AA Battery Powered Filament Welder

This project is a simple, low-cost filament welder designed for joining filament scraps, repairing broken spools, or extending short filament pieces.
It’s built with minimal electronics, recycled parts, and one custom 3D printed component — perfect for makers who enjoy practical DIY solutions.

The core of the design is a self-designed PTFE 4/2 mm tube holder, combined with a ballpoint pen spring used as a heating element. Power comes from a 2× AA battery pack salvaged from broken LED lights, which is an important detail — the pack already includes a built-in ON/OFF switch, making the welding process much easier and safer to control.

Required Parts

• 3D printed PTFE tube holder (4/2 mm) – custom design
• PTFE tube 4/2 mm
• Spring from a standard ballpoint pen
• 2× AA battery holder with built-in switch
  (reused from damaged LED lights)
• 2× AA batteries
• Wires (recycled if possible)
• Basic soldering skills

Assembly Instructions

1. Slide the ballpoint pen spring onto the PTFE tube.
2. Solder the positive and negative wires from the battery pack directly to the spring.
3. Insert the PTFE tube with the spring into the 3D printed holder.
4. Route the wires through the bottom of the printed part.
5. Glue the AA battery pack to the holder (hot glue works well).
6. Check all connections before inserting batteries.

Filament Welding Instructions

1. Insert filament pieces into both ends of the PTFE tube so they meet in the middle, inside the spring.
2. Turn ON the battery pack.
3. Wait a moment until you see a small amount of smoke coming from the spring (this means it’s hot enough).
4. Turn OFF the power.
5. Immediately push both filament ends together firmly.
6. Wait a few seconds, then gently pull and shape the still-soft filament section.
7. Let it cool — your filament is now welded.

Notes & Safety

• Use short heating times to avoid overheating the filament.
• Always test with scrap filament first.
• Different filament materials may require slightly different heating times.
• Work in a well-ventilated area.

Why This Project?

• Reduce filament waste
• Repair broken filament
• Extremely cheap & simple
• Battery powered — no power supply needed
• Great beginner electronics project

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