There are two types of plastic injection molding progresses, including cold runner and hot runner systems. The cold runner is the traditional system, while the hot runner is the recent system.
The difference between cold and hot runners is the runner (channel) connecting the melted plastic generator and the cavity. In cold runner, this channel is as a part of the cavity, so the finished plastic unit includes the part cooling and solidfying in the channel. This channel part will be broken from the final product and be discarded. In hot runner, this channel is as a part or extension of the melted plastic generator. This channel is wrapped by thermal insulation material or additional heator to keep the plastic melted status when goes through this channel. The finished product doesn’t contact the additional part.
| Cold Runner | Hot Runner | |
| Mold cost | cheap | expensive |
| Operation and maintenance | easy | more complicated |
| Space occpuied | small | big |
| Cycle time (production pace) | slow | fast |
| Raw material wasting | waste some | doesn’t waste |
| Theromal sensistivity of materials | less limit | more limit |
| When use this runner | small quantity of products or don’t have much experience | big quantity of products and have much experience |
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