The gun melts welding rod or pellets in a small extruder, preheats the sheet with a hot-air nozzle and pushes out a bead through a shaped shoe. Barrel and preheat temperatures are set on a trial weld, and the gun is purged before each weld so degraded material does not end up in the seam. Running the gun cleanly around a vertical pipe boot is the mark of an experienced seamer.
Gun wasn't purged, the first six inches of bead are brown, cut it out and start again.
Also heard as
- extruder
- extrusion gun
- hand extruder
Related terms
Extrusion weld
Geomembrane seam made by laying a bead of molten polymer along the edge of an overlap, used for patches and details.
Grinding
Lightly abrading geomembrane before an extrusion weld to remove the oxidized surface and dirt.
Trial weld
Short test seam made on scrap geomembrane before production welding to prove the machine settings and the operator.
Seamer
Welding technician who makes and repairs geomembrane seams on a liner crew.