Extrusion for 3d printing

An extruder for 3D printing, comprising an outlet for providing extruded material, and a feedstock inlet piece for receiving material into the extruder,

• the feedstock inlet piece including cooling means for cooling said material,
• a reservoir for melting material, and having a reservoir width, being connected to the outlet,
• a channel with a channel width, for connecting the feedstock inlet piece with the reservoir and introducing the material into the reservoir, where the channel width is lower than the reservoir width,
• the extruder further comprising:
• a first heater for melting material in a first reservoir part of the reservoir close to the channel and
• a second heater close to the connection of the reservoir to the outlet, for maintaining molten material in a second reservoir part of the reservoir close to the outlet at the same temperature as the material in the first reservoir part or at higher temperature, and
• a controller for controlling the temperature gradient of the material through the channel, the controller configured to maintain the level of molten material at least at the junction between the reservoir and the channel or along the channel during extrusion, for providing extrusion by the material introduced through the feedstock inlet piece and pushing on the molten material in the reservoir,
• wherein the first heater is distanced from the second heater by a thermal break separating the reservoir in the first reservoir part close to the channel and the second reservoir part close to the outlet.

A method for extruding material comprising:

• introducing material in an extruder through a feedstock inlet piece,
• heating material in a first part of a reservoir for obtaining a level of molten material,
• while preventing the heating of the material through the feedstock inlet piece, and applying a second heating in a second part of the reservoir to material leaving the reservoir, where the first part is separated by the second part by a thermal break,
• feeding material into the reservoir through a channel, the channel having a channel width and the reservoir having a reservoir width, where the channel width is lower than the reservoir width,
• controlling the temperature gradient along the channel for maintaining the level of molten material at the junction between the reservoir and the channel or along the channel during extrusion,
• so that introducing further solid material into the reservoir pushes the molten material in the reservoir through an outlet connected to the reservoir, thus forming extruded material.