To adjust for kerf or not to

I have imported .dfx files into Corel and sometimes they are connected but more times than not, they are all broken into segments. Easy fix with join nodes -non close curve which will close the shape by drawing an extra line between the first node and the last. Then export as .svg.

Otherwise and almost always…I design in Corel so its one conversion to .svg and then the Glowforge

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Anything that gets created in the AutoDesk123 Make program gets exported as discrete segments in the DXF.

It’s annoying as hell - I have to circle everything and Join, circle and Join…so yeah, it can be a problem if you are trying to do something that is spaced too close together.

One of the reasons that I listed all of the programs that I used in the Shared Free files that I posted was so that if Tony and crew needed to know which programs were causing problems with unconnected segments, they would be able to pinpoint the problem. (And I’m not sure if I bothered to join everything in all of those…probably left a few unjoined so they could test with it.)

That one is nice for aligning tabs and slots, but almost not worth the trouble of cleaning up the results for cutting.

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I have a feeling that a lot of my work will end up being run through Vcarve Pro as it will allow me to optimize vectors making sure they are closed and control start stop points.

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The DXFs exported from SolidWorks aren’t joined either. I agree that the state of the exported file cannot possibly be attributed to the program opening the file.

I wasn’t speculating about the workflows, I was describing the only way to get from SolidWorks to SVG using the software I have and the following constraints…

  1. I’m not willing to enter “fake dimensions” into my designs to adjust for kerf
  2. I’m not willing to be driven mad by watching my cloud-optimized laser cutter bounce around the bed randomly
  3. I’m not willing to select all the lines I want to join individually and I’m also not willing to clean up the mess left by joining lines in Illustrator. I didn’t know how CorelDraw handles that operation, but it sounds like it mimics Illustrator (in other words, it sounds like it’s garbage).
  4. I’m not willing to clutter my SolidWorks parts or assemblies with additional sketches that serve no purpose other than to adjust for kerf

One of my worries initially was the conversion to different file formats. In my experience, converting from a native file format has almost always been a headache and things don’t export into other formats very cleanly a lot of the time.

I don’t use solidworks but google is littered with people having similar problems.

https://forum.solidworks.com/thread/57975
https://forum.solidworks.com/thread/93203

Do any of those solutions help the final DXF export?

What are you willing to do to get a final project ready to send to the Glowforge? Anything? It sounds like you already have a problem with just the DXF format from Solidworks, unless, hopefully, one of the solutions above work?

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Yeah, switching formats can be problematic as well as being a hassle. SolidWorks’ being a bit of a POS when it comes to exporting doesn’t make it any better.

That first link you posted was actually extremely helpful. It’s actually one I’ve linked to before as well…

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Kerf is super important in inlay work.

Also, Kerfgate is my new favourite -gate.

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Yes, I can see how even .008" could be significant in an inlay where you want it to push in snug.

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Yep. I did some testing cutting text out of veneer, and you really do need that adjustment.

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I just wanted to try and be the 200th in this thread… Kerfgate T-shirts anyone?

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I’m surprised @jkopel’s description of “kerfuffle” hasn’t made it into this thread yet. It’s almost too perfect!

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I’m willing to ask Glowforge to make their software better than what people with two week’s experience will settle for.

re: my unwillingness to imput fake dimensions -
Kerf adjustment is STANDARD practice in CAM software. If people who have no experience with CAM software are confused by the word “kerf” for a couple minutes, so be it. Yeah, it’s a funny word, but the concept is as simple as can be. It’s basically “coloring inside the lines”, but with a laser instead of a crayon. I believe people are capable of learning. To those who don’t want to adjust for kerf, allow me to introduce you to the number “0”.

re: my unwillingness to watch the laser bounce around - It’s inefficient. Cutting line segments by randomly bouncing around the bed is, put simply, wrong. As I said, it’s not the end of the world, but I will not willfully allow it to happen, which leads to…

re: my unwillingness to spend hours tediously fixing disjoined files - I have Rhino, it joins lines perfectly, instantly, and doesn’t do anything stupid while doing it. I realize not everyone has Rhino, but (almost) everyone here has a Glowforge coming to them. I don’t think it’s unreasonable to ask Glowforge to save their customers hours by programming their cloud-based software to join lines intelligently.

re: my unwillingness to clutter my files with kludge-geometry - This isn’t entirely true, as this is basically what I do now. I draw something in CAD (whether it be in Rhino, SolidWorks, Fusion 360) or I obtain a drawing created by someone else, THEN I load the file into Rhino and basically use it as if Rhino is the CAM software for my Trotec. It’s not efficient and I wish it was different.

If I thought Trotec was interested in modenizing their software to get out of the late '90s, I’d probably be complaining on their forum (if they even have one). But I don’t think Trotec desires input from their customers, I think Glowforge does. Please tell me if I’m wrong about Glowforge.

