Model railroads are a very popular hobby recreation. In your childhood, you may have become accustomed to the Christmas trees with train sets. That may be where many of us started, but model railroad layouts can be large, complex and hyper-realistic, a far cry from the toy trains of our youth. Most items for model railroading can be purchased as a kit or ready-made. But with the advent of the 3d printer, you can home make many of the train and train accessories parts. Some are free STL models from such places as Thingiverse.Com, and others you will have to purchase the STL file from a designer.

You can 3d print model railroad rolling stock accessories and shells, and train layout accessories, like buildings, bridges, hills and other features. Wheels, couplers and track are still best purchased, as they require metal bearings and manufacturing to allow them to roll and work correctly (and to transmit power).
With 3d printing, you can reproduce almost everything to life, from people to buildings and even rolling stock shells. Additionally, you can add minor details to make them life like.
3d Printing in Railway Modelling
Hobby manufacturers, such as Bachmann and Hornby, have adopted 3d printing for many years when prototyping new models. Prototyping is the technique where the designers create one-off versions of their designs and observe whether the model fulfils the design requirements. It’s one thing to see it on a computer screen, and another to see a model in your hands or on a tabletop layout. 3d printing is ideally suited for prototyping, as it prints one at a time at relatively low cost. But those prototypes never make it down to the hobbyist, though. They’re strictly a step in the manufacturing process.
Though some modelers prefer to build their models traditionally, either from plastic kits or from scratch, using a myriad of materials, most modern brands have adopted some products available as 3d printed parts as a way for consumers to buy their products. The printer market has both cheap and highly detailed 3d printers, meaning you can have your own model railroad production facility right in your own home.
3d printing allows hobbyists to produce different models on any scale that the printer can fit in the print area. As a model drops in size, though, the walls of the model become very thin, and may not be suitable to print. A good compromise is to find HO scale models with robust walls for either scaling up to T or O scale, or down to N scale, or in extreme cases, Z scale. Specifically for Z scale and that size, it’s best to find models designed for smaller prints to avoid the walls or details becoming so small that they break easily or are too thin to properly print.
Of the two styles of home 3d printing (DLP resin and FDM filament), you’ll find the DLP resin is best for detailed models, like locomotive shells, rolling stock shells, detailed items (like signals or railings) and even dead tracks (that aren’t powered, of course). Larger items, like bridges or larger buildings are better suited to the FDM filament printer, as it can handle the larger size and the layer lines (usually thicker on FDM filament printers) are less noticeable.
I say shells above, as the bodies of the locomotives or rolling stock are fine to 3d print, but the trucks (the wheel assemblies) and the actual motors and wheels of a locomotive require precise metal engineering. That’s beyond home 3d printing. But you can certainly purchase a locomotive motor or model railroad trucks for a rail car, and attach them to your own 3d printed bodies and detail parts, to create finished models. This allows you to create items that aren’t otherwise commercially available, or just items that you can boast that you’ve created on your printer!
3d Designs Available On Thingiverse.Com
There are a ton of great models available for free on Thingiverse.Com. I’ve included several examples here of models in each of the categories of Locomotives, Rolling Stock, Accessories or Detail Items and Scenery Items.
Locomotives
Tasrail D Class Locomotive
https://www.thingiverse.com/thing:4521801
From lkernan
This shell for a locomotive is unique, as no one else is making Australian diesel locomotives. You’ll still need to supply the motor and running gear and couplers, but the body will go over top and look great on your layout!

VL-10 Locomotive
https://www.thingiverse.com/thing:567332
From tweaker123
This is another design that’s not made as a regular plastic model. You can customize or print as designed, and create a European electric locomotive that will be unique to your layout.

Rolling Stock
HO Scale Hopper Car With Three Different Loads
https://www.thingiverse.com/thing:4763843
From KraftTrains
While there are many hopper cars available on the market, this design allows you to create as many as you like, and vary the loads within. You could even use the loads as a template to create your own custom loads. You’ll have to supply the trucks and couplers, but the price will be vastly lower, and you can paint them in your favorite railroad livery.

TGR FE Class Log Wagon
https://www.thingiverse.com/thing:4338880
From lkernan
Here’s another Australian design that, although there are some log carriers already on the market, none match this Tasmanian design. It’s a good way to get unique items into your layout without breaking the bank!

Accessories or Detail Items
Athearn HO Scale Blue Box GP9 Air Tanks
https://www.thingiverse.com/thing:2559741
From pick013
The GP9 locomotive is a staple in North America, but many existing scale models don’t do the air tanks justice. Print replacement tanks and attach them to improve the detailed accuracy of your models.

Electric Locomotive Insulators
https://www.thingiverse.com/thing:4556873
From phildc
This is a common item that anyone doing an electric track layout will need. You’ll likely need a bunch. They’re simple designs, but with a 3d printer, you can print as many as you’ll need!

Scenery Items
Truss Arch Bridge
https://www.thingiverse.com/thing:272773
From wolverineboat
Mechanical steel bridges are perfect for 3d printers. The printer can make a beautiful design that would otherwise cost you quite a bit from a model manufacturer. And with a little design savvy, you could modify the length, to suit your specific layout.

Diesel Refueling Station
https://www.thingiverse.com/thing:4722092
From kabrumble
Resin DLP 3d printers can do the detail necessary for this sort of track-side accessory for your layout. It’s an eye-catcher, and well worth making. These older diesel refueling stations were common in the last century, and your layout will look the part with one alongside your layout.

Not everything is available or already designed, though, in either the ready-made model or even 3d STL form. If you have something specific in mind, you may need to design it yourself with 3d computer aided design tools (CAD) or find someone willing to do that for you. Designers usually charge a hefty fee to do this sort of work, and the more detailed, the more money (generally). Still, if you have to have that one item that’s going to make your layout unique, then designing for yourself is a neat way to go. For simpler designs, I rely on TinkerCad.Com as a browser-based design tool that will export STL files that you can print on your home 3d printer.
If you’re making a model railroad layout, you’re stuck with what’s available to everyone else. With a 3d printer, that all changes. You have access to more and varied designs, and you can customize items to make your layout unique and exactly the way you envision it. Happy railroading!
Related Questions
How do you scale a model for 3d printing?
You can adjust the scale of an item in your slicer software before loading the sliced file in the printer. For example, if you have a model that’s HO scale (1:87 scale) and you want to print in N scale (1:160 scale), adjust the scaling of the model in the slicer to 87/160, or 54.4%. Now your model will be sized for N scale.
What is the largest object that can be 3d printed?
Your 3d printer will determine the largest object that can be printed. So, on a print bed that’s 300mm by 300mm, a thin object that’s oriented diagonally could fit if it was around 400mm in length. Remember to take into account the length, width and height of the object. To print an object larger than the print bed, you’ll have to section the model into parts and print each separately. If you use this method, the size can be virtually unlimited.