Müller's colleague, David Frank from process technology, proudly presents the production cell. The process starts with a mixer which combines three main ingredients: the raw material in the form of granules, a dye and the production scrap ground residues. Sprue forms on the components during injection molding where the liquid plastic enters the mold. This is later removed and returned to the process. As a result, there is less waste for Freudenberg to dispose of.
The mixture is then melted and injected under pressure into the mold via a cylinder, always for four sealing rings simultaneously. In just a few seconds, the plastic hardens again. But the sealing ring is far from finished. First, the sprue is removed automatically. Robots then transfer the components to automatic quality control, which includes laser measurement. All parts that pass this test are placed in a drum together with an abrasive. The rotating movement of the drum grinds the remaining burrs from the sealing rings. “The surface must be very smooth for the seal to function properly later,” explains Frank.
But a crucial step is yet to come. The sealing rings are manufactured open, with a lock-like opening that closes the ring after it has been mounted around the shaft. At this stage, the rings are slightly oval. They still need to be brought into their final closed form. To do that, they are inserted into a heating unit by a feed system and heated to a temperature below the melting point of the high-performance plastic. “The experience of our US colleagues was very valuable when it came to setting up the plant,” says Frank. Freudenberg has been processing PEEK in the USA for almost a decade.
The Reichelsheim plant could also be manufacturing Levitas sealing rings within the next two years. Müller, who is responsible for marketing the innovative transmission seal, has not yet been able clinch a firm customer order. However, prototype testing is on-going. “Even though we will see an increasing number of electric and hybrid vehicles on the road in the coming decade,” says the expert, “it is important we continue to improve conventional petrol and diesel drives.” Converting a gearbox to low-friction seals is relatively simple. Only the contact point where the seal is pressed against the housing might need modifying. It must be wide enough and, above all, the metal surface not too rough – otherwise a continuous oil film may not form. Small steps often have the greatest effect, Müller concludes.