Color variety on a broad front
For 60 years, Nolte Küchen from Löhne in East Westphalia has been producing high-quality fitted kitchens that focus on people. For this reason, the company was named Germany's most popular kitchen brand for the third time in a row. Consumers give the brand very good ratings for design and a good price-performance ratio. The award was presented by the German Institute for Service Quality.
Nolte Küchen invests continuously
The need for individuality is increasing. "Kitchen fronts shape the look of a kitchen. Style-conscious and design-oriented consumers want an ever-greater selection of colors and color combinations," says Raphael Gottschalk, project manager at Nolte Küchen. This variety has to be produced in the shortest possible time and in a wide variety of quantities - from batch size 1 - in a customer-oriented manner. In order to meet these criteria in the future, the kitchen manufacturer is continuously investing. In this case, in a spray coating line with drying technology, which was projected together with Venjakob, the mechanical engineering specialist for surface processing.
The project objectives included cost optimization, quality aspects, reduction of throughput times, and greater flexibility in the production process," explains Raphael Gottschalk. Before deciding to finish the surrounding materials (side panels, visible sides, plinths, etc.) internally, Nolte Küchen resorted to external partners. As general contractor, Venjakob took over the complete implementation of the finishing line for coating and drying matt surfaces. With the exception of the sanding machine, all system components and the conveyor technology were designed, produced and installed by Venjakob. The external sanding machine was integrated into the plant control system. The plant was to be designed in such a way that kitchen furniture components of smallest sizes up to max. 2,800 mm length and 1,300 mm width can be coated automatically in a continuous process.
Color management system shortens set-up times
Nolte Küchen defined specific requirements for the performance of the system. Only water-based coatings are used. The challenge was the variety of colors. The system had to be able to run economically in small batches and allow up to 20 color changes," says Reinhard Prus, head of the Surface Department in Löhne. Since each color change takes time, a color management system was used.
This keeps set-up times as short as possible. The coating process is carried out by four spray guns in high-performance linear mode. The gun speed is infinitely adjustable and fully automatically controlled. A scanner in front of the spray booth determines the workpiece shape, number and position. The guns are switched on and off precisely above the workpiece. Each individual workpiece is detected separately. Workpiece measurement takes place automatically and is largely parameterizable. All relevant adjustable parameters can be preset in any quantity at a central operating point in front of the spray booth via a touch-screen computer and called up as a spray program. The individual programs can be easily changed by the operator and can be stored in the system. "All relevant process parameters are stored in the recipes," explains Christian Schulze, sales engineer at Venjakob.
Drying process with rising temperatures
Another customer requirement: short through feed times so that the kitchen fronts are completely dry after the finishing process and the rear sides can be coated directly afterwards. The drying process was coordinated with the manufacturer of the 2-component water-based UV coating material used. In addition, several test series were run in Venjakobs’ own technical center. Drying is carried out with rising air temperatures: After coating, the workpieces first pass through a leveling zone for two minutes. Then follows a flash-off channel with an air temperature of 30-35 °C. The components are continuously conveyed on closed belt conveyors. Now they pass into jet drying channel with a temperature of 40-50 °C. Following drying, the coated surface is cured with UV light. The UV curing oven has its own electrical control cabinet, but is controlled via the control system of the overall production line. A built-in real power control compensates voltage fluctuations that occur in overloaded or unstable power grids, ensuring consistent high-quality results.
Best finishing results due to special air supply
The required process air is supplemented by two central supply air systems, which were project-planned by Venjakob and integrated into the overall concept. In the area of spray coating, the supply air system works with humidification. Before it leaves the unit, the supplied air is heated, cleaned and humidified to ensure optimum air quality for the best coating results.
A second supply air system without humidification supplies the areas of the sanding machine, the dust removal system and the drying section.
Sanding machine can be used separately
There was a special feature in the conveyor technology. The sanding machine integrated in the finishing line was supposed to be used separately. For this purpose, a movable belt conveyor on flanged rollers was installed between the sanding and the spray coating machine. When rolled aside, this allows the sanding machine and the spray coating machine to be used separately. For combined operation (sanding + coating), the belt is in line and allows line operation.
Successful start of production thanks to trained team
Production at the Löhne site started immediately after the in-house training in July 2021. The output of the finishing line has been continuously expanded in 2-shift operation to date. With Nolte Küchen, Venjakob has another good reference. "Our requirements were fully met according to the specified parameters. The support and service after the final acceptance were also very flexible and top in every respect!", Reinhard Prus and Raphael Gottschalk confirm the good performance of the Venjakob team.