880 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1954 



Fig. 15 — Molding section of automatic die. 



projecting into both halves of the die cavity. These fins, used to guide 

 the mating twin contact wires in the finished relay, must be held to close 

 limits dimensionally and are thin to the point of fragility. To insure 

 satisfactory removal of the resin blocks from the upper half of the die 

 while simultaneously retaining them in place in the lower half when 

 the die is opened, spring loaded ejector pins in the upper die half push 

 down against the cured blocks. The ejector pins operate until the wdre- 

 resin cluster has been ejected from the upper die. Subsequently they are 

 retracted by contact with reset pins which butt against the lower die 

 half when the die is closed. The openings in the die half which accom- 

 modate these ejector pins serve as air vents when the resin is entering 

 the cavity. To prevent the plastic cull, i.e., the resin slug and associated 

 runners, from breaking off and damaging the die on the next molding 

 cycle, the pressure of the transfer ram is maintained on the slug until 

 the upper die surface has been cleared. 



The hydraulic ram bearing the lower die half continues to withdraw 

 until the lower ejector pins can function. These ejector pins are more 

 numerous and more complex in design than those in the upper die half 

 because, in addition to ejecting the resin blocks from the die cavities, 



