Its function is to act as a thermal barrier between the hot nozzle and the relatively cool sprue bushing
In addition, the sprue bushing
inherits dimensional information from the cavity layout.
This solidification is a result of heat being sucked out of the nozzle tip due to surface contact with the cold sprue bushing
When switching from one injection unit to the other, the carriage is unlocked and manually moved to the side, aligning the desired injection unit with the sprue bushing
For example, in the back of a zinc die casting die is a bushing called the sprue bushing
with a female radius on it.
It is typically located directly opposite the shank end of the sprue bushing
and its purpose is, as the name implies, to pull the molded sprue out of its bushing.
The assembly permits perfect radius alignment between the sprue bushing
and nozzle tip while compensating for misalignment up to .
This month we will focus on identifying and dealing with sprue bushing
issues out on the production floor.
But that doesn't mean cooling the sprue bushing
isn't critical, because it is.
That's often the extent of the consideration given to the sprue bushing
during the mold-design phase.
In addition, there can be a problem in cold runners, where you want the tip at melt temperature but it conducts heat to the sprue bushing
of a cold mold, so plastic freezes in the nozzle-tip orifice.
Caption: Shown above is a damaged sprue bushing
seat caused by misalignment.