For interlocking parts I have found that keeping the pieces aligned in their desired end position is best. This sucks for using least material but make much better fitting joints. So when you cut your legs you want it laid out as ‘n’ shape like in first picture. With the top piece offset up. If you cut the pieces like in second picture (all parallel) then small discrepancies between X & Y axis calibration become more pronounced. You also want to keep the joints ends as close as possible in layout - so don’t layout the top piece to be cut at the bottom of the legs. Finally you want to flip pieces on their shortest length. e.g. the top piece should be flipped around horizontal axis (upside down) rather than on vertical axis (flipped left to right).
Fusion360 struggles with pockets that have curves intersecting exterior cut paths. When making pocket cuts that fall of the edge of the piece you may want to extend the pocket about 2x cutting bit diameter beyond the piece. Fusion360 will not do this automatically and you need to create an offset path manually. This will stop the bit from following a previously cut path.
Make sure to slow down the speed of cut when hitting corners using “Reduced Feedrate” feature in CAM path settings.
Good calibration is critical:
- Make sure your sled rotates around a single point. With router on plunge into wood and manually rotate the sled 90 degrees each direction. Turn off router and check the hole - it should be perfectly circular. If its oblong your sled is not centered.
- Try to measure the “calibration test cut pattern” as accurately as you can. I use laser measure.
You certainly have vertical play in your Z-axis which is visible in the uneven depth pocket cut (5th picture).
The dimples around tabs are interesting. Are you pre-drilling holes? Or is this a multiple pass operation? Might be wobble in z-axis when raising or lowering.
Here’s a summary of settings that worked well for me: