Cold runner manifold

Three different types of cold runner manifolds (chosen depending on the application) can be differentiated ... 

FIGURE 1,252 Flash-free product (bellows) that was manufactured with a cold runner manifold... 

FIGURE 8.22 Nonoptimized (left) VS. optimized (right) cold runner manifold (graphics courtesy of PLEXPERT)... 

Function. Central nozzles and manifold nozzles differ only in that the former are designed to interact directly with the injection machine nozzle. Both a central and a manifold nozzle may be in the form of a hot sprue bushing leaving a small sprue and intended mainly for gating to a cold runner. 

Tooling. Tooling is relatively expensive for injection molds. Production molds are normally machined and burned (electro-discharge machined) from tool steels (P20) and must be sfructured to withstand high pressures. Precision is required to incorporate cooling lines, ejector pins, and cavity pressure transducers or temperature monitoring sensors. The use of hot runner manifolds adds further complexity and cost, but may be justified because cold runners and their associated costs are eliminated in manufacturing. 

The total costs can be reduced due to a change in the cross-section of cold-runner nozzle manifolds. The smaller the diameter, the less material is left over for postmolding disposal or granulation. 

This is similar in concept to the hot runner mould system. In this case, instead of having a specially heated manifold in the mould, large runners (13-25 mm diameter) are used. The relatively cold mould causes a frozen skin to form in... 

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