Planning and building a coating system for products that have not yet been clearly defined
GBneuhaus coats workpieces for customers in the automotive, building services and medical technology sectors, as well as the chemical and glass processing industries. For spray application, the contract coating specialist has now commissioned a paint booth developed together with Krautzberger.
“When we planned our new coating system, we did not yet know exactly which products we would coat in it,” says Torsten Müller-Uri, Head of Technology and Production at GBneuhaus GmbH. The company specialises in developing and applying nanocoatings, works as a contract coater in this field and decided in 2014 to install a new coating system. Nanocoatings allow layer thicknesses between 500 nm and 1.5 µm. Another special feature is that the coatings can be tailored to customer requirements with different functions, such as electrical conductivity, hydrophobic or hydrophilic properties and antibacterial effects.
Previously, GBneuhaus coated workpieces using the DipCoating process. However, because some substrates cannot be immersed, the company chose a system for spray application of nanocoatings. The aim was to coat substrates made of different materials (plastics, metals, wood, glass or mixed materials), in a wide variety of geometries, to customer requirements with high precision and reproducibility. “When we planned the system, we also did not know which functions our customers would want to add to their surfaces,” continues Torsten Müller-Uri. “In any case, it was important to us that we could paint coating samples for them and produce small batches.” Explosion protection also had to be considered, because the nanocoatings contain ethanol and butanol as solvents. Processing both substances requires special measures for occupational safety and explosion protection.
GBneuhaus developed the concept for the unique paint booth together with Krautzberger GmbH and KS Lüftungstechnik GmbH, “through creative brainstorming and several very constructive workshops,” reports Thomas Schneider, authorised signatory and Sales Director at Krautzberger. He adds: “We checked the process repeatedly in our technical centre and refined it until it ran reliably and consistently.” “Important elements of these tests were air conditioning, occupational safety and explosion protection,” adds Ulrich Dalheimer, Head of Project Engineering at KS Lüftungstechnik.
To thoroughly explore the possible uses of the system for the contract coater, Krautzberger also coated specific products during this test phase. “This enabled us to help GBneuhaus obtain its first spray coating order shortly after commissioning the system,” says Thomas Schneider.
The new coating system is a fully climate-controlled booth that maintains precisely defined tolerances for temperature (± 2 °C) and air humidity (± 5%). At its centre is a six-axis robot combined with a four-arm carousel. Each carousel arm has a rotating workpiece holder with a controlled axis. With the appropriate nozzle and nozzle extension, workpieces up to a maximum diameter of 1.50 m can be coated internally and externally. One special application feature is the fine spray jet, which enables a very thin, uniform layer. At the same time, overspray remains low.
The turntables are loaded through a window into the anteroom. Depending on the workpiece size, the employee enters this room through a door or a high-speed door. For climate control, the anteroom and paint booth form a single unit maintained at a slight positive pressure. Supply air enters through the ceiling in the anteroom and is extracted in the booth through the wall opposite the anteroom. The paint separation filters are also installed on this wall. To remove solids, the exhaust air passes through two filter stages in the booth and two further stages in the ventilation unit, followed by a heat and cooling recovery system before being discharged outdoors. To keep supply and exhaust air flows constant, the ventilation system uses differential pressure control. It also responds to filter contamination and automatically adjusts air volumes to the specified setpoints.
After coating and a defined coating setting time, the workpieces are removed from the turntables via the anteroom using special tools. Depending on the substrate, the coating is then crosslinked in an oven at 500 °C or with infrared radiation (130 °C).
Following inspection and approval by the responsible authorities, GBneuhaus commissioned the system in January 2017. What did the authorities’ measurements show, and how does GBneuhaus use the coating system? “The measurements showed that the system operates below the legally specified occupational exposure limits (AGW) and explosion parameters. We are very satisfied with the technology and coating results: for example, we can apply a high-quality nanocoating to the inside of a tube measuring 600 mm in length and 30 mm in diameter,” concludes Torsten Müller-Uri.
Source: PR Text-online, “besser lackieren”, June 2017
