3d printing has become so common at my house that my kids are actually bored of it. "Oh great, Dad 3d printed something. . .again." So when my 9 year old daughter wanted to make Minecraft heart cookies for the school bake sale the next day I saw an opportunity for redemption. We don't often have episodes of "Dad's 3d printing saves the day" at our house so I have to relish them when they come along.
The process is pretty simple:
Model your cookie cutters using any 3d modeling program
Print the cookie cutters using food grade filament
Then make your cookies as usual.
I'll show the basics of making the cutters and then the cookie making details specific to this project.
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Step 1: Designing Your Cutters
It takes a bit of time to learn 3d modelling, but this is such a simple design it would be a good project to start with. The trick is to draw the outside of your cutter as a solid, as if it it were entirely filled with cookie dough. Mmmm, cookie dough.
You can use any cad or 3d modeling program. Starting with the easiest, some good free choices are TInkerCAD, 123Design and Blender. This project is so simple that you could complete it as a first tutorial on any of these programs. If you just want to make the cool heart cookies I'll give you the files I made at the end of this instructable.
After you have drawn your design as a solid you will export it as an STL file and import it into the slicer software you use for your printer. Most slicers will allow you to print the object without top, bottom, or infill. This leaves just the walls which is exactly what you want for a cookie cutter. This is much easier than modeling the inside and outside of the cutter.
For most printers making the walls 2 shells thick will make a nice cutter which is sturdy without being too thick. You tell the printer you want 2 shells and it figures out exactly how thick that should be.
Advanced Tip: Simplify3d, an advanced commercial slicer, allows you to change the settings by layer. You can start by printing a couple of layers with 4 shells and then cut back to 2 shells for the rest of the print. This gives you a nice reinforcement around the top of the cutter similar to what you see on most store bought cutters. It stiffens the cutter nicely while still keeping a relatively fine cutting edge.
Step 2: Printing Your Cutters
We printed the cutters on a SeeMeCNC Orion which is an excellent machine. Its delta design is fascinating to watch. Whatever printer you use there are a few things to consider.
First, use food-safe filament. T-glase from Taulman3d is the best filament I know of which is specifically made from FDA approved material. It is the same type of material used to make plastic water bottles. Avoid using colored filaments especially the inexpensive Asian-made ones. Some of the pigments used in these filaments include lead and other toxic stuff. We don't really know how much of this stuff could leach out into your cookies, but who wants to take a chance with that?
Second, choose the lowest layer height your printer will support. This will give you the best surface quality you can get. The rough surface of 3d prints is difficult to sanitize so we want to make it as smooth as possible. Cookie dough isn't terribly hazardous as food materials go, but it does contain eggs. To be totally safe you can consider your cutters a single use item so you don't need to worry about cleaning them. If you want to reuse them you might consider sanitizing them by placing them in simmering 150F water for 5 minutes. This should be more than adequate to kill any bad stuff, but not so hot as to damage the cutters. Disclaimer: I am not a food sanitation expert so if this really matters to you, you will need to do your own research.
Step 3: Making the Dough
Any rolled cookie recipe will work fine so if you have a favorite recipe go ahead and use it. Just don't hold me responsible if Aunt Ester's prune-lentil icebox cookies aren't as popular as you had hoped. Lacking such a recipe, we chose the basic Rollout Sugar Cookie recipe from the King Arthur Flour website. Making the dough is straightforward. We follow the recipe except that we add red food coloring with the wet ingredients. I suggest gel type food coloring because it is concentrated so it doesn't upset the liquid balance of your recipe. We added about a teaspoon to a single batch, but you can use your own judgement as to just how neon and toxic you want your cookies to look. If you are concerned about food dyes you can use something else to color them. . .although I'm not sure exactly what.
My daughter and I talked about the appropriate color for the background cookie. In the game the background layer of the heart is black. Although you are unlikely to find it in the baking aisle, they do make black food coloring. But on further reflection we decided that a nice chocolate brown would make an acceptable, and infinitely more appealing, substitute.
After mixing up the dough, but before chilling, divide it into rough halves. Mix about a 1/2 cup of cocoa powder into the larger half. You can do this by eye until you get a nice chocolate brown. You may want to add 1/2 tsp of milk or water to maintain the consistency of the dough. Once everything is mixed wrap and chill your dough.
Step 4: Making Your Cookies
The larger cutter makes the chocolate back layer and the smaller one makes the red top. Roll, cut and bake as you would any cookies. My daughter, who made all the cookies herself, commented that the 3d printed cutters actually made it easier to get the cookies out because they could be flexed slightly.
Make sure your dough is well chilled and your cookie sheets are at room temperature. If you notice the second batch is a little less sharp than the first this may because your dough was too warm, or the cookie sheet was still warm from the first batch.
And don't over bake them. You aren't looking for a color change. Like most cookies these are better a little underdone than the slightest bit over done.
After baking and cooling the cookies, pipe a layer of frosting unto the back of the red cookies and assemble the hearts.
You can use your favorite frosting, although I would avoid the one that Aunt Ester makes with tofu and stevia. We make a quick buttercream by whipping a stick of room temperature butter in a stand mixer. Add a cap full of vanilla and enough powdered sugar to make it look like a self respecting frosting. This should take between 2 and 3 cups of powdered sugar, but it is more fun to do it to taste.
Step 5: Wrapping Up
That's about it except for cleaning up of course. If you want to make your own version of these cookies you can download the STL files for the cutters below. But you needn't stop with Minecraft hearts, you could make creepers or endermen or even, dare I say it . . . non-Minecraft things.
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