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Creating Bridges for Nested Shapes in Laser Cutting

Table of Contents

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 laser 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 than 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!

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Not sure about your design? Have a question or want advice? Shoot us an email at support@sendcutsend.com. We’ll get back to you as soon as we can. The more we can help you, the more it helps us provide you with the best and quickest laser-cut parts.

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Flush Standoff, 4-40, .250" Zinc plus Clear Chromate

Thread Size4-40 x .250″
Hole size in sheet (+0.003/-.0.000).168″
Minimum sheet thickness0.040″
Maximum sheet thickness.125″
Fastener materialSteel
Minimum distance hole C/L to edge0.230″
When determining the distance between two or more fasteners, you can calculate the distance by the formula, C/L to edge + 1/2 the diameter of the second mounting hole..314″
Recommended panel materialSteel/Aluminum
Coating typeZinc
Aluminum material ranges (5052, 6061, 7075)0.040″-0.125″
Steel material ranges (CRS, HRPO, HR)0.048″-0.119″