Sustainable coating for higher production output
Environmentally friendly and resource-saving industrial finishing with a simultaneous increase in production requires the use of new and intelligent combinations of patented technologies and processes. As general contractor, Venjakob has created a door painting system for the door manufacturer Garant that utilises a new air circulation process with state-of-the-art spraying technologies.
In 2021, around 800,000 doors and 700,000 frames left the production halls at the Garant plant in Wachsenburg, Thuringia, to find their way to wholesalers and specialist retailers. This figure is set to rise in future. To this end, a new automated "injection moulding robot production line" with state-of-the-art technologies for energy-efficient production has been commissioned. The aim is to increase production to secure capacity until 2030 without compromising on quality. As a well-known manufacturer for surface finishing in the furniture industry, Venjakob had already successfully integrated a robot cell into an existing painting line for Garant in 2020, so the company was also approached for this complex project.
Air recirculation is nothing new
Operating a door painting system in recirculating air mode is nothing new for Venjakob. After all, a lot of heating energy can be saved by using recirculated air. However, this would be required to a large extent if the fresh air entering from outside is to be brought to the temperature required for the painting process. "In addition, when using water-based paints, as is the case at Garant, the recirculated air flow would have had to be cooled, as it would have continued to heat up, which is not favourable for the painting process. This cooling would have consumed additional energy," explains Christian Streit, Business Unit Manager for Wood and Building Material Systems at Venjakob. The solution now lies in the combination of air circulation technology and a special air treatment system for air humidification. "With the humidification system, we utilise evaporative cooling and cool the air flow while humidifying it at the same time, so to speak. By using this combined process of modern air recirculation technology and innovative air treatment technology from a specialised partner company, we achieve enormous energy savings," emphasises Christian Streit. The combined air recirculation system was also designed in such a way that the humidified air is supplied to the 10-storey dryer as well as the paint booth. "This allows us to dispense with a separate water circuit for humidification in order to achieve the desired surface quality," says Dirk Wöllner, Plant Manager at Garant.
Saving additional resources
However, the new system not only reduces heating energy andCO2 emissions. "The pollutant load in the wastewater is also close to zero. The water discharged from the air treatment system only contains clay particles, no more pollutants," explains Thomas Heinze, the Garant project engineer responsible. the water-based UV coating is applied using the automatic AirCoat guns from surface specialist Wagner. A total of six guns are used: four guns for the surfaces and vertical edges and two more guns for the top and bottom edges. The guns are light and compact and ensure fine atomisation and low overspray thanks to the special design of the air ducts. In combination with the high humidity, the application efficiency is increased and less coat is used. Filter consumption for cleaning is also reduced by 30 % to 50 %," emphasises Christian Streit.
Integrated paint recovery system
Another technology that leads to high sustainability is the integrated paint recovery system from Venjakob. It consists of a patented V-belt and enables the operator to recover 90% of the overspray from the belt. "It works pretty quickly," says Christian Streit. The system feeds the recovered coat back into a central paint bucket without any significant drying losses. The coat can be reused directly without any loss of quality. "This results in potential savings of around 30% compared to other recovery systems for the coat used," emphasises Streit.
Quick colour changes, easy cleaning
Four high-pressure double diaphragm pumps from Wagner are used to supply the paint. Each pump comes with a high-pressure filter and a wall bracket that allows the pump to be mounted horizontally. Compared to normal piston pumps, the special technology of the Cobra pumps in combination with the small displacement ensures extremely low pulsation and an even material flow. These properties contribute to perfect coating results. Further advantages are quick colour changes and easy cleaning.
Spray guns save barcode
Garant is very satisfied. "The surface quality is excellent. Even when the system was commissioned, we had better results than with the old system. And that without any process-related adjustments or fine-tuning," says Dirk Wöllner. another important requirement was the continuous recognisability of the barcode attached to the base of the door. This meant that it had to be protected from paint mist so that it could be read in the subsequent machining process. Previously, the barcode was masked off manually and the protective strip removed again later. With the new Venjakob system, there was a better solution: the spray guns could be adjusted so precisely that the barcode was left out during the coating process.
Conclusion
The entire planning and implementation of the new door painting system for Garant, in which doors are painted in a continuous process, is designed to protect the environment and conserve resources. The energy balance per unit produced can be reduced thanks to innovative processes and proven technologies. "In dry coating technology, the balance gets better and better as production capacity increases. However, the plant is not yet fully utilised due to the total production in the factory," says Wöllner. This means that there is still room for improvement, as requested by Garant ..
