Clay,
It can be accomplished through ultrasonic welding. Ultra sonic welding is common in the plastics industry, however, it dose require a U/S welding unit. The unit vibrates at a high frequency producing heat below the surface of the parts causing the two to melt together with out distorting the outer surfaces. Pretty cool but normally not practical aside from long run projects.
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We are the pilgrims masters; we shall go, always, a little farther.