Well not directly…they still have to accept it and run the print…
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Yes, I know, but think of how easy it is to share ideas when you don’t have to shlep files around…
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Even better, once the forge is here… I can just cut the file! ROFL! 
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Just cut the new file with the .008 kerf adjustment, fits snug. I was thinking…when I initially measured kerf, I had just painted the boards…now I measured and kerf is .008. Wonder if there was a bit of swelling from the paint involved initially. I usually work in acrylic so medium stays the same but I would think wood can swell and contract based on humidity or excess moisture, like from painting…something to ponder…
Or my caliper was off the first time…lol
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Might have been the calipers - it’s just about impossible to measure that small accurately. (I’m hoping the ones I just picked up out of the mailbox do a better job than the ones I’ve got now. - Okay, yeah, they’re better.)
(Or could have been swelling in the wood too.)
So it fits perfectly with a 0.008 kerf…fantastic! 
Do you have any other material that you want to try, now that we have the kerf more or less figured out? If you have some smaller scraps of acrylic or something, but not enough to cut the whole box, we can test it by cutting just two adjoining pieces and see how they fit together.
Or if you have any chipboard or cardboard, we could test it on that as well. I would just need to know the actual thickness of the material, so i can run one last copy of the file.
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You’ve had kerf compensation figured out ever since before you made that tutorial. But if you change materials you’ll have to make another adjustment to your drawing (unless, of course, the new material coincidentally yields a similar “enough” kerf).
If you know the kerf, and then compensate for it, the parts will come out the right size. Tests aren’t really necessary once you know the cut parameters (speed, power, frequency, focal distance) and the kerf width for the material you’re cutting. The only caveats to this are the small radiuses in the corners and the taper of the edges.
A link to the tutorial that Jules wrote, in case anyone reading this thread hasn’t seen it yet…
OK, if you want to get technical... (click for disclaimer)
There are a couple more caveats, the material has to be consistent enough that the kerf stays the same size throughout the cut, the machine’s laser output and motion has to be consistent too. Parts that start on fire or melt as a result of being cut also won’t necessarily come out the right size. Thermal expansion may technically come into play if ambient temperature fluctuates. Acts of god, lost steps, inaccurate tuning, time/gravity disruptions, and/or black magic may negate this rule. “Rightness” of resulting parts subject to stacking errors introduced by inaccuracies with the machine, the kerf measurement, the final part measurement, and rounding when converting units or interpolating tool paths.
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I was talking above about figuring out what the actual kerf value is for the machine that she is currently using to cut these…we inadvertently started out with an inaccurate measurement for the kerf. 
The good news is:
As far as kerf-adjustment goes, yes the tutorial does work once you get a good handle on what your beam width is.
The bad news is:
For a couple of the files that I have in mind to build - I’m probably not going to be able to totally ignore the kerf. That’s a bit of a bummer, but I might just redesign the files to go with a mortise and tenon type join with glue, so that it doesn’t matter if it’s a little loose fitting, since it won’t be seen.
(I’ll probably ultimately wind up doing something like that, because it would improve the overall appearance.)
The last phase of the testing (on a different material) has nothing to do with kerf - it has to do with checking to see whether I have programmed the parametrics for the tabs and slots correctly. (Those are a whole lot trickier to set up than kerf. ) 
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But once you have them set…
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Yup! Big timesaver! 
(i should also mention…they are only tricky because I don’t know what the heck I’m doing yet. Chuckle!)
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Nobody did till the first time. 
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I’d suggest trusting the software as far as the material thickness variables are concerned. If 2mm material changes into 4mm material within Fusion 360 without breaking your model, you’re basically good to go. But I can understand why you might be trepidatious, especially if you’re used to art-centric design software like Illustrator instead of accuracy-centric design software like Fusion 360 or other CAD packages.
I’m really confused here. The machine isn’t the only variable in this equation. You didn’t figure out the kerf value for the machine. You’ve only figured out the kerf value for that machine, using that material, using those cut parameters (speed and power, primarily). If you change anything you will likely have a different kerf value.
If you change the material: you can bet the kerf will effected.
If you change the speed: you can bet the kerf will be effected.
If you change the power: you can bet the kerf will be effected.
