Planning an automated paint shop is not actually a very difficult task. However, it is a challenge to build a paint shop that meets all the customer's expectations and at the same time complies with all safety regulations. Adal has now completed such a project at one of its plants in south-western Poland.

Paint shops consist of a wide variety of machines. These include conveyor belts, lifts, loading stations, automated crane gantries and technical process applications in connection with the chemical preparation of products, powder and wet coating areas, as well as ovens for heat treatment. Customer expectations of both the process and the functionality of the application have set the bar high in the case of one of Adal's latest projects. The paint shop is designed for coating three product groups of different widths and two groups with different heating times in the oven. In addition, various materials can be processed: Mild steel, galvanized steel, aluminium or cast iron. Surface preparation takes place in a 14-tub spray and immersion washer. The paint shop can carry out cataphoresis or powder coating. A combination of both processes is also possible. A wide range of powder paints is available for coating. Priority modes for express orders are also possible.

Despite a very high degree of automation, human supervision is required to operate and control individual processing cells. For example, a technician has to take samples from a tray several times a day, with automated crane gantries carrying metal products moving over his head. A worker must check that the automated cleaning of the powder coating chamber has been carried out properly after a powder color change. Such situations require reliable safety measures. The individual processes must not be delayed for too long, as this could damage coated parts or render them useless.

Integrate a wide variety of sensors

Siemens S7-1500 PLC series devices are used as control systems for the paint shop, one of which is an F-PLC. All devices use Profinet, which enables the combination of standard and safety components in one network thanks to Profisafe technology. Due to the dimensions of the plant of around 100 x 60 m and the high number of safety signals, Adal decided to use compact fieldbus modules from Murrelektronik's MVK Metal Safety series for the safety I/Os. Different types of safety sensors are used in the system, for example limit switches, door switches with guard locking, light curtains and emergency stop buttons. These could all be easily connected and integrated with MVK metal safety modules. The main tasks of the safety outputs are to stop the drives and switch off the compressed air used.

The MVK Metal Safety fieldbus module combined with the S7-1500 PLC controller. (Pictures: Murrelektronik)

Various types of decentralized drives from SEW are used in the project. Depending on the operating mode of the drive, the STO inputs (Safe Torque Off) were used or an SS1 (Safe Stop 1) was implemented. The implementation of MVK Metal Safety allows all signals to be controlled while reducing hardware, cabling and installation costs - especially compared to IP20 solutions. Achieving high safety levels (PLd and PLe) is also no problem with Murrelektronik's products. Interestingly, Adal uses additional MVK metal safety modules in the automated crane gantries, which are controlled via wireless communication. Control and safety data are transmitted via WLAN and there is no need to set up a separate system for safety signals. am

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