Injection Molding Nozzle Assembly with Composite Nozzle Tip

Abstract

A nozzle assembly for an injection molding assembly has a nozzle housing having a melt channel extending therethrough, a nozzle tip, and a retainer that retains the nozzle tip against the nozzle housing. The nozzle tip is formed of a precipitation hardened, high thermal conductivity material and a precipitation hardened, high strength material, which 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, and the strength of the high strength material is greater than the strength of the high thermal conductivity material. The high thermal conductivity material and the high strength material can be precipitation hardened together under the same precipitation hardening conditions to achieve increases in the value of at least one strength aspect of the high thermal conductivity material and the value of at least one strength aspect of the high strength material.

Description

TECHNICAL FIELD[0001]The invention relates, generally, to injection molding systems, and more particularly, but not exclusively, to hot runner components and injection molding systems comprising such components, particularly nozzle assemblies and nozzle tips therefor.BACKGROUND OF THE INVENTION[0002]The state of the art includes various nozzles and tips for hot runner injection molding systems. Hot-runner nozzles are typically either a valve-gate style or a hot-tip style. In the valve-gate style, a separate stem moves inside the nozzle and tip acting as a valve to selectively start and stop the flow of resin through the nozzle. In the hot-tip style, a small gate area at the end of the tip freezes off to thereby stop the flow of resin through the nozzle.[0003]An injection molding system using a hot-tip style nozzle typically has a cooled mold with a small circular gate opening in which the tip of the nozzle is inserted. The tip is typically conical with a tapered point or other suita...

AI Technical Summary

Benefits of technology

[0015]The present disclosure provides a nozzle assembly having a nozzle housing, a nozzle tip, and a retainer. The nozzle housing has a melt channel extending therethrough. The nozzle tip includes a body having a bore extending therethrough. The body is formed of a precipitation hardened, high thermal conductivity material and a precipitation hardened, high strength material, which 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, and at least one strength aspect of the high strength material has a value greate

Problems solved by technology

Eventually the gate freezes, the mold is opened, and the part is ejected, thereby breaking the small amount of frozen plastic at the gate area.

This is known as a “gate stringing” and is unacceptable because the Waiting a long time for the gate to freeze is also unacceptable because it adds time to the molding cycle, which is desired to be as short as possible to optimize system productivity.

If the tip is not hot enough, the gate may not open and injection will not occur, or the gate will freeze too soon causing poor-quality parts.

If the operating window is narrow, it may be difficult for molds with multiple cavities to consistently make good parts in all cavities because of the many variables associated with the injection molding process.

One batch of resin may run adequately for a given set of processing parameters, but the next batch, having a different flow characteristic, may not produce good parts using exactly the same process settings.

If the nozzle does not provide enough heat at the tip to keep the gate from freezing before the part is fully injected and packed, the part may have voids or other quality problems making it unacceptable.

However, at these high pressures, existing nozzle tips exhibit an unacceptable failure rate.

For example, beryllium-copper alloys are precipitation hardenable, and thus, can provide relatively high strength and wear-resistance, but low fatigue resistance.

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