Planning and building a coating system for products that are not clearly defined
GBneuhaus coats work pieces for customers in the automotive, building technology and medical technology as well as the chemical and glass-processing industry. For the spray application, the coating contractor has started the operation of a paint cabin that was developed in collaboration with Krautzberger.
«During the planning of our new coating system, we were not sure yet, which products we would want to coat in it» explains Torsten Müller-Uri, Director of Engineering and Production at GBneuhaus GmbH. The company is specialized in the development and application of nano paints, and operates in this sector as a coating services contractor. In 2014, the company decided to install a new coating system. Nano paints can produce layers with a thickness between 500 nm and 1,5 µm. Another special characteristic: The paints can be customized based on client requirements with different functions such as conductivity, moisture repellence or with hydrophilic properties.
Until now, GBneuhaus has coated the workpieces with a dip-coating procedure. However, because there are substrates that do not support dipping, the decision was made to select a system for the spray application of nano paints. The objective was to coat substrates consisting of different work materials (plastic, metal, wood, glass or composite materials), in various geometries based on customer specifications, in a highly precise and reproducible manner. «When we planned the system, we did not know either what functionalities our client would want to utilize to enhance their surfaces», states Torsten Müller-Uri. «It was important to us in any case that we can paint coating samples for them as well as micro series.» Furthermore, explosion protection also had to be taken into consideration because nano paints contain the solvents ethanol and butanol. The processing of both materials requires special safety measures with respect to occupational health and safety as well as explosion protection.
The concept for the unique paint booth was developed by GBneuhaus in collaboration with Krautzberger GmbH and KS Lüftungstechnik GmbH – «in a creative brainstorming and several very constructive workshops», reports Thomas Schneider, authorized officer and Sales Director at Krautzberger. He adds: «We have checked the process several times in our technical lab and refined it until the operation was reliable and stable.» – «Important components of these tests where the conditioning of the air as well as occupational health and safety and explosion protection», explains Ulrich Dalheimer, Director of Project Planning at KS Lüftungstechnik.
As a way to comprehensively investigate the potential areas of application of the system on behalf of the coating services contractor, Krautzberger also coated specific products during the test phase. «This was our contribution to enable GBneuhaus very shortly after the start of the system to receive a first order for spray painting», proudly says Thomas Schneider.
The new coating system is a fully climate controlled booth that can maintain exactly defined limits for temperature (± 2 °C) and humidity (± 5%). A 6-axis robot with a 4-armed carousel is positioned in the centre of the spray booth. Each carousel features a rotatable workpiece receptor with controlled axis. In combination with the respective nozzle and nozzle extension, workpieces with a maximum diameter of up to 1.50 m can be coated on the inside and outside. The special characteristic of the application also includes the fine spray jet, which achieves a very thin and homogenous layer. Nevertheless, the overspray volume remains low.
The fitting off the turntable takes place via a window to the anteroom. Depending on the size of the workpiece, the worker enters this anteroom via a door or rapid rolling gate. Anteroom and spray booth form one climate-controlled unit, which has a consistent slight overpressure. The incoming air is injected via the ceiling in the anteroom and extracted in the cabin via the wall opposing the anteroom. The filters for the paint extraction are also installed on this wall. The exhaust air is cleaned through two filter stages in the cabin and 2 additional filter stages in the air-conditioning unit in order to remove the solid particles. It flows from the exhaust line through a heat and cooling recovery system before it reaches the outside. To keep the supply air and exhaust flow constant, the ventilation system is equipped with an active pressure control unit. In addition, the ventilation technology reacts to filter contamination and controls the air volume independently to match the set target air volume.
Following the coating process and upon observance of a specified paint curing time, the Workpieces are removed from the turntables through the anteroom using special tools and depending on the substrate, the paint is set in the furnace at 500 °C or with infrared radiation (130 °C).
Upon inspection and approval through the responsible authorities, GBneuhaus has started the operation of the system in January 2017. What are the results of the measuring carried out by the authorities and how does GBneuhaus utilize the coating system? «The measures indicated that the system operates within the legally stipulated specifications of the workplace limits as well as the explosion indicators. We are very satisfied with the design and the coating results, because we are able to coat the inside of a 600 mm long pipe with a diameter of 30 mm with high quality nano paint as one example», states Torsten Müller-Uri.
Sourcetext: «besser lackieren» June 2017
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