A guide by Dan Emery - originally posted to the Ponoko Blog.
A couple years back I sought to try and quantify the kerf of our laser cutter, or how much material the laser cutter burns away when cutting specific materials.
The idea behind providing this information is so you can make a more educated guess of what sizes to draw your shapes if you are needing a tolerance fit. This information is particularly relevant if you are creating inlays and slotting joints*.
Please note that these are old figures, which we are hoping to update soon - we cannot guarantee super-precise kerf widths at this time.
Prototyping for yourself is the best way to guarantee the perfect result but hopefully this info will give you an idea of what to expect.
So anyway here are the results...
For those using imperial:
And for those on the metric system:
So what does that mean?
If you are wanting to combine/inlay materials, say a white square within a red one, or something like ColinFrancis jewelry, then you can use this data to help determine what dimensions to create the shapes in your eps files at.
If you were to draw some parts to be cut from 3mm acrylic as dimensioned below,
The white square on the right would end up at 39.80mm and the hole in the middle of the red square would be 40.20mm.
However if they are dimensioned to allow for the laser burning material away, both the hole and the white square will come out at 40mm and they should fit snugly together.
This video shows what I am talking about. The square labeled '40' shows what happens in the first diagram, or when the dimensions for the hole and the bit to go into the hole are the same. The square labeled '40.20' shows a square drawn to allow for the laser kerf. The parts fit snugly together with a nice click.
Slotting joints also rely on the thickness of the material being consistent to be successful. All our materials have a thickness tolerance of +/- 10% of the material thickness.
Check out these guides for more information about interlocking designs: