A hot air plastic welder allows a fabricator or repair technician to precisely direct heated air into a plastic joint. When the parent plastic and compatible welding rod reach the proper welding condition, controlled pressure is used to create the joint.
Hot air welding may also be called hot gas welding, plastic hot air welding, thermoplastic welding or simply plastic welding.
What Is Hot Air Plastic Welding?
Hot air plastic welding is a joining process used with thermoplastic materials.
A stream of controlled heated air is directed toward the welding area. The heat softens the surfaces that will be joined.
In filler-rod welding, compatible plastic welding rod is heated at the same time as the parent material.
Pressure brings the softened materials together. As the joint cools, the thermoplastic solidifies.
How Does a Hot Air Plastic Welder Work?
A typical hot air plastic welding system has several basic functions:
Air Supply
Air moves through the welding tool. Depending on the equipment, the air source may be internal or externally supplied.
Heating Element
The welding tool heats the moving air to a controlled operating temperature.
Welding Nozzle
A nozzle directs the heated air toward the precise area where the thermoplastic is being welded.
Plastic Welding Rod
Compatible filler rod supplies thermoplastic material to the prepared joint when the welding procedure requires filler.
Hot Air Welder, Plastic Welder or Plastic Welding Gun?
People use several terms when searching for equipment used to weld thermoplastics:
- hot air welder
- hot air plastic welder
- plastic welder
- plastic welding gun
- plastic welding heat gun
- hot gas welder
- thermoplastic welder
- plastic repair welder
These terms may describe similar equipment, but not every tool sold as a heat gun is designed specifically for thermoplastic welding.
Hot Air Plastic Welder vs. Regular Heat Gun
| Feature | Hot Air Plastic Welder | General Heat Gun |
|---|---|---|
| Primary purpose | Controlled thermoplastic welding | General heating applications |
| Temperature control | Designed for controlled process heating | Varies by model |
| Airflow control | Often designed for welding requirements | Varies |
| Welding nozzles | Can accept specialized welding nozzles | May have limited compatible nozzle options |
| Speed welding | Suitable tools can use speed welding nozzles | Not necessarily designed for speed welding |
A general heat gun may soften plastic, but softening plastic is not automatically the same as producing a controlled thermoplastic weld.
What Plastics Can Be Hot Air Welded?
Many thermoplastics can be joined using hot air welding when the materials, filler rod and welding conditions are compatible.
| Plastic | Common Welding Rod | More Information |
|---|---|---|
| HDPE | Compatible HDPE welding rod | HDPE Welding Rod |
| Polyethylene | Compatible PE welding rod | Polyethylene Welding Rod |
| Polypropylene | Compatible PP welding rod | PP Welding Rod |
| PVC | Compatible rigid or flexible PVC rod | PVC Welding Rod |
| PVDF | Compatible PVDF welding rod | PVDF Welding Rod |
| ABS | Compatible ABS welding rod | ABS Welding Rod |
| PETG | Compatible PETG welding rod | PETG Welding Rod |
| TPU | Compatible TPU welding rod | TPU Welding Rod |
Plastic Welding Rod for Hot Air Welding
Plastic welding rod acts as filler material in many hot air welding procedures.
Common welding rod materials include:
- HDPE welding rod
- LDPE welding rod
- LLDPE welding rod
- MDPE welding rod
- HMWPE welding rod
- polypropylene welding rod
- PVC welding rod
- PVDF welding rod
- ABS welding rod
- PETG welding rod
- TPU welding rod
The filler rod should be compatible with the parent thermoplastic.
For a complete material-selection guide, see Plastic Welding Rod.
Plastic Welding Rod Sizes
Common round plastic welding rod sizes include:
| Metric Size | Approximate Inch Size | General Consideration |
|---|---|---|
| 3 mm | 0.118 in. | Smaller beads and detailed welding |
| 4 mm | 0.157 in. | Common general-purpose rod size |
| 5 mm | 0.197 in. | Greater filler volume for suitable larger joints |
| Triangle / Triangular | Profile dependent | Used with suitable tools and fabrication processes |
| Custom Profile | Custom | OEM and specialized applications |
Read our Plastic Welding Rod Sizes Guide.
Round Plastic Welding Rod
Round welding rod is one of the most common filler profiles used for hot air plastic welding.
Typical round rod diameters include 3mm, 4mm and 5mm.
Round rod can be hand-fed using a standard welding nozzle or used with a compatible speed welding nozzle.
Triangle Plastic Welding Rod
Triangle or triangular plastic welding rod is another filler profile used in thermoplastic fabrication.
Unlike round rod, a triangular profile is not completely described by a single diameter. Its actual dimensions and geometry depend on the profile specification.
The welding nozzle and equipment should be compatible with the specific triangle rod being used.
