3D printing, also known as “additive printing”, will benefit space activities in manifold ways as described in this ESA article : Ten ways 3D printing could change space – ESA.

For example, it can make structures that can’t be made with conventional machining techniques:

3D-printed_titanium_lattice_ball_node_full_image

A lightweight titanium lattice ball manufactured using the Additive Manufacturing
or 3D printing process. This design is a good example of AM capabilities: these
hollow balls possessing a complex external geometry could not have been
manufactured in a single part using a conventional manufacturing process.
But they are incredibly light while also stiff, opening up possibilities for future
space applications.

Close-up_of_3D-printed_titanium_lattice_ball_node_full_imageHere’s a close-up.

At the other end of the scale, entire large structures on the Moon and elsewhere could be built with the 3D printing technique:

Multi-dome_base_being_constructed_node_full_imageMulti-dome lunar base being constructed, based on the 3D printing concept.
Once assembled, the inflated domes are covered with a layer of 3D-printed
lunar regolith by robots to help protect the occupants against space
radiation and micrometeoroids

Update: The ESA article mentions making models with 3D printing. Here is a video showing an animation using 50 models made with 3D printing: