The Neckar flows through people's experience - at least in Baden-Württemberg and especially in Rottenburg. At the annual Neckar Festival at the end of June, 60 clubs and associations offer a comprehensive cultural program for three days - a highlight of the year not only for Rottenburg residents. The entire region southwest of Stuttgart joins in the celebrations. The Neckar River is included, square rafts made of raw tree trunks provide space for music and gastronomy.
The effort for the municipality is enormous. It therefore decided to charge an entrance fee for the first time - 5 euros for three days. The entrance ticket was to be bought only once and then worn visibly. Paper was out of the question, a kind of badge was needed. The Rottenburg company "Schnittenliebe" seemed to be the right address for the city council; "Schnittenliebe" offers 3D-printed sewing accessories - such as sewing utensils, collection containers or organization systems. The motif was quickly found: a Neckarfloß. It had to have a railing, like the real rafts, from which people can't just fall into the water.
But the task was too difficult for the 3D printer. There was the quantity of 30,000 pieces, which threatened to jam the printers for weeks in the leisurely 3D production process. And there was the railing, which, as in real life, should preferably not be made of the same material as the wooden raft. "Schnittenliebe" had met Solidtec at a generative process trade show, and inquired whether injection molding might not be the right process. Paul Bolko, moldmaking project manager, provided the advice.
"Our injection molds made of aluminum fill the gap between 3D printing and classic molds made of steel, but are much faster to produce." The clamping force of up to 420 t meets the vast majority of requirements, even for large or complex products. And the quantities that can be achieved with a Solidtec mold bridge usual series start-ups. They can reach into the millions, but are still economical even with low numbers. Depending on the complexity and the number of pieces required, a trade-off is made between automated and manual work. In the case of the entrance ticket, manual assembly was chosen for economic reasons.
The problem was the railing. Paul Bolko wanted to avoid unsightly pull marks that would have resulted from ejecting a one-piece raft model. The railing was therefore injection molded flat from polypropylene, minimally joined at the bends and given high-precision snap-in hooks for the holes in the raft. Insertion into the raft made of wood-filled PP is only successful if it is done correctly. This was done by the inmates of a correctional facility with great commitment.
Rottenburg, "Schnittenliebe" and Solidtec will come up with something new for next year.