You can’t think of the laser as a saw blade or other tool cutting through material, where the cut takes on the shape of the tool.
The laser power starts attenuating as soon as it reaches material and begins to be absorbed by that material.
The laser beam itself also has higher power concentration at the center of the beam and less near its outer diameter.
These two reasons are why the kerf is angled.
Focusing at the middle of a material will have the most noticeable affect when running scores through 1/4" clear acrylic where you can see the impact of the settings. You actually will get a deeper score by focusing at the middle because the outside diameter of the laser has already vaporized the material in front of the more focused power at the center of the beam. While the middle part of the score will be deeper, it will also be more narrow because the outer part of the beam has already been absorbed by the material.
That’s it. There are no exceptions. This is true for all rigid materials which hold their shape after being cut, from all suppliers, using any cutting tool, of any type, from any manufacturer. Anyone who says differently is wrong.
I’ve seen people say thing like “for tabs you have to do this or that differently”. Wrong. ALL closed shapes get kerf adjustment in the EXAXT SAME WAY as ALL OTHER CLOSED SHAPES.
Above there is something about adjusting for the full width when working with diameters. I suspect that person is right… maybe… but the wording is confusing. You ALWAYS offset by HALF the kerf width for ALL SHAPES. Full circles: half the kerf. Inside of a circle: half the kerf. Outside a circle: half the kerf. Inside a triangle: half the kerf. Outside a rectangle: half the kerf. Cutting out a kitty cat shape from acrylic: half the kerf (Want to keep the inside? Offset by half the kerf to the outside of the shape. Want to have the hole the exact size of your kitty cat? Offset by half the kerf to the inside of the shape.). Cutting Proofgrade: half the kerf. Cutting with a K40: half the kerf. Using a VMC: half the kerf. Using a table saw: half the kerf. Shooting a laser from space: half the kerf.
What is a “closed chape”? ANY shape. Is a line a closed shape? No. A squiggily line? No. What if the line is bent into the shape of the USA, but the two endpoints don’t quite meet? In that case you’d be looking at a line, not a closed shape. What if someone connects the endpoints? NOW you have a closed shape, and if you want to cut it out you will need to offset that line by half the kerf of whatever cutting tool you’re using.
The CAM export works great, if you use the Autodesk DXF post processor. I have been unable to get a good export with any SVG processor. This means that I have to bring the DXF into another app to convert to SVG.
As I mentioned in another post, I currently use Vectric VCarve Pro for the DXF->SVG conversion, since I have run into sizing problems with Illustrator or Inkscape; although, I think I figured out what I was doing wrong with Illustrator, but I have not had time to test it yet.
Yeah, that’s what I’m discovering. The SVG exports are all mostly broken. And for DXF, that add-on script is way easier to use than setting up a CAM process. I’ll save that for when it fails.
I don’t find the CAM process to be more than a few clicks. The other advantage is that it is really easy to change the origin orientation to setup the CAM process for different pieces of a model. I don’t recall if the DXFtolaser add-in supports that functionality.
Kerf=0 for proofgrade and kerf=20 for non-proofgrade?
Does the GF settings somehow adjust for kerf then and not for the non-proofgrade?
I’m new to the concept of the kerf but not Fusion360…I get that kerf is the beam that is cutting the material and that if you want exactly sized shapes you need to adjust for it. I just want to be clear that in proofgrade materials I won’t have to worry about this…
I can do some tests, but I thought I’d ask before wasting materials!!
So is the point then to determine the kerf adjustment you need for your designs to come out sized appropriately?
Does the kerf differ from proofgrade to non-proofgrade material? I assume the kerf changes when the laser settings change (changes to the beam intensity)…
If I’m correct then you’d need to do kerf tests/adjustments whenever you change settings/materials?
Yes, the kerf varies by material (based on the properties) and because of the thickness of the material.
There are a series of tutorials on adjusting for kerf in the 2D vector programs in the Matrix here , at or around line 118. (The Matrix changes with additions, so the line number changes.)
In F360, you can also just install the DXF for Laser plugin, linked in the Matrix here - it does automatic kerf adjusting. (I don’t generally use it, it’s use is limited.)
And you can also use the CAM functions to adjust for kerf in F360, there’s a tutorial in the Matrix for that as well.
So I’ve been playing with making boxes and tool holders for peg board in the garage. I’ve been testing different cuts out of different materials . I’m doing all of my work for this in AutoCAD - Jules do you think we could add a column or settings for AutoCAD?
Pretty much right now, either the 1/4 hardboard or 1/8 hardboard or 1/8 birch plywood is working with a 1/256 offset for the kerf. Draw what you want in AutoCAD, offset 1/256 an inch out, plot to PDF and cut. Works like a charm thus far, nice and tight fit.
