Page 447 - Injection Molding Advanced Troubleshooting Guide
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44.3 Stringers Troubleshooting 447
Figure 44.3 Thin thermocouple used for probing inside a hot drop
44.3.2.2 Mold: Tip-Bearing Surface
The amount of contact that the hot tip has with the mold is called bearing surface.
This contact between the mold and tip will impact the temperature of the hot tip. If
there is not enough bearing surface contact with the mold the tip will run hot and
result in drool or stringers. Too much bearing surface contact can lead to excessive
freeze off of the tip so bearing surface is very important to consider when trouble-
shooting hot tip related problems. Also keep in mind with valve gates that the only
cooling that the valve pin will experience is when it is in the closed position con-
tacting the bearing surface at the shut off with the tip.
