Transfer Molding process involves the following steps:
• A pre-weighed amount of a polymer mixed with additives and fillers (charge) is placed into the transfer pot.
The charge may be in form of powders, pellets, putty-like masses or pre-formed blanks.
The charge is heated in the pot where the polymer softens.
• The plunger, mounted on the top plate, moves downwards, pressing on the polymer charge and forcing it to fill the mold cavity through the sprue.
The mold, equipped with a heating system, provides curing (cross-linking) of the polymer (if thermoset is processed).
• The mold is opened and the part is removed from it by means of the ejector pin.
If thermosetting resin is molded, the mold may be open in hot state – cured thermosets maintain their shape and dimensions even in hot state.
If thermoplastic is molded, the mold and the molded part are cooled down before opening.
• The scrap left on the pot bottom (cull), in the sprue and in the channels is removed. Scrap of thermosetting polymers is not recyclable.