Hi, this is Ed from Other Machine Co.
Perhaps you're obsessed with Batman. Or maybe, like me, you have a kid who loves the cartoons. Either way, what better way to show your love than to make chocolate Batarangs to both play with and eat.
Step 1: Tools and Materials
Step 2: Get or Make a 2D Image
What we'll need to make the 3D shape is a 2D shape for the outline of the Batarang. This 2D shape will need to be a vector file in a SVG format. If you're handy with Illustrator or Inkscape, you can create your own and export a SVG file of the result.
If not, you can still create your own SVG file with the help of Google Image Search and Inkscape.
The image above is from here.
Step 3: Make an Outline in Inkscape
Step 4: Save a SVG File
It will look like nothing has happened, but really a new vector version has appeared on top of the original image.
You will see lots of little squares around the image. These are the points for the paths that make up the image. You can start messing around with the points to tweak the image, and I highly recommend learning that skill if you don't already have it.
You now have just the vector image. Save it to be able to use it in the next step.
Step 5: Going into Fusion 360
Now it's time to get into 3D!
Fusion 360 is a pretty new product from Autodesk that came out in 2013. It's a cloud-based software that lets you design in 3D. It also has CAM software built in. That means that you can create toolpaths for a CNC machine like the Othermill. Which is really, really awesome.
OK, so let's get back to the project at hand.
Step 6: Moving into 3D Shapes
The SVG is in a 3D space, but it is still a 2D shape. To make it 3D and give it volume, we need to pull it up a bit. Here's how:
If you just want a solid version of a 2D shape without any extra shaping, you can drag the blue arrow to make the object even taller. Don't worry about the numbers for now, just focus on getting the right proportions. Then you can skip to step 9.
Step 7: Copying and Moving Up
To get a tapered effect for the top of the object, it's quick and easy to use a copied shape. Here's how to copy the object and move it up.
Step 8: Modify Top Object
A quick and dirty way to get a quick bevel edge effect is to shrink the top object. The amount you can shrink it depends a lot on the design. For example, this design does not give much room at all, but it can still have a nice effect.
Step 9: Connect the Two Objects
Now that we have two variations on the same object, it's time to connect them. Luckily we have a great tool, Loft, that can merge them.
This creates a new object that joins the object on the bottom with the one on the top and creates a smooth transition between the two.
Step 10: Resizing, Part 1
Now that we're getting closer to the final shape, let's make sure that we're working in the right size. The width of the machining wax that we're using is 3 inches (76 mm). We'll also want about an 1/8" (~3 mm) margin around the positive part of the mold once we make it, so that gives us a max width of 2.75" or 70 mm.
So what we need to know is just how wide the current object is.
I can see that the distance here is 687.35 mm. That's huge! It's easy enough to scale it down, however. All we need to do is divide the end size we want, 70 mm, by the current size, 687.35 mm to get the scale factor we need: 0.1018.
Step 11: Resizing, Part 2
Now that we know the scale factor, it's just a matter of applying it.
And zoop! it shrinks down to a tiny object. Zoom in to see it up close.
Step 12: Fine Tuning the Shape
Now that we have the object at the right width, let's tweak the thickness.
Step 13: Check the Thickness
Now we'll use the Inspect tool to see how thick the object is.
The results here are 1.28 mm. This would make a pretty thin piece of candy so we'll make it a little thicker in the next step.
Step 14: Drop the Bottom
I'm pretty fond of chocolates that are 6 mm thick which means that we need another 4.72 mm in the object. To do that, we just flip the object over and pull on the bottom.
And we now have our final object! Whoohoo!
OK, relax for a minute, now get ready for the next bit.
Step 15: Stepping into CAM
CAM is what we do to go from a 3D model to creating instructions to send to the Othermill. With the CAM fille, the Othermill will be able to mill our shapes out of a piece of wax.
The first thing we need to do is determine the Setup. This covers the size of the material and the position of the model within.
Step 16: Set up the Size of Material
Copy the information in the image above. This is all for the material which is machining wax with the dimensions 76 mm x 76 mm x 12.6 mm.
Offsetting from the top by 1 mm makes sure that the mill will finish the top of the material. If the model was at the very top, the surface quality of the wax would be the surface of the final piece.
Step 17: Creating the Roughing Toolpath
Toolpaths are often broken down into multiple steps. There's the roughing toolpath and the finishing toolpath. When we want to clear a lot of material quickly we'll use a larger end mill. Here that's the 1/8" flat end mill. This clears out the large majority of the material, but still leaves a little bit around the model for a smaller end mill to clear away with more detail. It's a lot like painting a room where you use a roller brush to do most of the work and a small brush for the edges.
To create the roughing toolpath, I'm using the Adaptive Clearing option under 3D > Adaptive Clearing.
Recreate the settings in the pictures above. The second picture is how you choose the tool. Fusion 360 has a ton of tools to choose from. Here's how to quickly refine the tool search.
That narrows it down to just a few end mills. I selected the last option.
Step 18: Creating the Finishing Toolpath
Now we want to create a finishing path. The finishing path cleans up the details on the top of the object with a smaller end mill: the 1/16" ball end mill.
Step 19: Exporting Toolpaths
For each toolpath, we want to export these as files that the Othermill can use. This is done with the Post Process technique.
Step 20: Post Processor
Fusion 360 will soon be updated to include the Othermill post processor, but until then, here's how to add it.
Step 21: Setting up the Othermill
Yes! We've made it to the milling stage!
Step 22: Setting up the Job in Otherplan
Now we're very close to being ready to go. To get the file set up in Otherplan:
Step 23: Insert End Mill into the Collet
Place the 1/8" flat end mill into the collet, tighten it, and follow the instructions for setting the height.
If you have not done any jobs with the Othermill before, then be sure to check out the Hello World Instructable for more detail about this step.
Step 24: Mill the Wax
And with that, your piece should be done. Vacuum it off to clean it up, and you're ready to make a mold.
Step 25: Molding
Build a box around the wax to hold the mold in place. It doesn't have to be fancy, it just can't be made of material that is absorbent. The box I made here uses a popsicle stick and some torn up parts of a cardboard box. It's all held together with hot glue.
Once the box around your wax is ready, mix up two equal parts of the Copyflex Liquid Silicone. Stir it until it's well-mixed, about 20 seconds or so. It should be a consistent color.
Pour the silicone from 12 inches above the wax piece. This height allows the silicone to stretch out and release air that was mixed in during stirring. This is called a "stretch pour."
Once the wax is covered, let it sit for four hours to cure.
Step 26: Melt and Pour
Put the Ghirardelli Chocolate Melting Wafers into a glass or bowl and microwave it. Watch it carefully so that you only melt it just as much as you need. Stir it up and then pour it into the mold.
The chocolates can set in about 20 minutes.
Step 27: Eat!
You now have bat-shaped chocolates. Make as many as you want for Halloween or a superhero-themed birthday party.