State-of-the-art, tried-and tested coating technology coupled with a fully automatic chassis warehouse.
erfect surface coating for maximum protection against corrosion: The Krone Commercial Vehicle Group offers its customers state-of-the-art, tried-and-tested coating in combination with innovative automation technology at the new Coating Centre in Werlte. The goal: Highest quality in order for customers to have the best vehicles to meet the challenges of their business.
The new coating plant, which took 13 months to construct, is located in a facility measuring 120 by 130 metres and up to 20.5 meters high. An area of 16,500 square metres provides ample space for the Coating Centre to include an integrated, fully-automated chassis warehouse. The chassis are coated in the plant using a tried-and-tested coating concept: The cathodic dip painting (CDP) with final powder coating makes the vehicle highly wear-resistant. The plant is designed for a maximum weight capacity of four tons and accepts raw parts of all types.
»We are bringing the Werlte site up to the highest technical level of industrialisation currently possible.«
“The new coating plant brings the Werlte site up to the highest technical level of industrialisation currently possible,” explained Bernard Krone, Managing Partner of the Krone Commercial Vehicle Group.
At 40 million euros, this is the greatest single investment in the company’s history. This is a clear commitment to the site, to sustainable quality – and to protection of the environment: The Coating Centre meets the latest requirements, and CO2 emissions per coated chassis are reduced. The exhaust gas from the baking furnaces is also thermally treated, which greatly reduces odour emissions.
»WE HAVE SET OURSELVES HIGH GOALS AND HAVE ACHIEVED THEM TOGETHER«
Volker Perk, Head of Industrial Engineering of the Krone Commercial Vehicle Group, described the philosophy and technical masterpiece that is anchored in the heart of the new Coating Centre at the Werlte site.
Since the beginning of July, the first chassis have already been manufactured in trial operation at the new Coating Centre. What does this mean to you personally? I'm really glad that we were able to do so much together as a team. Together, we have set ourselves high goals and achieved them consistently ahead of schedule! All those involved have invested a great deal of energy over the past year and a half and have ensured that all our ideas have been implemented and all requirements met. The construction was also completed without impairing further production processes. This was a really special achievement. We were also able to smoothly integrate the new processes with the corresponding interfaces. And the topics, 'quality' and 'sustainability' were always of utmost importance in all of this. For me, the new Coating Centre perfectly embodies the quality concept for which the Krone company stands.
Why did Krone invest in such a modern Coating Centre? We wanted to set new standards for coating our chassis in terms of quality, corrosion protection and sustainability in regard to environmental protection and energy efficiency. The centre allows state-of-the-art automatic control of the entire coating process. Colouring and assembly are decoupled: This ensures the optimum sequence of coating and assembly.
What distinguishes the systems, especially in the light of future challenges? The high level of automation! It enables maximum reliability and also takes the pressure out of the shortage of skilled workers – high quality production is assured. A dynamic, fully automatic warehouse is integrated into the coating system with the sequencer, via which the products can be appropriately introduced into each processing stage up to delivery to the assembly department. Modern conveyor technology in combination with central process automation ensures that all processes are optimally controlled and implements all movements of the chassis within the Coating Centre. All programs are generated and processed automatically using object dependencies. Each processing step is digitally monitored accordingly and logged.
»The topics Quality and Sustainability are always at the top of the planning and implementation agenda.«
In what way is perfect corrosion protection guaranteed? We prepare the workpieces optimally so that the paint adheres seamlessly and firmly. The complete chassis is first cleaned and descaled by 3D blasting. The combination of splash, spray and immersion degreasing also contributes to this, as well as zinc phosphating with subsequent passivation. The CDP dip coating belongs to a series that has been optimally designed for corrosion protection. It has a special edge protection additive that provides better protection for every edge of the chassis through thicker layers. After thermal crosslinking at around 190 degrees Celsius, a homogeneous, diffusion- tight film coating is produced that reliably keeps environmental influences away from the substrate. The system is immersed in water and contains less than two percent residual solvent. In addition, the powder coating process is highly automated, thus we can meet all the customers' colour requirements. Last but not least, state-of-the-art furnace technology plays its part in ensuring that we can provide the best protection against corrosion.
How do you deal with the areas of the chassis are particularly difficult to reach? In complex simulation runs, we have designed the blasting machine so that the steel blasting material reaches the workpiece right to the last corner. It is optimally prepared for the coating: The combination of splash, spray and immersion degreasing ensures a completely clean and dust-free chassis – the optimum basis for the further coating process. Zinc phosphate reacts directly with the chassis material, and the CDP ensures that the chassis is coated uniformly, even in cavities and on intricate parts of the structure.
What role has environmental protection played in the design of the centre? It was very important to us to protect the environment as much as possible and to use all resources responsibly. We were able to achieve this through intensive planning, and we have reached a new level of efficiency with these systems.
Are there already next steps or goals? First of all, we are pleased to be able to offer our customers future-proof surface protection for their vehicles. Of course, we are constantly improving, and there will certainly be more exciting projects in the coming months and years – both small and large.
RAW CHASSIS BUFFER
The raw chassis are delivered in packages of four to the Coating Centre. The vehicles can pass through the delivery hatch with no need for difficult manoeuvres.
The buffer zone offers storage space – here, the individual chassis wait to be guided through the system. One step follows another like a string of pearls: A precisely planned, timed and automated process. The conveyor system takes over the raw chassis at a binding station with two overhead cranes.
