Nozzle Tip

The nozzle is the tip at the front of the barrel that connects the injection unit to the mold and channels the melt into the mold's sprue bushing, keeping it molten on the way through. It is the last metal the plastic touches before the sprue. ## Types of nozzle - General-purpose (open / free-flow): a simple open bore — most common, lowest pressure drop. - Reverse-taper: tapers so the cooled slug pulls back with the sprue; helps stringing on some resins. - Shut-off / valve nozzle: a mechanical or spring valve closes the bore to stop drooling, needed for free-flowing resins (PA, PP) or when the nozzle pulls away between shots. ## How it seats and heats The nozzle tip has a spherical nozzle tip radius and an orifice that must match the sprue bushing for a leak-tight seal. The nozzle has its own heater band, controlled as the nozzle temperature zone, because it is a small thermal mass touching the cool mold each cycle. ## Common problems - Drooling / stringing: nozzle too hot or no shut-off. - Freeze-off / cold slug: nozzle too cold — short shots and a plugged tip. - Flash or leak at the interface: wrong radius or orifice match with the sprue bushing. ## Related terms - See also: injection unit, barrel, sprue, nozzle tip, nozzle temperature ## What is the nozzle in injection molding? It is the tip at the front of the barrel that delivers the melt from the injection unit into the mold's sprue, with its own heater band to keep the plastic molten. ## What are the types of injection nozzles? General-purpose (open), reverse-taper, and shut-off (valve) nozzles, chosen by resin flow behaviour and whether drooling must be prevented. ## Why does a nozzle drool? Because it is too hot or has no shut-off valve, so low-viscosity melt seeps out between shots; a shut-off nozzle or lower nozzle temperature stops it.

A nozzle adapter is the threaded component that joins the nozzle to the front of the barrel (or, on some designs, extends/adapts the nozzle to reach the mold's sprue bushing). It carries the melt from the injection unit to the mold, sealing the flow path so plastic injects cleanly without leaking or the nozzle detaching under pressure. ## What it does - Connects & seals: threads the nozzle body onto the barrel end (or links nozzle to tip/extension), giving a leak-tight, high-pressure joint. - Adapts geometry: lets a standard barrel run different nozzle lengths, radii or tip styles, and lets the nozzle match the mold's sprue bushing seat. - Carries heat: usually heated as part of the nozzle zone (see nozzle heat band) so the melt stays molten through the adapter; its bore should match the flow to avoid dead spots. ## Why it matters - Leak & blow-back prevention: a poorly fitted or worn adapter lets melt escape at the barrel/nozzle joint — a safety hazard and scrap source. - Melt integrity: a smooth, correctly sized bore avoids hang-up, degradation and color/melt streaks; a mismatched seat to the sprue causes drool, cold slugs or flash at the sprue. - Serviceability: the adapter is a wear/maintenance point that lets the nozzle, nozzle tip or nozzle tip orifice be changed without replacing the whole barrel front. ## Practical notes Match the adapter's radius and orifice to the mold's sprue bushing, keep threads and sealing faces clean, and torque to spec — the joint sees full nozzle temperature and injection pressure every shot. ## Related terms - See also: nozzle, barrel, injection unit, nozzle tip, sprue ## What is a nozzle adapter in injection molding? The threaded part that connects the nozzle to the barrel (or extends it to the mold), carrying the melt from the injection unit to the sprue with a leak-tight, high-pressure seal. ## Why is the nozzle adapter important? It prevents melt leakage and blow-back at the barrel/nozzle joint, keeps the melt flowing without dead spots, matches the nozzle to the mold's sprue, and lets nozzle parts be serviced without changing the whole barrel. ## How do you prevent leaks at the nozzle adapter? Match the seat and bore to the sprue bushing, keep threads and sealing faces clean and undamaged, replace worn adapters, and torque to specification, since the joint sees full nozzle temperature and injection pressure each shot.

