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 .svg format. If you're handy with Illustrator or Inkscape, you can create your own and export an .svg file of the result.
If not, you can still create your own .svg file with the help of Google image search and Inkscape.
- Search Google images for "bat clip art."
- Your ideal image would be one that is black and white with no grays, like the one above.
- Save the image to your computer.
- If this is an .svg file, you can skip to Step 5.
The image above is from here.
Step 3: Make an Outline in Inkscape
- Open up Inkscape.
- Choose File > Import (Ctrl + I).
- Choose Path > Trace Bitmap (Shift + Alt + B).
- Select "OK."
- Close the Trace Bitmap window.
Step 4: Save an SVG File
It will look like nothing has happened, but really a new vector version has appeared on top of the original image.
- Move the image down.
- Choose the "Edit Paths by Nodes" tool (F2).
- Click on the image you just moved.
You'll 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 we highly recommend learning that skill if you don't already have it.
- Go back to the "Select and Transform Objects" tool (F1).
- Select the original image.
- Delete it.
You now have just the vector image. Save it.
Step 5: Go Into Fusion 360
Now it's time to get into 3D!
Fusion 360 is a 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. We’ve partnered with Autodesk to ensure a seamless experience when using Fusion 360 and the Othermill together. An Othermill CAM post-processor is included by default with Fusion 360, and a tool library is available for download.
OK, so let's get back to the project at hand.
- Choose Insert > Insert SVG.
- Choose a plane.
- Click on the small folder icon (see pic) to choose a file.
- Click "OK."
- If you don't see the image, it's probably big and off the screen so zoom out.
Step 6: Move Into 3D Shapes
The .svg file is in a 3D space, but it's still a 2D shape. To make it 3D and give it volume, we need to pull it up a bit. Here's how:
- Right-click on the bat shape.
- Choose "Press Pull."
- Pull it up a tiny amount. I'm using 1 mm.
- The color is now gray to show that it's a solid shape.
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: Copy and Move 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.
- Open up the "Bodies" folder in the browser on the left.
- Right-click on "Body1" to open up the menu.
- Select "Copy."
- Right-click on "Bodies."
- Select "Paste."
- Drag the arrow up or enter a value in the text box to move it up.
Step 8: Modify the 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 doesn't give much room at all, but it can still have a nice effect.
- Move into the top view so you're looking straight down.
- Select Modify > Scale.
- Select the "No Selection" text next to "Point" in the Scale menu.
- Select a point on the shape that you want to have in the center of the scaling effect.
- Change "Scale Type" to "Non-Uniform."
- Tweak the scaling numbers.
Step 9: Connect the Two Objects
Now that we have two variations of the same object, it's time to connect them. Luckily, we have a great tool, Loft, that can merge them.
- Move the view with the Orbit tool so you can see both shapes.
- Select Create > Loft.
- Select both objects.
- Select "OK" in the Loft menu.
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" (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.
- Select "Inspect."
- Click on the leftmost point of the object.
- Click on the rightmost point of the object.
- See what the distance is in the Results panel.
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.
- Select Modify > Scale.
- Select Object.
- Enter "0.1018" for scale factor.
- Select "OK" in Scale menu.
And zoop! It shrinks down to a tiny object. Zoom in to see it up close.
Step 12: Fine-Tune the Shape
Now that we have the object at the right width, let's tweak the thickness.
- Select Modify > Scale.
- Select "Non-Uniform."
- Change the settings for the axis that controls the thickness until it has the effect you want. Be sure to orbit around the piece to see the effect from different angles.
- Select "OK" in the Scale menu.
Step 13: Check the Thickness
Now we'll use the Inspect tool to see how thick the object is.
- Zoom in on the object.
- Select "Inspect."
- Select a point on the top of the model.
- Select a second point on the bottom of the model that is directly below the first point.
- See the results in the Measure panel.
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.
- Orbit around the object to see the bottom side.
- Right-click on object and select "Press Pull."
- Enter 4.72 mm in text field.
- Select "OK."
And we now have our final object! Whoohoo!
OK, relax for a minute. Now get ready for the next bit.
Step 15: Step 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.
- Choose "Setup."
- Select the "Top corner 1" for "Bounding Box Point."
Step 16: Set Up the Size of the Material
Copy the information in the image above. This is all for the machining wax material 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: Create 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.
- Select "Select" next to "Tool."
- Change "Tool Type" to "Flat End Mill."
- Enter "1/8" in bottom left text field.
That narrows it down to just a few end mills. Select the correct option.
Step 18: Create 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.
- Select 3D > Contour.
- Add the 1/16" ball end mill.
- Copy the rest of settings in the pictures here.
- Select "OK" at bottom of the menu.
Step 19: Export Your Toolpaths
For each toolpath, we want to export these as files that the Othermill can use. This is done with the Post Process technique.
- Right-click on "Adaptive Clearing."
- Select "Post Process."
- Enter in the information from the picture with the Othermill post processor selected.
- Save to a handy folder.
- Repeat the process for the "Contour" toolpath.
Step 20: Set Up the Othermill
Yes! We've made it to the milling stage!
- Turn on the Othermill and connect it to your computer.
- Place the purple machining wax in the front left corner of the bed. I'm using the alignment jig, but this is not necessary.
- Holding the wax, run a bead of hot glue around the bottom edges to keep it in place during milling.
Step 21: Set Up the Job in Otherplan
Now we're very close to being ready to go. To get the file set up in Otherplan:
- Select "Setup Material."
- Select "Machining Wax (Purple)."
- Select "Standard" size.
- Click "Continue" and "OK."
- Import the roughing toolpath file.
- Add "1/8 in flat end mill" as the "Tool to Use."
Step 22: Insert the 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 haven't done any projects with the Othermill before, be sure to check out the Hello World tutorial for more detail about this step.
Step 23: Mill the Wax
- Select "Start Cutting."
- Watch the Othermill to make sure the job is going correctly.
- Once the roughing pass is done, delete the file in Otherplan.
- Import the finishing toolpath.
- Insert the 1/16" ball end mill.
- Select "Start Cutting" to start the finishing pass.
And with that, your piece should be done. Vacuum it off to clean it up, and you're ready to make a mold.
Step 24: Mix and Pour the Silicone
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, for about 20 seconds or so. It should be a consistent color.
Pour the silicone from 12" 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 4 hours to cure.
Step 25: Melt and Pour the Chocolate
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 will set in about 20 minutes.