PAINT PREPARATION WITHOUT SHADOWS
Schlotterer is a leading manufacturer of exterior sun protection for buildings. The main products, external venetian blinds, roller shutters and insect screens, are made of aluminium. One of the quality-determining factors is the powder coating of the parts. Due to the process, the transport hangers also receive a layer of paint. Since mid-2016, this has been removed by a customised BUPI CLEANER® paint stripping system. With high efficiency and ergonomics, it ensures high process stability of the coating procedures and makes it easier for the Salzburg-based company to achieve its ambitious quality goals.
External sun shading makes a significant contribution to the energy efficiency of buildings, because dynamic sun shading systems reduce energy consumption for lighting, heating and, above all, cooling. All year round, they direct valuable daylight into the interior without glare, in the cold season they use the power of the sun for heating and in summer they act as passive cooling because they do not allow the heat to reach the window pane in the first place. In addition, external venetian blinds and roller shutters protect against unwelcome glances and reduce the risk of burglary.
The RETROLux daylight venetian blind from Schlotterer Sonnenschutz Systeme GmbH, the Austrian market leader for non-textile external sun protection, is a showpiece for modern, dynamic sun protection. Thanks to a special slat geometry, RETROLux keeps out direct sunlight and at the same time directs daylight deep into the room via the ceiling without glare. This helps to save energy for cooling and artificial lighting and protects floors and furniture from the sun’s rays. Thanks to a continuous change in the slat inclination over the hanging height, the modern external venetian blind also ensures an excellent view to the outside at all times. Like all its products, the Salzburg-based company developed RETROLux in-house and produces it at its main site in Adnet near Hallein.
Quality through powder coating
Schlotterer external venetian blinds and roller shutters mounted on the outside of the building are constantly exposed to wind and weather. To ensure consistently good function and appearance over a long product life, their parts, which are made exclusively of aluminium, are powder-coated. This quality-determining, central work step takes place in three painting cabins. Overhead conveyor belts transport the parts through two of them, while the third is used for manual coating of special parts. In powder coating, the paint layer is created by electrostatic adhesion of the paint particles to the metal.
For this to work, the powder coating cloud and the parts to be coated must have different polarity. Hangers and holding clamps of the overhead conveyor are therefore also made of metal. “It is unavoidable that when the parts are powder-coated, the hangers and holding clamps also receive a layer of lacquer,” says Dominik Lindenthaler, who is responsible for the operation of the powder coating systems at Schlotterer as a process and work technician. “An accumulating lacquer layer represents insulation and would considerably impair the coating result. It must therefore be removed.”
The challenge of paint stripping
“Originally, the hangers were stripped of paint weekly by an external service provider,” reports foreman Gerald Dygruber. “The result was good, but the time in between was too long. The growing layer of paint led to a loss of quality.” That’s why Schlotterer invested in an in-house eddy current paint stripping system a few years ago. In this, the paint was softened by induction heat to such an extent that it could be removed with a wire brush. “However, only two hangers could be stripped in one cycle, so that one person was occupied with this thankless work for 19 hours every day,” Gerald Dygruber explains its disadvantages. “Nevertheless, we could not remove the paint from the hanger after each coating process and there were no capacity reserves for future production increases.
Change of method in demand
Once a year, during the Christmas shutdown, the parts went for a deep pyrolytic cleaning and were then sandblasted. Because this produced a flawless result, there were considerations about a corresponding equipment in the house. However, this failed due to the size of the system and the installation costs. In addition, the unavoidable removal of material spoke against it.
That’s why Dominik Lindenthaler started looking for suppliers of chemical paint stripping systems at the end of 2015. The specialists of a manufacturer-independent supplier of parts cleaning systems recommended BUPI Golser Maschinenbau GmbH for the special task. “The company has an excellent reputation as a manufacturer of reliable, user-optimised, energy-efficient and sustainable cleaning systems with a large working area,” he says. “The proximity of the site in neighbouring Hallein also spoke in favour of turning to the experienced company with the special requirement.”
