Extruder system and additive manufacturing printer, comprising such an extruder
The extruder system includes a supply configured to receive raw material and comprising a heater configured to melt the raw material into extrudable material, an extruder configured to receive the extrudable material from the supply and comprising a screw conveyor configured to convey the extrudable material towards an extrusion nozzle of the extruder and cause an overpressure inside the extruder to allow selective extrusion via the extrusion nozzle. The extruder further includes a plunger arranged at or near the extrusion nozzle and configured to selectively release at least a part of the overpressure and thereby control a flow of extrudable material out of the extrusion nozzle to reduce oozing of extrudable material after stopping the flow.
1. An extruder system, comprising:
a supply configured to receive raw material and comprising a heater configured to melt the raw material into extrudable material;
an extruder configured to receive the extrudable material from the supply and comprising a screw conveyor configured to convey the extrudable material towards an extrusion nozzle of the extruder and cause an overpressure inside the extruder causing selective extrusion via said extrusion nozzle; and
a plunger arranged coaxially with the screw conveyor at or near the extrusion nozzle and configured to move against a spring to selectively release at least a part of the overpressure and thereby control a flow of the extrudable material out of said extrusion nozzle to reduce oozing of the extrudable material after stopping said flow.
2. The extruder system according to claim 1 , further comprising a drive that is selectively switchable between a first drive direction associated with driving the screw conveyor in a first convey direction for conveying the extrudable material downstream towards the extrusion nozzle, and a second drive direction, opposite relative to the first drive direction, and associated with stopping the flow of extrudable material out of said extrusion nozzle.
3. The extruder system according to claim 2 , wherein the drive, when driven in the second drive direction, is configured to stop driving the screw conveyor in the first convey direction.
4. The extruder system according to claim 2 , wherein the drive, when driven in the second drive direction, is configured to drive the screw conveyor in a second convey direction that is directed opposite to the first convey direction, wherein said second convey direction is associated with the screw conveyor moving the extrudable material away from and upstream relative to the extrusion nozzle.
5. The extruder system according to claim 2 , wherein the drive is configured to drive both the screw conveyor and a retraction of the plunger.
6. The extruder system according to claim 5 , wherein, when the drive is driven in the second drive direction, said drive is configured to simultaneously stop driving the screw conveyor in the first convey direction and move the plunger away from and upstream relative to the extrusion nozzle.
7. The extruder system according to claim 5 , wherein, when the drive is driven in the second drive direction, said drive is configured to simultaneously drive the screw conveyor in the second convey direction and thereby move the extrudable material away from and upstream relative to the extrusion nozzle, and move the plunger away from and upstream relative to the extrusion nozzle.
8. The extruder system according to claim 2 , further comprising a one-way bearing that is configured to:
decouple the drive and the plunger to allow the plunger to be maintained in an extended position when the drive is driven in the first drive direction; and
couple the drive to the plunger to allow the drive to retract the plunger to a retracted position when the drive is driven in the second drive direction.
9. The extruder system according to claim 8 , further comprising a coupling that comprises two coupling parts that are rotatable relative to each other and that each comprise a contact surface that exhibits a sloping part and an axial abutment, the coupling configured to:
rotate the coupling parts simultaneously with abutting contact between the axial abutments of their contact surfaces when the drive is driven in the first drive direction; and
rotate the coupling parts relative to each other by sliding contact along the sloping parts of their contact surfaces when the drive is driven in the second drive direction, to thereby axially extend the coupling and retract the plunger to the retracted position.
10. The extruder system according to claim 9 , wherein the sloping parts of the contact surface of the two coupling parts define a helical shape.
11. The extruder system according to claim 8 , further comprising a further one-way bearing that is configured to:
couple the drive to the screw conveyor and thereby drive the screw conveyor in the first convey direction when the drive is driven in the first drive direction; and
decouple the drive and the screw conveyor to stop driving the screw conveyor in both the first convey direction and the second convey direction when the drive is driven in the second drive direction.
12. The extruder system according to claim 2 , further comprising a valve arranged upstream relative to the extrusion nozzle and downstream relative to the screw conveyor, wherein said valve is configured to restrict or shut off the flow towards the extrusion nozzle, and wherein said drive is configured to at least partially close the valve when driven in the second drive direction.
13. The extruder system according to claim 12 , wherein the valve comprises:
a valve body comprising a passage having a circumferential edge defining a valve seat directed towards the extrusion nozzle; and
a valve plug configured to move upstream towards and abut the valve seat when the plunger is moved upstream relative to the extrusion nozzle.
14. The extruder system according to claim 13 , wherein the valve plug is:
arranged downstream of the passage; and
connected to the plunger via a spacer, wherein said spacer extends from the plunger through the passage of the valve body towards the extrusion nozzle.
15. The extruder system according to claim 13 , wherein the plunger reduces oozing via said valve without directly releasing at least a part of the overpressure.
16. The extruder system according to claim 1 , wherein the plunger is arranged in the screw conveyor.
17. The extruder system according to claim 16 , wherein the plunger is arranged in a tip of the screw conveyor.
18. The extruder system according to claim 16 , wherein the plunger is configured to axially move along a rotation axis of the screw conveyor.
19. The extruder system according to claim 1 , wherein at least one of:
the spring is configured as a pretensioner configured to force the plunger towards a tip of the screw conveyor;
the raw material is a granulate and the extruder system is a granulate extruder system;
the supply is integrated in an upstream part of the extruder; or
the extruder system is an extruder system of an additive manufacturing printer (AM printer).
20. An additive manufacturing printer (AM printer), comprising:
an extruder system according to claim 1 ; and
a controller configured to cause the extruder system to print an object by executing computer-executable printing instructions for printing said object.