Page 31 - Plastics News December 2021

FEATURE

Method D lead-in diameter is reduced. This is also one of the best designs for extremely
Method D is what I call a double-piloted an inexpensive method of forming a long-running molds with tight-tolerance
core pin. As the mold closes, the smaller- through hole. The advantage to this through holes.
diameter tip of the pin enters a mating method is that if the through hole in Venting and Cleanout
through hole in the cavity. The clearance the cavity begins to wear, the chance of
between this portion of the pin and the down-flash is minimal due to the step The hole in the cavity that the core pin
through hole is typically 0.0005 in. per on the core pin, which shuts off on engages should not be blind. It should be
side. Once engaged, the full pin diameter the face of the cavity. The downside of machined all the way through the cavity
then enters a counter-bored hole in the this method is basically the same as the insert or A-Plate. In fact, it is best if the
cavity, which typically has 0.0010 in. of downside of Method A. The core pin can through hole tapers outward or otherwise
clearance per side—or less depending make a slight impression in the cavity as increases in diameter after a sufficient
on the recommended vent depth for the the plates start to flatten over time, or it amount of land length. Everything from
molding material. This double-pilot or can generate side flash if the injection dirt, sub-gate flakes and flash to grease
prealignment method helps protect the pressure opens the parting line a little. and other debris will eventually fill up
larger hole from damage and wear. the hole. That can cause a pin to stick,
Method F compress, bend, buckle, or possibly
Method E Method F is a combination of the break.
Method E is similar to the single-piloted spring-loaded Method B, and the stepped
core pin in Method C, except that the diameter of Method E. This is probably

30 PLASTICS NEWS DECEMBER 2021 31 PLASTICS NEWS DECEMBER 2021