Designing a test tube stand

Recently we got some borosilicate test tubes for chemistry projects. The problem with test tubes is that they have a round bottom and they cannot stand up. Instead of buying a stand for the test tubes we decided to design one and to print it in the 3D printer which is more fun. As you can see in the photo we some big and some small test tubes. We decided to make all holes big enough for the big ones to fit inside. I used calipers to measure the diameter of the large tubes We designed it with a height that allows us to easily pick both types of tubes from the top easily We added some rings to the bottom platform so that the tube didn't slip or fall down Before printing the whole thing we printed a small prototype of the holes with 2 different sizes because 3D prints can shrink a little when they cool down. This allowed us to discover that the size of the hole we had chosen wasn't big enough once it printed. So we could change the design before printing the full stand. For design...