XXL cleaning system
BUPI Golser implemented a customised paint stripping system based on the proven BUPI CLEANER® POWERTEC PRO system series. During the cleaning process in these two-bath spray cleaning systems, the parts inserted into the cleaning system via a roller carriage rotate in the system while they are exposed to a hot cleaning medium from three sides under high pressure and high volume flow and are then rinsed.
The system family is characterised by its particularly space-saving and compact design. Its installation area is hardly larger than the footprint of the cleaning room. In the case of the system for Schlotterer, this corresponds to a standard size 5 system at 1,400 x 1,400 mm, but at 2,400 mm it is significantly higher than standard to accommodate parts up to 2,200 mm long on a carrier frame.
Long bath life due to paint separation
However, the challenge for BUPI Golser was not primarily the extraordinary dimensions of the plant. “If the cleaned paint were to contaminate the cleaning and rinsing fluids, these would have to be disposed of at short intervals at great expense,” explains Markus Wischenbart, technical manager at BUPI Golser. “We therefore continuously separate the old lacquer in a bypass process via a specially developed consumable-free filter.”
The experts first tested this process on the existing small paint stripping plants before optimising it for the large-scale plant. From the filter, the viscous mixture is filled directly into a plastic drum for easy disposal. Thanks to the bypass filtration in combination with an automatic re-dosing of paint stripping lye and rinsing water, the interval for the bath change with the associated plant downtime extends to several months.
Safety has priority
To prevent injuries from escaping chemicals during removal and replacement with an empty container, the paint separator is located inside a protective enclosure. Worker protection is also served by equipping the particularly energy-efficient Grundfos pumps with paired mechanical seals made of the special material Kalrez. A chamber permanently filled with sealing water between these prevents the escape of paint stripping liquor in the event of a leak. Since the system control also ensures automatic removal of the cleaning medium via a pipeline from the storage tank in the tank room approx. 50 m away, there is no need for employees to come into contact with the chemical.
Not only for the safety of the workers, but also to avoid plant downtimes, the plant is equipped with heating elements in the cleaning agent and rinsing tanks, which can be replaced from the outside without emptying the tanks.
The system also made paint stripping more worker-friendly. Whereas two people used to be fully occupied with a physically demanding job in two shifts, loading and unloading is now a secondary activity. Thanks to the simple operation of the system, which is equipped with a SIEMENS control system, this can be carried out by practically any employee without exertion or contact with dirt. A stainless steel steam condenser with cross-air cooling developed at BUPI Golser prevents the escape of steam vapours that may still contain media and thus ensures an undisturbed good air quality in the hall.
Capacity secures growth
During the paint stripping cycle, which lasts about one and a half hours, the customised BUPI CLEANER® system removes the paint from about 200 hangers. This allows complete cleaning of the paint from all hangers after each individual coating process, thus ensuring the highest quality of each subsequent powder coating. Equipped with two carrier racks and two manipulation trolleys, one of them can be unloaded and reloaded during a paint stripping pass, which ensures a consistently high plant utilisation. Since the commissioning of the plant in mid-2016, this has provided ample capacity reserves for future growth as well.
“The investment in a customised BUPI CLEANER® paint stripping system comes back several times over,” Schlotterer plant manager Robert Wagner is convinced. “The improvement achieved in process stability during powder coating makes it easier for us to meet Schlotterer’s ambitious quality targets and at the same time we have been able to significantly improve the safety of our workers.”
Operations Manager Schlotterer GmbH:
“By switching the paint stripping to a BUPI CLEANER® system, we were able to improve the process stability of the powder coating and at the same time the safety of our workers.”
Technical Manager BUPI Golser Maschinenbau GmbH:
“The old paint is continuously separated in a bypass process via a consumable-free filter and discharged separately. This guarantees simple and safe disposal of the paint and a long bath service life.”
Schlotterer is the Austrian market leader for non-textile exterior sun protection. At the site in Adnet (Salzburg), 370 employees produce more than 300,000 sun protection and insect screen elements annually in several thousand variants and more than 200 different colours. The product range includes roller shutters, external venetian blinds and insect screens. All products are developed and manufactured by Schlotterer itself. Schlotterer is part of the IFN Holding.