Fully automatic powder enameling from batch size 1

V-ZUG is the leading Swiss brand for household appliances. For over 100 years, V-ZUG AG has been developing and producing household appliances for the kitchen and washroom at its main production site in Zug, Switzerland, and, since 2013, also in the refrigeration sector in Arbon and, more recently, in Sulgen, Switzerland. In Zug, everything is produced in-house – from the sheet metal to the finished product. According to the premium claim, ovens, steamers, dishwashers, washing machines and tumble dryers are located in the upper price segment. Quality and functionality are top priorities for all products. To further develop this standard, the company invested in a new powder enamelling system. "We chose ASIS because they credibly proved in the run-up of the project that they can build and manage such a plant," says Roland Häfliger, Project Manager Parts Manufacturing & Surface Technology V-ZUG. "ASIS was also one of the few suppliers that offered to be the general contractor for the entire plant."

Growth

The V in the company name V-ZUG still comes from the founding days as a galvanizing plant. Since then, the town on the scenic Lake Zug has developed around the company. Due to the limited space available, production can only grow upwards. The plan is to produce twice as much in the future on almost half the space. All plant components of the approx. 1,400 m² coating center have been designed to fit into the second floor of a modern wooden building. The renewable resource wood is not only sustainable, it also creates a pleasant atmosphere in the so-called Zephyr Hangar, which is unusually positive compared to other industrial production halls. 40-50 different components can be coated automatically from batch size 1. The range includes four basic types of baking cases and various flat goods, such as hot-air or baking trays.

Automatic pickup

The ovens come out of the welding line every 50 seconds and are automatically transferred to a flat conveyor belt. Their first station is the clips and hanger station. There, clips are automatically applied. These cover certain areas to protect them from the enamel powder so that they remain coating-free for further processing. Hangers are then automatically attached and transferred to the Power & Free conveyor system by a transfer robot. The flat goods are fed in at a separate manual station.

Pretreatment

At the 5-zone spray pretreatment, all parts are cleaned of drawing oil and dirt for optimum coating quality. The spray pumps of the two-lane system are not controlled via butterfly valves as usual, but via frequency converters. This enables consistent integration into the PLC system control, and the most ideal operating state in each case, such as pause switching, can be set. The spray pressure is kept constant via electronic pressure pipe monitoring. Special attention has been paid to economical rinsing agent consumption with cascade control. After the blow-off zone, the workpieces are dried in the adhesive water dryer above so that no water remains on the surface.

Application combination

All powder applications take place in an air-conditioned housing. The baking cases and the flat goods are coated in a total of three powder booths. ASIS‘ experience in the household appliance industry has shown that the combination of robots and linear axes is an ideal setup. The economical linear axes coat the vertical, flat surfaces here, while the robots powder edges and interior areas. Two booths handle the basic powder application, while the third powder booth is for the special coating of steam cookers. Sensors detect which part is currently entering and the parameters and programs are optimally set accordingly.

Challenge accepted

"V-ZUG’s requirements were very high right from the start, and a lot of attention was paid to automation and digitalization," recalls Dietmar Binder, Project Management and Sales ASIS. "One challenge was that we wanted to use only one conveyor technology system, the Power & Free conveyor, and only one uniform carriage and hangers to run through the plant." This makes sense, of course, as the overall process is simplified and no additional sorting functions are needed in the plant. This was realized with a transfer robot and a carrier cleaning system designed by ASIS. The transfer robot removes all workpieces from the carriers, which are also covered with powder during the application. In the meantime, these are cleaned in the carrier cleaning system and the robot can transfer the workpieces to the same clean carriers, which then travel to the enamel baking oven.

The enamel powder is baked at a temperature of 850 °C. The specially built scale plate conveyor drags the wagons of the Power & Free conveyor through the oven without damage and then returns them. The flexible scales close off the top of the oven at all times so that no energy is lost and at the same time protect the wagon above as well as the conveyor chain, which are not designed for these temperatures. The still-hot baking chambers that are moving out radiate their energy onto the workpieces that are moving in. There are nine firing zones with different temperatures in the oven, which are heated by 16 burners. At the moment, the baking oven is still operated with natural gas, but a changeover to hydrogen is being worked out. Shiny black, like Swiss dark chocolate, they leave the oven and line up in the empty drawing buffer to cool down further.

You could almost think that they are now ready for assembly. Some parts are further enhanced according to the customer’s wishes. In another booth, a permanent non-stick coating is applied by a robot and then dried at 250 °C in a convection dryer.

Digitization and sustainability

"We chose ASIS because we place great value on functionality and quality, which includes the complete traceability of quality data during the processes," says Roland Häfliger. This is made possible by the Surface-Analytics 4.0 software. All process data of the plant are recorded in a central data storage. The user accesses it via smartphone, tablet or laptop. In addition to important key figures and reports for optimizing plant performance, each individual part can also be fully traced.

Only a few components that do not meet the high quality requirements in the first step are then brought up to top level in the rework booth. Of course, everything is recorded transparently and traceably via touch panel. Reworking instead of throwing away – this is also sustainability in the production process.

Precise pre-planning

The entire plant was set up digitally in advance. In addition to classic reachability studies, the robots were of course also simulated and their programs created offline. The robot simulation of all individual stations and the entire material flow in the plant were linked in an overall simulation. The different process times of the stations were taken into account. In this way, it is possible to make precise predictions about the design of the conveyor system with buffer sections, sources of error in the individual areas, zones working in parallel and the throughput to be expected.

"The highlight of the plant is difficult to determine, in fact it is the plant as a whole," Roland Häfliger sums up. "The entire plant in its functionality is unique." Each individual process was precisely coordinated, automated and linked with uniform control technology like Swiss clockwork. German engineering meets Swiss precision – through customer-oriented preliminary planning, robotics expertise and the use of digital solutions, the world’s most modern enameling plant in Switzerland was created.

More info at:

https://www.asis-gmbh.de/en/coating-systems/enamel/

Company description ASIS

ASIS solves challenging tasks in automated plant engineering worldwide. The internationally positioned systems supplier exports from four locations in Germany and a subsidiary near Shanghai to over 30 countries worldwide. The wide range of competences includes turnkey plants in the field of coating, application technology, quality control, surface treatment, electron treatment, process automation technology and digital simulation. The company differentiates itself from its market competitors through its high level of expertise in control technology and the use of digital intelligence. The claim "Connecting Technology and People" stands for perfect cooperation between man and machine and for sustainable value created in harmony with economy and ecology.

Company description V-ZUG

More than 100 years ago, V-ZUG set itself the task of making everyday life easier with high-quality, innovative household appliances. The company’s roots lie in the economic region of Zug in the heart of Switzerland. By 2033, a vertical technology cluster will be created here on a small footprint, making it easy for the company to implement innovations quickly and easily. V-ZUG AG markets its products in selected markets to a discerning clientele worldwide. The marketing of premium products under the "Swissness" label combines V-ZUG with its individual corporate culture and a strong service orientation towards the customer.