One-Hand Splice: a Simple Fixture for Clean Filament Fusion

Splicing filament shouldn’t feel like defusing a bomb with spaghetti. Most tools out there still require expert coordination, perfect timing, and a prayer to the Plastic Filament gods. But this fixture changes the game—making filament fusion precise, repeatable, and even doable while the filament is still loaded in your printer.

Designed for 1.75 mm filament (but easily adaptable), this tool uses opposing slotted collets, thumb screws, and a concentric sleeve to lock, align, and fuse filament ends with minimal fuss. Whether you're mid-print or prepping a new spool, this splicer gives you control without the chaos.

1. 3D printed splicer fixture (see design notes below)
2. Two thumb screws
3. Two slotted collets
4. Two collet collars
5. Teflon sleeve (sized for 1.75 mm filament)
6. Heat gun (with adjustable temperature)
7. Utility knife or blade

Use standard PLA or PETG. No supports needed if printed upright (brim suggested). Tolerances are tuned for typical FDM printers.

Slide the filament ends into slotted collets on the fixture ring.

Add collars to prevent screw slippage.

Tighten to lock filament ends in place. Ensure they touch and align concentrically.

Slide on Teflon sleeve. (Keeps filament ends concentric.)

Use a heat gun on low. Once the filament softens, gently squeeze thumb screws to fuse.

Let it cool, then remove screws, collars, and fixture. Slice off the sleeve.