The plant uses the warm air from the cooling areas in the coating process to ensure that the supplied chassis are heated to room temperature and transferred dry into the further process steps. A ventilation system directs this air directly to the raw chassis buffer.
BLASTING SYSTEM WITH DE-SANDING STATION
The first station that each chassis must pass through involves blasting and de-sanding: Because the chassis are delivered raw, the metal is precision shot-blasted using steel balls. This removes mill scale, cinder and impurities, resulting in a clean, bright, metallic surface with the pre-treatment and the CPD coating can optimally adhere to later.
The blast system is equipped with 22 turbines – more than twice as many as in the previous system. This enables an optimal blasting result to be achieved. The intelligent arrangement supports this goal: The turbines are arranged three-dimensionally in the blasting chamber so that they reach almost all surfaces of the chassis construction. During the blasting process, about 25 tons of the steel blasting material is fired at the chassis at a speed of up to 300 kilometres per hour. Falling blasting material is fed back to the process via screw conveyors.
After the treatment, many steel balls remain on the chassis and in cavities. The chassis is cleared of these at the desanding station: To do this, it is fixed to a device that moves it around its own axis several times with turning and tilting movements. What remains is a cleaned chassis with a clean, bare metallic surface.
The chassis is pre-treated in the tank stations and then CDP-coated. After a testing period, during which more than 1,000 metal sheets and test pieces were used, KRONE has opted for tri-cationic zinc phosphating – the best-proven technology currently available.
The system can be operated in three shifts: In the pre-treatment, the chassis is immersed in different tanks one after the other. The baths are circulated around the clock to keep bath parameters such as pH constant. The parameters are continuously checked. Each chassis passes through the following stations within approximately 90 minutes:
A) Splash and spray degreasing: The chassis is mechanically cleaned. As it enters the spray degreasing tank, it is rinsed off and then sprayed with a large number of nozzles while moving continuously.
B) Immersion degreasing baths and rinsing: In this station, the chassis is carefully cleaned and degreased again. Baths with special liquids are used for this purpose. The metal is dipped twice in the immersion degreasing baths and the rinsing tanks.
C) Preparation of the surface for a flawless CDP coating: Zinc phosphating is carried out before the actual coating by cathodic dip painting. This is a chemical process that prepares the material optimally for absorption of the paint. It is immersed in an acidic solution which triggers the desired reaction with the metal. Zinc phosphating increases the adhesion of the coating and protects against corrosion. The chassis is then rinsed twice more before a passivation bath completes the zinc phosphating process to perfection: As a result, the surface is completely and evenly sealed again. This is followed by a further rinse in demineralised water.
D) CDP coating: The final seal of the chassis takes place in a tank containing the CDP-coating. When immersed, the CDP coating preparation reaches even the smallest cavities to ensure an even and effective coating of the metal. The CDP coating is applied to the surface of the chassis at over 300 volts DC and around 2,300 amps. The components are then rinsed twice more, removing any excess paint.
A BRILLIANT PERFORMANCE ALL ALONG THE LINE
The raw chassis undergo a highly automated coating process for optimum sealing in the Krone Coating Centre, where energy efficiency, durability and the highest quality are combined.
The coating must be dried. For this purpose, the plant has ten large CDP furnaces, which are heated to a defined temperature of around 190 degrees Celsius. In this process, the CDP coating is firmly bonded to the surface of the chassis. Depending on the type of chassis, this takes about 40 to 60 minutes. The coating crosslinks to form a homogeneous, closed film that will effectively protect the component in future applications. Outdoor air is used to cool it down. A thermal oxidiser is used to clean the exhaust air from the furnaces.
Here, the chassis cool down passively and are then stored until they continue into the powder coating. In this step, the customer can choose their own colour scheme: All RAL colours are available. The desired colour is applied in one of the two powder chambers in the system – the powder system is changed accordingly for each new colour. Since process automation determines the coating sequence, the system automatically detects when a colour change is due and initiates the changeover in the powder chambers. The chassis can be stored dynamically via transfer bridges. This makes it possible to optimise colour changes – for maximum efficiency and to create as little waste as possible.
The sequencer installed by Krone allows for a dynamic and 100 percent automatic storage system: The components can be temporarily stored between all process steps using a push & pull conveyor system. Tractors push or pull the goods carriers in the direction of travel, and transverse movements are carried out via transfer bridges. This requires relatively little effort and enables the use of a light and energy-saving goods carrier. The sequencer holds around 200 chassis. The task of this dynamic storage is to decouple the coating system from the assembly. As a sequence controller, it also takes on the task of creating an optimum sequence with the aid of process automation prior to powder coating before the chassis enter the corresponding sequence for assembly and are passed on to the next finishing stage.
Powder is applied to the chassis in this station: The system sprays the smallest particles in powder form as a cloud onto the statically charged workpiece. The vehicle is completely measured via a 3D scanning grid as it enters the powder chamber, and the 47 automatic spray heads arrange themselves at the optimum coating distance around the chassis in order to apply a uniform powder layer. After this step, the chassis is moved to the second level of the Coating Centre.
The powder coating must also be treated in the furnace. The powder furnaces ensure that the particles slightly liquefy and then harden – in this way, they bond optimally to the CDP coating and firmly adhere to create a tough, impact-resistant surface.
BUFFER ZONES AND TRANSFER TO ASSEMBLY
The complete coating is finished, and the chassis is ready for installation. Thanks to process automation, it remains in the sequencer until it is requested. The assembly sequence for the chassis is already determined upon entry into the raw chassis buffer. When the assembly is requested, the finished coated chassis is placed in the specified sequence and sent for assembly.