I personally can't buy the idea that 3d printing is somehow inherently limited to parts and not entire items, especially in model making. I believe 3d printing is a huge part of the future in scale model railways for a number of reasons:

1) The Chinese-as-the-manufacturing-base model is at its sell-by date. The costs are very near the maximum one can import and sell the product for, so close in fact that inspection cycles are being dropped or inspection in whole dropped as a cost savings measure. The result is a rapid decline in quality and fidelity, further reducing what already is a questionable value.

Other costs are being passed on to the consumer as added fees rather than overhead as part of the sale price. An example is one American importer cutting out and charging a seperate "container fee" to keep retail below a price-point that is felt to be the tipping point between saleability and non-viability.

The situation is desperate, but no-one has been successful in finding a new manufacturing base with lower costs (labour being foremost) and the inability for companies outside China to recover their tooling and move it to a new manufacturing country is the stuff of legend at this point.

2) Now, on to 3d printing itself. The technology has been evolving rapidly. A print from just five years ago does not compare favourably to one from today as resolution of the printers gets rapidly better.

Along with that improvement in resolution is the increase in machine volume such that larger pieces can be printed at that improved resolution. The limit right now is the quantity of data to be manipulated as both resolution and volume goes up.

I'm betting that trend will continue until the quality from commercial/industrial grade machines rivals injection moulding. Then, like any technology, emphasis will shift from basic volume/resolution to improvements in reliability and user-friendliness. Who knows, I might live to see the day I walk into my hobby shop to pick up the order I bought on their website a couple days prior, present my receipt on my phone, and there will be the model I ordered, fresh from the bank of printers that occupy the space once devoted to aisles of kits. Perhaps even the decoration, lining, colour, lettering, will be part of the print.

As an example, I have this thing, a now two-year-old print with decent resolution and a length of 15 inches.



This is the carbody for a modern lumber car in 1/4" scale. You add the details, couplings, trucks/bogeys, paint and lettering. No, not a ready-to-run model and there is work to be done, but the bones are quite good

Two years before that thing was printed, the notion would have been laughed at. Today, the same guy is doing a passenger coach at over 20" long and the resolution is even better than you see here.

3) Lastly, 3d printing is a hobby onto itself. Until now, I've been talking of commercial and industrial grade machines and their potential. Meanwhile, I can buy a hobbiest grade machine, master a home version of SolidWorks or similar, and print detail parts and OO wagon-sized bodies. The model railway hobby is evolving as we old guys die off and the new generations take charge.

Theirs is not gluing up bits of wood or plasticard, soldering brass, hand-laying track chair by sleeper. That was us. Theirs is the control of ready-to-run models, an animation technology hobby. Theirs is also the model-building itch being scratched using computer and 3d printer, rather than knives, soldering iron, and PVA. Good thing, too, because there have always been wailings this hobby is "dying" to be heard during my entire life in it (some sixty years of serious modelling). I don't believe it for a minute as the new generations enjoy it their own way with their own take on it and their techniques they grew up being exposed to and excited by.

3d printing is but one of those techniques, and it really has a strong future both commercially and as a medium for the individual hobbiest.