The Liwell technology was developed over 40 years ago, in Germany, in order to make accurate separations of materials that are difficult to screen. There are over 2000 machines in operation worldwide in a wide variety of applications. The LIWELL® screen operates on the FLIP FLOW PRINCIPLE. Elastic polyurethane screen panels are alternately tensioned and relaxed. In the final tensioning phase, the screen panels are overstretched, changing the surface of the screen mat and the hole size. Adherent particles are freed and stuck particles are released. Acceleration forces of up to 50 G are achieved, while the screen frames are exposed to only 2-3 G. The screen deck operates free from blinding or plugging, even with difficult materials. The end result is the effective screening of sticky, moist, and abrasive materials, at cutpoints as low as 50 mesh.