That looks great, thanks for the links. I will check it out. I want to be able to create the boxes in fusion with G-code for the MPCNC. This looks like a lot of the work must be already done.
Lasers can do 90* inside corners. Spinning router bits can’t. Work was noted on the forums a while back on joints working within the spinning bit limitations.
I couldn’t find anything in the forums but, if you watch the Carbide Create Pro video it basically makes a small indent with the bit where there corners are. You definitely won’t get square corners but its good enough for what I am looking for. I am most likely going to create a script for Fusion 360 that will allow you to specify the size of the box then it will create the sketch needed including the undercuts in the corners. (that’s my plan anyway).
That’s some interesting approaches. I want to make it fairly simple. I think more complex geometry makes it more difficult to predict the outcome. I do like the one with the different shapes for joints that is cool.
With CAD, the outcome is far from uncertain or unpredictable. Perhaps difficult to achieve. If you read through the thread, @jamiek did a fair amount of modelling and virtual testing to make sure the basic design was solid as far as having two identical shapes that fit together. The trial and error portion was all about dealing with the variables of his machines foibles and the imperfections of real life objects (especially organic ones). I just re-read it, making sure it was apropos, and it appears that he stopped working on it either because he got it “good enough”, or he realized his machine was too far out of square to progress any further at that time. Besides, as was noted several times in the thread, the smarter way to do it is to cut a hole in the middle of your table, and mount your workpieces so that you can mill their edges/ends.
These indents are generally known as “dogbones” in the CNC world. I’ve never used Fusion myself, but I’m absolutely certain there is a tool of some sort in the CAM / G-code generation functionality to generate the “indents”. It is an extremely commonly needed capability.
Note that the indents are not usually “modeled” as part of the box, but rather they are generated in the CAM process, because the size of the indents required is a function of the diameter of the bit used to cut out the box.
I’ll be very surprised if there isn’t a finger jointed box generation widget somewhere in Fusion as well.
I’ve been using FreeCAD for both CAD modeling and CAM, and it has tools for both functions.
Yeah I was going more for novelty value in the 3d shape, and it’s more practical to use extra clearance in the corners to accommodate the bit size.
What I struggled with was runout (or something else that had the same effect) which caused the inside and outside dimensions to be off, so they were loose or wouldn’t assemble. I found it was inconsistent if I removed the bit and put it back in, as if it were orientation dependent. So the ultimate workflow would have been to make a test cut, measure the error, and punch in an adjusted tool diameter into CAM before generating the actual job. And then I have to re-do those steps every time I switched tools.
Hopefully my tool is worse than usual. If it were at least consistent then it wouldnt be much of a problem to compensate to get tight joints.
I used to use FreeCAD but switched to Fusion, I almost switched back when AutoCAD made changes to the license but they have maintained a free option for hobbyists.
These indents are generally known as “dogbones” in the CNC world. I’ve never used Fusion myself, but I’m absolutely certain there is a tool of some sort in the CAM / G-code generation functionality to generate the “indents”. It is an extremely commonly needed capability.
I haven’t seen it in Fusion, the reason I started this thread was for info like this so I don’t waste time reinventing the wheel however, it doesn’t look like its been done yet.
Hopefully my tool is worse than usual. If it were at least consistent then it wouldnt be much of a problem to compensate to get tight joints.
It is a novel approach but, I was looking for a more traditional finger joint just so I could take some ply wood, cut out the shapes from one piece of wood and bang them together.
I found an “add-in” that does the dogbones. They are modeled into the part. There is no standard feature that does them. Dogbone Add-in for Fusion
I can’t find a finger joint add-in - There are a lot of people doing them with parametric designs using a table to create the fingers.
Heh…Guess I’m absolutely wrong! 8^)
That add-in looks like a good solution.
Altough, to my mind it is sub-optimal to “model” the dogbones.
As noted, the size of the indent required is a function of the radius of the tool. I think it would be better to accommodate this in the CAM. That way if you design it with a router and 1/4" bit in mind, but later decide to cut it with a laser, you don’t have to go and change the model.
I am surprised.
You might find this thread interesting.
I created a video to show where I am with this script Automatically Creating Finger Joint Boxes in Fusion 360 I would love to get your feedback on the approach and any tips you may have. - I am pretty sure I can have it produce a complete model automatically then it’s just a matter of adding some tool paths.
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Very cool. Seeing a few seconds of python code really opens up possibilities for if I wanted to create plugins too. Thanks for that.
A different direction, I also wonder if I could use javascript to generate an svg or dxf file which would also be useful in Estlcam.
I am more than willing to share the code once its fully functional. I am scared that you wouldn’t be able to work through it as it stands now. - I am hoping to publish it on bitbucket and have other contribute to it. (hint, hint).
There is a site that already does laser version that you can create an SVG or DXF from. I looked at that but didn’t want to use that in preference of something that would be native in Fusion.
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In sandify, I just added an export to svg. That was not very hard, with the d3 library (which has 1000 functions, and I’m using 1). SVG can support a ton of shapes, but just writing out a path is the easiest.
Don’t publish early (or at all) on my account, I had just never considered the possibility of writing plugins for Fusion, and seeing that it’s Python and it looks easy (relatively), opens up all kinds of possibilities. Parametric models are one thing, and already possible in other ways, but perhaps I could make procedural models? Now I just need to come up with a project that would require such a thing and is really challenging otherwise.
What about your fancier finger joints?
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I have fully functional Python script to create automatic Finger Joints in Fusion 360. I have a video showing its use and a link to where you can get the script and how you can install it. Let me know what you think.
Automatic Finger Joints
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I created a short video on using the fusion 360 API for anyone interested in creating their own scripts or add ins
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Creating Tool Paths for Automatically Created Finger Joint boxes in Fusion 360 - I have significantly upgraded the script to create both closed and open top boxes. - Let me know what you think!
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