I use SketchUp for almost all my 3d model drawing. It works well for the kinds of things we draw for model railroads - objects made of rectangular and cylindrical shapes without a lot of weird compound curves. Here's some additional hints on using SketchUp to make a design. Once you have the design, you can save it as an STL file, and then print it on a friend's 3d printer, or upload the design to Shapeways and have them mail you a model.


SketchUp was intended as an architectural drawing tool, but it's also an easy-to-use tool for making 3d models for printing. SketchUp is commercial, but is available as a free download for non-commercial uses. You'll need to download and install the "SketchUp STL" extension to generate the files needed for 3d printing. It's available here.

If you'd like to see what a reasonable 3d model for a freight car looks like, you can download a free design for a Southern Pacific flat car. This is one of my first models; it's actually a design that Southern Pacific never bought. On Thingiverse, you'll find the STL file to 3d print the model, as well as the SketchUp file.

If you'd like a first SketchUp project, try drawing a wood deck on the flat car. When I drew that model, I intended to glue wood decks on, but found I couldn't lay the boards neatly enough. To add a new deck thicken the top face of the car, then emboss lines for the board edges. Finally, extend the board ends a few inches past the frame. I intended to add wood decks to the model, but found I could never do it neatly enough.

General Hints with SketchUp

  • With SketchUp, you can draw shapes roughly, but you can also type in exact measurements. For example, if you draw a rectangle, then type ' 12", 12" ', then SketchUp will size the rectangle to 1 foot square. You can also do this to set lines to a specific length, or to set the radius of a circle.
  • SketchUp is really great for objects that are mostly rectangular (like our trains.) It's not as good at drawing curved surfaces. Curves are always painful in SketchUp. Try to avoid complex curves. If you do circles or cylinders, note that the default circle has 24 faces - printed objects look faceted. If you type "48s" in the dimensions box immediately after drawing a circle, it will be drawn with 48 sides which has much less prominent facets.
  • Do your design both "bottom up" and "top down" - that is, start your design by alternately working on a rough overall shape for the model and adding detail, but also try focusing on key individual parts and try to make sure those are working. For example, with the Track-Pull tractor, I started by roughing out the shape of the tractor to get the size and overall shape correct. I also experimented with the caterpillar tread in detail to get it right. With the Battleship gondolas, I started with a rough box representing the overall car and adjusted the design, but I also focused on getting the side doors correct early on.
  • SketchUp loves to snap lines to existing points or lines, so draw temporary lines to give SketchUp a place to draw to. If you want to set rivets 3" apart, draw a 3" long line, and then draw a circle starting at each end point. Delete the line before you try using the "pull up" tool to extrude the circle into a cylinder and rivet.
  • SketchUp allows you to group shapes together in a single element. Groups are great so you don't accidentally change a sub-assembly, and also lets you move that subassembly around relative to the rest of the model. Groups also give you a way to get a sub-assembly out of the way - grab it with the move tool and lift it 10 feet above the model. You've now got room to work on a different part. Move it down 10 feet to get it back in the model; use the ability to type measurements to move it exactly.
  • Making piping is difficult in SketchUp because of the effort of making turns and intersections. I do smaller piping with hex shapes so I can quickly draw right angle turns, and can edit the shapes easily. The printed objects still look round.
  • Work from plans whenever possible - you'll often find detail you didn't see in photos.
  • Common problem with Sketchup: extra faces inside the model confuse things. Try to prune these out. I think Shapeways gets rid of them for you, but the native Formlabs software doesn't. I occasionally used netfabb basic to identify and remove extra faces, but I also looked for previews in the Formlabs software for problems and then searched for an extra face that got the printer confused about the inside and outside of the model.