I stumbled across some dxf files at CNCzone.com, one of which was a train engine puzzle.
The material I used was some left over luan. It was about .180" thick. I had to scale the drawing so that the assembly slots would fit. The slots were drawn with square ends. This would be fine if I were using a laser to do the cutting but since I would be cutting this with an end mill modifications were in order.
The original slot on the right was drawn with square corners. The curves inside show the limits of where the 1/8" end-mill could cut. The slot on the left is modified to make a flat bottom so the parts will mate correctly.
Another view of the modified slot.
Here is the cutout about halfway through the program on the router table.
Here we have the mostly assembled puzzle.
I don't have a place for all of the parts and seem to be missing a few. I think I will redesign a few pieces and maybe add a few to make everything work out to my liking. After that I intend to cut it in Baltic birch plywood for my soon-to-be six year old nephew. He is really into trains.
My plywood came in on Thursday and I scaled the drawing up to allow for 6mm baltic birch. It is about 30% larger than the prototype above. I was able to use a 3/16 end mill since it would fit in the new wider slots.
It turned out every bit as nice as I had hoped. I need to give it a coat of shellac and it will be ready to go.