Runner & Sprue Components

Locating rings, C-type sprue bushings and hardened runner puller pins — the parts that carry melt from the machine nozzle into the mold and hold the mold on centre while it does it.

Locating rings

A locating ring registers the mold to the machine platen and positions the sprue bushing under the nozzle. It is specified by outside diameter – bore × thickness: the outside diameter must match the locating hole in your platen, the bore clears the sprue bushing, and the thickness sets how far the ring stands proud.

One thing that catches people out on a replacement: if the old ring is worn, measure the platen hole rather than the old ring. A ring that matches a worn ring locates the mold to the wear, not to the centre. An off-centre mold shows up as an off-centre sprue and drool at the nozzle seat — and the nozzle usually gets blamed for it.

Sprue bushings and the nozzle interface

The machine nozzle's spherical nose seats against the concave seat in the sprue bushing, and that contact is what seals the melt path under clamp pressure. Two dimensions decide whether it seals:

• Matching seat radii. The nozzle SR and the bushing SR should share the same nominal, with the nozzle very slightly the smaller radius so it seats on a line contact rather than on the rim.
• Concentricity of the bore to the sphere. If the melt channel is off-centre relative to the spherical seat, the contact cannot be even all the way round. Under pressure you get a crescent-shaped gap and melt creeps into it — which is drool, sprue flash, and a sprue that will not release cleanly. Changing the orifice size does not fix it.

If you are quoting a replacement bushing or nozzle from a measured sample, add one line to the drawing for concentricity of the bore to the spherical seat. A caliper records diameters faithfully and records no relationships at all, which is why measured-sample parts check good on every dimension and still leak.

Runner and sprue puller pins

Hardened puller pins with Z-type, undercut, ball or drawing-defined end geometry. The end form has to match how your runner releases — tell us the runner layout or send a photo of the existing pin.

For a quotation

• Machine make and tonnage, or the mold standard you work to
• Locating ring: platen hole diameter, bore, thickness, bolt-circle and register
• Sprue bushing: seat radius, bore, taper, head and overall dimensions
• Material, hardness, tolerance, quantity and destination

The nozzle, locating ring and mold interface have to be checked as one assembly. A brand or type reference alone does not confirm fit.