"Made in Germany" is an integral part of Mesto’s brand promise. The entire value creation is produced at the corporate headquarters in Freiberg am Neckar in southern Germany, and this is to remain unchanged in future. For the production floor this means continuous increases in efficiency, integration of processes and as much automation as possible. The main challenge here: maintaining high flexibility. Together with its partner Wittmann, Mesto develops manufacturing solutions made to measure to meet these complex requirements.
“We have a particularly large product range”, explains Élise Sellmayr, Head of Process Optimization, during our visit in Freiberg am Neckar. Economical distribution of liquids is Mesto’s specialty. Here, the South German company with more than a century’s corporate history ranks among the globally leading suppliers. This unwieldy-sounding description is all about products everyone is familiar with: pressure sprayers, backpack sprayers, foam pressure sprayers, trigger sprayers and suction devices. These are found just as naturally in households and allotment gardens as in agriculture, professional horticulture, workshops, in the trades and on building sites, being used for cleaning, disinfecting and pest management, as well as in a great variety of different industries.
All products are available in different versions; major customers such as DIY stores and workshop chains can have their sprayers branded in their own corporate design. This diversity leads to small batch s and frequent setup processes. Therefore, flexibility is the main key to efficient production and competitive unit costs.
“We have no typical mass production here”, says Sellmayr and shows us an example. She holds up a small white piston made of a copolyester, which serves as a pressure gauge in all pressure sprayers with a plastic housing and which has a great deal of responsibility. “The piston pressure gage functions as a safety valve”, explains Sellmayr. Sprayers with housings made of plastic are approved with internal pressures of up to three bar. If more air than that is pumped in, the excess pressure is let out via the piston gage. In the "Primer" and "Profi" series of appliances for professional use, the pressure gages are printed on and perform internal pressure control. Piston valves without print are used in the smaller devices of the “Pico" series destined for private households and gardens.
For a long time, injection molding and printing were two entirely separate production steps. What is new for Mesto: the printing unit now forms an integral part of the injection molding system.
The change happened after the injection molding machine previously used for making the pistons stopped working. This was taken as an opportunity to scrutinize the entire production process for overall efficiency.
“When walking through the production floor, I always keep my eyes open and think about which processes could be optimized effectively”, Sellmayr emphas. Here, she gets many valuable hints from Wittmann, her supplier of injection molding machines and linear robots. The idea of having the printing process integrated into the injection molding cell was also raised during a joint factory tour, since the printing system used up to then had become somewhat obsolete as well. “We were immediately convinced that we could improve the efficiency and quality of the prints by optimizing the entire process and not just the injection molding side,” says Sellmayr.
Integrated on smallest possible floor space
The main challenge in developing the new integrated production process was extreme time pressure. Here, Mesto was fortunate that there was just a used, but still very young Insider production cell available for immediate delivery. It consisted of a SmartPower 80/525 injection molding machine with a linear robot and conveyor belt, so it was predestined for producing the piston pressure gages. Mesto seized the opportunity and commissioned Wittmann to integrate a new printer solution.
Wittmann’s Insider concept is already designed from start to finish for minimal space requirements and maximum efficiency. The protective housing is mounted right next to the conveyor belt. Temperature controllers or other components can be easily placed underneath. Compared to conventional solutions, the required production floor space is reduced by up to 50 per cent. At Mesto, Wittmann succeeded in integrating the new printing station in such a way that it takes up hardly any extra space. It connects to the rear of the conveyor belt, and its depth remains within the grid dimension of the protective housing.
A four-cavity mold is used for production. At the end of each cycle, the Wittmann linear robot removes the four pistons and deposits them on the vertical domes of a small transport carriage, which takes them to the three print heads. The pressure gages are printed on as they pass by. To this end, the domes rotate on the carriage so that the print heads can work all around them without changing their own position. Each piston is given two rings, one red and one black, plus a scale.
Following printing, the gripper of the linear robot picks up the parts again and places them on the conveyor belt. When pistons are manufactured for the "Pico" series, which requires no marking, the printing station can be simply passed by. In that case, the robot places the pistons on the conveyor belt directly after demolding.
