Insulated runner

A recent development of the insulated runner principle is the distribution tube system. This overcomes the possibility of freezing-off by insertion of heated tubes into the runners. However, this system still relies on a thick layer of polymer forming an insulation layer on the wall of the runner and so this system is not suitable for heat sensitive materials. 

Note that both the insulated runner and the distribution tube systems rely on a cartridge heater in the gate area to prevent premature freezing off at the gate (see Fig. 4.40). 

Fig. 2-7b. Types of injection molds illustrated here are insulated runner, hot manifold, and stacked (1).

An example of a hot-runner mould an insulated runner mould with heated probes (after Modern Plastics Encyclopedia). 

These materials have been successfully molded in all types of mold, for example, 2-plate, 3-plate, insulated runner, stack and hot runner, en using the hot manifold type of runnerless mold, the runner channel must be streamlined so that there are no dead spots (nil flow areas) which are likely to cause degradation accurate temperature control of the manifold is essential. To maintain the sparkling clarity of this material, use vacuum smelted steel as this can take a very high polish and is non-porous. 

Hot-runner mold (insulated-runner mold) n. An injection mold for thermoplastics in which the runners and sometimes the secondary sprues are insulated from the chilled cavity plate so that they remain hot during the entire cycle. The plastic in the runners remains molten and is not ejected with the molded part, thus avoiding the normal handling, grinding, and reprocessing of sprues and runners. 

Figure 5.67 Molds (a) two plate, (b) three plate, (c) stack, (d) insulated runner, and (e) hot runner,...

Molds are also classified by their runner systems. In a cold-runner mold, the sprue and runner solidify and are ejected with the part. Insulated runners have much larger diameters than standard runners. As a result, the outer part of the runner solidifies while the center remains fluid. This reduces the scrap generated during molding and facilitates the changing of materials or colors. Insulated-runner molds are more difficult to operate because the gate tends to freeze off. With hot-runner molds, the runner is always in the melt state. 

The runner systems can be operated in either an insulated or heated mode. Insulated runner systems are preferred for larger objects, whereas heated systems are used to attain more rapid cycles. 

Standard U 3 Plate Stripper Hot Runner D insulated Runner r Other (Specify ... 

Gating nozzles, hot-runners and insulated runner molds, nozzle manifolds, and valve gating nozzles are used for obtaining sprueless moldings. Elimination of the sprue and runner system reduces costs through scrap and labor savings. 

In the insulated runner mold no heat is added to the runner. The outer circumference of the run-... 

In this type of insulated runner mold design, the runner plate and cavity plate are bolted together and are only opened to remove the solidified runner after breaks in the molding cycle or to remove fireeze-ups. 

Figure 7-6. Runnerless Mold in Which No Additional Heat Is Supplied to Runner (Wide diameter insulated runner allows the outer circumference of the melt to solidify against runner walls while the central core remains molten in preparation for the next shot.f...

Figure 7-7. Heated Probes Added at Gate of Runnerless Mold Which Also Uses an Insulated Runner (Referred to as runnerless since no scrap runner is produced with part) ...

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