A three-loop skirt around a 60 mm cube, drawn in 0.45 mm lines at 0.2 mm height, is 75.6 mm³ of plastic. In PLA that is 0.094 g — about three centimetres of 1.75 mm filament pulled off the reel.
At $22 a kilogram it costs a fifth of a cent. This is not a setting to economise on.
What the skirt is buying you
It is a priming and diagnostic feature, not an adhesion one. Three loops give the nozzle time to establish a consistent bead after the initial ooze, and they give you three chances to watch the first extrusion and abort before the part starts.
That second function is worth more than the plastic several hundred times over. A skirt that comes out thin, patchy or too high tells you the print will fail, at a point where cancelling costs nothing.
A brim is a different proposition
A 5 mm brim around the same cube covers 1,400 mm² and uses 280 mm³ — 0.347 g, close to four times what the skirt costs.
Still trivial in material terms. The real cost of a brim is removal: it has to be cut or peeled off every part, and on a batch that is minutes of hands-on work per plate rather than fractions of a cent of plastic.
Where these actually matter
Scale changes the picture. On a plate packed with two dozen small parts, each with its own brim, the brims collectively can outweigh a small part — and every one of them has to come off by hand.
The pattern is worth noticing because it recurs throughout print costing: features that are negligible per part become the dominant term per plate, and the term that scales is almost always the human one.
Practical settings
- Keep the skirt unless you are printing a plate so full there is no room for it. It is the cheapest insurance on the machine.
- Use a brim only when the part needs it — tall and thin, small footprint, warping material. It is not a default.
- Raise skirt loops rather than skirt height if you want a longer prime. More loops on one layer costs less and leaves nothing attached to the part.
Model your own skirt or brim as a single-layer footprint in the print time estimator, and see when a brim is genuinely needed in the bed adhesion guide.