Cold runner: It is the part between the mold entrance and the gate.Plastic is kept flowing by injection pressure and its own heat in the runner, which is part of the forming material but not belongs to the product part.So when we design the mold, we should consider the filling effect and how to save material by shortening and narrowing the flow passage. Ideally, this is the case, but in practice, it is difficult to achieve the best of both.
Hot runner: as a common part of injection molding system, it is used to ensure that the plastic in the runner and sprue remains molten by heating.Since there are heating rods and heating rings near or in the center of the runner, the whole runner from the nozzle outlet of the injection molding machine to the gate is in a high temperature state, so that the plastic in the runner remains molten. After shutdown, it is generally not necessary to open the runner to take out the condensate. When starting up, it is only necessary to heat the runner to the required temperature.Therefore, the hot runner process as a hot collector system, or as channel-free molding.
Hot runner --High cost but saving product material cost. Suit for high productivity product
Cold runner --Lower cost but waste of raw materials , suit for some low-productivity product