In this chapter, you will learn about how a mold actually moves with animated graphics. See “Parts Role – Undercut Process” for details on an important point (slide core and loose core) in each step.
Opening Mold (Start) . . . . Mold closed
Molten plastics fills the mold, and when cooling and solidification is complete, the mold, which is closed under high pressure, gradually starts to open.
If there is an undercut on the part at this point, it will be processed at the same time. This is done by an angular pin and a slide core, which requires the following correlation between the angled pin and the slide core.
If the tilt angle of slide core α is not greater than that of angular pin β then they may interfere with each other when opening/clamping mold.
The value should be : α=β+ clearance angle (clearance angle = 2 to 5, however, b 20)
Opening Mold (Complete) . . . . Mold fully opened
After the angular pin comes off completely from slide core, the mold opens quickly. The slide core must be completely off of the undercut part at this point.
Ejecting Part (Start) . . . Ejector plate ascending
The ejector plate lifts up the ejector pin and the loose core by the ejection of the molding device, and the part is gradually coming off. Be extremely cautious to check that there are no ribs and bosses in the direction that the loose core moves (the space for stroke). This is because the loose core can not be moved to the inside of the ribs or bosses.
Ejecting part (Complete) . . . Ejector plate fully up
When the ejector plate is completely up, the loose core must move to the inside where the part can be removed. Be cautious about the following point when processing undercut using an loose core.
If the loose core has not moved to the inside where the part can be removed, the part will not be removed.
B : Value for undercut
The value should be : A =B + (3 to 5) m/m
Also, if the ejecting stroke of the part is h, the tilt angle slide rod a@ should be:
α=(A/h)tan-1
Be cautious not to let loose core slides interfere with each other when a loose core is completely pushed out.
