper venting is extremely important to the rotational mold design process. Poor venting leads to air pockets, voids, or incomplete parts. And for materials like XLPE or Nylon 6, venting becomes even more critical due to their behavior at high temperatures. Your mold design partner will ensure vents are strategically placed to allow airflow without leaking material.
Mold Materials and Construction
Molds for rotomolding are typically made from aluminum or steel, depending on the application. Aluminum molds are lightweight and offer excellent heat transfer for faster cycles. They’re ideal for complex or large parts and moderate production runs. Steel molds are more durable and better suited for high-volume production, though they’re often more expensive.
Partner with GVL Poly on Your Next Mold Design
Great parts begin with great molds. Trust the experts at GVL Poly with your next project. Whether you have a fully fleshed-out concept or just an idea, our team can help. With decades of experience, a problem-solving mindset, and a dedication to precision, we’re here to make sure your product performs exactly as it should. Reach out today for an initial consultation.
