Flexible door lacquering for individual production requirements
The focus at RWD Schlatter, the Swiss market leader for functional doors in the contract sector, is not on mass production standards, but on variety. The aim is to produce this variety in the shortest possible time and in the most diverse quantities - from batch size 1 - in a customer-oriented manner. Cost awareness, quality aspects and greater flexibility in the production process were decisive reasons for carrying out the surface treatment in-house using a modern door painting line. To this end, the production hall at the headquarters in Rockwill was extended and a Venjakob door painting line, individually tailored to customer requirements, was installed and put into operation during ongoing production.
In Switzerland, the requirements for manufacturers of functional doors are particularly challenging. Due to the small-scale nature of urban development and the diversity of buildings, there is less demand for standards in the contract sector, but a wide range of doors. RWD Schlatter develops and produces door blanks for fire, smoke and noise protection for general contractors, architects, module builders and the specialist trade. With in-house product development and its own test laboratories accredited to European standards, as well as a high degree of automation in the production process, RWD Schlatter aims to serve its customers individually and efficiently. According to the company, around 80,000 door blanks are produced each year.
External surface treatment cost-intensive
Before deciding to paint the doors in-house, the door manufacturer relied on external partners. "Too cost-intensive," said Anton Zöchbauer, Head of Process and Traversing Technology at RWD Schlatter. In addition, the quality was not as good as it is now. "The unfinished door leaves had to be delivered to the external paint store by a freight forwarder and then transported back again for finishing. This often resulted in damage during transportation. This has an impact on quality. Just like the fact that hand spray painting does not meet the market standard of an industrial surface," explains Zöchbauer. Anton Zöchbauer was able to see the improved surface quality for himself at the Venjakob technical center in Rheda-Wiedenbrück before the contract was awarded. There, a batch of door blanks was painted on the Ven Spray Perfect spray painting machine and compared with the batch from the previous suppliers. The door manufacturer was particularly impressed by the exact reproducibility of the surface quality, which is only possible with an automatic spray coating machine.
Commission production requires high flexibility
Door production for the contract business at RWD Schlatter is based on the fir tree principle. Depending on the order, the stacks of door blanks to be processed are completely different in terms of length, width, thickness, material, coating requirements and further construction. The machine manufacturer Venjakob had to take this into account during the planning stage. The customer wanted the complete package: a highly dynamic, flexible surface processing center with a high degree of automation and possible interface integration of the grinding machine from a third-party manufacturer. Venjakob took on the role of general contractor and developed an economical overall concept, from the conveyor systems and control system to the centerpiece, the spray coating lines with a sophisticated color management system that has extremely short color change times.
Surface coating in batch operation
Since May 2020, the automatic door coating line from Venjakob has been coating around 95 percent of doors and 5 percent of door panels, lining strips and door latches, partly in 3-shift operation. A self-sufficient wide belt sanding machine from Weber was fully integrated into the system, as requested by RWD Schlatter. A Venjakob door edge sanding machine, which flexibly sands both the longitudinal and top edges in continuous operation without cycling, rounds off the sanding process without compromise. The complete surface coating system operates in batch mode. This means that doors and door elements are coated and dried uniformly within a batch. Two-component water-based UV coating systems are predominantly used. Any number of parts of different lengths can be used in a batch, as long as they have the same thickness, remain within a certain document size (5,500 mm x 1,600 mm) and the maximum weight per batch remains below 300 kg. As a rule, two doors with a maximum door length of 2,600 mm are run one behind the other in a batch. Longer doors run individually per batch. For door stacks that are very different in their sequence, it is also possible to run with batch size 1 if there is no other option.
Variable drying system for different paints
The drying system of the coating lines with four different drying units is also designed for variability. This means that different types of paint can be used with different drying times and drying methods. A distinction was made between three scenarios: 1. always the same paint type; 2. paint systems that dry quickly and stains; 3. paint systems that require a long drying time, such as special colors or special paint types. These can, for example, be painted last in the late afternoon, dried overnight in a 10-day dryer and then stacked manually in the morning.
Fast color changes and paint recovery
If you want to react flexibly to your customers' design requirements, you need a spray painting machine that is designed for all colors, can carry out quick color changes and delivers reproducible surface quality. The installed fully automatically controllable spray painting machine is equipped with a reinforced high-performance linear drive and can be operated with up to 12 spray guns. The gun speed is infinitely variable and sprays at the same speed across the entire working width. All spray guns are connected to a circular flushing system for fast spray material changes. To ensure that as much paint as possible can be used, the belt cleaning system was equipped with a V-rake device to return the paint from the belt to the container. A special color management system for 2K and 3K paints was also installed. This enables fully automatic color changes within a very short time. One of the reasons for this is that the relevant components are "piggybacked" to the rear of the spraying machine above the axis with very short paint lines. Should a system malfunction occur, it can be diagnosed via a remote maintenance system. This enables rapid assistance. To support quality control, several digital cameras were also installed to monitor the entire system. All components required for maintenance are easily accessible or simple to remove.
First collaboration with Venjakob
This was RWD Schlatter's first collaboration with Venjakob. Project manager Anton Zöchbauer became aware of the machine manufacturer due to its good references in the door and furniture industry. Venjakob now has another good reference in RWD Schlatter. "Our requirements were met in full according to the specified parameters. The support and service after final acceptance was also very flexible and excellent in every respect," says Zöchbauer, confirming the good performance of the Venjakob team.
The following components are included in the overall "door painting line" concept:
- Conveyor systems, designed for batch operation
- Door edge sanding machine
- Automatic wide belt sander
- Dust extraction system for use after sanding
- Spraying machine with special color management system, designed for 2K or 3K technology
- Dryer: flash-off dryer, 10-storey dryer with longitudinal flow process
- Nozzle drying channel
- UV drying channel
- Control cabinet
- Remote diagnosis system
- Supply air system incl. humidification
