CNC Box (Finger) Joint Box

With suitable toolpaths, the preview seems fine:

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Except of course for the matter of how to open up the box — for hand-held boxes it’s fine to saw them in half to open them (if a bit nerve-wracking), for CNC, it’s easier to just design it into the file.

Rather than just a horizontal opening we’ll add some visual interest by making the lid open at an angle — since it would be jarring to have a horizontal cut along the front edge we’ll want to specify an angle where we can cut out a matching slope along the front edge (since we can’t flip the back over we’ll accept a straight edge there).

Next we have to draw up the tool and how deeply it will need to cut to make the desired angle and enter it.

Helps if we rotate at the correct angle. Seems the endmill is defined in terms of taper and not nominal angle:

Next, we re-rotate things for the sides and box.

Thusly:

In order to make a through cut so as to get the 3.6 degree angle we would need to cut an 0.98195mm wide design:

using a 10.6 degree V endmill:

Except of course the angle is only right for the cut from the inside at either the top or the bottom depending on if the piece is at the front or back so that the wrong pieces have to be cut as a second setup from the other side or left proud and filed off to the correct angle.

Working on directly getting G-Code out.

EDIT: wired up the gcode output part selection and fixed the top/bottom and improved the G-Code generation:

Design into 3D_ Fingerjoint.zip (2.3 KB)

which puts lines such as:

ECHO: "G0 X0 Y0 Z8"
ECHO: "G1 Z-3.175 F150"
ECHO: "G1 X0 Y4.20625 F600"
ECHO: "G0 Z8"
ECHO: "G0 X6.89856 Y0 Z8"
ECHO: "G1 Z-3.175 F150"
ECHO: "G1 X6.89856 Y4.20625 F600"
ECHO: "G0 Z8"

into the console which can be extracted with a command line option — now just need to get someone to afford a menu command to write out only a filtered version of the echoed text and customize the file extension and it’s good to go.

Following as this is very very interesting! Just downloaded OpenSCad to ty it also. :slight_smile:

Thanks!

FWIW, I’d suggest starting with BlockSCAD:

https://www.blockscad3d.com/

I tried to document this sort of workflow pretty thoroughly at:

https://willadams.gitbook.io/design-into-3d/3d-project

and did put up a test cut in a different thread:

Hopefully I’ll get another top/bottom cut this evening and then put one together.

Wrote up a detailed examination of this at:

https://willadams.gitbook.io/design-into-3d/fingerjoints

Here are two Carbide Create files:

carbidecreate fingerjoint vertical parts.c2d (65.1 KB)

carbidecreate fingerjoint vertical cuts.c2d (39.8 KB)

They want a #102 or other 1/8" endmill (I’ve been using a downcut) — actual setup and cutting photos presently.

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While one could carefully measure the fingerjoint width and then adjust the mechanism, it’s easier to just cut a small fixture to hold the boards in their relative positions:

which is ready to cut once unioned:

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It’s always a bit nerve-wracking cutting boxes apart, but the groove helps a lot, and isn’t too much wider than the saw kerf:

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and post processing and hardware installation went well:

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Here are the files for this box:

top and bottom.c2d (10.2 KB)
carbidecreate fingerjoint vertical cuts_3488.c2d (169.7 KB)
carbidecreate fingerjoint vertical parts.c2d (89.5 KB)

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