This is 3D printed parts for a very small and heavy drive unit for moving wagons on the travers. There will be one on each track. The two on the upper left are from I materialise and the two upper right from Shapeways. Material is blackened stainless steel. They have schrinked about 4-5% which gives me problems. Also they are a bit out of square shape. Shapeways are best here. I found the steel to be quite hard and I had problem to cut threads for 1.2mm screws. One solution is to 3D print a larger hole and pressfit a brass tube into it. Then making threads in brass is easy