About Extruder Welders
Extruder welders are the right tool when wall sections get thick. Above about 6-8 mm of material thickness, hand-held hot-air welding becomes slow and the bead quality suffers. An extruder welder melts plastic welding rod inside a heated screw barrel, then extrudes the molten plastic directly into a pre-heated joint — producing a fully homogeneous, high-strength weld in a single pass.
This is the technique used to weld:
Polypropylene chemical-resistant tanks and bunds (food-grade and chemical-handling fabrications).
HDPE water tanks, pipework joints and large-bore HDPE fittings.
Polyethylene pond and landfill liners at wall sections beyond hot-air range.
Plastic-fabricated ducting, scrubbers and industrial process equipment.
The Plastic Welding Tools NZ extruder welder range covers small-output micro extruders (around 0.5 kg/hr for tight access and small repairs) through to high-output BAK and Techspan industrial extruders (up to 4-5 kg/hr for production fabrication). Most run on 230 V single-phase NZ power; the higher-output machines require 400 V three-phase.
Extruder welders are typically heavier and noisier than hand-held hot-air tools, and they take a few minutes to come up to temperature, so they earn their keep on long seams and thick sections rather than spot repairs. Heating elements, drive screws and feed rollers are supported in New Zealand. To understand when an extruder welder is the right tool, see our guide on welding large-section plastics.
When an extruder welder is the right tool
An extruder welder melts plastic welding rod inside a heated screw barrel and extrudes the molten plastic directly into a pre-heated joint — producing a fully homogeneous, high-strength weld in a single pass. It's the right tool when wall sections get thick.
Typical applications
- Polypropylene chemical-resistant tanks and bunds — food-grade and chemical-handling fabrications.
- HDPE water tanks, pipe joints and large-bore fittings — pressure-rated infrastructure work.
- Polyethylene pond and landfill liners at wall sections beyond hot-air range.
- Plastic-fabricated ducting, scrubbers and process equipment — heavy industrial fabrication.
Output range
| Class | Output | Best for | Power |
|---|
| Micro extruder | 0.5 kg/hr | Tight access, small repairs, plastic moulding rework | 230V single-phase |
| Workshop extruder | 1.5-2.5 kg/hr | Tank fabrication, ducting, general PP/HDPE work | 230V single-phase |
| Industrial extruder (Techspan) | 3-4 kg/hr | Production tank fabrication, pipe joining | 230V or 400V |
| Industrial extruder (BAK) | 4-5 kg/hr | Heavy production HDPE work, large liner fabrication | 400V three-phase |
Extruder welder versus hot-air welder
Use hot-air when…
- Wall section is under ~6mm
- You need tight detail and small-radius welds
- The job is mobile or access is awkward
- You're welding membranes, tarps, or thin fabric
Use extruder when…
- Wall section is 6mm or thicker
- You're running long structural seams
- You need maximum bond strength (e.g. pressure-rated fabrications)
- You're working on PP or HDPE tanks, pipe, large fittings
Practical note
Extruder welders are heavier and noisier than hand-held hot-air tools, and they take a few minutes to come up to temperature. They earn their keep on long seams and thick sections rather than spot repairs. For occasional thick-section work, plan the day around the warm-up — get the machine running once and weld everything you need in one session.
Frequently asked questions
When should I use an extruder welder instead of a hot-air welder?
Once wall section exceeds about 6-8 mm, hot-air welding becomes slow and bead quality suffers. At those thicknesses an extruder welder is faster and produces a stronger, more homogeneous weld. The crossover point depends on the material — HDPE and thick PP fabrications almost always need extruder welding; PEMD bumper repairs almost never do. See our large-section welding guide.
What output (kg/hr) do I need?
For occasional thick-section welding or small repair work, a 0.5-1 kg/hr micro extruder is sufficient. For workshop fabrication on tanks and similar, 1.5-2.5 kg/hr is the common range. For full production HDPE pipe joining and large liner fabrication, 4-5 kg/hr is the industrial benchmark. Higher output means faster long-seam runs but more weight and noise.
Can the same extruder weld PP and HDPE?
Yes — most extruder welders are designed to handle PP, HDPE and other polyolefins by changing the welding rod and adjusting the barrel temperature. You should run the machine empty to purge the previous material before switching, particularly if going from a contaminating plastic like recycled material to a clean food-grade run.
How long does an extruder take to come up to temperature?
Typically 5-15 minutes from cold, depending on output and ambient temperature. The barrel needs to heat through to ensure consistent melt flow. Don't try to extrude before the machine signals ready — cold welds will fail.
Are extruder welds tested differently from hot-air welds?
The same testing approaches apply — tensile peel coupons, spark testing on conductive tank linings, and visual inspection for bead consistency. For HDPE pipe joints, ultrasonic or radiographic inspection is sometimes used on critical infrastructure work, but tensile coupons remain the standard for fabrication QA. See our weld testing equipment.
Need help choosing the right extruder welder?
Tell us about the job: the plastic you're working with, the wall thickness, and how often you'll use the tool. We'll recommend the right kit, welder or accessory for the application.
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