Finger/Box Joint Software

[Burkhardt]

I am working on another piece of custom CAM software. I have not forgotten about finishing the Maze software but I dug out a (currently more fascinating) old project to create tool paths for flat machined void free finger/box joints.

While I use my dovetail software occasionally, most of my project joints are just cut as plain box joints for simplicity and because I can cut the whole part out of a sheet or board without re-clamping. However, it bothered me that such simple box joints need dogbone fillets for the inner corners to avoid interference with the sharp cut edges.

The whole idea is to cut the joints with a ball end mill and to allow for some decorative patterns using varying finger lengths, either two sided or half blind. The pattern generation was not too bad but I gave up last year over the calculation of the tool paths. Anyway, after a few sleepless nights I finally figured out how to do it. Getting all the bugs out will take a lot more work but today I made my first successful joint.

[Bob Eustace]

Excellent concept Gert. Hope you perfect it.

[khalid]

Excellent as usual What programming language you use

[zeykr]

Very Nice!

[Burkhardt]

Thanks guys, this is a fun project. And probably more useful than mazes for other wood workers. I am envisioning to expand this with a kind of box/drawer wizard so that you just input the outer dimensions and it cuts everything automatically from a board or a sheet without drawing a single line in CAD.

On the practical side, I am struggling a bit with the clamping. The boards have to be held down flat better than 20/1000" or the joint will have visible gaps on the inside. That is easy with plywood sheet but boards are usually a bit warped or cupped. A surface skim would help but is not really practical. Any ideas?

Khalid: I am almost embarrassed to admit but I never got the hang of VB or other more modern visual tools. All my PC code is written in text based Liberty Basic (and compiled with the R.T. Russels' Liberty Basic Booster tool). It makes the GUI a bit more work since it is not as simple as dragging boxes on the screen but I have all the code in one piece. I am just not a professional and old dog refusing new tricks. For microcontroller code I use Forth, an even more arcane programming language.

[dlcw]

On the practical side, I am struggling a bit with the clamping. The boards have to be held down flat better than 20/1000" or the joint will have visible gaps on the inside. That is easy with plywood sheet but boards are usually a bit warped or cupped. A surface skim would help but is not really practical. Any ideas?

Here is the board clamp down method I use. It is comprised of 3/4" MDO with tracks. I made simple hardwood hold down clamps for the tracks. I put the MDO on the CNC table, turn on the vacuum and it sucks the MDO flat as a pancake. I make sure my boards are flat using traditional flattening methods (jointer, planer, etc.) then use a wide drum sander to take any snipe out of the board. Then sand it using an ROS.

[khalid]

Khalid: I am almost embarrassed to admit but I never got the hang of VB or other more modern visual tools. All my PC code is written in text based Liberty Basic (and compiled with the R.T. Russels' Liberty Basic Booster tool). It makes the GUI a bit more work since it is not as simple as dragging boxes on the screen but I have all the code in one piece. I am just not a professional and old dog refusing new tricks. For microcontroller code I use Forth, an even more arcane programming language.

Ohhh ....Thats a hell of work you doing then. However, this make you a perfect programmer. I bit you can program anything what you have in your mind
If you learn Visual Basic then you can make a CAD/CAM software without spending too much time on GUI
I really appreciate your efforts and programming skills