Of everything a factory can print, jigs, fixtures and gauges pay back fastest and most reliably. They are low volume by definition, they are needed quickly, they are usually not strength critical, and the alternative is a machinist making them from aluminium at a cost that dwarfs the print. Most printers that earn their keep in a factory earn it here.
Why the payback is so fast
A fixture is a one off, so there is no volume to amortise a machining setup across. It is needed now, because the job is on the machine. And it does not usually need certified material properties. Printing turns a two day machining job into an overnight print, and it removes the queue in the toolroom, which is often the real constraint.
What to print
Assembly jigs, drill guides with pressed in bushings, welding positioners, inspection go and no go gauges, soft jaws, part nests for measurement, ergonomic handling aids, and end of arm tooling for robots. Anything that positions a part rather than resisting a large load is a good candidate, and adding a metal bush or insert covers the wear points.
What not to print
Anything that carries a large or repeated load, anything that has to stay dimensionally stable over years, anything exposed to solvents that attack the polymer, and anything that is itself a measurement standard. A printed gauge that has crept is worse than no gauge, so gauges are checked on a schedule or made conventionally.
Materials that survive a shop
Sintered nylon is the general answer: tough, isotropic enough, resistant to shop chemicals and dimensionally reasonable. Filament printed polymers with a glass or carbon fill are stiffer and cheaper for larger fixtures. Filled resins are good for detail and poor for impact. Add metal inserts, bushes and threaded inserts wherever a fastener or a tool touches the part.
Questions people ask about 3d printed jigs and fixtures
Why are jigs and fixtures the best printing application?
Because they are one offs needed quickly and rarely strength critical, so printing removes both the machining setup and the toolroom queue.
Which material should shop fixtures use?
Sintered nylon for general use, filled filament for large stiff fixtures. Add metal bushes and threaded inserts wherever wear or fasteners occur.
Can printed fixtures be used for inspection?
For go and no go checks, yes, if they are verified and rechecked on a schedule. They are not measurement standards and should not be treated as such.
How much does a printed fixture cost?
Usually a small fraction of the machined equivalent, because there is no setup and no toolroom time. That gap is why the payback is so quick.