What is kerf?
Ponoko lasers focus a beam of light to cut through materials and the amount of material that the laser burns away is known as kerf.
The head of the laser directly follows the paths in your design file, meaning the kerf is centered on these lines.
The dimension of the kerf starts at about 0.2mm and varies depending on both your material and your design:
The thicker and/or harder a material, the longer it takes to cut all the way through and the bigger the kerf is going to be.
Natural materials (eg wood) aren't always completely flat, meaning that the laser may not be perfectly focused in parts giving you a wider kerf in sections
The laser cuts curved lines slower than straight lines, therefore the kerf is bigger on curved paths
The beam of light has a cone like shape, therefore edges are not always perfectly 90 degrees and squares and circles will not be perfectly symmetrical (this is more noticeable on our thickest sheets of material) .
Designing to allow for kerf
If you are using one of our laser cut metals, you do not need to compensate for kerf in your design. Our metal laser cutting machines auto offset lines to compensate for kerf.
For all our other materials, you may want to consider kerf in your design setup.
Put simply, parts will be smaller and holes larger than in the cutting file.
Let's take a look at some specific examples....
Cut parts will be smaller than your file:
The average kerf for our 3mm clear acrylic is 0.2mm and kerf is centered on cutting lines. You’d expect a square submitted at 40mm will result in a part that is approximately 39.8mm in this material:
To achieve physical a part size closer to 40mm you’d want to submit a file with a size of 40.2mm.
Cut holes will be larger than your file:
The average kerf for our 3mm clear acrylic is 0.2mm and kerf is centered on cutting lines. You’d expect a hole submitted at 40mm will result in a hole that is approximately 40.2mm in this material:
To achieve a physical hole size closer to 40mm you’d want to submit a file with a hole size of 39.8mm.
But how do I know the kerf for my chosen material?
Material specific average kerf sizes are listed on our materials pages under technical specifications. Check this as well as minimum feature and part sizes before finalizing your files.
Please note that CO2 lasers have dimensional accuracy of +/- 0.005in (0.13mm). This means there can be a small variation in resulting part size between orders even when kerf is accounted for. It's advisable to prototype new designs and materials or best outcomes.
If you are making 3d interlocking designs please find some additional design tips here.