Every printing process has a build volume, and a part bigger than it has to be split and joined, printed on a large format machine, or made another way. All three are viable, and which is right depends on whether the part needs to be one piece structurally or merely one piece visually.
The practical size limits by process
Filament machines scale most cheaply and large format ones exist at room size. Powder bed polymer machines are limited by chamber size and by how evenly the chamber can be heated. Resin machines are limited by the light source area. Metal powder bed machines are the most constrained of all, which is why very large metal printing uses directed energy deposition or wire arc processes instead.
Splitting and joining
Splitting a part into printable pieces and bonding them is routine and often cheaper than a large format machine. Design the split with locating features so alignment is not left to hand and eye, put the joint where it is not visible or where a seam is expected, and choose an adhesive suited to the polymer. The joint will not be as strong as the material, so keep it out of the load path.
Warping is the dominant problem
Thermal contraction scales with length, so a large printed part pulls harder at its corners and its bed adhesion than a small one. Heated chambers, brims, careful material choice and generous fillets all help. This is why large filament parts are often printed in PLA or PETG rather than ABS, and why large format machines invest heavily in chamber temperature control.
Large format extrusion
Pellet fed extrusion machines lay down beads an order of magnitude larger than a filament nozzle, so very large parts print in hours rather than days. Surface finish is coarse and usually machined afterwards, which suits the main application: tooling, moulds, patterns and fixtures for composites and thermoforming, where a printed and machined tool beats a fully machined one on both cost and lead time.
Questions people ask about large 3d printing services
How big can a 3D printed part be?
It depends on the process. Filament and large format extrusion scale to room size; powder bed and resin machines are limited by chamber and light source; metal powder bed is the most constrained.
Is splitting and bonding a good idea?
Often, and it is cheaper than a large format machine. Design locating features into the split and keep the joint out of the load path.
Why do large printed parts warp?
Because thermal contraction scales with length, so the corners pull harder. Heated chambers, material choice and generous fillets are the mitigations.
What is large format extrusion used for?
Tooling, moulds, patterns and fixtures. The surface is coarse and machined afterwards, and the combination beats fully machined tooling on cost and lead time.