When you’re preparing to purchase high quality urethane components for your unique application, it makes sense to educate yourself on the distinct differences between the two most common processes used for manufacturing polyurethane parts. Open cast molding and injection molding are the two most popular methods for transforming urethanes into an extensive variety of parts and components. Open cast molding involves liquid polyurethane being poured into an open mold and then placed in a heated compression press to spread the material evenly throughout the mold. Injection molding requires liquid polyurethane to be injected into a closed mold with holes or “bleed gates” which allows air to be pushed out of the mold during injection so the polyurethane can spread evenly.
While these two methods seem relatively similar at first glance, there are many differences between them. In the battle of open cast molding vs. injection, open cast molding is often the winner, and there are several reasons why.
Range of Durometers
Durometer is the measurement of hardness in a material, a term which can also dictate the material’s resistance to indentation. Open cast molding allows for the most extensive durometric range for the final product, with the ability to produce components from 00 to 80D, meaning very soft to very hard. The ability to manufacture products with such a wide range of hardnesses means that open cast molding allows for increased versatility of part design.
Low cost tooling
While injection molding can be fairly inexpensive when manufacturing larger quantities of a product, there is a clear discrepancy in terms of quality. When working with small to medium sized production runs, open cast molding offers the combination of a low cost paired with superior quality. Additionally, because open cast molding yields a higher quality end product, more money can be saved over time as the product will outlast those made by injection molding.
When your component requires the ability to snugly adhere to another part, open cast molding is a far superior option when compared to injection molding. While injection molding is fast and cheap, it yields less uniform parts with increased likeliness of uneven or rough sides. The slow cure process of open cast molding allows the liquid urethane to spread evenly within the mold, ensuring smooth surfaces when the component is removed. While a rough surface from injection molding can be smoothed, additional time will be needed for tooling, resulting in an increased cost.
If it’s a priority for your end product to be resistant to breaks, open cast molding is the answer. Since the heat curing process builds strong links in the hardening urethane material, the finished material features superior molecular bonds to that of injection molding. An open cast molded component offers superior tensile strength, making it ideal for products that will be subjected to high levels of vibration or impact. Since injection molding doesn’t involve the same slow heat curing process, the resulting material doesn’t have the same closely linked structure in the hardened polyurethane material, making it more susceptible to breakage.
If you still have questions or aren’t sure whether to choose injection molding or open cast molding for your application, Mearthane can help. As the industry authority in the numerous processes and methods for manufacturing polyurethane components, we can explain the pros and cons of each, giving you honest insight and suggesting the best fit for your unique specifications. We manufacture an extensive selection of open cast polyurethane products for dozens of different industries, each featuring beneficial features like high abrasion resistance, outstanding tensile and tear, noise dampening, and phenomenal load bearing capability with a weight far less than metal. At Mearthane we offer a fast turn around time paired with a commitment to unmatched quality, ensuring that you’ll receive components that you can be proud of. Want to learn more? Contact Mearthane today!