Cart 0

Fillet Sharp Points

Posted by Laser Tech on

Most people think you can just draw anything and it will laser cut just fine, and it's true the design will cut out, but how strong will it be? How can you make it stronger? Will the people who use it be disappointed or surprised at how it holds up?
Acrylic is a brittle material and much more delicate than the metal charms average consumers are accustomed to. But there are many little tricks you can do to make your project more sturdy, now we will focus on FILLETS.

Filleting - Fillet (pronounced FILL-it, not like a fillet-o-fish) is the action of rounding off a sharp corner.
Interior angles are sharp angles that go into your piece. Protruding angles stick off your piece, like a spike.
If you fillet a corner, even by .01cm, it will greatly reduce the stress on that corner, reducing the likelihood of cracking or chipping off.

To illustrate the difference from a filleted corner vs. non-filleted corner we can use polarized light (any LCD monitor, your laptop monitor will work just fine) and polarizing glasses (some high-end glasses are polarized, as are most fishing glasses)

If you want to take pictures of your laser-cut pieces for analysis you can use a camera with a polarized filter.

This photo shows a polarized filter (held by hand) in front of a clear piece of acrylic laid over a white LCD computer screen brought up to the Google home page. The sample test shows several different U shaped cuts and V shaped cuts with varying sharpness of fillets. You can see that with no physical hands-on stress applied to the piece of acrylic, you can still see the stress on the acrylic as it has been melted to form that shape.

 Now in this photo we can see how by pressing on the edges of the clear acrylic as it is perched on top of another piece of white acrylic, the stress marks grow and show more clearly where the piece is most likely to crack.
The broad stress marks are indicative of the stress dissipating through the plastic which means low likelihood of cracking. Sharp, concentrated stress marks mean that the piece will most likely give in and crack. So the more you can fillet your design, the better. Of course you don't have to fillet in a way that will take away from your design, but it is a good practice to select all nodes after designing a given project and fillet by .01cm

Different programs have different terms for filleting.
Here is a key to help you out:
CorelDraw - Window > Dockers > Fillet/Scallop/Chamfer
Adobe Illustrator -  Effect > Stylize > Round Corner
Inkscape - No quick-fix yet, but see this you-tube for details on how to fake it. Or let us know if there is an add-on for Inkscape that allows quick generation of fillets.

Share this post

Next Post →