As in ship-mounted manufacturing? You can certainly assume that Labs/Workshops are capable of one-off work, but larger scale manufacturing could take a lot more space, depending on Tech Level, the product itself, and the desired volume per week. At a reasonable TL I could certainly see a relatively small ship being able to take raw ore in one end and deliver widgets out the other, as long as the widgets are not too large. Fusion power and gravitics make smelting and fractionation trivial, and not having to deliver the ingots more than twenty feet (as opposed to entering a trans-continental distribution system) simplifies the output of the smelting process.