So, in truth, I am willing to do it, but I won’t forget that doing it this way is… wrong. I’ve already enumerated why adjusting for kerf within your main design file is riddled with problems in a post above. Yes, it DOES work. It CAN be done that way. If you’re willing to live with the inherent problems that creates, there’s nothing stopping anyome from doing it that way. It goes without saying, but I’ll say it a second time anyway, having manual kerf adjustment in the Glowforge software won’t stop anyone either, as long as they remember the number “0” exists.

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Agree. It makes the design file material and machine dependent. I hate the tedium of adjusting as I switch materials or power & machines. So I’ve got different files set for different machines (I keep them segregated by machine & material in separate folders). Makes for lots of redundant work.

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The folks that did the Codex Silenda KickStarter laser-cut book generated the files with kerf-adjustments in 0.005-in increments for wood in thicknesses between 0.190 and 0.250-in - that’s a lot of files!

It would be so much easier to work with a nominal cut file and specify the material thickness at the time of cutting. That might be a good reason to use a cloud-based controller.

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Kerf will be so wonderful to have in the app as a nondestructive mod to your art file. (inside outside or center, and by how much). yep +1

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Did we get the proofgrade auto kerf compensation yet?

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No

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I know this is very late to the party and I read the first 1/3 of the replies, but since a lot of them predated shipping units, I think there is something very important to point out about the kerf and comparisons to CNC/CAM software.

A CNC mill uses a tool that cuts through a given material. Let’s set aside the wearing down of the tool surface for a minute and assume that the tool is a consistent size for cutting. It cuts/chews through a material to make a cut. That is a fairly consistent thing outside of some materials breaking down differently at the cut point and thus kerf adjustments (assuming software and mechanical movements aren’t also contributing).

A laser burns through a material. This adds a big variable to the kerf equation that CNC/CAM doesn’t have to deal with. When a material burns it behaves in a wide variety of ways and the burn/consumption rate is different for every material - if the material is made up of only one consistent fuel type. Most plywood contains wood from different trees with different levels of moisture, oils, cell structure and more. MDF contains a variety of materials that all burn at different rates. The laser (in simplest terms) burns completely through a given part of the material, but the fringes of that burn are where things get complicated and inconsistent.

A good simple example is when you light a piece of newspaper on fire and you blow it out. Very often you still see glowing orange embers on the edges of the area that burned that continue to “eat” away at the paper till there isn’t enough heat left to support combustion. That is a more extreme example of what’s happening when a laser burns through material and the edges left behind are cooling. Every single material and thickness is going to behave differently with this burn rate. Wood will burn differently than acrylic. Cast acrylic will burn differently than extruded acrylic.

So you have the following variables:

  1. Material composition and the burn rate of that specific material

  2. Speed of the moving laser (or fire let’s say) which affects how quickly the material around the cut area heats, consumes and cools.

  3. Power of the laser (or heat of the fire) and how that heat affects the area around it (again, heating, cooling, expansion, contraction, consumption).

So you could imagine how GlowForge could learn the kerf/burn characteristics of their Proofgrade materials that are consistent in material, thickness and presumably construction from batch to batch. But if you don’t want to use Proofgrade materials (or in my case I need thinner materials not available in Proofgrade) then you have to purchase material elsewhere and do a lot of testing to see where the limitations and compensations are.

The main point, is that this is NOT comparable to CNC/CAM software where there is a fairly consistent kerf variable (more or less). It is a bit more complicated when you burn through material. I could have 1/8 inch maple in the GlowForge and the kerf at 25 power and speed 1000 is going to be different than the kerf at 100 power and 50 speed. And that’s with the same thickness and material composition.

Now, all that said, manually being able to enter a kerf value would be a helpful addition for some people. That itself is a little complicated too from a GUI standpoint as you may only want to apply kerf to a given cut line in the interface and how you go about selecting just that cut line, face or side of a drawing. I can see situations where someone doesn’t want kerf applied to a given part but may want it applied to other parts.

Anyway, if you made it this far, thanks for reading and hopefully it helps explain why this kerf situation isn’t that simple.

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Believe it or not, some people will read long posts as long as they are broken into paragraphs and reasonably well written. Yours is both.

I totally agree with all your points here and have had arguments with people here that have CNC experience but had not seen the :glowforge: .

One thing your essay leaves out though is that different joint types need different kerfs. The solution is methodological testing. For complex (lots of joints) projects I always make sample joints to figure out the amount of kerf compensation needed.

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Yes kerf will vary a lot and may need to measured but once you have a value offsetting the design is just the same as any other CNC device. You dont specify where it should be done, outlines get expanded outwards and holes get offset inwards. So all it needs another input field.

The object should always be that the finished piece matches the dimensions in the design file.

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