Nozzle shut off for injection molding system
An injection molding apparatus and method of fabricating a molded part are provided. The apparatus may include a barrel, a nozzle enclosing an end of the barrel and defining an opening in fluid communication with an inside of the barrel, and an extrusion screw positioned at least partially inside the barrel and rotatable relative to the barrel. The extrusion screw may include a screw tip. Relative axial movement between the barrel and the extrusion screw may open or close the opening of the nozzle to permit or prevent, respectively, material flow through the opening of the nozzle. The method may include clamping a mold, opening a nozzle, rotating the extrusion screw to pump a molten material into the mold until the mold is filled, closing the nozzle, and unclamping the mold to release a molded part.
1. A method of molding a part, comprising:
rotating a screw within a barrel to extrude a molten material through a nozzle opening of a nozzle into a mold cavity; and
after extruding the molten material through the nozzle opening, inserting a free end of the screw that is defined by a cylindrical tip portion and corresponding in geometry to the nozzle opening into the nozzle opening along an entire axial length of the nozzle opening to displace all of the molten material from the nozzle opening, wherein the cylindrical tip portion rotates with the screw, and wherein the cylindrical tip portion comprises a consistent circular cross-section extending along a longitudinal axis of the screw.
2. The method of claim 1 , wherein inserting the tip portion of the screw into the nozzle opening comprises inserting the tip portion of the screw into the nozzle opening until the tip portion of the screw is substantially flush with an exterior surface of the nozzle.
3. The method of claim 1 , wherein inserting the tip portion of the screw into the nozzle opening comprises sealingly engaging the tip portion of the screw with the nozzle along the entire axial length of the nozzle opening.
4. The method of claim 1 , wherein rotating the screw within the barrel causes the molten material to flow around the tip portion of the screw, through the nozzle opening, and into the mold cavity.
5. The method of claim 1 , further comprising sealingly engaging an interior surface of the nozzle with a transition portion of the screw.
6. The method of claim 5 , wherein the tip portion of the screw has a smaller axial length than the transition portion of the screw.
7. The method of claim 5 , wherein the transition portion of the screw extends outward from the tip portion of the screw.
8. The method of claim 7 , wherein the transition portion of the screw extends rearward from the tip portion of the screw.
9. A method of molding a part, comprising:
injecting a molten material through a nozzle opening of a nozzle into a mold cavity; and
after injecting the molten material through the nozzle opening, inserting a cylindrical tip of a screw that is positioned at a distal end of the screw and corresponding in geometry to the nozzle opening into the nozzle opening along an entire axial length of the nozzle opening to displace all of the molten material from the nozzle opening, wherein the cylindrical tip rotates with the screw, and wherein the cylindrical tip comprises a consistent circular cross-section extending along a longitudinal axis of the screw.
10. The method of claim 9 , wherein injecting the molten material through the nozzle opening comprises rotating the screw within the barrel.
11. The method of claim 10 , wherein rotating the screw within the barrel causes the molten material to flow around the tip of the screw, through the nozzle opening, and into the mold cavity.
12. The method of claim 9 , wherein inserting the tip of the screw into the nozzle opening comprises inserting the tip of the screw into the nozzle opening until the tip of the screw is substantially flush with an exterior surface of the nozzle.
13. The method of claim 9 , wherein inserting the tip of the screw into the nozzle opening comprises inserting the tip of the screw through the nozzle opening such that the tip of the screw seals the nozzle opening along the entire axial length of the nozzle opening.
14. The method of claim 9 , wherein inserting the tip of the screw into the nozzle opening comprises sealingly engaging the tip of the screw with the nozzle along the entire axial length of the nozzle opening.
15. The method of claim 9 , further comprising sealingly engaging an interior surface of the nozzle with a portion of the screw located rearward of the tip of the screw.
16. The method of claim 15 , wherein the portion of the screw extends outward from the tip of the screw.
17. The method of claim 15 , wherein the tip of the screw has a smaller axial length than the portion of the screw.
18. A method of molding a part, comprising:
rotating a screw within a barrel to pump a molten material through a cylindrical nozzle opening of a nozzle into a mold cavity; and
after pumping the molten material through the nozzle opening, inserting a cylindrical tip of the screw corresponding in geometry to the nozzle opening into the nozzle opening along an entire axial length of the nozzle opening to displace all of the molten material from the nozzle opening, the cylindrical tip portion defining a distal end of the screw, wherein the cylindrical tip portion rotates with the screw, and wherein the cylindrical tip portion comprises a consistent circular cross-section extending along a longitudinal axis of the screw.
19. The method of claim 18 , wherein the tip of the screw is spaced apart from the nozzle opening while rotating the screw within the barrel to pump the molten material around the tip of the screw, through the nozzle opening, and into the mold cavity.
20. The method of claim 18 , wherein inserting the tip of the screw into the nozzle opening comprises inserting the tip of the screw into the nozzle opening until the tip of the screw is substantially flush with an exterior surface of the nozzle.