Dogbone
Add a small round relief in every inside corner, so square tabs fit slots and pockets cut on a CNC router.
- Dogbone AdvancedPart Studio toolbar
| SchoolCAD | Onshape | Fusion | SOLIDWORKS |
|---|---|---|---|
| Dogbone | – | Nifty Dogbone (add-in) | – |
A CNC router cuts with a spinning round bit, so it cannot cut a sharp inside corner. The inside corners of a routed slot come out rounded, and a square tab will not go all the way in. Dogbone fixes this. It cuts a small round relief (a little extra cut) into every inside corner, so the tab fits.
SchoolCAD finds the inside corners for you, on every part you choose. Dogbone is a feature in the feature tree, so the reliefs update when you change the design.
How to use it#
- Make the slots, pockets and tabs first. Dogbone only finds corners that are already there, so add it near the end of the feature tree.
- Click Dogbone. If you selected parts first, only those are ticked. Otherwise every part you can see is ticked.
- Click a type: Corner, Minimal, Long side or Short side.
- Type the Cutter Ø: the diameter of the router bit you will cut with.
- Read the line under the parts list. It says how many dogbones were made, and on how many parts.
- Check the preview, then click ✓.
Options#
| Option | What it does |
|---|---|
| Corner | The relief goes right into the corner and clears it. The usual choice. |
| Minimal | Leaves a tiny bit of material in the corner, so the parts push together tightly and hold (a friction fit). |
| Long side | A T-bone: a half-circle cut into the longer wall at each corner, and not into the other wall. |
| Short side | A T-bone cut into the shorter wall at each corner. |
| Cutter Ø | The diameter of the router bit, in mm. It starts at 6. |
| Clearance | A little extra added to the cutter size, in mm. 0.1 to 0.2 mm helps the CAM program (the program that plans the router's path) fit the bit into each relief. |
| Corner interference | Minimal only: how much material to leave in the corner, in mm. 0.1 is a good start. |
| Corners from … to … | Only inside corners between these two angles get dogbones. A square corner is 90°. |
| Parts | The parts that get dogbones. Tick them, or click them in the view. With nothing ticked, every part you can see gets them. |
Tips#
- Set Cutter Ø to the bit your school's router really uses.
- Under Corners from, a line tells you how far each relief opens along the walls of a square corner.
- Dogbones go in corners that are square to each part's biggest flat face, such as the face of a sheet. Each relief goes down to the floor of a pocket, or right through the part.
- Sharp corners (less than 90°) also get the path the bit needs to reach right into the corner.
- You do not need dogbones for the laser cutter. The laser beam is so thin that it cuts sharp corners.
- To cut the parts on the router, export a STEP file for the CAM program.
If it does not work#
- No inside corners to add dogbones to (check the corner angle range). Check that Dogbone comes after the features that make the slots, and that the corners are inside the Corners from range.
- Every inside corner is too tight for a 6 mm cutter. Try a smaller cutter. The bit is too big to fit into the corners. Use a smaller bit, or make the slots wider.
- 2 corners are too tight for a 6 mm cutter, so they were left as they are. Those corners have no dogbones. Use a smaller bit, or give the bit more room there.