Cold runner vs Hot runner
Cold Runners Hot Runners ☞ Runners are not heated
☞ Longer cycle time
☞ Creates waste (sprue)
☞ Gate mark big
☞ Secondary operations (removal of cold runners, re-grinding, etc.)
☞ Fewer skills required for setup and operation.☞ Runners are heated
☞ Shorter cycle time
☞ Less wasted plastic
☞ Gate mark small
☞ Higher productivity yield (due to shorter cycle time)
☞ More control over the injection process. Therefore quality improved.
Cold runners
Cold runner molds can be two-plate or three-plate injection molds. Cold runners are not heated up. Therefore after the injection, sprue, runner and gate are cooled with molded parts. In consequence, runners and gates are ejected with molded parts which make the cost can be double or even more. And the cycle time is longer than hot runners, even optimized cold runners still cause typically 50% to 100% longer.
Two Plate vs Three Plate Cold Runner Injection Molds
Two plate injection mold ☞ Sprues, runners, and gates are ejected with the molded component.
Three plate injection mold ☞ Sprues, runners, and gates are automatically separate from injection-molded plastic parts during the opening of the mold.
Hot runners
Hot runner is an assembly of heated components used in a plastic injection mold that inject molten plastic into the cavities of the mold.
Hot runners are complicated systems, they have to maintain the plastic material within them heated uniformly while the rest of the injection mold is being cooled in order to solidify the product quickly.
A hot runner controller is a temperature controller used to control the temperature in the hot runner.
The reason why people use the hot runners more is that systems produce less wasted plastic (sprue), have shorter cycle times, use less energy, and require less manual labor for runner handling, trimming, and regrinding.
