How much material does the laser burn away? September 11
This week 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*. These figures are averages and the usual caveats apply. Prototyping for yourself is the best way to guarantee the perfect result but hopefully this info can mean one less prototype.
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.
Anyway, I hope that can be some inspiration for you. Happy making.
* 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. I will create a post in the future which will address slotting joints in more detail but for now you can refer to here for notes about nodes or ask a question in the forums.
September 11th, 2008 at 6:06 pm
Excellent information! I have been wondering about how to tackle Ponoko laser kerfs within my SketchUp plugin - now I have all of the information I need (I just have to find time for coding).
September 12th, 2008 at 6:01 am
Could you cut and paste those numbers into the post instead of using screenshots of Excel?
September 12th, 2008 at 9:14 am
This is super helpful!!!! Thanks so much for the research!
Bre
September 12th, 2008 at 12:23 pm
For thin materials it wouldn’t make much difference, but for some jobs one should consider the angle produced by the laser’s cone-shaped beam.
I.e. the vertical edge has a slight taper on it, (depending on the focus point and the lens used) so the 40mm square could be a wee bit bigger on the bottom than the top.
It follows that for a *really* neat fit, one of the pieces should be inverted.
The thicker the material, the more taper from top to bottom of the cut.
Bob
September 28th, 2008 at 1:52 pm
Exactly what I needed,
many thanks for this detailed information.
Gilbert
November 3rd, 2008 at 7:58 pm
[…] Nodes are little bumps located in the slots or on tabs in your product that are there to help compensate for material thickness variations and the laser kerf. This idea is they compress when a product is assembled providing friction at points rather than along the whole surface of the slot. This means the slot can be fractionally wider at the opening allowing the pieces to be slotted together easily but still create a snug joint. […]
November 23rd, 2008 at 7:44 pm
This is somewhat of an oversimplification that can get you into trouble. The laser kerf width is very much a function of the speed of the laser. Long straight edges have a narrower kerf than slow curved edges.
November 27th, 2008 at 8:14 am
[…] The tolerance advice posted at ponoko.com doesn’t apply for all situations. It’s slightly off when dealing with very small inlays such as on my first project. They didn’t quite fit. After some careful caliper measurements, I’m trying again. This time with a a modified design and an inset/outset distance of 0.19mm. […]