My maternal Grandfather game me a game like this when I was a kid, but the molded plastic has broken numerous times. I have no idea what this game is called.

I made use of tbuser's 8bit font (http://www.thingiverse.com/thing:2054) for the numbers on the dice. I made no attempt to balance the dice as I do not throw them.

I printed this in white with 3 extra layers and no infill. After printing, I colored all six faces of the center die and one of the exterior die with a wide tipped black Sharpie leaving the numbers white. The other five dice I filled in the number with a fine point black Sharpie. Modifying this for multiple colors is left as an exercise for those with multiple extruders. ;-)

By happy coincidence the maximum dimension is ~98mm so it should fit on Makerbots or larger platforms, (thing-o-matics may need to rotate by 30º?). Either way, the scad is included so feel free to modify if necessary.

The game is played by randomizing the dice (I usually just roll the whole thing around in my hand or up and down my arm) and then placing on a flat surface. The values of the two black die are added to determine the target value. You must then use the values of each of the 5 white dice exactly once along with any mathematical operations you want to reach the target value. There are usually multiple solutions, but I believe some combinations are impossible.

You can add any other house rules you want to increase/decrease the challenge (must use dice in clockwise direction, time limits, head to head, can/can't use lesser known operations like modulo, etc.)

E.g. For the numbers in the picture the target is 40 + 2 = 42. One possible counter/anti clockwise solution is: (2 + 3) * (6 + 3) - 3 = 42. Another is: 2 ^ 3 * 6 - 3 - 3 = 42. Moving clockwise: ((3 / 3) + 6) * 3 * 2 = 42. In no particular order: 6 * (3 + 3) + (2 * 3) = 42.

Yes, many of the above parenthesis are extraneous and yes, I always consider the number a 6 even if it looks like a 9.

Sorry about the large filesize. What's the easiest (preferable open source or at least free) software to reduce stl filesize?