Compatible ink.

Ink made by somebody other than the machine's manufacturer and sold to drop straight into that machine's system; STS, for one, describes its whole business as inks compatible with most major brands of large-format printer. Three things are exposed and shops usually count only the first: the warranty and the service contract, then head life, because a printhead is a filtered fluid path tuned to one ink's viscosity, surface tension and pigment grind, then every ICC profile and linearisation on the RIP, all of which describe the old ink and stop describing the machine the day the fluid changes. The consumer folklore does not reach a production floor. The tie-in prohibition that stops a manufacturer voiding a warranty over third-party supplies lives in the Magnuson-Moss Warranty Act, and the FTC's own guide limits that Act to consumer products, meaning property normally used for personal, family or household purposes, and says it does not apply to products sold for commercial purposes. A production DTG or DTF printer is not one. The saving is counted per litre and the loss is counted per printhead, plus the days the line stands still waiting for one, so the defensible version is a documented trial: one machine, a fresh profile, wash-tested prints, and only then the second machine.