The laser isn’t the same as a saw or router bit. For all intents and purposes, a typical “consumer” circular saw blade will leave a kerf of ~1/8", regardless of the material you’re cutting. Same for a router bit. If you use a 1/4" router bit to cut a channel into a piece of material, you can be pretty damn sure the kerf is going to be very close to 0.250" wide, whether that material was plywood, solid wood, plastic, foam, aluminum, pumpkin, whatever.
Lasers don’t work the same way. You’ll have a kerf of 200 microns in one material and 80 in another, even though you’re using the same machine with the same laser tube and same optics.
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@Jules, since it might seem like I’m just trying to give you a hard time I’d like to offer to cut one of your designs. I’ll donate an entire sheet (well, a ~1’ x ~2’ sheet) of 1/8" baltic birch plywood (a $2 value! ).
I’d hope that you give me a design that’s complicated enough that it’s not immediately apparent whether or not it’s going to work by just looking at the design (in other words, no boxes please). If you post a NON-kerf-compensated DXF file and tag me in the next week or so, I’ll try to cut it within a day. I’ll even screen record opening the file, compensating for kerf, and record the cut and assembly processes. No need to “clean up” the DXF as long as it’s readily apparent which lines are supposed to be cut and which ones should be ignored. A link to the Fusion 360 file would be even better (as long as the dimensions are “real” and not altered to compensate for kerf).
I can post the video to YouTube as an “unlisted” video so that the only way people are likely to see it is by visiting this thread. I can also skip all the video stuff and just post up a photo of the result, your choice. Or, if you don’t want to share a complicated design (I understand completely!) maybe you could point me to another design on the forum that you’d like to see cut.
I don’t really want to mail it or anything, so this will only be a proof-of-concept kind of thing. Just a test of a design.
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Oooh! Great word! 
Chuckle! Yeah…that’s exactly what I am.
I have trust issues. 
[quote=“Hirudin, post:41, topic:3250”]
If you change anything you will likely have a different kerf value.[/quote]
Yeah, I know. I’m not actually overly concerned with the kerf on these files, this was just a quick side test of the tutorial instructions.
I won’t have any initial control over the speed, power and focal settings with the GF, (all of which can affect the kerf if I understand correctly)…that part is going to be automatically done for me. (i hope*)
*(I know we will have manual over-ride ability for those settings, but there is plenty of time for me to test for that once the machine arrives.)
I was interested in seeing how much of an impact on kerf there was for the same rough thickness but different, fairly similar materials. I’m expecting the difference in the kerf itself to be a fraction of the total kerf for materials of similar density, rigidity and thickness. The kerf for foam is going to be a lot different from the kerf for plywood and acrylic, but foam is not a material that people will be using to create the 3D files I’m working on.
And pumpkin will definitely not work. ROFL!
I’m basically trying to design at this point for the material…as I learn more about other materials, i will design for those as well.
Kerf is really a side thing for me right now - I’ll be putting together a little chart with kerf information as I learn more about the process, and see what the actual impacts are. (I like to back up theory with testing, it’s just the way I am.) This wasn’t meant to be the be-all end-all discussion on kerf. It’s just a little initial testing and @smcgathyfay offered to test one for me on another thread, and I gratefully took her up on it.
That’s all we’re doing here.
Not at all! And if you want to volunteer to help with testing, you’d better believe I’ll take you up on it! (Although I’ll tell you what I told @smcgathyfay , you might come to regret offering!)
Do you have the ability to do variable depth engraving with your current machine?
I have another design that I just reworked for laser yesterday that does (barely) fit on a single sheet, it’s not kerf adjusted, and it has no tab issues, but I would dearly love to see how it looks in plywood. (Given the size, I was reconciled to waiting until the machine got here to test it.) It’s a layered design for height, so the parts would need to be clamped and glued, and it is designed for 1/8" ply.
This is what it looks like in plastic, it’s a snippers/pliers stand:
Let me know if you’re interested in tackling that one, and I’ll PM you the file.
I’ve got two others that deal with tab/slot adjustments but they are very complex and will probably take multiple sheets to cut, and they will need to be cut and assembled multiple times in order to test them for the correct size and placement for the tabs and slots. That is why we are working with a small simple box first to test for that function.
If you want to try one of those, I need to do a lot more work on the file before it will be ready. And you will need to be able to cut exactly halfway through the wood for the mortise and tenon joins, so that’s the reason for the question above on the partial depth engraving.
