In the descriptions and socket names of the two items, Printer and Disintegrator, they refer to a special type of "fuel" called Pixels. In action, the printer will require pixels depending on (I think) the number of pixels for each object in the selected blueprint (vehicle.) If it is told to print anyway, it will wait until it gets enough pixels to print the full blueprint.

Turns objects into pixels to fuel a printer. When an object gets in its way (in front of the long gray bar) and "Enabled" is true, you will see the object shrink down into the size of a singular pixel, except the pixels of the object don't shrink at all, just move into one place. It must be connected to a printer with a pipe.
It will also output the amount of pixels it has collected.

In the context menu, you'll have to select a blueprint. This is something I missed for some time. The blueprint is a vehicle either you saved, or you subscribed to it, or it's a built-in example. Eitherway, it should cost more than one pixel. The printer must be connected to a disintegrator with a pipe to get pixels to print with. When you select a blueprint, there'll be an outline that represents the amount of space the blueprint will take up. Very useful for not guessing.

When told to print (activated,) if it has enough pixels to make the selected blueprint, it will spawn. If it does not have enough pixels, but (I think) if it has more than one pixel, it will wait until it has enough pixels. When it does, it will immediately print again with no needed activation.