Extruder with axial displacement

An extruder for extrusion of material, the extruder comprising a screw, a barrel, and a controller,

• the barrel comprising a barrel inlet for receiving an amount of the material and a barrel outlet,
• wherein at least a section of the screw is conical and wherein at least a section of the barrel is conical and wherein the screw and the barrel are formed such that the screw can be positioned in the barrel so that the conical section of the screw fits in the conical section of the barrel with a leakage gap through which the material can pass in between the barrel and the screw,
• wherein the extruder is configured such that, during operation, rotation of the screw advances the material, which is added to the barrel inlet, towards the barrel outlet,
• wherein the extruder is adapted for displacing the screw in an axial direction of the screw, such that by an axial displacement of the screw with regard to the barrel a size of the leakage gap between the screw and the barrel is modified,
• wherein the extruder comprises a force sensor for measuring an upward force of the material at one or more positions in the extruder and/or an upward force on the screw, the upward force of the material at the one or more positions in the extruder and/or the upward force on the screw acting in a direction parallel with the axial direction and opposite to the material net axial movement,
• characterized in that the extruder is adapted for obtaining operational characteristics and that the controller is adapted for controlling the axial displacement of the screw, during operation of the extruder, as a function of the operational characteristics of which at least one is the upward force of the material at the one or more positions in the extruder and/or the upward force on the screw.