The Molding Cycle, continued
Now things get a bit more complex. The addition of "cores" allows holes to be created in areas of the mold where it is not possible or practical to have the hole as part of the cavity design. The core pin is extended into the cavity under pressure to create a hole in the part. If you look closely, the core pin is represented in the animation by the small red rectangle at the top of the mold.
1. The mold closes, with the guide pins aligning the sliders and pulling them
tight to the "protrusion" (for lack of a better term) and builds pressure to
keep it closed.
2. The plastic is injected into the mold under high pressure (up to 1000psi) to form the part to the cavity.
3. The core pin(s) extends into the mold cavity, forming a "plug" to keep plastic from being injected into that area - leaving a hole in the finished part
4. The mold stays closed while the injection unit refills, also allowing time for the part to cure.
5. The core pin retracts to keep it from damaging the mold cavity, breaking the pin and various other really bad things that doo happen from time to time.
6. As the mold opens, the sliders move away from the "protrusion" on the stationary half of the mold. They are spring loaded to move to this position, with the guide pins to pull them in tight to form the shapes needed. The mold opens fully, with the part staying on one half of the mold. The protrusion on the stationary side is set up as a group of wedges, allowing it to collapse upon extension of the ejectors.
7. When the mold opens, the ejector pins come forward to push the part off of the mold face.
8. The ejector pins retract, and it all starts again.
Again, this is a highly simplified explanation of the process.