Hot Runner System with Composite Nozzle Tip

1 . A hot runner assembly for an injection molding assembly, the hot runner assembly comprising:

an injection unit adapted to contain a flowable material;

a manifold having a first segment of a melt channel formed therein, the melt channel in fluid communication with the injection unit;

a nozzle assembly connected to the manifold in fluid communication with the melt channel, the nozzle assembly comprising:

a nozzle housing having a second segment of the melt channel extending therethrough;

a nozzle tip comprising a body having a bore extending therethrough and an outlet opening therein, the bore having a third segment of the melt channel extending therethrough and the outlet opening in fluid communication with the melt channel, the body formed of materials comprising a precipitation hardened, high thermal conductivity material and a precipitation hardened, high strength material, wherein:

the high thermal conductivity material and the high strength material are integrally joined together to form the body,

the thermal conductivity of the high thermal conductivity material is greater than the thermal conductivity of the high strength material,

at least one strength aspect of the high strength material has a value greater than the corresponding value of the same strength aspect of the high thermal conductivity material, and

the high thermal conductivity material in an unhardened condition and the high strength material in an unhardened condition are precipitation hardenable together under the same precipitation hardening conditions to achieve:

an increase in the value of at least one strength aspect of the high thermal conductivity material relative to the unhardened condition, and

an increase in the value of at least one strength aspect of the high strength material relative to the unhardened condition, and

a retainer that retains the nozzle tip against the nozzle housing such that the bore communicates with the melt channel; and

a mold cavity in fluid communication with the outlet opening, wherein the hot runner assembly is adapted to allow the flowable material to flow from the injection unit into the mold cavity.

2 . The hot runner assembly of claim 1 , wherein the high thermal conductivity material and the high strength material can be precipitation hardened together at 450° C. to achieve at least a 96% increase in at least one strength aspect of the high-strength material within three hours.

3 . The hot runner assembly of claim 1 , wherein the high thermal conductivity material has a thermal conductivity of at least approximately 80 W m −1 K −1 .

4 . The hot runner assembly of claim 1 , wherein the high thermal conductivity material is a copper alloy.

5 . The hot runner assembly of claim 4 , wherein the high thermal conductivity material is a beryllium-copper alloy.

6 . The hot runner assembly of claim 5 , wherein the high thermal conductivity material contains approximately 0.2-0.6% Be and 1.4-2.2% Ni, with balance Cu.

7 . The hot runner assembly of claim 1 , wherein the precipitation hardened high strength material has an ultimate tensile strength of at least approximately 2000 MPa, a yield strength of at least approximately 1950 MPa, or an endurance limit fatigue strength of at least approximately 850 MPa.

8 . The hot runner assembly of claim 1 , wherein the high strength material is an iron alloy.

9 . The hot runner assembly of claim 8 , wherein the high strength material is a maraging steel.

10 . The hot runner assembly of claim 9 , wherein the high strength material contains approximately 18.5% Ni, 7.5-12.0% Co, and 3.25-4.8% Mo, with balance Fe.

11 . The hot runner assembly of claim 1 , wherein the high thermal conductivity material and the high strength material can be precipitation hardened together under the same precipitation hardening conditions to achieve at least a 96% increase in at least one strength aspect of the high strength material within six hours.

12 . The hot runner assembly of claim 1 , wherein the high thermal conductivity material and the high-strength material are integrally joined together by welding.

13 . The hot runner assembly of claim 1 , wherein the body of the nozzle tip further comprises a flange, and the retainer engages the flange to retain the nozzle tip against the nozzle housing.

14 . The hot runner assembly of claim 13 , wherein the high thermal conductivity material forms the entire bore and the high strength material forms at least a portion of the flange.

15 . The hot runner assembly of claim 1 , wherein the precipitation hardening conditions comprise an aging temperature in the range of from 315° C. to 540° C.

16 . The hot runner assembly of claim 15 , wherein the aging temperature is in the range of from 425° C. to 510° C.

17 . The hot runner assembly of claim 16 , wherein the aging temperature is approximately 450° C.

18 . The hot runner assembly of claim 1 , wherein the at least one strength aspect of the high strength material and the at least one strength aspect of the high thermal conductivity material each comprise at least one of ultimate tensile strength, yield strength, and endurance limit fatigue strength.

19 . The hot runner assembly of claim 1 , wherein the at least one strength aspect of the high strength material and the at least one strength aspect of the high thermal conductivity material each comprise ultimate tensile strength, yield strength, and endurance limit fatigue strength.

20 . The hot runner assembly of claim 1 , wherein the at least one strength aspect of the high strength material and the at least one strength aspect of the high thermal conductivity material each comprise ultimate tensile strength.

21 . The hot runner assembly of claim 1 , wherein the at least one strength aspect of the high strength material and the at least one strength aspect of the high thermal conductivity material each comprise yield strength.

22 . The hot runner assembly of claim 1 , wherein the at least one strength aspect of the high strength material and the at least one strength aspect of the high thermal conductivity material each comprise endurance limit fatigue strength.