Having a 3D printer as a railway modeller is very useful as the price of small models for the hobby is pretty astronomical these days.
Some of the items I have 3d printed for my model railway are shown below.
Having purchased a fair few second hand wagons with broken buffers I had the need to be able to produce Hornby Wagon pattern buffers for replacements. This was the primary driver for getting a 3d printer of my own.
I also sell these sometime on my Ebay Account.
I have been developing working point levers and am currently on version 3.4.
The concept is to produce levers that will move when the point blade is moved via point motor, hand or rod-in-tube. For my layout it is via rod-in-tube.
The levers are 3D printed with resin, and currently are still in the testing stage with samples out in the model railway community. However, it does appear that I need to use a stronger resin.
There is a full page dedicated the 4mm scale 3D printed point levers.
Once they are considered robust enough I will sell them through my Ebay Account.