Large Diameter, Threaded Workpieces

The large diameter workpieces are fairly flexible while hot, hence they can be pulled of the thread-forming core by a simple plate as show in Fig.6.66.

If the diameter of the workpiece is fairly large(60-100mm), it can be pulled off the core forming the extemal or intemal thread without unscrewing, if the height of the thread is not greater than 1.5% of the diameter(or, in the case of polyamide max. 20%), and if the thread is round(profile is semi-circular). In this case-as shown in the section drawing(Fig. 6.66)the mold is designed with a simple stripper plate, so that it pulls the piece ott the core when the mold is opened.

A circular ring was designed around the mouth of the workpiece(cup of vacuum flask through which the material flows into the cavity, otherwise the material solidifies before it fills the cavity because of the thin wall of the workpiece and the extemal-intemal cooling used for the short cycle time. A 0.3-0.4 mm thick gap comesponding to the size of the gate exists between the circularring and the workpiece. This partly facilitates separation of the ring from the workpiece, and partly, due to the heat generated by the high velocity, the material is heated up directly before the inflow and thereby it helps to fill out the cavity

ate he design of the telescopic stroke limiting screw is interesting, because it enabled the height mold to be considerably reduced.

Eight pieces of uniformly distributed 3 mmx002 mm vent grooves were used by the Jacket of the eight inserts forming the lower part of the workpiece the air

The formation and size of the nest for the sealing ring(O-ring) used on the jacket of cup 18 require special care. If the groove is too narrow the rings are sheared off, but if it is too wide the sealing is imperfect.

The mold is highly productive, safe and its production is simple