I’ve given you tips on how to know how much material you have left on your spools, but what are you supposed to do when the filament leftover has never been enough for a complete print? I have a couple of different techniques and uses for that scrap of filament that’s too much to throw away but seems like it isn’t enough for anything useful. Let’s jump in!

Color Swatches and Spreadsheets

After you’ve spent some time checking if it would be enough for anything small that you need and not finding anything suitable, consider printing a swatch. I have started printing a small block with a hole in the corner so I can very easily keep on hand a tangible sample of filaments I’ve used so I know exactly the color I need for a project without having to lug around larger printed parts comparing material color. A supplementary spreadsheet listing out all the important details like price, manufacturer, mass, $/kg, a link to where to buy it, and any print settings of note makes it easy to come back to this material later if I need more.

Color swatches are a great way to both use filament scraps and keep things organized for future 3D prints.
Color swatches are a great way to both use filament scraps and keep things organized for future 3D prints.

3D Print Welding

A 3D printing pen like the 3Doodler is a great way to utilize that last bit of filament. You don’t need a lot to be able to create things with it, so a little goes a long way. Or if you don’t have the intent to create anything with the pen, you can at least use it to create some fairly solid weld between two different printed parts.

3D printing pens are a helpful tool for joining together two 3D prints.
3D printing pens are a helpful tool for joining together two 3D prints.

If you don’t already have a 3D printing pen, what better gap filler for 3D prints than the filament it’s made from. With a soldering iron in one hand and the filament guided by the other, you can use filament to help blend the edges between two separate 3D prints and be able to sand it down for a virtually invisible seam.

While less controlled than a 3D printing pen, a soldering iron works as well.
While less controlled than a 3D printing pen, a soldering iron works as well.

Pins and Hinges

For those that commonly split up large models and print them in separate pieces, alignment pins are invaluable to maintain that everything lines up and you don’t have a skewed seam. While metal or wooden dowels are regularly used, filament is a quick and easy solution as well. 1.75mm filament works decently well, but 2.85mm filament performs a lot better since it’s stiffer. With either of these though, you’ll need to experiment with tolerances to make sure the holes are large enough to accommodate the filament but still be tight enough to keep everything lining up.

Alignment pins make the seams in multi-part assemblies a lot cleaner by having a more consistent interface between parts.
Alignment pins make the seams in multi-part assemblies a lot cleaner by having a more consistent interface between parts.

Similar to the alignment pins, I’ve used filament as a pin for a hinge. Unlike alignment pins, there’s a lot more margin for error, since all it needs to do is slide through two parts and if it wants to slide out, just glue it in place in one of the hinges. The key with this is to have one of the two parts have a tight enough tolerance to hold onto the filament, because the tighter the tolerance the harder it will be to fully insert the pin.

Rather than sourcing a dowel or metal rod, you can simply use filament to hinge two 3D printed parts.
Rather than sourcing a dowel or metal rod, you can simply use filament to hinge two 3D printed parts.

Filament Changes

Just because the filament you have isn’t enough for a complete print doesn’t mean you can’t use it for a 3D print; all you have to do is start a print and keep an eye on it and swap it out for more filament before it runs out. If the color of the finished part doesn’t matter because it’s just prototype that doesn’t need to look pretty or you’re going to paint right over it, then this is a great way to use all of the leftover filament that you have. I have three different techniques for this:

  • Completely manual. This is the most high risk option as it’s really easy to miss the material runout and ruin the entire print. I will load what’s left of the filament and do a multitude of things to make sure I don’t run out: loop some object onto the filament so I will hear it drop when there isn’t enough filament left to support it, set a timer for a rough estimate for when I believe the filament will run out, and I sit over it and watch it when things start getting close. I prefer not to use this option if I can avoid it, because it takes a lot of my attention to make sure I don’t miss it.
  • Runout sensor. It’s a lot more commonplace to find a runout sensor on a 3D printer, which triggers a switch when filament runs out and automatically pauses the print. I don’t need to watch or listen for anything to fall and can instead focus on my tasks and wait until I glance over and notice that the print is paused or I hear that it has stopped moving, two much more obvious changes than trying to catch the filament running out on my own. Printers with multiple extruders can sometimes switch to the next extruder when they detect a runout like the Ultimaker Material Handling Station or any of Craftbot’s IDEX printers.
  • The Mosaic Palette. Any of Mosaic’s Palette Multi-Extrusion Systems (the Original, 2, 2S, and Pros) all feature multi-spool mode, so you can load four different filaments into it and it will feed your printer filament as the print progresses. Once it runs out of one of the inputs, it will cut it off and splice on the next strand of filament to allow the print to continue uninterrupted. You can of course utilize this so that it runs off of four full-size spools to ensure that even the longest print won’t run out of material.

With a filament sensor, you can utilize nearly ever length of filament for your 3D printing projects.
With a filament sensor, you can utilize nearly ever length of filament for your 3D printing projects.

Finding different uses for material that would otherwise be trash is actually one of my favorite things to do with these scraps. Personally I like to print out little Phils and keep some in my backpack to hand out whenever I strike up a conversation with someone interested in 3D printing. Doing this also helps alleviate some of my packrat tendencies, so maybe this article will be of some help to you too. And these are just a few of the different things you can do, so if you have some other idea I’d love to hear about it in the comments down below.

Happy Printing!