Dürr has developed a new return system that enables VOC-free color changes for two-component (2C) clear coats, eliminating volatile organic compound (VOC) emissions in the paint booth during flushing processes. The system, which has been successfully deployed in two topcoat lines for over a year, allows mixed 2C paint systems to be fed directly back into the return system within the atomizer for the first time.

Reducing VOC Emissions in Paint Booths

Traditionally, flushing and color changes in 2C paint systems release significant VOC emissions, with over 70% of booth air affected by VOC pollution. Conventional processes flush residual paint forward into a funnel or directly into the washout, requiring extensive air filtration. Dürr’s EcoBell PurgeBox system, which uses special filter mats, reduces VOC emissions by up to 60%.

Dürr’s new return system further reduces the VOC load by enabling a return process for 2C clear coats, similar to standard one-component (1C) processes. Previously, this was not possible for mixed clear coat systems that combine hardener and stock paint. Using a patented process sequence, mixed 2C materials are now flushed back into the atomizer’s integrated return system without curing. This lowers VOC emissions to just 5%, occurring only during bell disk cleaning in the EcoBell Cleaner D2—with no VOC release during flushing or color changes.

The green paint is mixed in the atomizer and applied. 

Note: The clear coats are shown in green and blue for demonstration purposes.

Optimizing Cycle Times and Effect Finishes

In addition to environmental benefits, the new return system improves efficiency and reduces cycle times. Cleaning the bell disk and atomizer surface in the EcoBell Cleaner D2 now occurs simultaneously with flushing and priming—previously sequential steps. This parallel process takes just 15 seconds, cutting color change time in half and increasing system capacity.

This technology also enables tinted clear coats to be applied without cycle time losses, making effect finishes—once limited to exclusive vehicle segments—more widely accessible.

Once painting is complete, the mixed green 2C paint is returned in the atomizer. 

During this process, the blue paint is already mixed and can be applied without any loss of cycle time.

Integration With EcoBell4 Pro

In combination with the EcoBell4 Pro rotary atomizer, the new system offers maximum flexibility. Each robot arm integrates two returns for 2C material (2x2C), allowing stock paint and hardener for the next body to be prepared in parallel while the current body is being painted.

This setup ensures that even when manufacturers use multiple paints and hardeners that are chemically incompatible, each material can be applied via separate channels. Dürr also verifies compatibility of customer clear coat systems in its test center, confirming that all 2C clear coats tested so far can be returned and collected via the atomizers.

Reducing Costs in Paint Booth Operations

The return system for mixed 2C materials is available in the EcoBell4 Pro 2x2C and 1x2C variants, while the EcoBell3 can be retrofitted with 1x2C capabilities. Another system using this new technology is currently being commissioned.

Beyond reducing VOC emissions and flushing agent consumption, the return system lowers investment costs by eliminating the need for:

• Funnels
• EcoBell PurgeBox units
• Additional fixtures and fittings in the paint booth

For over a year, the return system has proven effective at a leading electric vehicle manufacturer, operating in two topcoat lines with 42 high-rotation atomizers.

Learn more at www.durr.com. 

*Images courtesy of Durr.