Flexible wet and powder coating of large-format components

A large-format coating line combines powder and liquid coating with the pretreatment of various metals. The flexible system design makes it possible to coat a wide range of components and production volumes.

The Mühlbauer Group manufactures and supplies precision solutions for identity, microchip, and energy systems worldwide. In addition to technologically advanced industries, government agencies and authorities also utilize the technology developed by the company, which was founded in Roding, Bavaria. A key factor in the Group’s success is the high degree of vertical integration it has achieved at its locations. For some time now, a Jumbo-Coat coating system from Meeh has been complementing the technology center in Nitra, Slovakia, and—thanks to its size and flexibility—is strengthening the company’s strategic direction.

“Our goal is a complete manufacturing cycle, from sheet metal processing to assembly,” explains Ladislav Paskrta, managing director of Mühlbauer’s Slovakian branch in Nitra. In doing so, he underscores the globally active group’s commitment to offering all services from a single source. The group’s portfolio includes comprehensive solutions for industries, security agencies, and government authorities, ranging from chip automation and identity systems to energy technologies. The technology center in Nitra began operations in 2009 and today brings together two key business units: Muehlbauer Technologies s.r.o. and Muehlbauer Automation s.r.o.

At the end of 2021, the decision was made to invest in a coating plant to complement the surface treatment center in Roding. The specifications and supplier selection were carried out in close coordination with the surface treatment specialists there. In December 2022, the contract was ultimately awarded to Meeh, with whom the Bavarian main plant already collaborates successfully. Meeh’s modular Jumbo-Coat technology enables the flexible system configuration that Mühlbauer requires. It combines powder and liquid coating processes, offers pretreatment for various metals, and integrates manual and automated steps. As a result, it accommodates the impressive range of products and production volumes that have passed through the system since it went into operation in July 2024. The system was assembled using a lead-assembly approach, allowing on-site technicians to familiarize themselves with the system technology at an early stage.

The plant’s capacity and efficiency alone are remarkable. Surface treatment, sheet metal fabrication, and welding operations are integrated across 10,500 m². The coating facility occupies about 40% of the space and processes workpieces up to 12 x 2.5 x 3 m in size and weighing up to four metric tons. It includes nine process booths, a spacious parking lot, and two loading docks arranged in two rows along the material flow. In a single line, the blasting booth, parking area, continuous-flow powder dryer, and automatic powder coating booth follow one after another. Arranged in parallel are the wet painting and drying booths, two semi-automated washing booths, two chamber powder dryers, and a powder booth for large parts equipped with aerial work platforms.

The parking area is accessible from both sides and connected to all areas via two manual conveyor tracks. A total of five electric traverse platforms are available for workpiece transport. Three of these ensure circulation between the booths, while two narrow platforms with integrated lifting and lowering stations are primarily used for loading and unloading. Only the sandblasting booth is supplied via forklifts. Three supply air units, each with a capacity of 8,000 m³/h, supply fresh air to the facility. “This is absolutely necessary, because a single wash booth alone extracts approximately 12,000 m³ of air per hour from the facility,” explains Ulrich Meeh. The supplied air creates a slight overpressure, which prevents dust from settling on the components. To save space in the hall, Meeh has housed the washing equipment and paint supplies in the basement.

In addition to the size and practical workflow, Paskrta particularly appreciates the Gema automatic powder coating booth. “That’s probably the biggest advantage of our system.” It enables Nitra to process even large production runs efficiently and with minimal manual effort. The integrated push-pull system guides the crossbeams collision-free through the chamber using staggered friction drives, photoelectric sensors, and distance lasers. To do this, an employee positions a loaded cross-travel platform at the entrance and starts the process. An automatic pusher then pushes the frontmost crossbeam into the powder chamber, where friction drives take over for further transport. Inside the chamber, horizontally arranged automatic spray guns apply the powder evenly. Photoelectric sensors continuously measure the height and width of the workpieces and adjust the depth position and number of active spray guns accordingly. The maximum object width in the production line is limited to 0.5 m. After coating, the automatic puller pulls the crossbar onto a waiting transverse conveyor. The system continues to cycle automatically until it is fully loaded. Finally, an operator transfers the product carriers to the adjacent continuous-flow powder dryer.

Since Mühlbauer places great emphasis on efficiency and sustainability, Meeh has systematically equipped the plant with recovery systems. A device in the blasting cabinet separates the blasting media into magnetic and mineral particles and feeds the cleaned particles back into the process. The aqueous pretreatment system also operates in a closed loop. Separate washing cabinets for aluminum and steel facilitate the separation of process chemicals. All components undergo four wash cycles, during which they are degreased and, depending on the metal, phosphated or pickled, rinsed twice, and post-treated with deionized water. Aluminum parts undergo an additional passivation step.

Meeh produces the required deionized water using a fresh water treatment system with reverse osmosis and cascades the baths to extend their service life. A vacuum evaporator treats the resulting wastewater and returns the recovered distillate to the system. This keeps fresh water consumption and disposal costs to a minimum. The automatic powder coating booth also operates in a closed-loop system and recycles excess powder. Only the powder coating booth for large parts operates in a non-recovery mode, as recovery is virtually impossible due to frequent color changes. Here, employees apply the powder coating using a mobile Gema manual coating device that operates from standard powder coating cartons.

Both the continuous-flow and the two chamber powder dryers operate efficiently. An intelligent control system automatically shuts off the gas burner as soon as there are no crossbeams in the oven. To save additional energy during heating, Nitra assigns fixed temperatures to the redundant chamber ovens, thereby avoiding repeated heating and cooling cycles. The combined wet painting and drying booth also uses energy efficiently. Heat recovery and an energy-saving mode during work breaks reduce annual average consumption by about 50%. The system has now been in operation for two years, and in addition to its own products, Nitra also provides contract coating services. For Paskrta, the decision to invest in the Jumbo-Coat system has proven to be the right one: “We are now able to accommodate nearly all requested sizes and quantities.” (OM-9/26)