Plastic welding is not metal welding
This needs stating because search results constantly conflate them. MIG, TIG, MMA, stick and flux cored are electric arc processes for joining metal. They melt metal with an electric arc. None of them has any application to geomembrane, liner, tarpaulin or any other thermoplastic.
Thermoplastic welding works on a different principle entirely: heat the material until it softens, press the softened surfaces together, let them cool as one. No arc, no flux, no shielding gas. The machines are unrelated and not interchangeable, and a buyer searching for a welding machine can easily end up looking at entirely the wrong category of equipment.
The three processes used on liner work
Hot wedge welding. A heated metal wedge melts the facing surfaces of an overlap and driven rollers fuse them under pressure while the machine self-propels. Used for production seams. Its defining feature is the dual track weld with a testable air channel. See wedge welding machines.
Extrusion welding. A screw in a heated barrel melts filler rod and extrudes it onto a preheated joint, building a fillet bead. Used for patches, penetrations, corners and repairs. See extrusion welding machines.
Hot air welding. A stream of controlled hot air softens both surfaces and a roller presses them together. Used for tacking liner, preheating, and welding PVC, tarpaulin and roofing membrane outright. See hot air welding machines.
Variants within each type
| Process | Variants | Typical use |
|---|---|---|
| Hot wedge | Dual track, single track, wedge with hot air assist | Geomembrane production seams, coated fabric |
| Extrusion | Hand extruder, high output extruder, fixed workshop unit | Liner detail, tank and duct fabrication |
| Hot air | Hand gun, automatic hot air welder, hot wedge hybrid | Tacking, PVC fabric, roofing membrane |
| Butt fusion | Manual, hydraulic, fully automatic | HDPE pipe, not sheet liner |
| Electrofusion | Control unit with fittings | HDPE pipe fittings, not sheet liner |
Butt fusion and electrofusion appear in the same catalogues and are sometimes confused with liner equipment. They join pipe, not sheet, and are not used on geomembrane seams.
Why three machines rather than one
Because the geometry of a lining project demands it. A wedge welder must roll in a straight line along an overlap, so it cannot weld around a pipe or into a corner. An extruder can reach anywhere but produces no testable channel. A hot air gun tacks and welds thin material but cannot make a certifiable primary seam in HDPE. Each covers what the others cannot.
Frequently asked questions
What are the three types of welding machines used on geomembrane?
Hot wedge, extrusion and hot air. The hot wedge welder makes production seams and is the only one producing an air testable dual track weld. The extrusion welder handles patches and detail. The hot air welder tacks panels and welds thin material. MIG, TIG and MMA are metal arc processes and are not used on liner.
Is a heat gun the same as a plastic welding machine?
No. A hardware store heat gun for stripping paint drifts in temperature, has coarse settings and is not built for continuous duty. A professional hot air welding gun holds its set point under load within a few degrees, takes precision nozzles and runs for hours. Welding to a specification with a paint stripper produces seams nobody can certify.
Everything above ships from the same stock as the rest of our geomembrane welding machine range.