Joining short pieces of left over filament

In the middle of a LARGE print and running low on filament on the spool. Had a couple of 3 to 4 meter pieces off previous spools.

Thought i’d try joining the short pieces together so I don’t run out (hopefully, this piece is 33 hours into it so far, still have 25 mm of height to go). Using a 200 watt soldering iron and the flat plate tip for the iron, I heated the ends and held them together until the joint cooled. Works! Had to file the squash off so that the diameter is close enough to go through the head. Using 3 mm ABS and happy so far with the weld!


If you enable the filament swap option in Marlin, you can also use this function (best when the printer is working on infill).

This is something I may have to revisit… I hate wasting filament. Searching online, yielded the rolling the two filaments together in aluminum foil then heating with an open flame. Theoretically, the aluminum foil keeps the consistent diameter. This worked once or twice, but the bond was weak on a few tries also… A soldering iron would probably help quite a bit.

Thanks for the tip.