(The complex ones, and this one, will need to be handled privately until I have tested them a few times, I’m trying to decide whether it’s worth the hassle to offer them for sale or not. I swore after the last go-round of cutter file sales that I wasn’t going to ever do that again, but here i am…getting sucked in one more time.)
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Sorry for the delayed reply!
That’s a cool lil’ stand! Are you’re planning for the bottom to be two layers (one with the web of cutouts and one just for the lip going around the perimeter) and then the a round things to be a few layers (six or so?) that would be stacked up and glued? It that close? That sounds very doable, but I don’t think it would be much of a “test”, if you know what I mean. I’m guessing you’d agree, but maybe you have different plans that would be more of a “test”. Also, although I bet I could get all the layers to be stuck together, I have my doubts about being able to do it without getting unsightly glue squeeze-out all over the place.
I can do engraving, but getting an engraving to be close to half the depth might be tricky. I did an engraving matrix/test/sample on this material, and most of the power/speed settings I tried only went down about 1mm (roughly 1/3 of the thickness) or less. After the ~1mm engraves they jump to going almost all the way through.
I see that you saw that Fusion 360 tutorial where they showed how multiple layers can be used to make effective mortise and tenon joints. This one…
Although I like the idea of simply engraving the mortise, getting the depth right might be a task other people have decided is more trouble than it’s worth (not just me). With thicker material I would guess that you could just make the mortises deeper than they need to be, but that doesn’t seem practical with 1/8" stock.
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Yep - I do agree that the first one isn’t much of a test…that base is 4 or 5 layers and the columns take it to a total of 13 layers. It should cut without any problems. It’s just the only one I had that was roughly one full sheet.
Oh, wait a minute…I forgot the brush stand…that one might fit on a single sheet, and it has a couple of parameters for thickness built in, and no engraving…let me see how it lays out on a sheet - so far it is still in 3D form.
(That will give me something to play with today while the workers are swarming.)
For the complex ones…I figured that the engraving part would be a bit touchy, so I actually have the tenons set to be 0.2 mm shorter than the depth of the engraving, which is set to half of the total material thickness. Might need to fiddle with that formula a bit as well…I still haven’t seen if we have that much control over the depth of the engraving…might have to be flexible there with how I treat it.
I’m actually in a pretty good mood this morning…I caught a design error in the complex designs and figured out how to parameterize it yesterday. (A brief shining moment of getting to be proud of myself before being tossed back into Never-Never land. Chuckle.)
Give me a couple days and I’ll take a look at the brush stand to see what phase of completion it is, and check it over for errors…then I’ll post it here temporarily for testing…that one might work well enough for our purposes here. (Going to take at least that long because of all the distractions around me this week.)
Thanks for the collaboration!
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Yes this is the really disappointing thing about Glowforge (besides the 1 year delay). When I bought it I thought it had 1000DPI vertical resolution, hence why it was described as a 3D printer. I thought it must use the head camera to get depth feedback.
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It probably will, they just haven’t been delivered yet so it’s hard to design for them before they arrive.
Have a little faith…we’ll eventually get there. I’m just trying to be ready for it when it comes.
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Okay, @Hirudin, took a little longer than I thought…(got a wee bit distracted this morning by all the cool new beta projects)…but i got the Kitchen Brush Holder file to fit on one 12 x 24 sheet.
I need to know the exact measurement (calipered) of the thickness of the plywood you plan to use, so I can refine the slots for the actual measurements. (Which I’ll do tomorrow if you don’t mind…it’s getting late, and I’m pooped.)
Just let me know how thick it is, and I’ll temporarily post the file tomorrow.
This is what it looks like:
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Cool. It’s basically 1/8", give or take 10-thousandths (I bet). I’ll go grab a sheet and do 8 measurements (3 per edge).
Let’s call it 0.117" (most were close to 0.1170" with a low of ~0.1155" and a high of ~0.1235" (micrometered)).
The material I have isn’t terribly flat, unfortunately. I might suggest adding a piece to the top of the holder to maintain the spacing. Maybe something in the middle too. I guess that won’t matter for this test though.
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No this is just a tab fit test - I’m hoping it won’t be too tight because the slots are deep. (Not going to adjust for kerf on this one.)
Should have it later tomorrow morning…lot of copying and pasting. Thanks! 