This requires rather shallow broad threads similar to those on a lamp bulb. Then make sure that the part can expand (for a female thread) or contract (for a male thread). Then make the mold and try it. Tinker with the design until it works.
What about the processing conditions? I heard that the cycle time must be very short, lower than 6 seconds. At which themperature is possible to eject the part? And how is with shrinkage, warpage and visible marks on the part.
tomysux,
It's hard to make a call without seeing the geometry of the part. PP and PE are good materials for 'bumping off' threads but a lot of the mechanics in doing it is down to the design of the mold. When you have the design right obviously you can play around with variables like cycle time and temperature.