I started making my own hamburger buns a few months ago -- to great success. It's very easy to do and the benefits are pretty good: fresher, better taste, not mushy! The only part of the experience that was sub-par was the finished, sliced bun. I either sliced too high or too low, or, most often, some of each. My finished bun was cut almost as bad as the commercial buns. Most helpful hints in this area suggest using a cutting board as a guide. This proved to be awkward and impractical.
But hey! I've got a 3D printer and OpenSCAD.
Here's what I came up with, and it works remarkably well. My bun slicing guide is large enough to accommodate buns up to 4 1/2 inches in diameter. The slicing height is maxed at 3/4 inch (that's a 3/4-inch bottom) and is adjustable down to about about 1/4 inch, in 1/4 inch steps using the spacer disks. Just print the number of discs you think you need, but only 3 will fit under the gripper ribs. The gripper ribs keep the bun from spinning as you slice away at it. (which version 1 lacked and which turned out to be much needed.)
To use it, place any needed spacer disk on the cutting tray, put the bun in place and hold your knife flat against the two side rails and grip the guide's handle, keeping your fingers behind the guard and well away from the cutting path -- the knife edge will be passing through the back part of the guide (see the pic) and no one wants to have their day ruined. Just take your time and be aware of where the knife edge is at all times -- basic kitchen safety.
If you have an electric knife, use it for better quality cuts. If not, a bread knife will work almost as well, and its what I use when I don't want to be bothered getting out the electric knife.
One last key to making this work well -- put some rubber feet on the bottom (see pics). The added stability is worth the minor cost since it makes the guide much easier and safer to use.
You will need to enable supports, but they're perpendicular to the two surfaces and those surfaces (where the knife blade goes) are going to be scratched by your knife blade, anyway.
I started off with this excellent recipe from All Recipes: http://allrecipes.com/recipe/233652/homemade-hamburger-buns/ and have modified it slightly. Since I live a mile above sea level, minor adjustments - mostly to the process - were needed. I replaced 4 oz of AP flour with bread flour to help the structure and I bake for 18-20 minutes at 350 instead of 15 minutes at 375. Non-altitude-related changes: I use a bread machine to make the dough. I portion and freeze the dough balls before the first rise and use them one-at-a-time, as needed. I don't use the egg wash, but a light mist of milk right before baking makes a nicely-browned top.
PLA or ABS - either is fine.
This print covers a fair amount of surface area and will not fit on many of the smaller printer beds. I'm sorry about that -- can't be helped. I understand the frustration well, having started this hobby with a plywood Printrbot Simple. I could make a smaller version of the slicing guide -- perhaps for slider-sized buns -- if there is a need. My model is in OpenSCAD and is almost completely parameterized, though I haven't test-dropped the diameter down that far. Those silly-but-needed ribs on the inside curve add almost an hour to the rib-less,5-second, full render in OpenSCAD. I'll see if I can figure a way to optimize the code.
If I can get the code parameterized well enough, I'll put this model in the Customizer, though the current published render works as-is with various-sized buns.