Choosing a Paint Curing Oven for Your Finishing Application

Finishing is one of the final steps in the manufacturing of a product and typically involves powder coating or painting its surface to provide an attractive “Finished” appearance. In addition to enhancing the appearance of a product, a high-quality finish also improves durability and corrosion resistance. In order to obtain these qualities, the paint or powder must be effectively and uniformly cured in a properly designed industrial oven. This is why choosing the right paint curing oven is so important to ensuring consistent, high-quality finishing results.

In this blog, we will guide you through the considerations that should be at the top of your list when selecting a paint or powder curing oven for your finishing application.

Paint Curing Oven Basics: Time and Temperature

Before you can begin the process of selecting a paint curing oven, you will need the cure temperature and process time required for your coating. Ask your paint or powder supplier for this information, as it will be used to determine the performance requirements for your oven. Most industrial ovens designed for curing are rated at a maximum of about 500° F (260° C). Some typical process temperature ranges are:

• Powder Coating generally cures at 350°F to 400°F (177°C to 204°C). At higher temperatures the cure time can sometimes be reduced, depending on the coating, which can increase the production throughput of the oven. Sometimes the substrate is preheated before the powder is applied, which can further decrease the cure time.
• Wet Paint (industrial enamels, acrylics, epoxies, etc.) usually cures between 250°F to 400°F (121°C to 204°C). Once again, a higher temperature will often reduce the drying time. 

Another question to ask your coating supplier is what temperature uniformity is required. A common uniformity tolerance for paint or powder is ±10°F (5.5°C), for example, which means the temperature through the entire oven heating chamber will not vary more than 10°F (5.5°C) from the setpoint temperature. This is important to avoid under or over-cured areas on your parts. Poor uniformity is a common problem with cure ovens, and reputable oven manufacturers perform a temperature uniformity survey (TUS) in each oven before shipment, to avoid this issue. The TUS involves locating a web of nine (9) or more thermocouples throughout the heating chamber to record and validate the temperature at each location.

Recirculation System: The Heart of a Paint Curing Oven

A properly designed air recirculation system is essential for both powder and paint curing applications. It ensures that heated air is evenly distributed throughout the chamber and around your parts for consistent curing. A combination airflow configuration is the most common airflow pattern used. It provides good uniformity by delivering heated air from both side walls near the bottom of the chamber. The air then passes through and around the product while being drawn up into the return duct located at the top of the work chamber. It is important to avoid top-down airflow designs in batch ovens even though they can be less expensive. This configuration directs the air vertically downward onto the load and often leaves the bottom of the product insufficiently heated and undercured. 

When evaluating the volume of recirculated air, make sure the oven delivers 10 air changes per minute (6 to 12 is a common range) based on the oven's internal volume. This can vary depending on the oven design but is a good guideline. For example, a 6’ W x 12’ L x 8’ H work chamber has a volume of 576 cubic feet (6 x 12 x 8). A sufficient recirculation fan size would be 10 x 576, or 5,760 CFM. This is important because undersized recirculation fans may lead to uneven curing, while oversized fans can consume excess energy or blow powder off the parts during powder curing. 

Build Quality Makes a Difference

Not all paint cure ovens are built the same. When choosing an industrial oven manufacturer, look for a well established company with a solid reputation and a long warranty. A few specifics:

• Ball bearing door hinges that resist door sagging, offer a longer life, and ease of opening/closing.
• Large ergonomic door handles that stay cool to the touch for improved operator comfort and reduced fatigue.
• NEMA 12 enclosure with name brand components and EMT style conduit on the oven.
• 3 or 5-year warranty that covers all non-wear components. 
• NFPA 86 compliance to ensure the oven meets industry-accepted standards of safety.
• High efficiency construction to reduce energy use and provide a cooler oven exterior.
• Direct drive fans for longevity, reduced energy use, and minimal maintenance since there are no drive belts.

These features may seem small, but they can make a big difference in performance and reliability over the lifetime of your oven.

Powder vs Paint: Special Considerations

While both powder and wet paint curing share many oven design fundamentals, powder coating requires special features to optimize the curing process:

• Air velocity must be carefully controlled to prevent the powder from being blown off the part before it gels. This is done by designing the air supply ductwork properly.
• Adjustable air supply louvers allow fine-tuning and balancing of airflow.
• Full size return duct that covers the entire roof (or side wall). This ensures the heated air passes directly and fully through the load area, properly bathing the parts in heat. Some ovens have no return duct at all, which results in cold spots and poor temperature uniformity.
• Variable frequency drives (VFDs) can be used to reduce fan speed at the start of the cycle to avoid powder blowoff, then increase it after gelling of the powder, optimizing both performance and finish quality.

We'll dive deeper into these considerations in our next blog: Optimizing Oven Design for Powder Coating Applications.

Why Choose Wisconsin Oven for Your Curing Application?

At Wisconsin Oven, we've spent decades perfecting industrial oven designs for both powder and wet paint applications. Our paint curing ovens are:

• Configured specifically to meet your specific time, temperature, and uniformity requirements.
• Built with premium components for durability and performance
• Fully assembled and tested before shipment for trouble-free installation.
• Backed by robust warranties - our 3 and 5-year warranties are the longest in the industry!

Coming Up Next: Optimizing Your Industrial Oven Design for Powder Coating Applications

In our next blog, we'll focus specifically on powder coating oven design by diving deeper into airflow control, variable frequency drives, and more!