This is a project from my archives but i think it really shows good, simple process to make a significant amount of a thing.
I was contracted to make a 500 piece batch of small plastic toys. The design was a simple extrusion of an existing company logo.
I ran through the possible processes to do it, the volume needed was too high to use just a 3-d printing solution and too small to justify the cost of traditional manufacturing.
Step 1: Basic geometry
Once we had the scale decided i used a high res 3-d printer to print a test mold which was a simple negative cavity made from the original 3-d file. I used this just to prove the process and make sure the geometry of the part wouldn't cause any casting problems and to check that the final cast part would be durable enough.
Step 2: Making the master
You can use any method you are comfortable with to get to this point; cut, carve, print, sculpt, spit, whatever the important thing to remember for this project is it was going to be a simple 1 sided mold. All of my geometry needed to rise from a single ground plane.
Basically i wanted to make slightly complex ice-cubes.