WIKI': STKAI(!IITENIN(! A\U MOLDlNd FOR KKLAYS 



S79 



MOLDING 



Dies with four cavities are used for all comb molding operations. The 

 cavities are locatfxl around tlie plastic transfer area as ilhist rated in l*'ij>;. 

 15. Aho\-e the transfer area a cyhnchical opening extends \-ei t ic;illy 

 throutih the ujjper die hah" to permit i)assa<i;e of the transfer ram. By 

 closing the die, the transfer area is enclosed e.xcept for small orifices 

 leading to each of the four cavities. The heated preform is dropped into 

 tlie center of the transfer area ahead of the transfer ram. This ram, oper- 

 ated by hydrauHc pressure and heated l\y contact with the hot die, 

 forces or transfers much of the heat softened resin through the orifices 

 and into the che cavities. The resin residues which are left in the pass- 

 ages between the ram and the cavity gates upon completion of the mold- 

 ing cycle are called runners. The heat of the die, approximately 360°F., 

 further softens the plastic resin enabling the pressure of the ram to 

 force it into intimate contact with all die cavity surfaces. Continued 

 application of heat and pressure hardens or cures the resin by the process 

 of polymerization, after which it is permanently infusible. 



To successfully operate on an automatic basis, the cluster of wire, 

 plastic blocks, ram slug, and runners must be removed from the mold- 

 ing cavity. This is complicated in the single wire comb because the 

 plastic block at the contact end of the wires has very thin fin sections 





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k^^P 



I IK- 14 — Anchoring section of automatic die. 



