HOW TO SPLICE FILAMENT TOGETHER

Splicing fuses two pieces of filament end-to-end into one continuous strand strong enough to feed through your extruder. Two scenarios: rescuing the end of a spool that's not enough for your next print (splice it to a fresh spool to use the remnant), or running a multi-material print on a non-MMU printer (manually splice colour changes at predetermined heights). Done right, the splice is barely visible in the finished print - a small colour transition or texture change at the joint. Done wrong, the splice breaks in the extruder mid-print and you have a tangled mess to clear.

Splice when: you have a spool with 50-200 g remaining and your next print needs more - splice it to a fresh spool. Or you want a colour transition mid-print on a single-extruder printer. Or you're running an MMU / Palette system that requires intentional multi-material splicing. Don't bother when: the remnant is under 30 g - just save it for small prints. Or your printer has an AMS / MMU - the system handles material changes natively without splicing.

Manual butt-welding (heat-shrink-tube method): 1. Equipment: PTFE tube (4 mm OD, 2 mm ID), lighter or small torch, sharp knife or filament cutter. 2. Cut both filament ends square - critical for a strong joint. 3. Push both ends into a 30-50 mm length of PTFE tube until they meet in the middle. 4. Heat the tube exterior with a lighter evenly along its length, rotating constantly. The PTFE keeps the filament aligned while heat melts the ends together. 5. Wait for the joint to cool (10-30 seconds). 6. Slide the PTFE off - the joint should be a clean filament-shaped strand. If misaligned, repeat. 7. Smooth any bumps with a fine knife so the splice fits through the extruder gear without snagging. Manual butt-welding (no tube, fast method): 1. Cut both ends square. 2. Hold ends 1 mm apart. 3. Briefly touch both ends with a lighter flame until they're molten. 4. Push them together quickly while still soft. 5. Cool, then sand smooth. Less reliable than the tube method - splices fail more often. But faster. Filament splicer (heated tool): - Tools like the Palette+ heated splicer use a small heated chamber to melt and fuse ends. Reliable, uniform splices. - Cost: $30-100 standalone, included with Mosaic Palette systems. - Best for: regular splicing or multi-material printing. MMU / Palette automated splicing: - Mosaic Palette: feeds two filaments into a heated splice chamber and outputs a single multi-coloured strand to your printer. - Use case: full-colour multi-material printing on a single-extruder printer. - Setup is involved - follow Palette docs. For colour-change in a print: - Insert M600 (filament change) command at the layer where you want the splice. - Printer pauses; you swap filament manually (no splicing needed - just unload-and-load). - For a true splice (no pause): pre-splice the two filaments at the right length using the manual or splicer method, calculate carefully so the splice arrives at the desired layer.

Cutting at an angle. Angled cuts make weak splices. Square cuts only. Over-heating. Too much heat melts filament back from the joint, leaving a thin neck that breaks. Just enough to soften, not flame-broil. Splicing different filament types. PLA-to-PETG splices fail in the extruder. Always splice same material to same material. Skipping the smoothing step. Bumpy splices catch on the extruder gear, jam, or grind. Sand or trim until uniform. Trying to splice mid-spool when an MMU would work. If you're doing colour changes regularly, get an MMU / Palette - manual splicing is tedious and unreliable for multiple changes per print. Splicing TPU. TPU's elasticity makes splices unreliable. Don't bother - finish the spool or use M600 pause-and-swap.

If you're splicing because you frequently run out mid-print, see how-to-store-filament for keeping more spools ready. For multi-material prints without manual splicing, look into AMS / Palette systems specific to your printer.