Abstract: A compactor for the preparation of thermoplastic materials placed between two approximately disc-shaped work surfaces at least one of which is rotatably connected to a rotary driven drive shaft and to a rotatable work surface and to a sleeve that surrounds the drive shaft, which can be operated axially with the drive shaft, whereby the sleeve is fitted with an exterior screw thread, wherein the sleeve cannot rotate, and wherein the sleeve is surrounded on its exterior by a rotatably mounted component that by means of an interior screw thread meshes with the exterior screw thread on the sleeve, whereby the rotatably mounted component is capable of operation in two directions by means of a driving mechanism.