What Is a Speed Welding Nozzle?
A speed welding nozzle is designed to guide plastic welding rod toward the joint while directing heated air at the rod and parent plastic.
The nozzle helps the operator control:
- Rod position
- Welding angle
- Heat direction
- Pressure
- Travel speed
Speed nozzles are available for different rod sizes and profiles.
Round Nozzle vs. Speed Welding Nozzle
| Method | How It Works | General Use |
|---|---|---|
| Round nozzle / freehand welding | Operator independently controls the hot air and filler rod | Repair, detail work, tack welding and specialized joints |
| Speed welding nozzle | Nozzle guides the rod while directing hot air at the joint | Longer welds and more controlled rod feeding |
How to Hot Air Weld Plastic
Identify the Plastic
Confirm the thermoplastic material before selecting welding rod or establishing welding conditions.
Select Compatible Plastic Welding Rod
Match the filler material to the parent polymer and, when necessary, the actual resin grade or formulation.
Clean the Welding Area
Remove dirt, grease, oil and other contamination using a cleaning method appropriate for the material.
Prepare the Surface
Mechanically prepare the welding surfaces as required for the material and procedure.
Prepare the Joint
Groove, bevel or otherwise prepare the joint according to the component thickness and weld design.
Select the Welding Nozzle
Choose a nozzle suitable for the welding method and filler rod diameter or profile.
Set Temperature and Airflow
Establish suitable starting conditions for the actual thermoplastic, welding tool, nozzle and rod.
Make a Test Weld
When possible, make a test weld on representative material and adjust temperature, airflow, speed and pressure.
Heat the Parent Plastic and Rod
Direct hot air so both the filler and parent material soften at the welding interface.
Apply the Welding Rod
Feed the softened filler into the prepared joint using controlled pressure and consistent travel speed.
Allow the Weld to Cool
Allow the thermoplastic to cool before heavily loading, flexing or testing the joint.
Inspect the Weld
Inspect for consistent fusion, bead shape, voids, gaps, contamination and signs of overheating.
Plastic Welding Temperature
There is no single temperature that applies to every plastic welding job.
Different thermoplastics soften and weld under different conditions.
The required hot-air-tool setting depends on:
- Polymer type
- Resin grade
- Material formulation
- Welding equipment
- Airflow
- Nozzle geometry
- Rod diameter
- Material thickness
- Travel speed
- Welding pressure
See the Plastic Welding Temperature Chart for material-specific starting ranges and process information.
Hot Air Welding HDPE
HDPE is one of the most common thermoplastics used in tanks, sheet fabrication, liners and industrial components.
Hot air welding HDPE requires compatible HDPE filler material and proper preparation of the polyethylene surface.
Read: How to Weld HDPE and HDPE Welding Rod.
Hot Air Welding Polypropylene
Polypropylene is widely used for tanks, ductwork, chemical-processing equipment and fabricated thermoplastic components.
Use compatible PP welding rod and consider the actual polypropylene grade when known.
Read: How to Weld Polypropylene and Polypropylene Welding Rod.
Hot Air Welding PVC
Rigid PVC is commonly hot-air welded in industrial plastic fabrication. Flexible PVC can also be weldable, but formulations vary substantially.
Read: How to Weld PVC and PVC Welding Rod.
Hot Air Welding PVDF
PVDF is used in chemical-resistant and specialized industrial fabrication.
Material cleanliness, grade compatibility and controlled welding conditions are especially important where the finished component has chemical or high-purity service requirements.
See PVDF Welding Rod.
Hot Air Welding ABS
ABS welding is often associated with plastic repair, equipment housings, automotive components and fabricated parts.
Use compatible ABS filler rod and confirm the parent material before welding.
See ABS Welding Rod.
Hot Air Welding PETG
PETG can be used in fabricated sheet components, equipment guards, covers, displays and other thermoplastic applications.
See PETG Welding Rod.
Hot Air Welding TPU
TPU, or thermoplastic polyurethane, includes a broad range of flexible thermoplastic formulations.
Hardness and formulation can significantly affect welding behavior, so use compatible TPU filler material.
See TPU Welding Rod.
Why Plastic Welding Rod Melts but Does Not Stick
One of the most common plastic welding problems occurs when the filler rod melts but does not properly fuse to the parent plastic.
