The maximum size of your parts depends on the material and manufacturing process you choose to have your 3D-printed or CNC-machined parts produced in.
All CNC Materials (Mill, X,Y,Z)
1828mm x 500mm x 152mm (72" x 20" x 6")
All CNC Materials (Lathe, D,H)
152mm x 394mm (6" x 12")
PLA (Fused Deposition Modeling, X,Y,Z)
300mm x 300mm x 300mm (11.8" x 11.8" x 11.8")
ABS (Fused Deposition Modeling, X,Y,Z)
406mm x 355mm x 406mm (16" x 14" x 16")
PETG (Fused Deposition Modeling, X,Y,Z)
300mm x 300mm x 300mm (11.8" x 11.8" x 11.8")
Nylon (PA 12 and PA 12 Glass Beads) (Multi Jet Fusion, X,Y,Z)
380mm x 284mm x 380mm (15" x 11.1" x 15")
Nylon 12 (Selective Laser Sintering, X,Y,Z)
700mm x 380mm x 580mm (27.5" x 15" x 22.8")
All Vero- Materials, Rubber-Like, ABS-Like, Multi-Material (PolyJet, X,Y,Z)
490mm x 390mm x 200mm (19.3" x 15.3" x 7.9")
Accura 25 (Stereolithography, X,Y,Z)
254mm x 254mm x 254 mm (10" x 10" x 10")
Urethane Casting (may depend on material and geometry, X,Y,Z)
2200mm x 1200mm x 1000mm (86.6" x 47.2" x 39.3")