White goods become colourful

BSH Electrodomésticos España recently replaced a 30 year old powder coating plant. The dense phase technology has resulted in an increase in quality while at the same time increasing flexibility and cost-effectiveness.

The fast color changing is one of the various advantages of the new system. Image: Nordson

The Spanish company coats Bosch, Siemens, Neff and Balay equipment with powder coating. Here, the trend towards color diversity was recognized early on and a state-of-the-art, future-oriented system with dense phase technology was realized in a system partnership with Nordson. The new system was to implement the following six cornerstones:

1. increasing the coating capacity to cover the peaks of production
2. optimization of the coating quality to avoid costly reworking
3. high flexibility for fast product and color changes
4. high degree of automation with intensive process control
5. significant energy savings
6. compliance with the highest ecological standards

Jose Castillo, responsible at BSH for the new powder plant, visited several Nordson coating plants in the region based on recommendations. On this basis the final decision was made in favor of Nordson. “I was particularly impressed by the ability to carry out a complete color change in just ten minutes – without any coat drag-out!”
In the new system the powder is applied by four “Encore HD” automatic powder guns arranged horizontally on each side. The powder guns were specially developed for dense phase technology, where more powder is pumped to the powder gun at low speed using less air. The resulting soft cloud leads to a very good initial application efficiency and maximum process control. “At the maximum belt speed of 2.80 m/min, we achieve a coated area of 530 m2 per hour – on both sides,” says Jose Miguel Lopez Alzorriz, Production Engineering Metal Processing at BSH Electrodomésticos España. In combination with the “ColorMax3” coating booth and the “Spectrum HD” powder center, the powder guns form an efficient color change system. The powder center with fresh powder supply provides the required color at the right time. The “Encore HD” spray system conveys the powder from a cardboard box to the guns using “HDLV” pumps. Twin cyclones with an hourly air throughput of 16,000 m3suck the overspray out of the booth. The excess powder is fed to the powder center for reuse. Both the fresh powder and the recycled powder are processed using a 200 µm ultrasonic sieve.
With the aim of being able to coat three main colors in parallel at the end, two more “ColorMax3” booths were set up in 2018. To feed all three booths evenly, the capacity of the chain conveyor must also be increased. This is achieved by installing a splitter, which also facilitates and accelerates the introduction of different colors. The system is now also able to coat roof and front panels as well as other products.
The “GoingGreen” package has been integrated for further energy savings. An intelligent control system adapts the consumption of the devices to the energy demand currently required. “For example, we constantly monitor the energy and compressed air requirements in order to make further optimizations,” reveals Alzorriz.
The new system has more than doubled capacities, even though the variety of products and colors has increased significantly. Also very pleasing: At the same time, energy and powder consumption have decreased. Castillo sees the reason above all in the controllability of the process: “Of course it is a complex plant. You have to understand the functionalities and their interrelationships. But then the system provides a variety of options for fine-tuning individual parameters, and with a little experience you can quickly approach the optimum result.

Further information: www.nordson.com/powder

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