The nozzle tip orifice is the small hole through the nozzle tip that the melt passes through on its way from the nozzle into the mold's sprue. It is the final, narrowest restriction in the injection unit before the plastic enters the tool — so its diameter directly shapes flow, pressure and several common defects. ## Why its size matters - Smaller than the sprue: the orifice must be smaller than the mold's sprue-bushing orifice (and the tip radius slightly smaller than the sprue radius) so the tip seats and seals cleanly — otherwise melt leaks around the seat or the cold sprue can't pull free. - Flow & pressure: a smaller orifice raises shear and pressure drop (more shear heat, can help mixing) but can choke fill on big shots; a larger orifice eases flow but risks drool and slower freeze-off. - Freeze-off & drool: the orifice is often where the melt freezes between shots; sized and temperature-controlled wrong, it gives cold slugs, melt stringing or drooling. ## Selecting it Match the orifice to the shot size and resin: large enough to fill without excessive injection pressure or injection speed, small enough to seal against the sprue and control drool. It is a wear point and a quick service item on the nozzle tip/nozzle adapter — orifices erode and round over time, shifting the process. ## Related terms - See also: nozzle tip, nozzle, sprue, nozzle adapter, melt ## What is the nozzle tip orifice in injection molding? The small hole in the nozzle tip through which molten plastic flows from the nozzle into the mold's sprue; it is the last flow restriction before the mold and must be smaller than the sprue orifice to seal. ## Why must the nozzle orifice be smaller than the sprue? So the tip seats and seals against the sprue bushing without melt leaking around the joint, and so the solidified sprue pulls free cleanly on mold opening; a too-large orifice causes leaks and sprue-sticking. ## How does nozzle tip orifice size affect molding? A smaller orifice raises shear, pressure drop and heat but can restrict fill; a larger one eases flow but risks drool and slow freeze-off — so it is sized to the shot and resin to balance fill, sealing and stringing.

The nozzle tip radius is the spherical radius machined on the end of the machine nozzle. It must match the concave radius of the sprue bushing in the mold so the two seat together leak-tight when the nozzle contacts the mold. ## Standard radii The two most common (SPI) standards are 1/2″ (12.7 mm) and 3/4″ (19.05 mm). The nozzle radius and the sprue-bushing radius must belong to the same family — a 1/2″ nozzle does not seal in a 3/4″ bushing. ## The matching rule Two classic rules keep the interface tight: - Radius: the nozzle tip radius should be about 1/16″ (1.5 mm) smaller than the sprue-bushing seat radius, so contact happens on the inner ring and seals fully. - Orifice: the nozzle orifice should be about 0.5–1 mm smaller than the sprue-bushing entry hole, so the cooled sprue pulls cleanly without an undercut. ## Why it matters A mismatch leaves a gap at the interface: material drools or flashes there, the sprue sticks, cold slugs form, and you lose the thermal seal. Correct radius matching is part of basic nozzle-to-mold setup and prevents a whole class of sprue defects. ## What radius should the nozzle tip be? Match it to the mold: use the same standard family (1/2″ or 3/4″) as the sprue bushing, with the nozzle radius about 1/16″ (1.5 mm) smaller than the bushing seat radius for a tight seal. ## How do you match the nozzle to the sprue bushing? Keep the radius about 1.5 mm smaller and the nozzle orifice about 0.5–1 mm smaller than the sprue bushing. This seals the contact and lets the sprue release without an undercut.

Sprue is the main channel of the mold that receives molten plastic directly from the machine nozzle and conducts it to the runner (or directly to the cavity in single-cavity molds). In cold-runner molds it is the first piece of scrap generated each cycle. ## Sprue geometry - Conical shape with 2 – 4° per side (4 – 8° included) for clean ejection - Entry radius equal to or larger than the nozzle radius - Entry diameter: 2 – 6 mm depending on part - Exit diameter: 4 – 12 mm - Length: as short as possible, typically 30 – 80 mm ## Mold types - Standard sprue bushing: hardened-steel insert (H13, P20) bolted to the plate - Hot sprue: heated, eliminating the scrap cone - Direct gate: sprue feeds directly into the cavity, no runner (single cavity) - Cold sprue eliminator: hybrid with extended nozzle ## Sprue extraction In cold-runner molds the sprue must come out with the runner via: - Sprue puller (Z-pin, reverse-taper retention) - Robot with cutter - Gravity drop if mold geometry allows ## Common issues Sprue sticking to the nozzle (insufficient radius or draft), drooling at open, gating of the cone to the stripper plate, and premature wear of the sprue bushing with glass-fiber-reinforced resins.