PURPOSE: To drive and control a continuous filter bonded with the plug by forcing it out of the exit port using the pressure of the thermoplastic material.

CONSTITUTION: The heated thermoplastic material flows into the filter outlet port 18 (but not into the sealed inlet port 16) to bond to the filter 22 for making a plug 44 in cooperation with cooling system 38. The pressure of the thermoplastic material in the filter passage forces the plug out of the exit port 16 into contact with an external stop 28. The stop 28 is moved selectively to the release point and heated by a heater 40 to accommodate melting and exhaust of the plug. The new part of the filter is pulled into the passage 12 through the inlet 16 when the plug is pushed out from the outlet 18.