Filament spool: what it is and what matters

What you find on a spool

A spool is like a bobbin for thread, only bigger. The filament is wound in tight layers and the end is pushed into a hole in the rim so it does not unravel. On the label the manufacturer gives the material, colour, diameter (mostly 1.75 mm, more in the filament diameter entry), weight and the recommended nozzle and bed temperature.

The standard is 1 kg, but shops also sell 250 g and 500 g spools for trying colours and 2 to 3 kg for large production. An empty spool weighs 150 to 250 g, so on a kitchen scale you can see how much filament is left only if you know its weight.

Why the spool matters

Uneven winding can cause the strand to catch, and the printer then stops feeding material. Tangled filament causes under-extrusion or a stopped print. The size of the spool has to fit the holder on the printer, since very wide or tall ones will not fit, and storing them somewhere dry matters just as much (filament moisture).

Spools with us

We print on Elegoo Centauri Carbon 2 printers with an automatic filament changer for up to 4 colours, so several spools are connected at once. With multicolour printing, it is the time for changes and the purge tower that raise the price, not the number of spools. We charge for material by the actual grams (PLA €8 per kg, PETG €9 per kg), as worked out by the print preparation, not by the whole spool.

What to watch out for at home

When buying, look at the weight without the spool and at the stated diameter tolerance. Keep spools out of direct sunlight and put them back in their bag after printing. We do not sell filament, so you cannot buy a spool from us.

How to choose a spool at home

If you buy filament, look not only at the price per kg but also at the quality of the winding and the stated diameter tolerance. Cheap spools are sometimes badly wound and the strand jams. For a long print, a spool that unwinds smoothly is worth it, meaning one that turns easily on the holder. If you plan a print longer than a few hours, check there is enough filament left on the spool, otherwise the print will stop in the middle.

After use, tuck the ends of the filament into the hole in the rim so it does not tangle. Store the spool in a sealed bag with a desiccant and out of the sun.