Correct design of the hot runner plates is important to molding success. The hot runner plates must perform the job of firm and stable support while being exposed to high mechanical loadings from both the hot runner components and the molding machine. Hot runner plates encompass a backing plate and manifold plate that when affixed together create the structural shell of the hot runner system.

The manifold plate has 3 key functions – support & line up the hot runner components, offer a surface area for backing plate bolting, and back up the cavity plates and their components. Manifold plate design needs to consider these 3 important functions for effective operation.

Hot runner systems employ thermal expansion to develop a sealing force between components. The sealing force is formed when the bond between the backing and manifold plate repels, yielding to the thermal expansion of the manifold components. The sealing force needs to be adequate to stop plastic leakage at utmost machine pressures and can surpass 12,000 lbf for each nozzle. Moreover, hot runners for high cavitation molds use cross manifolds, which can add as much as 80,000 lbf to the forces working to separate the plates.

Clamp tonnage & forces from the machine nozzle also act on the hot runner plates and need to be considered when designing the plates. Clamp tonnage is transferred via the hot runner plates to the parting line. The hot runner plates must both safeguard the internal manifold components from the cyclical forces of clamp tonnage and repel refraction that can wear the mold components. Furthermore, other forces acting on the manifold include the machine nozzle & the plastic pressure – both of which act alongside the sealing force to separate the backing and manifold plate.

The hot runner plates must encompass cooling lines to decrease wear and even out the plate temperature. Correct cooling in the hot runner plates prevents the transfer of the heat to the mold or the machine platens.

Hot runner plates play a pivotal role in the performance of the mold. Alongside supporting the hot runner components, the hot runner plates can have an impact on the lifespan of the mold and molded product’s quality. Awfully designed plates can prompt worn slides, damaged cores, and eventually higher costs to keep the mold in a functional state. It’s critical to the mold designer & processor to comprehend the purpose of the hot runner plates and the design options that need to be taken into consideration.

Need help with Runner Plates Refurbishment? Feel free to get in touch with Canadian Babbitt Bearings.