Creating Bridges for Nested Shapes

You're familiar with stenciled letters. Stencil letters have bridges that connect the holes of the letters to the space around the letter. Something we come across quite often is shapes that don't apply to this same rule. We will call them nested shapes.

Nested shapes (shapes inside shapes) need to include bridges just like that stenciled text we just talked about. Let's say you wanted to cut a donut from your metal sheet. Once the outer circle has been cut out, there is nothing left to cut the inner hole from. You need something to connect or hold onto that inner circle.

For example, let's say you're designing some Christmas ornaments. In the example on the left below, I have highlighted "good cuts" with green. These cuts are connected to the shape of the ornament. The "lost cuts", which are outlined in red, have no connection to the outside shape and therefore will be lost.

Now for a more complex example. Maybe you designed a really cool wall clock back using a geometric pattern. Just keep in mind that all your cut-out shapes must somehow be connected to the outer shape.

Creating Bridges

Some steps or vocabulary may vary depending on your design software, but we'll go over the basics. In this example, I am using Adobe Illustrator.

Let's go back to that Christmas ornament. When adding bridges, you want to make them look like they are part of the intended design and not just thrown on as a quick fix. You'll also want to keep in mind things like your material thickness and design complexity. Lines and shapes should not be less that 1.5x your material thickness.

Let's first remove any small and unnecessary shapes. You'll see I removed three shapes from my design.

Next, let's add our bridges. There are many ways to go about this. This is my method. Draw a shape where you want your bridges to be placed. Selecting both the shape of the reindeer and my bridge shapes, use the Minus tool in the Pathfinder Palette. This will subtract the bridge shapes from the reindeer shape.

We now have bridges. View your design in Outline mode to make sure no empty shapes have been created using the Minus tool. I found three. These will need to be removed before proceeding. 

I like to round out my corners. This is easier on the laser, and, makes it easier to remove your shapes once cut. Once the reindeer shape is as you want it, the last thing to do is cut it from the ornament shape. Selecting the shape of the ornament and the reindeer, use the Exclude tool in the Pathfinder Palette.

That's it!

When saving from Adobe Illustrator, please send us the .ai file. Before you upload your file to us, be sure to go through the pre-flight checklist:

My file is 2D
My file is built at a 1:1 scale
All my type is outlined
I have no open contours
Reversed type has bridges
I have cleaned up all stray points, empty objects and text areas
All my objects are on the same layer
All holes and cutouts are at least 1.5x material thickness
No feature or detail is smaller than 0.010"


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