Last time I was lucky enough, and/or the CAD/CAM job was really neatly done. Outcome: the wooden container came out to be a beautiful piece with finished details.
This time the techno CNC sorcery won, I could not make a seamless wooden joint after a several attempts. As always I worked on the assignment on weekend when the shop is usually empty. I did some sketching first with paper and pen, looked at the reference examples on Subtraction class page, and then made vectorworks drawings:
I tried Oval-shoulder halving and Tenon halving with ellipse and rounded square shaped window. For the oval shoulder I tried two different drawings: One with zero tolerance and other with a 0.01″. The pieces with zero tolerance needed a lot of sanding, and the ones with 0.01″ tolerance were somewhat simpler to assemble.
It required considerable efforts on sanding the surface areas and hammering the pieces to fit them together, but this could have been a lot better and easier with more tolerance.
I ran into and learned a lot from two issues-
1. Stupid mistake I did in CAM: I made a significant mistake in the parts that had oval and rounded square windows. In setting contour and engraving orders, I had put the engraving first, then outside contour for the whole piece, and then the contour for window inside the piece. As a result the piece was not stable when the oval window was being cut. I had to pause the router and fix the piece into the spoilboard with two screws so that it wouldn’t wobble. The oval window got completely spoiled though, but I was able to manage it in time for the square window.
2. Bad quality of the material: The ply had an uneven, kind of burnt layer underneath the oval window piece. The layer got chipped off as engraving reached a certain depth.