Transfer-molding cull

Figure 2.3 shows the molding cycle of pot-type transfer molding, and Figure 2.4 shows plunger-type transfer molding (sometime called auxiliary raw transfer molding). The taper of the sprue is pot-type transfer is such that, when the mold is opened, the sprue remains attached to the disc of material left in the pot, known as cull, and is thus pulled away from the molded part, whereas the latter is lifted out of the cavity by the ejector pins (Figure 2.3c). In plunger-type transfer molding, on the other hand, the cull and the sprue remains with the molded piece when the mold is opened (Figure 2.4c).

FIGURE 2.3 Molding cycle of a pot-type transfer mold, (a) Molding compound is placed in the transfer pot and then (b) forced under pressure when hot through an orifice and into a closed mold, (c) When the mold opens, the sprue remains with the cull in the pot, and the molded part is lifted out of the cavity by ejector pins. (After Frados, J. ed. 1976. Plastics Engineering Handbook, 4th Ed., Van Nostrand Reinhold, New York.)... 

FIGURE 1.4 Molding qrcle of a plunger-type transfer mold, (a) An auxiliary ram exerts pressure on the heat-softened material in the pot and (b) forces it into the mold, (c) When the mold is opened, the cull and sprue remain with the molded piece. (After Vaill, E.W. September 1962. Mod. Plastics, 40, lA, Encycl. Issue, 767.)... 

Cull kol [ME, fr. ME cuillir, fr. L colligere to bind together] (13c) n. (1) A rejected material or product. (2) In transfer molding, the material remaining in the transfer pot after the mold has been filled. A certain amount of cull is usually necessary for the operator to be confident that the cavity has been properly filled. 

Shot weight (shot) n. In injection and transfer molding, the entire mass of plastic delivered in one complete filling of the mold, including the molded parts, sprue, runners, cull, and flash. 

Figure 6.12 Transfer molding sequence (a) the mold is closed and material is placed in the pot (b) the plunger descends into the pot, causing material to melt and flow through runners into cavities (c) after cure, the press opens, the plunger retracts, and the parts are ejected with cull and runners.

At the end of the cycle, when the mold is opened, the remaining polymer solidifies into a disk shape cull). It is removed as a single piece along with the sprue. The part is removed by lifting the middle section of the mold followed by ejection pin action. In the transfer molding method, it is desirable to keep the sprue and the cull attached, contrary to injection molding. 

Cull Remaining material in the transfer vessel after the mold has been... 

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