IS KERF DESTROYING YOUR LASER PROJECTS?

[@ModeltreinenSchaalHO187]

Thank you. Very clear explained.

[@SteveMakesEverything]

Glad you liked it

[@createinspain]

Thanks! I knew there would need to be compensation but i had no idea what it is called. I've had some experience with it in CNC projects.

[@SteveMakesEverything]

Very welcome!

[@ruftime]

Thanks Steve! One of the many reasons I love Lightburn software is their kerf compensation❤️

[@SteveMakesEverything]

I’ve said it before and will no doubt say it again: I wish FSL offered support for Lightburn

[@dannybrandt1231]

Yeah, that's the only way to go, go cutting with a cnc and you do the generating g-code from your design with the right tools selected, so why on earth should we do it different when using a lasercutter? Makes no sense at all those kerf compensating in your design.

[@LowVisionUKTerrysView]

Thanks so much for your very responsive video to the queries sent to you only a day or two ago Steve. very much appreciated. I have watched this video a couple of times now, and will next watch it alongside replicating it as I use my laser, so that I fully get to grips with it. Im so grateful for your help with this, thanks so much

[@SteveMakesEverything]

Happy to help - lots of people were asking about the same thing. Be sure to download the template file (link in the description)

[@TrevorGreen]

What I want to figure out is if the kerf is different at different speeds, I'm pretty sure the answer is yes. That the laser is going to kerf less the faster you go. So I was testing 6000 mm and doing multiple passes in order to see how those settings cut and then switch the same circle to 15 mm 100 to do a quick cut of it and it was larger. So I think doing kerf tests at different speeds and power levels is maybe important if you really want to dial in your design. I haven't tried this yet. I need to build your test and try it.

[@SteveMakesEverything]

Hmmm, this is an interesting experiment, though my money would be on the kerf remaining constant. Regardless of the speed, the beam size is constant and that's what is causing the kerf. The only reason the kerf would be larger at slower speeds is if there is significant charring happening because the beam is causing the material to burn out. In that case, though I would argue that the kerf measurement is invalid. I think you would have to get the cut settings correct (i.e. minimal charring) and then measure the kerf.

[@TrevorGreen]

@@SteveMakesEverything I don't know what correct cut settings means. There is just what the laser does at different speeds and intensities. So testing it is how you pick what you think is correct. Think about low power repeating at high speed, when I did that I think I had less kerf. But it wasn't a kerf test I did, it was a circle cut for a magnet. So I would have to do a broader test to see if there is a difference.

[@RSP13]

It varies a lot with material, thickness and focus distance. And to a lesser degree with power, speed and air assist.

[@rdavis0521]

Thank you much for the great video, but I’m confused about one part. The calculation of the 0.233 kerf offset makes perfect sense. However the application to your cross piece doesn’t make sense to me. I don’t understand adding two kerf to the side pieces, and then in turn increasing the width of the slot by two kerf? That seems to be basically a net gain of nothing? Decreasing the height of the slot by the two kerf makes perfect sense to adjust for the tightness. What is it that I seem to be missing in the need to widen the slot and widen the two cross pieces? Thank you.

[@SteveMakesEverything]

Well in short it's the width of 2 kerfs because there are two cuts. The rule of thumb I typically use is to remove kerf from a slot and leave the matching tab alone. This means the slot gets a bit a bit narrower ( by 2 kerfs - one for each side of the slot). This makes the tab fit snuggly into the slot it goes into. If you were using something like Lightburn then you could click a button to make kerf compensation happen automatically. Alternately if you are using a proper CAD tool like Fusion 360 you can do kerf compensation in the tool before you ever export to your laser. You still need to go through the process outlined in the video so you know what your kerf actually is regardless though. The would be a great feature to have added to RE3 (FSL are you listening?)

[@rdavis0521]

Thank you for the response. Makes perfect sense.

[@BitSmythe]

4:30 I notice that each square is fully cut - 4 sides. That means that the interior verticals are getting two passes. What's the resultant effect here?

[@SteveMakesEverything]

It’s cutting air so it’s minimal impact, but admittedly I should have created single lines

[@Hotecce1]

Hi steve. I need help finding the Kerf setting. Its not showing under the common tab in layers/cuts using lightburn. im using Creality Falcon 2. im using the trial version at the moment.

[@SteveMakesEverything]

You can find this setting if you select the cut/layer tab in Lightburn and double-click on any of the layers you created. This will bring up an advanced settings dialog and you will see kerf compensation there.

[@Hotecce1]

@Steve Makes Everything I just happen to notice I was in beginner mode. did a quick Google search on how to turn it off. that solved my problem and now have the kerf setting and advance tab.

[@SteveMakesEverything]

@@Hotecce1 Note that you can skip a lot of the detail in this video if you are using Lightburn. Once you establish what your kerf is, you can just use that value in Lightburn

[@jessetutterrow4320]

After adjusting for kerf is there still enough space for woodworking glue?

[@SteveMakesEverything]

That's really up to you when you do your kerf adjustment. If you are using regular carpenter's glue then you wouldn't need at lot space, but something like Gorilla Glue expands a fair amount so you would need to add that to the amount of kerf you would like to leave.

[@otherdogdesign8666]

So a question about kerf: when you are cutting out a part, wouldn't half the kerf come out of the piece and half out of the waste? Why do you increase the size by kerf x 2 instead of just one which accounts for 1/2 from each side?

