Dürr’s latest development enables mixed 2-component paint systems to be fed directly in the return system within the atomiser for the first time. This eliminates VOC emissions in the paint booth during flushing processes and colour changes. The new solution has been successfully deployed in two top coat lines for over a year.
The green paint is mixed in the atomiser and applied. Note: The clear coats are shown in green and blue for demonstration purposes. Image Credit: Dürr
Until now, significant amounts of volatile organic compounds (VOCs) were released into the paint booth during flushing and colour changes with mixed two-component (2C) paint systems. In conventional processes, residual paint is flushed forward into a funnel or directly into the washout, leading to VOC pollution in over 70 percent of the booth air. The EcoBell PurgeBox collecting system with special filter mats already reduces VOC emissions by up to 60 percent.
Dürr’s new development further reduces VOC load by enabling a return system for 2C clear coats, similar to the classic 1C process. Previously, this was unthinkable for mixed clear coat systems consisting of hardener and stock paint. Using a patented process sequence with precisely coordinated parameters, mixed 2C materials can be flushed back via a return system integrated in the atomiser without curing. This technology includes up to two main needles in the atomiser and the established diaphragm valve technology, which ensures high mixing quality with minimal mixing volume. Low VOC emissions of only 5 percent occur solely during the bell disk cleaning in the EcoBell Cleaner D2, with no VOC release during flushing or colour changes.
Effect Finishes Within Normal Cycle Times
The return system for mixed 2C materials is not only environmentally friendly, but also saves time. During cleaning of the bell disk and atomiser surface in the EcoBell Cleaner D2, flushing and priming can occur parallel. These steps, previously performed sequentially, are now completed in parallel within just 15 seconds, reducing colour change time by half, increasing system capacity, and allowing more time for painting. Tinted clear coats can now be applied without any cycle time losses, enabling car manufacturers to make much broader use of effect finishes, which were previously limited to exclusive segments.
In combination with the EcoBell4 Pro this setup offers maximum flexibility. Two returns for 2C material (2x2C) are therefore integrated in each robot arm. This means that while one body is being painted, the stock paint and hardener for the next body can be prepared in parallel on a second channel. Even if manufacturers use multiple paints and hardeners that are chemically incompatible, these can be applied through separate channels. Dürr verifies the compatibility of customer clear coat systems in its test centre. So far, all 2C clear coats have been compatible with this new technology and can be returned and collected via the atomisers.
Return System Reduces Costs for Fixtures and Fittings
The EcoBell4 Pro rotary atomiser is available with the return system in the 2x2C and 1x2C variants, while the EcoBell3 can be retrofitted with 1x2C. Another system using this new technology is currently being commissioned. Beyond eliminating VOC emissions during flushing and colour changes and significantly reducing flushing agent consumption, this solution also offers low investment costs by eliminating the need for funnels, EcoBell PurgeBox units, and other fixtures and fittings in the paint booth.
For over a year, the return system for mixed 2C material has demonstrated its effectiveness at a leading electric car manufacturer, operating in two top coat lines with 42 high-rotation atomisers.