Possible causes include:
- Wrong welding rod material
- Incorrect parent plastic identification
- Parent plastic is too cold
- Surface contamination
- Poor surface preparation
- Travel speed is too fast
- Incorrect airflow
- Heat is concentrated primarily on the rod
- Insufficient welding pressure
Signs of Too Much Heat
Possible signs of overheating include:
- Burning
- Scorching
- Discoloration
- Excessive sagging
- Bubbling
- Smoke
- Material degradation
Signs of Too Little Heat
Possible signs of insufficient heat include:
- Rod remains stiff
- Rod sits on the surface
- Poor wetting
- Visible gaps
- Weak fusion
- Rod easily separates after cooling
Hot Air Welding vs. Extrusion Welding
| Hot Air Rod Welding | Extrusion Welding |
|---|---|
| Welding rod is typically fed into the joint by hand or through a speed nozzle. | An extrusion welder plasticizes and deposits a larger volume of filler. |
| Well suited to smaller weld beads, repair and detailed fabrication. | Commonly used for larger welds and heavier fabrication. |
| Heat is supplied by the hot air welding tool. | Surface preheating is combined with extruded thermoplastic filler. |
| Commonly uses round or profiled welding rod. | Feedstock requirements depend on the extrusion welding equipment. |
Read our Extrusion Welding Guide.
Hot Air Plastic Welding Applications
Plastic Tank Fabrication
Thermoplastic sheet can be welded into tanks and containment structures using suitable welding processes.
Plastic Tank Repair
Some damaged thermoplastic tanks can be repaired when the material, design and service conditions allow it.
Plastic Sheet Fabrication
Sheet materials can be joined to create boxes, guards, enclosures, ductwork and process equipment.
Plastic Repair
Cracks and damaged thermoplastic components may be repairable with compatible filler rod and proper preparation.
Ductwork
Thermoplastic duct systems may use welded joints in industrial ventilation and process applications.
OEM Manufacturing
Plastic welding can be incorporated into production of custom thermoplastic components and assemblies.
Plastic Welding Safety
Hot air welding equipment operates at high temperatures and should be used with appropriate safety procedures.
Consider:
- Burn hazards from the tool and nozzle
- Hot plastic surfaces
- Ventilation
- Material-specific decomposition products
- Electrical safety
- Fire hazards
- Safe handling of tanks or containers previously holding chemicals
Always review the safety information for the thermoplastic material, welding equipment and application.
Frequently Asked Questions About Hot Air Plastic Welding
What is hot air plastic welding?
Hot air plastic welding uses controlled heated air to soften compatible thermoplastic surfaces and, when required, plastic welding rod so they can be joined.
What plastics can be welded with hot air?
Suitable grades of HDPE, polyethylene, polypropylene, PVC, PVDF, ABS, PETG, TPU and other thermoplastics can be hot air welded. Material compatibility must be established for the actual application.
Do you need plastic welding rod?
Many hot air welding procedures use thermoplastic filler rod. The rod should be compatible with the parent material.
Can I use a regular heat gun to weld plastic?
A heat gun can soften some thermoplastics, but a purpose-built hot air plastic welder generally provides better control over heat, airflow and specialized welding nozzles.
What is a plastic welding gun?
"Plastic welding gun" is a common term used for handheld hot air tools designed or used for thermoplastic welding.
What is a speed welding nozzle?
A speed welding nozzle guides filler rod toward the joint while directing heated air toward the filler and parent plastic.
What size plastic welding rod should I use?
The appropriate rod size depends on the joint, material thickness, welding nozzle and procedure. Common round sizes include 3mm, 4mm and 5mm.
Why does my plastic welding rod not stick?
Possible causes include wrong filler material, insufficient heating of the parent plastic, contamination, poor preparation, excessive travel speed or insufficient pressure.
Is hot air welding the same as extrusion welding?
No. Both are thermoplastic welding processes, but extrusion welding uses an extrusion welder to plasticize and deposit a larger volume of filler material.
Hot Air Plastic Welding Resource Center
- Plastic Welding Guide
- Plastic Welding Rod
- Plastic Welding Rod Sizes
- Plastic Welding Temperature Chart
- How to Weld Plastic
- How to Weld HDPE
- How to Weld Polypropylene
- How to Weld PVC
- HDPE Welding Rod
- Polyethylene Welding Rod
- Polypropylene Welding Rod
- PVC Welding Rod
- PVDF Welding Rod
- ABS Welding Rod
- PETG Welding Rod
- TPU Welding Rod
- Extrusion Welding
- Plastic Welding Tools
- Plastic Welding Troubleshooting
- Thermoplastic Welding
- Plastic Fabrication
Need Plastic Welding Rod?
New Image Plastics Manufacturing produces plastic welding rod for industrial fabricators, distributors, OEMs and plastic repair applications.
Materials include LLDPE, LDPE, MDPE, HDPE, HMWPE, polypropylene, rigid and flexible PVC, PVDF, PETG, ABS, TPU and other thermoplastic materials.
Capabilities include 3mm, 4mm and 5mm round rod, triangle and specialty profiles, custom colors, spool packaging, private labeling and custom extrusion.
Phone: 330-854-3010
Email:
newimageplastics@sbcglobal.net