[@SteveMakesEverything]

Well only the two end pieces cut into the waste. However when cutting in a real project you will also be cutting into waste and kerf will be consistent. If you find that your parts are slightly too small or too large you can make minor adjustments. The goal here is to get you close.

[@gokhanisler3740]

btw how do you get rid of burn marks and residues without sanding?

[@SteveMakesEverything]

Mask the material. I typically use transfer tape (amzn.to/3f9bu1S) which is like masking tape but a bit thinner and not as sticky.

[@gokhanisler3740]

@@SteveMakesEverything Thanks. Do you use on both sides?

[@SteveMakesEverything]

@@gokhanisler3740 Not necessary. You only need to mask the side the laser hits since that's where all all the action happens. The back would rarely get subjects to any smoking/charring.

[@gokhanisler3740]

@@SteveMakesEverything But if there is a very thick smoke on the back of the material. Do you raise your materials using something like pins.. I do not know how to get rid of these burn marks on the back side😔

[@SteveMakesEverything]

@@gokhanisler3740 If you're getting burn marks on the back then your power might be a bit high or speed a bit slow. The back should be pretty clean

[@jf6720]

Great video but you lost me at the test piece. Why not cut the test piece with the kerf offset instead of re-designing your test piece? Isn't that what you are trying to accomplish?

[@SteveMakesEverything]

When I did this I did it for the Muse 3D laser which doesn’t have kerf compensation. I’m not sure lightburn supported this at the time either.

[@jf6720]

Makes sense, thanks@@SteveMakesEverything

[@brucewoods9377]

@@SteveMakesEverythingkerf off set is supported in the latest version of Lightburn

[@SteveMakesEverything]

@@brucewoods9377 Yes, Lightburn has supported this for a long time. Accuracy depends on your laser, though, because on most diode lasers, the kerf in the vertical is different than the horizontal, and Lightburn doesn't handle this. It's fractions of millimeters, so LB comes close enough. But lasers like the Muse 3D and several others can't run Lightburn, so you sometimes need to use first-principles. I do think it's important to understand kerf regardless, though, since even in Lightburn, you still need to know what the kerf is.

[@gokhanisler3740]

I think one day the laser technology will be develoved, unless it's already developed and not available commercially, so that there will be no kerf issues or will be negligeble kerfs.

[@SteveMakesEverything]

Well at ~0.2mm the kerf is pretty negligible already. Not matter what there will always be some sort of kerf. Physics would get in the way of making the kerf zero thickness 😃

[@gokhanisler3740]

@@SteveMakesEverything I mentioned no kerf issues even if my child knows if you cut something there will be space between cut portions. What I meant to say was the fact that whenever you draw something you'll be able to send that drawing to the laser machine without thinkin about the kerf. But as you showed before sending something to machine you have to make some adjustment for the kerf.

[@SteveMakesEverything]

@@gokhanisler3740 Indeed it would be sweet if there was a kerf option in something like Inkscape that automatically adjusted dimensions to compensate for it. At this point I do this in Fusion 360 by adding a kerf object in the places where it matter and then setting a user parameter to define what the kerf value. Unlike Inkscape, Fusion 360 has some understanding of how the parts are assembled so determining where kerf is needed is generally easier to understand. I should probably do a video on using Fusion 360 for laser work because there are many things like this that a proper CAD system can do that a simple drawing program can't.

[@gokhanisler3740]

@@SteveMakesEverything Thank you very much for this response. Yep, Fusion 360 video from start to end for a project will be awesome. When you adjust kerf using Fusion 360 do you get tight fittimgs? or do you still face some problems?

[@SteveMakesEverything]

@@gokhanisler3740 Certainly Fusion 360 won't do anything relating to kerf automatically, so you'll still have to know your kerf for a specific material and thickness. However Fusion 360 will simplify the process of accounting for kerf - especially if you decide to change materials. You can change a single parameter and everything will recalculate on the drawings

[@valleypivot]

You had 2 cuts between each block which would add to the kerf

[@SteveMakesEverything]

It might, though it's on exactly the same path that was cut before so unless the focus of the laser changes, it is inconsequential. It's easy to create a single larger rectangle and then lay down equally spaced lines to ensure a single cut if you want.

[@Duraltia]

Mhh... Is this a Test you'd usually have to make on a per Material basis? 🤨

[@SteveMakesEverything]

Likely not. The kerf is fairly constant since it's a measure of beam size rather than material attributes. Having said this, some materials like soft wood may be subject to a bit more energy absorption and hence more charring along the cut. This might soften the cut edge causing some of the ash to break away and make the kerf appear larger.

[@StephenBoyd21]

Sadly you have made the mistake of not dividing your kerf by 2. The 2.33mm was the distance of 10cuts but this is 10 cuts on both sides. So you in fact have 20 kerfs, not the 10 as stated. This is why your fit was really snug. You’ve overcompensated.

[@SteveMakesEverything]

Not quite correct. The second pass through each cut is on the same path, which wouldn’t increase the kerf by a factor of two. I have however built a better test model that uses only a single pass through each cut - but this is more good housekeeping than to correct anything. After some investigation the snugness was coming for a slight alignment problem resulting in cuts not being perfectly vertical to the material surface.