Published on : Friday, November 1, 2019
Economic coating of cabinet doors frequently requires extremely flexible systems. A modular plant concept is an efficient option for implementing customized solutions.
Nowadays, a modern spray coating system should be configured based on a combination of required process steps, a flexible design of the higher-ranking plant control systems and consideration for economic factors. For this purpose, Venjakob has developed a modular base concept, which permits combination of the respective machines to create a complete optimized plant for any application. In the application configuration shown here, the equipment of the respective machines has been optimized to achieve the best possible coating quality for furniture components while maintaining a high degree of versatility.
For instance, the plant can process both traditional high-quality PU wood varnish on a solvent basis and water-based lacquer types. Moreover, the plant control systems’ higher-ranking communication level ensures flexible and reliable coordination of individual components.
The workpiece processing sequence begins with a workpiece cleaning step, in which ionized air and consumption-optimized, rotating air nozzles are used to remove contaminants with zero contact. An efficient extraction system then removes suspended particles. After the cleaning step, the static charge of the workpiece surfaces is neutralized. An ionization system ensures that the workpieces leaving the pre-cleaning process are truly clean and neutralized.
Highly flexible and quality-oriented
An enclosed conveyor belt system transports the workpieces to a robot station, where an ABB robot arm performs thorough, systematic pre-coating of the outer edges. This first coating layer flashes during subsequent transport to the flat-bed coater (reciprocator).
In a second step, the cabinet surfaces are coated by four spray guns moving at right angles to the running direction.
The edges are also coated once again. Together with the higher-ranking plant control, a color management system permits the quickest possible fully automatic paint change. All necessary cleaning steps are also automated. Moreover, any paint can be prepared during ongoing production and activated within barely any time at all. Nine varnish pumps, two curing agent pumps and three cleaning agent pumps permit processing of various varnish types – up to and including 3-component systems. To optimize job efficiency, a workpiece scanner on the feed side scans the workpieces. The machine control system then calculates the most efficient switching points for each installed spray coating gun. Moreover, the spray coating machine is equipped with an extraction system that is specially adapted to the application and that, in conjunction with a sophisticated fresh air supply system, permits optimum extraction of any generated overspray. Any coating material falling onto the conveyor belt in the workpiece edge offset area is removed by the belt cleaning system. Any coating material volumes collected in this manner can be filtered and reused, provided the coating material and application allow for it.
The cleaning system was designed for different water- and solvent-based paint systems. If further reduction of non-productive times is required, an optional second cleaning unit may be the ideal solution, as it permits external cleaning of the belt cleaning components during ongoing production.
The drying system consists of modules, which allow free, application-based configuration of process engineering variables such as air speed, temperature and, optionally, humidity. An evaporation channel with laminar air flow is used for pre-drying. In this section, freshly coated surfaces are left to evaporate in filtered air for approximately five minutes to achieve the initial stabilization of the sensitive surface. Afterwards, they are transported in batches to the multi-level dryer Ven Dry Vario Time. It has 62 levels with a length of 5,500 mm each to store workpieces for curing and drying them continuously based on the FI-FO principle. The drying temperatures can be individually adapted to the coating material system in use. Afterwards, the cured workpieces exit the dryer and can either be returned directly for a second coating process or removed from the plant for sanding or packaging. The modular design of the plant permits relatively easy retrofitting of a UV channel.
Multi-flexible and high availability
The individual machines and components of the plant described here are equipped with modern actuators and sensor systems for their wide variety of functions. An integrated communication system using Ethernet makes all relevant system parameters available at all times, allowing pre-selection and setting of these parameters on the central plant operating panel. This makes it possible to create a separate recipe for each product.
In order to amortize the capital investment, a finishing line should have the highest possible availability. Therefore, Venjakob has taken this idea asfoundation for the design of the technical equipment. Furthermore, Venjakob has taken into account the during the process of spray coating given division of the total production time in production time and cleaning time, because this ratio has a high impact on the efficiency and productivity of the plant.
That is why the plant manufacturer,located in Rheda-Wiedenbrück/Germany, makes a point of ensuring that all work on the machine line can be performed with the lowest possible effort. In addition, the modular platform gives customers the option to turn their machine into a system that permits a practically continuous production process without interruptions.
Evaluation of machine and process data
The increasing importance of traceability of individual production steps and constant readiness for production has made modern plants increasingly dependent on evaluable information within the systems. As Venjakob equips its coating lines with state-of-the-art information technology and intelligent actuators, this evaluation is already a reality in some components.
Status data is recorded centrally and specially adapted evaluation software provides each machine operator with all necessary data.
Characteristic data is monitored to inform the service department of necessary wear-related work.
The production management receives reliable data about productivity, allowing it to meet all specified targets. Material flows and requirements planning become easier within the information network, as all requirements are detected early. Flexible planning of the entire supply and discharge logistics chain is also possible, as users are always aware of the current productivity level. Through collection and reproducibility of process data, it becomes possible to evaluate production quality without any gaps, helping to create the foundation for a confident, trusting collaboration between customers and suppliers. In particular, the modular machine design provides customers with a requirement-based initial investment, which can be expanded with additional function modules at a later point, thereby allowing adaptation to future challenges.